Cardiff School of Sport DISSERTATION ASSESSMENT PROFORMA: Empirical 1

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1 Student name: Cardiff School of Sport DISSERTATION ASSESSMENT PROFORMA: Empirical 1 Rebecca O Brien Student ID: St Programme: SES Dissertation title: Supervisor: Comments The different mechanical modifications made between males and females over the two conditions of shod and barefoot recreational distance running. Marianne Gitoes Section Title and Abstract (5%) Title to include: A concise indication of the research question/problem. Abstract to include: A concise summary of the empirical study undertaken. Introduction and literature review (25%) To include: outline of context (theoretical/conceptual/applied) for the question; analysis of findings of previous related research including gaps in the literature and relevant contributions; logical flow to, and clear presentation of the research problem/ question; an indication of any research expectations, (i.e., hypotheses if applicable). Methods and Research Design (15%) To include: details of the research design and justification for the methods applied; participant details; comprehensive replicable protocol. Results and Analysis (15%) 2 To include: description and justification of data treatment/ data analysis procedures; appropriate presentation of analysed data within text and in tables or figures; description of critical findings. Discussion and Conclusions (30%) 2 To include: collation of information and ideas and evaluation of those ideas relative to the extant literature/concept/theory and research question/problem; adoption of a personal position on the study by linking and combining different elements of the data reported; discussion of the real-life impact of your research findings for coaches and/or practitioners (i.e. practical implications); discussion of the limitations and a critical reflection of the approach/process adopted; and indication of potential improvements and future developments building on the study; and a conclusion which summarises the relationship between the research question and the major findings. Presentation (10%) To include: academic writing style; depth, scope and accuracy of referencing in the text and final reference list; clarity in organisation, formatting and visual presentation 1 This form should be used for both quantitative and qualitative dissertations. The descriptors associated with both quantitative and qualitative dissertations should be referred to by both students and markers. 2 There is scope within qualitative dissertations for the RESULTS and DISCUSSION sections to be presented as a combined section followed by an appropriate CONCLUSION. The mark distribution and criteria across these two sections should be aggregated in those circumstances.

2 CARDIFF METROPOLITAN UNIVERSITY Prifysgol Fetropolitan Caerdydd CARDIFF SCHOOL OF SPORT DEGREE OF BACHELOR OF SCIENCE (HONOURS) SPORT AND EXERCISE SCIENCE THE DIFFERENT MECHANICAL MODIFICATIONS MADE BETWEEN MALES AND FEMALES OVER THE TWO CONDITIONS OF BAREFOOT AND SHOD RECREATIONAL DISTANCE RUNNING. Dissertation submitted under the discipline of Biomechanics. Rebecca O Brien ST

3 THE MECHANICAL MODIFICATIONS MADE BETWEEN MALES AND FEMALES OVER THE TWO CONDITIONS OF SHOD AND BAREFOOT RECREATIONAL DISTANCE RUNNING.

4 Cardiff Metropolitan University Prifysgol Fetropolitan Caerdydd Certificate of student By submitting this document, I certify that the whole of this work is the result of my individual effort, that all quotations from books and journals have been acknowledged, and that the word count given below is a true and accurate record of the words contained (omitting contents pages, acknowledgements, indices, tables, figures, plates, reference list and appendices). Word count: 11,748 Name: Rebecca O Brien Date: Certificate of Dissertation Supervisor responsible I am satisfied that this work is the result of the student s own effort. I have received dissertation verification information from this student Name: Date: Notes: The University owns the right to reprint all or part of this document.

5 TABLE OF CONTENTS Title Acknowledgements Abstract Page i ii CHAPTER I 1.0 Introduction Literature Review Injury Rates and Prevalence in Distance Running Mechanics of Injury Factors Affecting Injury (Footwear and Gender) Mechanics of Running The Gait Cycle in Running Foot Placement at Touchdown The Impact Force and Loading Rates Produced at Touchdown Kinematics Produced at Touchdown Shod Versus Barefoot Shod and Barefoot Distance Running The Impact of Barefoot Running on Injury Methods of Approach Research Design Data Collection Kinematics Kinematics Data Processing Data Analysis Summary 18

6 CHAPTER II 3.0 Methodology Participants Protocol Data Collection Data processing Data Analysis 23 CHAPTER III 4.0 Results Foot Placement at Touchdown Joint Kinematics at Touchdown Kinetics at Touchdown 29 CHAPTER IV 5.0 Discussion 33 CHAPTER V 5.0 Conclusion 39 CHAPTER VII 6.0 Reference List 40

7 APPENDICES APPENDIX A The information sheet given to prospective participants to outline what is involved in the study and what they need to do. A APPENDIX B A participant consent form given to the participants taking part in the study B APPENDIX C A Physical Activity Readiness Questionnaire (PAR-Q) given to the participants to fill out before completing in the study. APPENDIX D Information regarding the pilot that was completed before the actual testing. C D APPENDIX E Information collected from participant s pre testing regarding their physical characteristics and footwear. E APPENDIX F An example of one trails in which a residual analysis was carried out F APPENDIX G An example of the graphs used to extrapolate the information required from the CODA motion software used for one trial. APPENDIX H The foot strike types of each participant recorded. G H APPENDIX I The raw kinetic data collected from each trial. APPENDIX J The raw kinematic data collected for each trial APPENDIX K The ethical approval forms I J K

8 LIST OF TABLES Table no. Title Page Table 1. Table 2. The total percentages (%) of foot strike patterns The mean ± standard deviation values of discrete mechanical measures for barefoot and shod running

9 LIST OF FIGURES Figure no. Title Page Figure 1. The stance and swing phase of the running gait. 5 Figure 2. The stance and sub phases of the running gait. 6 Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. The VGRF- time graph during the stance phase of the running gait. A graph showing the force and foot strikes of a runner. A plan of the set up of equipment used in the data collection based on adaptations made from pilot study. The CODA markers and drive boxes placed on right side of participant. Variables measured during data collection. Adapted from Lieberman et al., (2010). A graph taken from the CODA motion software and the variables that were measured. Angle at touchdown of males and females in both shod and barefoot conditions. (A) ankle angle, (B) knee angle and (C) hip angle. The vertical loading rate of males and females over shod and barefoot conditions with the percentage difference between each condition being shown

10 Acknowledgements Most importantly, I would like to thank Marianne Gitoes for supervising me through my dissertation and the time she has given me to answer my endless questions; I have learnt a lot from her and always felt supported throughout the process. I am also grateful to my participants, without whom this study would not have been possible. Finally, I want to thank my friends and family who offer unconditional support to me each and every day and have put up with me over the last few stressful months! i

11 ABSTRACT Background: The risk of overuse injuries are high in distance running and the impact barefoot running may have on reducing overuse injuries and the mechanical responses of females compared to males has received little attention in the barefoot running debate. Aim: The study explored the different mechanical modifications made between males and females over the two conditions of shod and barefoot distance running. Method: Twelve participants were recruited for this study, six male (age: 20±0.8 years; mass: 63.3±0.9 kg: height: 167.2±6.8 cm), and six female (age: 20±0.8 years: mass: 73.8±3.1 kg: height: 174.3±9 cm). Normal running attire and neutral running shoes were worn as each participant completed a 40 M run in both shod and barefoot conditions. Sagittal plane kinematic angle measurements were taken using the CODA motion software and one Kistler force plate was used to gather kinetic data. Results: The results showed a significant increased flexion in the ankle in the barefoot by 9.61±1.1º (males) and 11.2±1.47º (females). The rate of loading was also found to be significant (P< 0.05) between shod and barefoot in the males with an increase from 2.05±70 (barefoot) and 1.16±0.4 (shod). The foot placement changed significantly in the shod and barefoot conditions with males and females responded similarly. Conclusion: The findings conclude that there are different mechanical modifications made between shod and barefoot running however there are very little differences of males compared to females. Whether barefoot running will reduce injury for either males or females is yet to be determined and future studies should incorporate a barefoot training programme to study the long term effects. ii

12 CHAPTER I INTRODUCTION & LITERATURE REVIEW

13 1.1 Introduction Long distance running popularity has increased over the last few decades with many people continuing to choose running as the form of exercise they peruse both recreationally and competitively (Thordarson, 1997). This has increased the need for the assessment of general biomechanical characteristics which can fall into two categories; performance or injury based. The link between performance and injury is evident but research focuses on one element which indirectly affects the other. Recreational running is defined as running at a comfortable pace in which exercise can be sustained for a large duration (De Witt et al., 2000). The increase in the popularity of recreational running has seen an associated rise in injury prevalence (Hreljac et al., 2000b), thus research has been critical to understanding the implications. To understand the link between distance recreational running and injuries it is imperative that knowledge of the mechanical characteristics is attained. Biomechanics has been used to determine potential causes of injury by examining and providing an insight into the kinematic and kinetic factors associated with a higher susceptibility to injury (McClay, 2000). There is a debate in biomechanics currently between barefoot and shod running, with the proposed rationale behind barefoot running as a preventative mechanism to reduce many common injuries associated with long distance running (Perl et al., 2012; Squadrone and Gallozi, 2009; Jenkins, 2005). There is controversy due to the timely nature of studying injury and the long term effects of barefoot running are still unknown. Although controversy exists as to whether barefoot running decreases running rates; it has been accepted that the ground contact interface in both shod and barefoot conditions in significantly different (Logan et al., 2010). It is reported that females are twice as likely to sustain patella femoral pain, illiotibial band friction and tibial stress fractures (Taunton et al., 2002 and Ferber et al., 2003). In comparison, it is noted that males are more likely to experience plantar fasciitis, meniscal injuries, patella tendonitis and achillies tendonitis (Taunton et al., 2002). 1

14 Despite the differing injury rates between genders, the cause of the gender variations are not fully understood (Taunton et al., 2002). Currently, there have been no research to determine the different modifications made between males and females in both shod and barefoot running and therefore this is the aim of the present study. This study reports on running mechanics and gender differences in running, focusing in particular on the difference in barefoot and shod conditions between male and female recreational runners. Biomechanical analysis is used to determine whether differences can be shown and to investigate the extent of these differences. The argument is that if females and males produce different mechanical modifications two barefoot and shod conditions, future studies will have a basis of the different modifications to examine further the injury difference between males and females. 2

15 2.1.1 Injury Rates and Prevalence in Distance Running Overuse injuries of the musculoskeletal system occur when a structure is exposed to a large number of repetitive forces and are the most common form of running injuries (Hreljac, 2004). They equate to 75% of all running injuries, with up to 70% of runners sustaining an overuse injury in a period of one year (Hreljac and Ferber, 2006). The most common site of injury is the knee, ankle and foot where injuries such as stress fractures, shin splints chondromalacia patellae, plantar fasciitis, and Achilles tendinitis occur. Due to the repetitive nature of long distance running, the disposition for lower extremity injury is high (McClay, 2000). Although there has been extensive literature focused on running and running related injuries, the number of runners who get injured has not been reduced (Taunton, et al., 2002; Clement and Taunton, 1981). It has been suggested that many factors cause overuse injuries but speculation suggests that the biomechanical factors have the greatest significance in overuse injuries (Hreljac, 2004). The difficulty in researching running injuries is the timely nature of the research. The period in which injuries may last is unknown and the biomechanics of the athlete pre, during and post injury needs to be obtained in order to provide insightful information Mechanics of Injury Running can be most injurious at the moment the foot collides with a collision force of times Body Weights (BW) being produced (Lieberman et al. 2010). Impacts are defined as repetitive reductions of a whole body movement that aim to generate an advantageous force for the following step. Studies have shown that the magnitude of these impact forces can cause overuse injuries (Cavanagh and Lafortune, 1980; Clement and Taunton, 1980) when comparing impact forces produced when running. The vertical ground reaction force has links with overuse injuries (Grabowski and Kram, 2008). The findings of this article and others have concluded that within shod running, VGRFs of up to 3.25 times body weight are common when running at a velocity of 4.5 m s -1 (De Wit et al., 2000). Running injuries have also been found to be caused by biomechanical variances and improper running gait, such as over pronation, running with a RFS, increased rotation and eversion in the ankle (Divert et al., 2005). Similar to this study, Hrejack 3

16 (2004) carried out a study between a group of injured runners and a group of runners who were injury free. Vertical force impact peak and the maximal vertical loading rate were greater in the injured group. These results suggest that runners who have developed stride patterns that incorporate relatively low levels of impact forces and a moderately rapid rate of pronation are at a reduced risk of incurring overuse running injuries. Other studies in agreement of this have also stated the vertical loading rate is greater in injured athletes (Logan et al., 2010; Daoud et al., 2012). Milner et al., (2006) carried out a study on 20 participants who had previous history of sustaining a tibia stress fracture compared to subjects who had no history of such injury. Kinematic and kinetic data were collected during over ground running at 3.7 m.s(-1) using a six-camera motion capture system, The results outlined that the injured group had higher vertical impact peak and average loading rate compared to the control group. However a recent review of literature surrounding the loading rate and impact forces produced has concluded that there is a lack of definitive data to suggest this (Murphy et al., 2013). This article suggested that the evidence that has been found does not definitively attribute larger impact forces to a higher injury rate. However, Milner et al. (2006) found a higher impact peak in athletes with a tibia stress fracture compared with athletes that were not injured, suggesting that a higher impact peak is linked to injury. It has been argued that the data produced does not outline the positive or negative correlation between impact and injury to suffice this conclusion to be drawn (Bramble and Lieberman, 2004) Factors Affecting Injury (Footwear and Gender) Many studies have found that efforts to mitigate the effect of these factors on injury have used either graded training programs or prescriptions of shoes and orthotics which have either modest or non-significant effects (Daoud et al., 2012). Therefore, one key factor in the running injury debate is the footwear athletes choose to run in. It is important to explore how running shoes alter the biomechanical variance of the lower extremities. Modern day running shoes offer several different types; thick sole, arch support and neutral shoes. The development of running shoes has focused on reducing the load of the lower extremities and to enhance performance and reduce injury (Braunstein et al., 2010). Developments are now focusing on minimalist shoes such as the Nike 4

17 FiveFingers and Nike Free runs which are designed with the intention to mimic barefoot running mechanics whist protecting the foot from the environment (Squadrone and Gallozzi, 2009). 75% of shod runners typically RFS compared to barefoot or minimally shod runners who more often FFS. It has been shown that minimally shod (barefoot replicated running shoes) tend to FFS because unlike RFSs, this generates no impact peak (De Witt et al., 2000). The advantages of running with shoes have been outlined to be rear-foot control, cushioning, shock distribution and heel stabilization (Divert et al., 2005). However, the effects of shoes on the lower extremities are still under debate (Lieberman, 2012). Some studies have reported that there is no modification of running patterns or mechanical difference between different shoe types. Nigg and Nachbauer, (1993) did not show any difference in the force applied to a force plate when comparing three different types of footwear. The force generated between different footwear has been outlined to show a mechanical difference (Logan et al., 2010; Lieberman, 2012). The demand of specific running footwear for females compared to males in important. Female s susceptibility to overuse running injuries provides a key issue within the discipline of footwear biomechanics. Sinclair et al., (2010) found that female do not require different footwear than males based on shock attenuation finding no difference between females and males. In contrast, Stefanyshyn et al., (2006) suggested that females require footwear with additional shock attenuating properties based on a study carried out focusing on heel cushioning for female runners. Literature has propounded that the difference in running injuries can be attributed to a number of factors. The anatomical structure and body alignment differs between females and males (McClay, 2000). Pelvis angle (Schultz et al., 2009), Q angle (Horton and Hall, 1989), valgus posture (Nguyen and Shultz, 2009), distribution of muscle mass and bone density (Pohl et al., 2008) are factors that are thought to alter running mechanics. Furthermore, gender differences in lower extremity kinematics during running have been suggested as a contributing factor (Ferber et al., 2003; Schache et al., 2003). Previous investigations have determined gender differences in 5

18 hip motion also exist during walking (Kerrigan et al., 2009; Hurd et al., 2004), indicating this observation is not specific to the running gait. Gender differences in kinetics and lower extremity kinematics during running have been suggested as a contributing factor (Ferber et al., 2003; Schache et al., 2003). Ferber et al., (2003) focused on comparisons of the hip and knee three-dimensional joint angles and negative work during the stance phase of running gaits between genders. The results showed that Female recreational runners exhibit significantly different lower extremity mechanics in the frontal and transverse planes at the hip and knee during running compared to male recreational runners. Similar to this study, Malinzak et al., (2001) investigated gender differences in coronal and sagittal plane knee motion. It was demonstrated that the whilst the coronal plane knee excursion was similar between genders, women were found to exhibit less peak knee flexion and a lower range of motion in the knee compared to men. Both studies contributed to knowledge reading kinetics and kinematics however they failed to investigate ankle kinematics or observe the kinetic loading parameters between genders. 6

19 2.2.1 The Gait Cycle of Running The gait cycle of running has two main phases; the stance phase and the swing phase (Figure 1). The gait cycle is described as a series of movements of the lower extremities beginning with the foots initial impact with the surface until it reconnects with the surface at the end of the cycle (Dicharry, 2010). The stance phase occurs during the period of contact between the foot and the running surface. These phases occur in both walking and running. When one lower extremity is in the stance phase, the other is in the swing phase. Figure 1. The stance and swing phase of running. Within the scope of biomechanical research focusing on injury perspective, the stance phase has been linked to overuse running injuries due to the high impact produced between the foot-ground interface during the stance phase of the running gait (McClay, 2000). During the stance phase it is thought that both kinetic and kinematical characteristics can be studied, the swing phase only provides kinematical analysis (Kerrigan et al., 2009). Injuries in running have been shown to be a contribution of kinetic and kinematic biomechanics, therefore justifying the utilization of studying the stance phase during the gait cycle of running (Bartlett et al., 2007). The stance phase of running has been explained by the first half concerning force absorption and the second half focuses on propulsion. It has also been demonstrated the stance phase can be sub categorised into three components, shown in figure 2 as; initial contact, mid stance and toe off (Dugan and Bhat, 2005). 7

20 Figure 2. The stance phase and sub categories of the gait cycle. Lieberman et al., (2010) outlined the impact force of body weights produced in the initial collision of the stance phase. The average distance runner produces 170 steps per minute during distance running. Furthermore, the rate of loading, measured in vertical ground reaction force is between BW per minute. The absorption of this force is a key role of the lower extremities in running and therefore it is clear to see the vunerability of long distance runners to injury in this stance phase of running due to the repetition of such forces through the lower extremities. Research conducted by Jenkins (2005) found that 70% of running injuries are a result of the stance phase mechanics. Furthermore, other evidence suggests that 75% of all injuries occur in the stance phase of the running gait (Braunstien et al., 2010; Logan et al., 2010; Murphy et al., 2013). The foot ground interaction during the stance phase means that foot placement is a key kinematical characteristic that should be considered Foot Placement During Touchdown It is widely accepted that there are three patterns of foot strike at touch down; rearfoot strike (RFS), fore-foot strike (FFS) and mid-foot strike (MFS). Lieberman et al., (2010) demonstrated that the three patterns are classified based on which part of the foot that contacts the ground initially in the stance phase of running; RFS are landings in which the heel strikes first, FFS where the ball of the foot lands before the toe and MFS is simultaneous landing of ball and heel. 8

21 Cavanagh and Lafortune (1980) classified foot strike patterns by the centre of pressure at landing relative to shoe length. A RFS was less than 35%, MFS between 34% and 66% and a FFS 67%. This method was criticized due to the anatomy of the foot being different for certain participants and thus led to the classification of FFS and MFS to be placed in the same bracket. Foot strikes vary and there is no consensus on how to define and measure those (Daoud et al., 2012). Hasegawa et al., (2007) research showed that the nature of the foot placement during the initial contact with the ground directly implicated the force produced and the sites for potential injury. Similarly, Daoud et al., (2012) also researched the implication to injury of different foot placements during touchdown. 52 college cross country runners were studied with 69% used a RFS and 31% used a FFS. Due to the training magnitude it was no surprise that 74% of runners experienced a moderate or severe injury each year. It was also found that those who RFS had approximately twice the rate of repetitive stress injuries than individuals who habitually FFS. In line with these result it has also been shown that the majority of the population who RFS will produce a double peak force profile (Derrick et al., 2002). Studies have shown that the vertical ground reaction characteristics are different between RFS and FFS patterns (Lieberman et al., 2010; Bobbert and Schamhardt, 1991; Cavanagh and Lafortune, 1980; Wilt, 1973) The Impact Forces Produced and Loading Rates The mechanics of the impact forces produced during the stance phase of running are important to understand when comparing lower extremity kinetics. The ground produces a force that is equal and opposite to the force the foot produces in the upward and forward direction, known as the vertical ground reaction force (VGRF) (Miller, 1990). As well as the VGRF there are forces in the anterior- posterior direction; the braking and propulsive forces. Compared to the VGRF, the anteriorposterior and medio- lateral are relatively small; with less that 5% contributing to the ground reaction forces (Munro et al., 1987). Therefore research tends to focus on the VGRF in relation to injury due to the strong links with overuse injuries. The higher impacts produced during the foot-ground interface, the larger force produce and therefore the likelihood of injury increase (Grabowski and Kram, 2008). 9

22 The kinetic characteristics produced during the stance phase of running can be shown on a VGRF force-time curve (Figure 3) which shows two peaks; passive and active. The passive peak occurs within the first 10% of the stance phase (Divert et al., 2005). The active peak takes place over the last 60-75% of the stance phase. The movement of a runner during foot contact determines the active peak (Daoud et al., 2012). The forces produced can be between 1.5 to 5 body weights, lasting for a short period of time. Furthermore, outlined in the previous section, foot-strike type has an impact on force produced with barefoot FFS producing 0.58 BW compared to barefoot RFS and shod RFS producing 1.89 BW and 1.74 BW respectively (Lieberman et al., 2010). The rate of loading is also an important factor to consider. Watkins (2007) Outlined that increasing loading rate (how quickly the impact force is applied) increases strain on body and can increase likelihood of injury due to stiffness of lower limbs. A RFS has a rate of loading of BW per second in contrast a forefoot and MFS has a lower rate of loading due to being more compliant and involves the exchange of less momentum and, thus, does not generate a conspicuous impact peak with a high rate and magnitude (Laughton et al., 2003). Higher loading rates have been shown by some studies to correlate significantly among RFS runners with lower limb stress fractures (Milner et al., 2006), plantar fasciitis (Pohl et al.,. 2009) and other injuries in the knee, hip and back. Figure 3. The VGRF- time graph during the stance phase of the running gait Kinematics Produced at Touchdown It has been suggested that the angle of the ankle, knee and hip at the touchdown phase of the stance period of running can alter the impacts produced, decreasing the 10

23 vertical ground reaction forces produced (Kersting et al., 2006). However, this research only studied a specific population; elite cross country males, and therefore may only apply to this population. Based on these results however, it is important to assess joint angles at touchdown in order to alter the impact force produced. Watkins (2007) explored the joint angles at touchdown and suggested that a greater flexion at the knee and ankle joint will decrease vertical ground reaction force produced. Lieberman et al., (2010) focused on the foot strike patterns of distance runners and the effect this had on the ankle and knee joints. This outlines the link between kinematic and kinetic variables in distance running. The angle at the ankle directly impacts the foot placement during the stance phase of running; a FFS is linked with a greater joint angle and a RFS is linked with a smaller angle (Figure 4). Two reasons given for the variation between foot strike patterns and impact peaks produced have been given (Lieberman, 2012). The first explains that during a FFS, the plantar flexion of the ankle upon impact then undergoes dorsi flexion at the ankle. In a RFS this change is not apparent; the angle remains dorsiflexed. This causes a much greater moment of impact in the RFS patterns (Dierks et al., 2008). The second reason given to explain the variation is the lack of marked impact peak recorded in FFS patterns (Divert et al., 2005). The FFS runners ankle is dorsio flexed and the knee flexes more during impact compared with RFS patterns which allow the lower extremities to dampen the VGRF produced (Lieberman et al., 2010). Figure 4. A graph showing the force and foot strikes of a runner. (A) rear-foot strike, (B) fore-foot strike. 11

24 2.3.1 Shod Versus Barefoot Running The comparison between barefoot and shod (trainer) running has been linked to the process of evolution; the fact that humans have been running for millions of year without shoes suggests humans are more suited to barefoot running (Lieberman et al., 2010). However, further research is needed in order to understand the long term effects of barefoot running. Lieberman et al., (2010) conducted research on five groups from two populations; USA and Kenya. It was found that habitually barefoot endurance runners often land with a FFS and habitually shod runners mostly RFS. In contrast, Hatala et al., (2013) studied 39 habitually barefoot runners from Kenya and found that not all habitually unshod people prefer a FFS or MFS. Rather, the Daasanach subjects in this study preferred a RFS at their self-selected endurance running speeds, and thus differed from the Kenyan runners studied by Lieberman et al., (2010). Both studies provided a comparison of habitually barefoot runners compared to shod runners. The peak vertical force magnitudes were approximately three times lower in habitual barefoot runners who FFS than in habitually shod runners who RFS (Lieberman et al., 2010). This is important as the habitually barefoot runners provided accurate data about the foot strike patterns and impact forces produced; because a difference can be seen between the two conditions it is evident that barefoot running does affect the mechanical characteristics. Furthermore, other studies have focused on experienced barefoot runners and the modifications made when they run in the shod condition (Squadrone and Gallozzi, 2009). This is important as a change in characteristics when barefoot running may take a few weeks therefore it has been argued that studies that require shod runners to be tested in barefoot conditions may not give a true representation of the modifications made (Hatala et al., 2013). However, in order for barefoot running to impact habitually shod runners studies must test the modifications made by shod runners taking off their shoes. De Witt et al., (2000) studies 9 trained male distance runners tested neutral shoes and barefoot running at three velocities of and 5.5 ms-1. Five joint markers were placed on toe, ankle, knee, hip and shoulder joints. The analysis of foot placement and impact forces was tested during the stance phase of the running gait for both conditions. This is an important factor to consider as previously outlined it is 12

25 thought that most running injuries occur in this phase. It was found that there was a flatter foot placement at touchdown in barefoot running. In agreement with these results, Divert et al., (2005) studied the biomechanical comparisons between shod and barefoot running of the same subjects. 35 subjects were tested over two 4 minute bouts of exercise at 3.33m.s on a treadmill. It was found that barefoot running had a lower contact and flight time and lower impact peaks over prolonged steps. This study focused on prolonged steps as it was outlined that over a limited number of steps taken runners can sustain higher impacts but in running for a prolonged period, 4 minutes in this case, it allowed the runners to reduce the high mechanical stress occurring. In contrast to the previous literature examined (Hatala et al., 2013; Lieberman et al., 2010; Squadrone and Gallozzi, 2009) this study focused on habitually shod runners being tested in barefoot conditions. Loading rate has been shown to be greater in barefoot running compared with shod running (De Clercq et al., 1994; De Wit, et al., 2000). This result could be related to the reduced cushioning available without footwear. Wright et al., (1998) define loading rate as the time derivative of the vertical ground reaction force (GRF). De Clercq et al., (1994) found that the heel pad compresses over 60% when running barefoot compared to 36% when shod. Logan et al., (2007) found that runners adjust to the increased loading rate and impact peak. The body adapts by having lower foot angles (<45º), shorter contact time and a shorter amount of distance between each step. This is similar to the results of DeWitt et al., (2000) and Dufek et al., (2000). The importance of assessing the knee angle at touchdown (TD) has been identified as a means of modifying the magnitude of the impact force. To decrease ground impact force a greater flexion at the knee has been found to decrease limb stiffness and reduce this force by up to 3 BW (Watkins, 2007). A larger plantar flexion (larger angle) leads to FFS and rear foot has been outlined by a greater dorsi-flexion of the angle (Lieberman et al., 2010). A further study focused on 9 experienced barefoot runners and assessed the mechanical changes made in the foot-ground interface of these athletes. The participants ran on a treadmill in barefoot, shod and minimalistic running shoes. It was found that barefoot condition plantar flexion at the ankle (larger angle) decrease impact peak (Squadrone and Gallozzi, 2009). 13

26 2.3.2 The Impact of Barefoot Running on Injury It has been accepted that a barefoot runner s foot ground interface is significantly different that a shod runner. The FFS found in barefoot runners creates a smaller collision force and ground reaction force that the shod runner leading to speculation that this may reduce injury (Murphy et al., 2013; Lieberman et al., 2010; Squadrone and Gallozzi, 2009). Furthermore, it has also been outlined that during the stance phase barefoot runners have less contact time with the ground, creating smaller peak forces (Daoud et al., 2012; Lohman 2011). Furthermore, the average loading rate has been shown to be three times less in barefoot conditions compared to shod (Lieberman et al., 2010). Studies conducted have shown a greater increase in loading rates of injured runners compared to healthy (Pohl et al., 2009) and therefore barefoot running causing a decrease in loading rates may impact injuries sustained when distance running. The impact force has been outlined as being the highest and most rapid force experienced in running. It has been argued by one study who found that rear foot strikers had a lower injury rate than forefoot strikers (Nigg, 2001) that this impact force has no effect on the injury rates of runners. This contradicts much of the current research which suggests that the magnitude and impact peak in runners is a predictor of injury (Davis et al., 2010; Milner et al., 2006). It is based on the current literature that has been previously outlined that suggests foot ground interface and forces produced when running that leads researchers to believe that these factors increase the likelihood of injuries in distance runners. It is with this in mind that there has been an interest in barefoot running 14

27 2.4. Methods of Approach Research Design Comparing barefoot and shod conditions has been done previously a number of different ways. Lieberman et al., (2010) and Daoud et al., (2012) used participants that habitually shod ran compared to habitually barefoot runners. This provided insightful information regarding the biomechanical differences found however in order for barefoot running to have a direct impact on recreational shod runners, the participants used in this must represent habitually shod runners in barefoot conditions. This research design therefore will focus on the comparison between habitually shod runners and the modifications made when they are tested in barefoot conditions similar to previous studies carried out (Logan et al., 2010; Divert et al., 2005). The speed of participants has also differed during studies between a selected speed and self-selected speed based on the research question (Daoud et al., 2012; Lieberman et al. 2010; Divert et al., 2005; De wit et al., 2000). Self-selected speed allows a true representation of distance running to be gained if focusing on recreational basis however if athletes are focusing on a particular event or race for example the 800 meters it would be appropriate to select a speed in which to test at. This is dependent upon the research question being explored. In order to successfully determine the biomechanical characteristics of distance running it is important to collect data under conditions that replicate this form of exercise to the best of the researcher s ability (Mullineaux, 2001). Research suggests that using a 25 m approach to the force plate is adequate to ensure participants reach a comfortable running pattern (Logan et al., 2010; Lieberman et al., 2010) Data Collection Kinematics Kinematic data assessing running gait has been a key measurement taken in comparing barefoot and shod conditions. The data collected can outline stride length and time (De Witt et al., 2000), foot placement (De Witt, 2000) and joint angles at 15

28 each phase (Dauod et al., 2012). This has been done using a variety of methods including; high speed cameras (Utz-Meagher et al., 2011) and automatic motion analysis (Perl et al., 2012; Lieberman et al., 2010). There are different types of automatic motion analysis systems, either using passive or active markers (Richards, 2009). Using passive markers reflect light back to a sensor and coordinates are digitalized. Active markers send the coordinates back to the system directly. In comparison to high speed cameras, automatic motion analysis is more costly and involves the estimation of centres of joints but is more time effective (McGinnis, 2005). Video based analysis is one of the most widely used analysis in kinematic research Within the stance phase of the running gait CODA motion analysis has been widely used to gather kinematical data (Liberman et al., 2010; Fukuchi and Duarte, 2008; Leskinen et al., 2007) Kinetics The kinetic data collected during the stance phase of the running gait is collected with the use of a force plate. Many studies comparing barefoot and shod running have been undertaken using a force plate (Daoud et al., 2012; Utz-Meagher et al., 2011; Lieberman et al., 2010; De Witt et al., 2000). The force plate is designed to assess forces in 3 axis. A load on the plate deforms a pedestal on the load location and direction. The manufacturer of the plate provides calibration parameters that are used to convert the voltages into force and moment measurements. In running assessment, typically the vertical force component is studied. However, a key limitation with assessing running using a force plate is the fact that field research is difficult to carry out and therefore the validity of results may be slightly less accurate (De Witt, 2000). A further limitation is the net force that is measured on the force plate, it is an overall force. However, in terms of running the upper body is not relevant in these studies and therefore the limitation does not affect the results of the studies discussed Data Processing The data produced by the kinetic and kinematical analysis outlined previously produces unwanted additional noise (Winter, 2009). Noise reduction is usually 16

29 performed with either smoothing or filtering. Smoothing involves cubic or quintic splines. There are two major ways to reduce noise with filtering; digital filters or noise residual analysis. The Butterworth filter is used regularly as a way to alter cut off frequencies (Robertson et al., 2004). The main decision regarding the use of the filter is the choice of cut-off frequency, which must be appropriate to the movement being analysed. Residual analysis is analysis of the difference between filtered and unfiltered signals over a wide range of frequencies. This method aims to achieve best compromise between signal distortion and noise attenuation (Winter, 2009) Data Analysis The kinetic and kinematical characteristics will be taken from the motion analysis system of CODA and the Kilster force plates. Kinematic variables within the running gait have been widely researched and the use of CODA motion analysis is a popular method to use (Lieberman et al., 2012, Daoud et al., 2010; Divert et al., 2005). The assessment of kinetic variables is commonly done with the use of force plates; allowing a greater knowledge to be gained in sporting context such as that of Cavanagh and Lafortune (1980), along with more recent ones, such as Hreljac and Feber (2006). From the collected data the difference between males and females can be assessed using a students T-test and finding the root mean square difference (RMSD), each are presented in units of per cent (normalised). 17

30 2.5 Summary It is clear to see that there is extensive research focusing on barefoot distance running and the potential to decrease injury rates. The mechanics of running discussed has outlined the importance of the stance phase period when assessing injury rates. It has also been examined the differences in injury rates between male and female participants. With the rise in recreational runners, the rise in biomechanical research focusing on injury reduction has been exponential. The literature provides evidence that the modifications made between shod and barefoot trials are significant, warranting further research into the potential of injury reduction in barefoot conditions. There have been no previous studies exploring gender differences over the two constraints of barefoot and shod recreational distance running. Therefore this study will examine the different mechanical modifications made between males and females over the two conditions of shod and barefoot. This is relevant to enhance the current knowledge in the barefoot running debate due to the specific population the results would target. Hopefully based on this research a greater understanding of whether males or females are more suited to barefoot running as a preventative mechanism of distance running injuries will be obtained. 18

31 CHAPTER II METHODOLOGY

32 3.1 Participants Twelve participants were recruited for this study, six male (age: 20±0.8 years; mass: 63.3±0.9 kg: height: 167.2±6.8 cm), and six female (age: 20±0.8 years: mass: 73.8±3.1 kg: height: 174.3±9 cm). These statistics are presented as mean± standard deviation (SD). All participants were volunteers recruited from Cardiff Metropolitan University (CMU). The criteria in order to take part in this study required each participant to be a recreational long distance runner. It has been purported that recreational sport can be defined by the miles one trains (Daoud et al., 2012) and therefore recreational running in this study was defined as running up to 3 times a week for no more than 25 miles a week. All participants were free from injury for six months or more. Injury was defined as a pain or discomfort felt by the individual which alters their running technique or gait cycle. The footwear required to be worn by the participants were neutral running shoes which are defined in the data collection section. The participants were all habitual shod runners and had no experience of barefoot running. Ethical approval was granted by the Ethical Committee of Cardiff Metropolitan University and was granted before the study commenced ensuring the protocol and data collection were ethically sound. Each participant was given an information sheet outlining what the testing required them to do, what measurements will be taken and any dangers involved with this study (Appendix A). After this information was given, each participant signed a fully informed consent form (Appendix B) and filled out a PAR-Q (Appendix C). 3.2 Protocol The test was constructed to examine the gender modifications made over two running conditions of shod and barefoot running. Therefore the protocol was composed with priority to manipulate the footwear worn by both males and females. Following the pilot study that was completed prior to the data collection (Appendix D), the participants were asked to come to the training session wearing their usual running attire of shorts and a short top suitable for markers to be placed on the participant. The shoes worn by each participant were defined as being neutral and less than one year old. According to Perl et al. (2012) neutral shoes have cushioned elevated heels, arch supports and stiff soles. Therefore during this study the shoe 19

33 design of each participant was examined before testing and any shoe that replicated minimal support, for example Nike free runners, were not used. In order to ensure running trainers were suitable, the same person examined all participants shoes in order for there to be no discrepancies based on personal perception. If a shoe was deemed to not be neutral the participant was asked to return to another training session with a suitable neutral running shoe. Each participant was asked to perform a 400 meter warm up prior to testing. Characteristics of each participant were taken before the testing began (Appendix E). Each participant then completed a test trial in the shod and barefoot condition to allow them to become familiar with the testing procedure. This required them to run at a self-selected comfortable pace over 40 meters and hit the force plate. The aim of this was to get the participants comfortable with the trial procedure and also to see if the participants hit the force plate with their right side (side of the body with markers on). It was outlined that the participant should keep note of the foot they start on and if the force plate was missed they were instructed to start on the other foot. To reduce the likelihood of force plate targeting, the force plate was embedded into the track and covered with synthetic flooring to reduce the likelihood of participants focusing on the force plate. During the data collection participants were required to run 40 m, which has been outlined as a distance in which a comfortable running technique is adopted (Logan et al. 2010), over the force plate. Three successful trials were needed in the shod condition and then three successful trials in barefoot condition. The number of trials was prescribed based on previous studies that demonstrated three trials per participant was sufficient and ensured more participants could be studied rather than more trials of the same participant (Logan et al., 2010). In order to eliminate fatigue as a factor, the participants were given a sufficient level of rest in between each trial (from 1 to 3 minutes). The participants were instructed to run at their natural training pace which was defined as 65-70% of maximal effort, this method was similar to previous studies (Logan et al., 2010; Lieberman et al., 2010). It was decided for the participants to self select their running pace due to the findings of previous work which demonstrated the repeatability of kinematic and kinetic data to be greater when athletes self select the pace (Queen et al., 2006). Based on previous literature it has been found that participant s results can be altered by force plate targeting 20

34 (Morley et al., 2010) and therefore the participants were instructed to look ahead and not at the force plate which was monitored by the researcher; if a participant was demonstrating force plate targeting by looking at the ground and visibly changing their running pattern they trial was deemed to be unsuccessful and was repeated. A trial was labelled successful if the participant hit the force plate with the right foot during the whole stance phase from touchdown to toe off and no major alterations were observed in running form. Information collected for each trial including data of if the trial was successful or not. 3.3 Data Collection The equipment set up used to collect the VGRF, ankle and knee angles, loading rate, time to take off and duration of stance phase for each respective trial is demonstrated in figure 5. A single force plate (9287BA, Kistler, Switzerland) operating at 1000 Hz was set up 40 meters away from the starting point of the running trial. The VGRF, timing and angles recorded by the force plate was analysed using the software CODA motion V (Charnwood Dynamics Ltd, Leicestershire, UK) operating at 400 Hz, which was located parallel to the force plate. The force plate was located in NIAC (National Indoor Athletic Centre) at the end of a 100 m track. The force plate is concealed to reduce the chance of force plate targeting with a Mondo track surface (Mondo, Warwickshire, UK). Additional readings were taken of the self selected running speed of each participant with the use of Smart Speed Light Gates (Smart speed, Fusion Sport, Brisbane, Australia) positioned 10 meters from the force plate. The smart speed light gates were triggered as the participant ran through them calculating the average velocity of each participant. This consisted of two light beams and two reflectors which were either side of the run up. Figure 5. A plan of the set up of equipment used in the data collection based on adaptations made from pilot study. 21

35 Prior to the testing, the force plate origin defined as the centre of the force plate needed to be calibrated. The central measure of the force plate was established using a tape measure and a laser was used to identify the origin of the force plate (Figure 5). The laser was used to identify the origin of the overall force plate and the tape measure was used to establish the central measure of each side of the force plate. The active CODA markers, used to obtain 3D joint centre coordinate information, and drive boxes were placed on the participants skin and surface of shoe as shown in figure 6. It has been shown that even though the foot markers were placed on the shoe of each participant this is still an accurate indicator of bone motion (Pohl, 2008). The active CODA markers were used to obtain 3D joint centre coordinate information and the placement was decided upon based on previous research which placed the markers on the joint centres of the ankle and knee (Logan et al., 2010; Lieberman et al., 2010). The participants were asked to move each joint in different planes to allow the marker to be placed correctly on the centre of the joint. The same researcher placed the markers onto every participant to keep joint identification consistent. The active markers were then aligned with the force plate by a participant walking over the force plate. The necessary procedure of aligning the Coda markers on the force plate to ensure that a 0, 0, 0 reference frame was formed at the origin and the two systems are integrated was also carried out. Figure 6. The CODA markers and drive boxes placed on right side of participant. 22

36 3.4 Data Processing Active noise as a result of high frequency data was eliminated from the kinetic and kinematic data collected through use of a residual analysis profile (Winter, 2005). Kinematic data (Joint at TD, TD time and angle at max VGRF) usually has a higher level of active noise compared to kinetic data (VGRF and loading rate) due to the active markers being placed on soft tissue, therefore the optimal cut off frequency was obtained through the ankle angle found in 1 barefoot and 1 shod trial. The two trials were randomly selected and the whole kinematic recording was used in order to gain an understanding of the whole data set not just the stance phase. Residual analysis allows a compromise between signal distortion and noise reduction by assessing the difference between filtered and unfiltered data; 14Hz was identified as the optimal cut-off frequency (Appendix F). 3.5 Data Analysis Before analysing the data, the variables that were needed in order to address the research question were chosen and are outlined in figure 7. Figure 7. Variables measured during data collection. Adapted from Lieberman et al., (2010). 23

37 The kinetic and kinematic variables outlined in figure 7 were chosen to be analysed to allow a comparison to be made between the results found and those found in studies outlined in the review of literature (De Witt et al., 2000; Braunstien et al., 2010; Lieberman et al., 2012; Daoud et al., 2012). Figure 8 shows the kinetic data that was extracted from the CODA motion software. Figure 8. A graph taken from the CODA motion software and the variables that were measured. Touchdown was described as being the first point of contact of the foot on the ground and the toe off was when the foot left the force plate, touchdown to toe off was defined as the stance phase of the gait. When no force was placed on the force plate there was a value of 20 N and therefore a threshold of 30 N was used to detect contact made with the force plate. The kinematical variables measured in the sagittal plane, were the ankle, knee and hip angles at touchdown which were taken directly from the CODA markers placed on the ankle, knee, hip and shoulder joints. The angles were defined as MTP and knee (ankle), ankle and hip (knee), knee and shoulder (hip). The angle graphs were extracted directly from the CODA motion software based on the defined angles. The kinetic data was taken from the force plate which included the active and passive vertical ground reaction force (VGRF), time to VGRF, stance time (the time in which contact is made with the force plate) and rate of loading; where the loading rate was defined as the peak VGRF divided by the time to the peak VGRF (Watkins, 2007). The force plate data was normalised 24

38 by converting the values into BW in order for a comparison to be made between each participant. The data was processed and firstly a test of normality was carried out (Kolmogorov- Smirnov Test). This was carried out in the statistical analysis software of the social sciences software (SPSS inc., 17.0, Chicago, IL). The shod and barefoot data in the male and female participants was then analysed based on the results of the test of normality which concluded all of the data was normal. An independent t-test was carried out (P<0.05) to establish if there was a significant difference between the average male and female data over the two conditions. The male and female data was derived from gathering a mean value from each participant over the three trials in both the shod and barefoot condition. Also, a paired T-Test was also carried out to compare the male shod to barefoot and the female shod to barefoot data. To show the difference between the females versus males and barefoot versus shod an average for each participant was calculated and the percentage difference was then found. This outlined the exact percentage difference that was found between the barefoot and shod condition. Percentage difference equation: 25

39 CHAPTER III RESULTS

40 4.1 Foot Strike Pattern at Touchdown Table 1 shows the percentage of forefoot, mid-foot and RFSs in the male and female participants over barefoot and shod conditions. The results show that the both the females and males had a higher percentage of trials (66.7 and 72.2) in the forefoot condition. The lowest percentage in the barefoot condition for both male and females was RFS, with MFSs remaining the same for male and female. In the shod condition the highest percentage was the same for males and females with 83.3 and 66.7% with a RFS. Females had a higher number of trials in the MFS in the shod condition with 22.2 % difference; however for both samples this was the dominant foot strike pattern. There was a consistently in the forefoot strike for both males and females as being the least popular with percents of 11.1 and 5.6%. The MFS had a large variation between males and females with females having a percentage of 27.8 and males 5.6%. The average approach velocity prior to stance (mean ± standard deviation) for females was 6.58 ± 0.4 m s -1 in the shod condition and 6.60 ± 0.3 m s -1 in barefoot condition. Males produced a velocity of 6.53 ± 0.7 m s -1 in the shod condition and 6.55 ± 0.8 m s -1 in the barefoot condition Table 1. The total percentages (%) of fore-foot, mid-foot and rear-foot strike patterns found for each trial of males [N=18] and females [N=18] over the two conditions of barefoot and Barefoot (%) Shod (%) Male Female Male Female FFS MFS Rear-foot Strike

41 Figure 9. Angle at touchdown of males and females in both shod and barefoot conditions. (A) Ankle angle, and (B) knee angle. With * representing a significance difference between the data (P<0.05) 27

42 4.2 Joint Kinematics at Touchdown Figure 9A shows the joint angles in the sagittal plane of the ankle, knee and hip at touchdown, over the two conditions. The ankle angle showed a larger platar-flexion by 9.61±1.1º (males) and 11.2±1.47º (females) more in the barefoot condition at TD compared to the shod condition. The male and females in the barefoot and shod conditions was very similar with only a small difference in angles produced; 2.28 º and 0.70º with the females having a slightly more extended angle. The percentage difference of the males over the two conditions of barefoot was 7.9 % and females were 8.38 %. The percentage difference between the males and females in the two conditions was (barefoot) 1.74 % and (shod) 0.58 %. Showing the percentage difference to be relatively low between males and females and shod and barefoot for the ankle angle, thus showing similar results. This shows the largest percentage difference was found in the comparison between males over the two conditions as was found to be significantly different (P<0.05). Also, females in barefoot and shod was found to be significant along with males versus females in the barefoot condition (P<0.05). The comparison of barefoot versus shod was relatively small for both females and males. These findings can be linked to the foot strike types found; the barefoot condition produced more FFS types due to the larger plantar-flexion found at the ankle during touchdown. Similarly, the RFS was found more consistently during the shod condition, demonstrating a larger dorsi-flexion at the ankle. Figure 9B shows the knee angle was similar in the barefoot and shod condition with only an increased flexion of 1.42±3.69º (males) and 1.96±0.31º (females) in the barefoot condition at TD compared to the shod condition. Also, the males and females in the barefoot and shod conditions produced similar results with only a slight difference of angle degree 1.41±2.53º and 0.87±1.47º with the males having a more flexed knee at touchdown. The percentage difference of the males and females over the two conditions of barefoot and shod was 0.87 % (males) and 1.2 % (females). Similarly to the ankle angle the largest percentage difference was found with the males over the two conditions. The barefoot versus shod condition in both the female and males was found to be similar with no significance difference found. 28

43 The overall findings from the ankle and knee angles has shown that the ankle angle correlated to the foot strike types found in both males and females with a FFS producing more plantar-flexion at the ankle in the barefoot condition compared to the shod condition. The knee showed very little difference across the gender comparison and the shod versus barefoot. The hip was significantly different between males and females and across the two conditions of shod and barefoot. 4.3 Kinetics at Touchdown Figure 10 shows the peak vertical loading rate in BW of males and females over the two conditions of barefoot and shod running, with the larger loading rate found in the barefoot condition with an increase of 0.44±0.30 BW/s (males) and 0.29±0.68 BW/s (females). Females demonstrated a higher loading rate in the barefoot condition which is linked to the foot-strike patterns found; females had a tendency to produce a higher percentage of FFSs in the barefoot condition (72%) thus showing that the FFS type does have an influence of the loading rate. The difference between the males and females over the conditions were (barefoot) 0.26±0.21 BW/s with females producing a higher loading rate and (shod) 0.11±0.17 BW/s with females also producing the larger loading rate. 29

44 Vertical loading rate (BW/s) 2.50 M Barefoot V Shod % difference: % F Barefoot V Shod % difference: % M v F Barefoot % difference: % M v F Shod % difference: 7.53 % Male Female Barefoot Shod Figure 10. The vertical loading rate of males and females over shod and barefoot conditions with the percentage difference between each condition being shown. With * showing a significant difference of (P<0.05). Table 2 demonstrates the overall characteristics measured between the two conditions of shod and barefoot of male and female participants. The total stance time was greater for both males and females in the shod condition with an extension of 0.01±0.01(male) seconds and 0.013±0.014 seconds (female). The active vertical ground reaction force peak produced had differing results between males and females. Females produced a higher peak (BW) during the barefoot condition with a difference of 0.78 BW with males producing a larger peak during the shod condition with a difference of 0.05 BW. The time to the active peak in the shod condition increased by 0.27±0.08 seconds (male) and 0.17±0.09 seconds (female) compared to the barefoot condition. The difference between the males over shod and barefoot were found to be significant (P<0.05). The maximum angles during the VGRF are shown in figure 11. The ankle produced a larger plantar flexion during the barefoot condition for both males and females with an increased extension of 7º and 10º, again linking to the FFS type found in barefoot running. The knee angle was also extended further during the barefoot condition in both males and females with a difference of 3º and 2º. 30

45 Table 2. The mean ± standard deviation values of discrete mechanical measures for barefoot and shod running. With * showing a significant difference. Barefoot Shod Male Female Male Female Stance time (s) 0.167± ± ± ± ± ± ± ±0.23 Active Peak VGRF (BW) 1.41± ± ± ±0.34 Time to active peak (s) Passive Peak VGRF (BW) Time to Passive peak VGRF (s) Active loading rate (BW/s) Passive Loading rate (BW/s) 2.63± ± ± ± ± ± ± ± ±0.70* 1.79± ±0.4* 1.5± ±0.7* 1.06±0.02* 1.21±0.65* 1.4±0.37* Touchdown ankle Angle (º) ±0.91* ±4.37* ±2.01* ±2.93* Touchdown knee Angle (º) ± ± ± ±3.42 Angle ankle at max Fz (º) ± ± ± ±5.12 Knee ankle at max Fz (º) ± ± ± ±

46 CHAPTER IV DISCUSSION

47 5.0 Discussion The aim of this study was to examine the different mechanical modifications made between male and females participants over two conditions of barefoot and shod recreational distance running. To address this research aim the running characteristics of males and females were examined in both shod and barefoot running conditions and then analysed. There are some discrepancies in barefoot running research as to whether barefoot running does decrease the likelihood of injury due to the nature of running injuries; there have been little research that studied the long term effects of barefoot running on injury (Lieberman et al., 2010; Logan et al., 2010; Murphy et al., 2013). Therefore the incentive of this study was to determine the different mechanical modifications made between males and females differs in shod and barefoot running at touchdown in the sagital plane ankle, knee and hip angles at this point in time. The assessment of the mechanical characteristics of males and females in shod and barefoot distance running was conducted in the stance phase of the running gait. The strike types observed in this study between males and females concluded that a FFS was predominantly utilised in the barefoot condition (66.7 % males) and (72.2 % females). As shown, this study found that the foot strike types were similar in males and females. These findings were in agreement with Lieberman et al. (2010) who also found that 75 % of a habitual barefoot running population produced a FFS when running at self-selected pace; however this study only focused on male athletes. This has also been supported by Squadrone and Gallozzi s (2009) who also found barefoot running produced 72 % of FFS types. In accordance to the barefoot condition, shod running produced a different foot placement with (83.3 % males) and (66.7 % females) producing a RFS pattern. This can be explained by the work of De Wit et al. (2000) who found that the foot placement during barefoot running at touchdown was significantly more horizontal that shod running. The foot placement between shod and barefoot conditions differed slightly within this study; 6.5% more females displaying a FFS type in the barefoot condition compared to the males. In the shod condition there was a 16.6% increase in RFS types in males compared to females and therefore males had a higher VGRF in the shod condition compared to females who had a higher VGRF in the barefoot condition. This demonstrates that both participant groups differ in their response to barefoot running; this may be due 33

48 to the different ankle angles that were found in males and females which are corresponded by current literature (Ferber et al., 2003). The trials completed found 54 % of participants completing a RFS pattern in the shod condition, showing a change in technique were evident. Similarly, research conducted by Hasegawa et al. (2007) found that 75% of participants tested RFS at moderate speeds on flat, hard surfaces. Lieberman et al. (2010) compared habitual shod runners with habitual barefoot runners in both shod and barefoot conditions; finding that the habitual shod runners produced a RFS pattern in shod conditions compared to the habitual barefoot runner who produced a FFS pattern in the shod condition. This demonstrates the influence of having barefoot running experience when studying this. One reason for this that has been given by Logan et al. (2010) who suggested that the impact peak produced when contact is made with the ground forces barefoot runners to reduce this shock attenuation by adopting a fore-foot strike. In the shod condition there was a 16.6% increase in RFS types in males compared to females and therefore males had a higher VGRF in the shod condition compared to females who had a higher VGRF in the barefoot condition. This demonstrates that a RFS pattern does then lead to a higher VGRF due to the lack of shock attenuation that is found in the FFS. It is also important to understand that different populations have been tested; habitual barefoot runners, habitual shod runners or in the case of this study habitual shod runners taking their running shoes off and therefore the slight difference in results could be accounted for by this variable. The foot placement of runners can be explained by a number of biomechanical variables. The joint angles produced in the sagital plane of the ankle and knee are important determinants of foot placement (De Witt et al., 2000; Logan et al., 2010; lieberman et al., 2010; Murphy et al., 2013). In the barefoot condition the ankle angle demonstrated a larger (P<0.05) platar-flexion by 9.61±1.1º (males) and 11.2±1.47º (females) showing a significant difference between the ankle angle in the shod compared to the barefoot condition. Lieberman et al. (2010) suggested that a factor contributing to the predominance of RFS patterns in shod conditions is due to the cushioned sole of running shoes, originating the sole of the foot to have 5º less dorsiflexion causing the ankle to remain dorsiflexed during the stance period. In contrast, a FFS pattern creates a larger plantar flexion as demonstrated in this study. The male and females in the barefoot and shod conditions was very similar with only 34

49 a small difference in angles produced; 2.28 º and 0.70º with the females having a slightly more extended angle. The gender response was very similar in the ankle angle at touchdown. Interestingly, Delgado et al. (2013) found the perception of habitual shod runners to be that a RFS is a more comfortable landing pattern, despite the larger shock attenuation found with this compared to a FFS. It has been suggested that the difference in location of overuse injury found in males compared to females is due to males becoming more prone to injury in the ankle with males more prone in the knee (Taunton et al., 2002). However, the results found in this study demonstrate that the response in the ankle was very similar in males and females. The knee angle was similar in the barefoot and shod condition with an increased flexion of 1.42±3.69º (males) and 1.96±0.31º (females) in the barefoot condition at TD compared to the shod condition. In contrast, Divert et al. (2005) found that knee flexion is significantly larger in the barefoot condition compared to the shod condition with an increase in flexion of ~ 10º. In accordance to this study, De Witt et al. (2000) also found that there was a larger knee flexion in the barefoot condition due to the flatter foot placement in barefoot running causing a more vertical shank segment. Similarly, Lieberman et al. (2010) also found that knee flexion was greater in the barefoot condition at touchdown by ~ 9º. This was explained by the FFS pattern associated with barefoot running; there is no shock absorption found when barefoot running and therefore a more flexed knee allows the lower extremities to dampen the force. This current study however found that the response to barefoot compared to shod running was very similar, with only an increase in flexion of ~2º. The differing results found compared to this study may be due to the participants used; Lieberman et al. (2010) studied habitual barefoot runners and this current study focused on habitual shod runners taking their shoes off which previous studies have also focused on (De Witt et al., 2000; Divert et al., 2005; Hasegawa et al., 2007; Kerrigan et al., 2009). The knee and hip angles at touchdown of both males and females over both conditions were very similar with a variation of only ~ 1. A further observation is that even though the male and female participants demonstrate different percentages of foot strike patterns at TD, the angles of the ankle, knee and hip remain relatively similar; which may contradict the previous research and findings 35

50 that have suggested that the foot placement does influence the ankles at the ankle, knee and hip joints. Lieberman (2012) suggested the limitations of studying habitual shod runners taking their shoes off. It is argued that subjects will not have adapted biomechanical habits of barefoot runners and therefore will run differently to those who have grown up barefoot running. This is an important fact to consider however this study aimed to examine how habitual shod runners would react without shoes on; in order for the results to be valid for a population of habitual shod runners they must be the participants used and therefore the validity of this study is high. Within the current research it has been found that due to the RFS pattern shod running lends its self to; there is a larger vertical ground reaction force produced after touchdown. The findings of this study showed males produced a larger (P<0.05) VGRF during the shod condition with an increase of 1.02 BW compared to the barefoot condition. This has been demonstrated by Divert et al. (2005) when comparing barefoot verses shod running; the results showed averaged values of VGRF in the barefoot condition producing a result of 2.60 BW compared to the shod VGRF of 2.70 BW.. This is consistent with the findings of De Witt et al. (2000) who also found that during the shod condition there was found to be a larger VGRF during the touchdown phase. In comparison, the female participants were found to have a higher VGRF at touchdown during the barefoot condition with a difference of 1.17 BW. This differs from the findings of the male participants and also the previous literature as it has been previously stated that a higher VGRF was found in the shod condition. However, there has been limited research that focuses only on females and therefore this is an area that needs further development in order to determine whether female participants find barefoot running to cause a higher VGRF at touchdown. The results shown in this study with 66.7 % males and 72.2 % females producing a FFS in barefoot running and the studies of Divert et al. (2005) and De Witt et al. (2000) indicate that a change in foot placement alters the mechanical variables between shod and barefoot running. This has been outlined to be caused by the contact of the skin on the surface of the ground during barefoot running; allowing the 36

51 sensory information gathered through proprioceptors in the foot to cause the lower extremities to adjust specific mechanical functions to cope with the impact force ( Maffetone, 1999; Shakoor and Block, 2006). Hence the different mechanical responses shown between RFS and FFS. Furthermore, in accordance with this explanation, Squadrone and Gallozzi (2009) described the flatter foot placement found in barefoot running (larger plantar flexion in the ankle angle) may be employed to reduce the impact force created which a RFS pattern is known to produce; explaining why the males who produced FFS patterns in the barefoot. condition had a lower VGRF in the barefoot condition. To interpret the vertical GRF in this current study, the link between higher VGRF and increased risk of overuse injury can be suggested; showing that the shod condition may be linked with an increase in the potential to sustain an overuse stress injury due to the increased vertical GRF in males. Males however have reacted differently in the barefoot condition, therefore suggesting that perhaps males would not decrease the risk of overuse injury in barefoot running but increase it. The vertical rate of loading during impact also produced differing results in this current study compared to previous results. The larger loading rate found in the barefoot condition with an increase of 0.44±0.30 BW/s (males) and 0.29±0.68 BW/s (females) showing a significant difference between the barefoot and shod condtion (P<0.05). In contrast to the findings of this study, it has been found in other research that the rate of loading of vertical GRF during the initial part of stance are lower in fore-foot strikes than shod RFSs (Lieberman et al., 2010). Similarly, Milner et al. (2006) carried out a study on 20 injured participants and found that the injured group had a 33 % higher average loading rate compared to the control group. However a recent review of literature surrounding the loading rate and impact forces produced has concluded that there is a lack of definitive data to suggest this (Murphy et al., 2013). In contention with this, Watkins (2007) outlined that increasing loading rate increases strain on body and can increase likelihood of injury due to stiffness of lower limbs. A rear- foot strike has a rate of loading of BW per second in contrast a fore-foot and mid-foot strike has a lower rate of loading due to being more compliant and involves the exchange of less momentum and, thus, does not generate a conspicuous impact peak with a high rate and magnitude (Laughton and Davis, 2003). In contrast, the difference in the results found in this study may be due 37

52 to the fact that not enough time was given for habitual shod runners to adapt to the barefoot condition. Some researchers have argued that a larger VGRF and loading rate are not a cause of injury because studies have shown injury rates are not affected by hard surfaces and shock absorbing shoes (Nigg, 2010). In contrast, several studies have found that the maginitude and rate of the VGRF in runners is a predictor of injuries such as: tibial stress fractures, patellofemoral pain syndrome, plantar fasciitis, and lower back pain (Milner et al., 2006; Pohl et al., 2009). 38

53 CHAPTER VI CONCLUSION

54 6.0 Conclusion The comparison between males and females over the two conditions of shod and barefoot conditions is a relatively new area of research with no studies currently comparing the modifications made between the two. It has been accepted that females are at a greater risk to sustain overuse injuries in running (Hrjelack, 2004). However, due to the lack of research comparing the modifications made between males and females in barefoot and shod conditions there is definitely a gap in the knowledge in this area. Based on the results of this study, it can be concluded that males and females in a recreational population do react similarly in both barefoot and shod conditions in the angles produced at touchdown and the foot strike patterns. However, there was a difference found in the VGRF and loading rate in males and females. The argument whether barefoot running is less injurious for either males or females is still yet to be determined and therefore it would be beneficial for future studies to incorporate a barefoot training programme and determine whether there are any long term differences found between male and female participants. This study has enhanced the knowledge of gender responses found in the two conditions and it has confirmed that barefoot running does change the mechanical characteristics of a both females and males in a similar way, therefore barefoot running could be a way to prevent injury in distance running. 39

55 CHAPTER VII REFERENCE LIST

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59 Laughton, C. A., Davis, I. and Hamill, J. (2003). Effect of strike pattern and orthotic intervention on tibial shock during running. Journal of Applied Biomechanics, 19, Leskinen, A., Hakkinen, K., Virmavirta, M., Isolehto, J. and Kyrolainen, H. (2009). Comparison of running kinematics between elite and national-standard 1500-m runners. Sports Biomechanics, 8(1), 1-9. Lieberman, D. (2012). What we can learn about running from barefoot running: an evolutionary medical perspective. Exercise and Sport Science Review, 40(2), Lieberman, D. E., Venkadesan, M., Werbel, W. A., Daoud, A. I., D Andrea, S., Davis, I. S., Mang Eni, R. O. and Pitsiladis, Y. (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature, 463, Logan, S., Hunter, I., Hopkins, J., Feland, J. and Parcell, A. (2010). Ground reaction force differences between running shoes, racing flats, and distance spikes in runners. Journal of Sports Science and Medicine, 9, Maffetone, P. (1999). Complementary Sports Medicine: balancing traditional and nontraditional treatments. United States of America: Human Kinetics. Malinzak, R, A., Colby, S, M., Kirkendall, D, T., Yu, B. and Garret, W, E. (2001). A comparison of knee joint motion patterns between men and women in selected athletic tasks. Clinical Biomechaincs, 16(5), McClay, I. (2002). The evolution of the study of the mechanics of running: Relationship to injury. Journal of the American Podiatric Medical Association, 90, McGinnis, P, M. (2005). Biomechanics of Sport and Exercise: Second Edition. Leeds, UK: Human Kinetics. Miller, D. (1990). Ground reaction forces in distance. Biomechanics of distance running. Champaign, IL: Human Kinetics 43

60 Milner, C., Ferber, R., Pollard, D., Hamill, J. and Davis, S. (2006). Biomechanical factors associated with tibia stress fracture in female runners. Medicine of Science and Sports Exercise,. 38, Milner, C.E., Davis, I.S., Hamill, J., (2006). Free moment as a predictor of tibial stress fracture in distance runners. Journal of Biomechanics, 39(15), Monaghan, K., Delahunt, E. and Caulfield, B. (2007). Increasing the number of gait trial recordings maximises intra-rater reliability of the CODA motion analysis system. Gait and Posture, 25, Morley, J., Decker, L., Dierks, T. Blanke, D., French, J. and Stergiou, N. (2010). Effects on varying amounts of pronation on the mediolateral ground reaction forces during barefoot versus shod running. Journal of Applied Biomechanics, 2, Mullineaux, D. R. (2000). Methods for quantifying the variability in data. Proceedings of the 18th International Symposium of Biomechanics in Sport. Hong Kong: The Chinese University of Hong Kong. Munro, C.F., Miller, D.I. and Fuglevand A.J. (1987) Ground reaction forces in running: a reexamination. Journal of Biomechanics 20(2), Murphy, K., Curry, E. and Matzkin, E. (2013). Barefoot Running: Does It Prevent Injuries? Sports Medicine, 43, Nguyen, A. and Schultz, S, J. (2009). Identifying relationships among lower extremity alignment characteristics. Journal of Athletic Training, 44(5), Nigg, B, M., Cole, G, K. and Nachbauer, W. (1993). Effects of arch height of the foot on angular motion of the lower extremities in running. Journal of Biomechanics, 26(8), Nigg, B. (2001). The Role of Impact Forces and Foot Pronation: A New Paradigm. Clinial Journal of Sports Medicine,11, Perl, D., Daoud, A. and Lieberman, D. (2012). Effects of footwear and strike type on running economy. Medicine and Sports Exercise, 44 (7), Pohl, M., Hamill, J. and Davis, I. (2009). Biomechanical and anatomic factors associated with a history of plantar fasciitis in female runners. Clinic of Journal of Sport Medicine, 19,

61 Pohl, M., Mullineaux, D., Milner, C., Hamill, J. and Davis, I. (2008).Biomechanical predictors of retrospective tibial stress fractures in runners. Journal of Biomechanics, 41, Queen, R., Gross, M. and Liu, H. (2006). Repeatability of lower extremity kinetics and kinematics for standardized and self-selected running speeds. Gait and Posture, 23, Richards, C., Magin, P., Callister, R. (2009). Is your prescription of distance running shoes evidence based? Journal of Sports Medicine, 43, Robertson, G, E., Caldwell, G, E., Hamill, J., Kamen, G. and Whittlesey, S, N. (2004). Research Methods in Biomechanics. Leeds, UK: Human Kinetics. Schache, A., Blanch, P., Rath, D., Wrigley, T. and Bennell, K. (2003). Differences between the sexes in the three-dimensional angular rotations of the lumbo pelvic hip complex during treadmill running. Journal of Sports Science, 21, Shakoor, N. and Block, J. A. (2006). Walking barefoot decreases loading on the lower extremity joints in knee osteoarthritis. Arthritis and Rheumatology, 54(9), Shultz, S, J., Nguyen, A. and Levine, B, J. (2009). The relationship between lower extremity alignment characteristics and anterior knee joint laxity. Sport Health, 1(1), Sinclair, J., Bottoms, L., Taylor, K., Greenhalgh, A. (2010). Tibial shock measured during the fencing lunge: the influenceof footwear. Sports Biomechanics, 9, Squadrone, R. and Gallozzi, C. (2009). Biomechanical and psychological comparison of barefoot and two shod conditions in experienced barefoot runners. Journal of Sports Medicine and Physical Fitness, 49(1), Stefanyshyn, D.J., Stergiou, P., Lun, V.M.Y., Meeuwisse, W.H., Worobets, J.T., (2006). Knee angular impulse as a predictor of patellofemoral pain in runners. The American Journal of Sports Medicine, 34 (11), Taunton, J, E., Ryan, M, B., Clement, D, B., McKenzie, D, C., Lloyd-Smith, D, R. and Zumbo, B, D. (2002). A retrospective case-control analysis of 2002 running injuries. Bristish Journal or Sports Medicine, 36(2),

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63 Appendices 47

64 APPENDIX A THE INFORMATION SHEET GIVEN TO PROSPECTIVE PARTICIPANTS TO OUTLINE WHAT IS INVOLVED IN THE STUDY AND WHAT THEY NEED TO DO. 48

65 Participant information sheet Project title: The different mechanical modifications made between male and female recreational distance runners over the two conditions of shod and barefoot running. Researcher: Becky O Brien Contact details: st @outlook.cardiffmet.ac.uk Supervisor: Marianne Gittoes magittoes@outlook.uwic.ac.uk/ Dear participant, Purpose of this information sheet This information sheet is to outline the study that is going to be conducted at Cardiff Metropolitan University. This will outline what the study entails and whether or not you wish to take part. The study is looking for willing, volunteers and if you wish to do so you can withdraw from the trial at any time. Background This study will attempt to research the different modifications made between males and females over two conditions of barefoot and shod running and evaluate which condition is more beneficial to reducing injury. Running shoes have been worn for decades; offering support, comfort and provide a method of injury reduction. However, recent researchers are questioning whether barefoot running decreases the risk of injury. Aims of the research Based on previous research suggesting that barefoot running decreases the risk of injury in comparison to shod this study aims to look at the modifications made between males and females over both conditions to assess whether males and females react differently to the two different conditions. The data collection will use CODA motion analysis and a force plate to study the forces produced and angles at the ankle, knee and hip joints. What will happen once you agree to participate in the study? You will be required to attend one test session in the National Indoor Athletic Centre (NIAC). You will be required to complete a physical activity readiness questionnaire(par-q), fill in details regarding your height and weight and sign a consent form. The test session will last between minutes with a short warm up followed by three successful trials in the shod and barefoot condition. Each trial will consist of running 25 meters onto the force plate, at a recreational pace. What type of participants are we hoping to use in the study? The research will be aimed at recreational runners (6 male and 6 female) who are free from injury and are above 18 years old. What are the risks of participating in the study? The risks associated with this study are minimal and the exercise testing will be less strenuous than a normal run or training session. Benefits to you, the participant You will be given your specific results over both barefoot and shod trials and hopefully this can be some use to your running in terms of reducing injury.. Benefits to us, the research team

66 The data collected from the research will be used to better the understanding of why injury is reduced in barefoot running and the difference between males and females. Additional benefits include the broadening of the knowledge in this area and facilitating future researchers in this area of biomechanics. What will happen to the data and information collected during the study? The data collected will be sorted by numbered and therefore individual identification will not be possible. You will receive a copy of your results at the end of the testing period. The data used for the research will be secure and only the researcher will have access to this. What next? If you have any further questions regarding this study please contact me via the details given. If you wish to consent to this study, fill out the attached consent form and you will be contacted regarding the date and time of the test session. If you take part in this study come to the testing wearing trainers that have less than 30 miles use and tight running clothing. Many thanks, Rebecca O Brien

67 APPENDIX B A PARTICIPANT CONSENT FORM GIVEN TO THE PARTICIPANTS TAKING PART IN THE STUDY.

68 Signed consent form Title of Project: Biomechanical modifications made between male and females over the two conditions of barefoot and shod distance running. Name of Researcher: Becky O'Brien Participant to complete this section: Please initial each box. 1.I confirm that I have read and understood the information sheet provided for this study and have had the opportunity to ask and have any questions wandered relevant to this study. 2.I understand that the participation is voluntary and that it is possible to stop taking part at any time. 3. I understand that the information for the study will be used for reporting purposes but I the participant will not be specifically identified. 4. I agree to take part in this research. Name of Participant. Date. Signature of Participant. Name of researcher Date. Signature of researcher C

69 APPENDIX C A PHYSICAL ACTIVITY READINESS QUESTIONNAIRE (PAR-Q) GIVEN TO THE PARTICIPANTS TO FILL OUT BEFORE COMPLETING IN THE STUDY.

70

71 APPENDIX D INFORMATION REGARDING THE PILOT THAT WAS COMPLETED BEFORE THE ACTUAL TESTING.

72 Pilot study The Purpose of the pilot study was to test if the methods suggested worked as outlined in the data collection section. The aim of the pilot study was to finalise and alter any data collection parameters that needed altered; the run up distance was a concern and thus one key area that needed to be verified. One participant took part in the pilot study who fell into the bracket of those participants being tested in the research (female or male recreational runner free from injury). The pilot test was conducted at the same time of day in which the real testing was taking place using the same researcher and same equipment. This was all kept the same for the actual testing. The run up of the testing was the element that was altered due to the pilot test, changing from 20 M to 25 M to allow the participants enough space to get into their normal running form. The other vital information gained through the pilot test was the success of each trial; there was a 40% success rate in the pilot study. This allowed the researching team to gather a rough approximation of the time that would be required for each participant.

73 APPENDIX E INFORMATION COLLECTED FROM PARTICIPANT S PRE TESTING REGARDING THEIR PHYSICAL CHARACTERISTICS AND FOOTWEAR.

74 Participant Number F/M Age (years) Height (cm) Weight (kg) Shoe size Type of shoe worn 1 F ASICS BALANCE 2 F New balance 3 F Asics Galaxy 6 4 F Saucony wave 8 5 F Asics Galaxy 6 6 F New balance 7 M Asics Gel cumulus 8 M New balance 9 M Asics gel phoenix 10 M Asics GT M New balance 12 M Asics Galaxy 6 Average weekly running distance (miles) Free from injury (Months) 8 miles 6 months + 7miles 12 months 11 miles 6 months 12 miles 6 months 10 miles 6 months 10 miles 6 months 12 miles 6 months 11 miles 12 months 8 miles 12 months 8 miles 12 months 10 miles 12 months 10 miles 12 months

75 APPENDIX F AN EXAMPLE OF ONE TRAILS IN WHICH A RESIDUAL ANALYSIS WAS CARRIED OUT.

76

77 APPENDIX G AN EXAMPLE OF THE GRAPHS USED TO EXTRAPOLATE THE INFORMATION REQUIRED FROM THE CODA MOTION SOFTWARE USED FOR ONE TRIAL.

78

79 APPENDIX H THE FOOT STRIKE TYPES OF EACH PARTICIPANT RECORDED.

80

81 APPENDIX I THE RAW MALE DATA COLLECTED FROM EACH TRIAL IN THE BAREFOOT CONDITION, WITH TABS SHOWN FOR SHOD CONDITION.

82

83 APPENDIX J THE RAW FEMALE DATA COLLECTED FOR EACH TRIAL IN THE BAREFOOT TRIAL WITH TABS SHOWN FOR SHOD TRIALS.

84