Sport performance and perceived musculoskeletal stress, pain and discomfort in kitesurfing

Transcription

1 International Journal of Performance Analysis in Sport 2011, 11, Sport performance and perceived musculoskeletal stress, pain and discomfort in kitesurfing L. Lundgren 1, S. Brorsson 1, M. Hilliges 1 and A-L. Osvalder 1,2 1 Centre for Research on Welfare, Sport & Health and Biological & Environmental Systems, Halmstad University, SE Halmstad, Sweden 2 Division of Design and Human Factors, Chalmers University of Technology, SE , Gothenburg, Sweden corresponding author: lina.lundgren@hh.se (L. Lundgren) Tel: +46 (0) , Fax: +46 (0) co-authors: sofia.brorsson@hh.se; mhi@du.se; alos@chalmers.se Abstract The purpose of this study was to obtain an overview of the specific movement patterns in kitesurfing, and the participants perceptions of musculoskeletal stress, pain and discomfort. Task analysis and survey studies were used to provide an overview of the sport, and to identify problematic issues associated with the performance of the tasks. Three different methods were complimentary used for data collection: observations (n=8), a web questionnaire (n=206) and interviews (n=17). Participants were contacted through kitesurfing events and online forums. Their ages ranged from years. The results showed that participants experienced high musculoskeletal stress for short times during a session (jumps, tricks and strong winds), and lower, static musculoskeletal stress over a longer time (crossing). High stress was most frequently perceived in abdominal muscles. Knees and feet were the sites most frequently experienced as painful, followed by the shoulders and elbows. This study provides additional information on the performance of kitesurfing and perceived musculoskeletal stress, pain and discomfort. The results can be used as input data to develop training methods and equipment for safe and comfortable performance. Keywords: Sport performance, movement pattern, survey 1. Introduction Sport activities exert stress on the musculoskeletal system, which can be beneficial in maintaining good physical health and performance. Musculoskeletal stress and injuries due to excessive loading have been studied for many sports and workplace situations, to improve safety and performance (Patel and Baker 2006, Hincapié et al. 2008, Hogan and Gross 2003). In some board sports such as windsurfing, wakeboarding and snowboarding, 142

2 sport-specific patterns of movement and physical capability have been studied to understand the loads exerted on the body that can affect performance and the risk of injury (Delorme et al. 2005, Carson 2004, Takahashi et al. 2004, Krüger and Edelmann-Nusser 2009). An important aspect of these sports is that the disciplines demand acrobatic moves such as jumps and tricks, that cause high loads on the musculoskeletal system (Delorme et al. 2005, Kirkpatrick et al. 1998, Carson 2004, Funk et al. 2003). Furthermore, studies of windsurfing have shown that upper body muscles and the gluteus maximus are important for sport-specific movements (Dyson et al. 1996). Buchanan et al. (1996) concluded that the biceps femoris appears to be important in maintaining body position and balance on a windsurfing board. However, for some of these board sports, there is limited knowledge about the effect of musculoskeletal stress during performance. In the case of newer board sports such as kitesurfing, the studies performed so far have mainly reported on injuries and accidents. A prospective study showed that the most common sites of injury in kitesurfing are the foot and ankle complex, followed by the head, knees and thorax (Nickel et al. 2004). The same authors estimated the injury rate to be 7.0 injuries per 1000 hours during practising and twice that during competition. Accidents have often been the result of problems with the safety systems, such as inability to release oneself from the kite in a hazardous situation, or environmental factors, e.g. a sudden change in wind, obstacles or shallow water (Petersen et al. 2005, Spanjersberg and Schipper 2007, Ziegler et al. 2009). Another study has presented the physiological demands and characteristics of kitesurfing a study by (Vercruyssen et al. 2009). They came to the conclusion that crossing (transportation over the surface of the water) requires work of moderate intensity, i.e. 81% of the maximum oxygen consumption (VO 2max ), involving a mainly static body position, similar to that in Laser sailing and windsurfing. They also found that those with a higher value of VO 2max were able to reach the goal in crossing faster, hence suggested that increased physical training could enhance the performance of kitesurfers (Vercruyssen et al. 2009). However, the specific movement patterns and the participants perceptions of musculoskeletal stress have not been fully described in the scientific literature on kitesurfing. This information could be useful for further studies of movement and muscle activation, as well as for the development of training methods to increase performance and measures to decrease the risk of injury. This is especially important in kitesurfing as performance is related to extreme characteristics, which in turn are associated with high risks of musculoskeletal stress, pain and discomfort (Spanjersberg and Schipper 2007, Slanger and Rudestam 1997). The actual number of participants in kitesurfing is unclear, but is increasing. In 2006 there were about kite surfers worldwide, and it was estimated that this number would increase by 35-50% by 2008 (Bryja 2008). The overall purpose of this study was thus to obtain an overview of kitesurfing with respect to specific patterns of movement and the participants perceptions of musculoskeletal stress, pain and discomfort. The goals were: (i) to describe the movement patterns in kitesurfing and their elements, (ii) to identify which parts of the musculoskeletal system that are perceived as most stressed according to the participants, and (iii) to elucidate which elements of kitesurfing that cause perceived musculoskeletal discomfort or pain. 143

3 2. Methods A survey study based on task analysis was used to provide an overview of the sport, its patterns of movement and the problems associated with the performance of the sport. Task analysis was carried out in a hierarchical form, as is common prior to usability or ergonomic analyses (Stanton 2006), to develop questions and forms for the data collection. Data were collected through live and video-filmed observations, a web-based questionnaire and interviews (Sandelowski 2000, LaPorte et al. 1985) Participants The inclusion criteria for the participants in this study were the ability to perform crossing and controlled jumps, meaning that all participants were competent at an intermediate level of kitesurfing, at least. The study was approved by the Ethics Committee at Lund University in Sweden Observations Eight kitesurfers who were active on the days of data collection were studied by live observations and video recordings. A form developed from the task analysis describing each kitesurfing element was filled in by the analyst while watching the participants in an authentic environment (Hauw and Durand 2005). Inter- and intra-reliability tests were conducted on the video recordings using two independent observers. The observed elements of kitesurfing were classified into: (i) crossing (transportation over the water surface), (ii) jumping (using the lift from the kite, by steering it upwards, to leave the water) and (iii) pop tricks (tricks performed using the board and the tension in the lines to gain lift, keeping the kite at a constant angle). Each jump or trick was divided into the sequences take-off, air time and landing, and these were described qualitatively in greater detail regarding movements and body position (Stränger et al. 1996) Questionnaire The questionnaire was developed according to the guidelines of Couper (2000), and was distributed as an open web questionnaire in English. QuickSearch Dialog Manager was used to conduct the survey (Couper 2000, Couper et al. 2001). The questionnaire was available for three months (July to September 2008). It took about ten minutes to complete, and contained questions concerning; (i) general information (gender, age, profession, country of residence etc.), (ii) other physical activities, (iii) perceived musculoskeletal stress (reported as low, moderate or high stress in different parts of the body), (iv) perceived discomfort and pain (reported in terms of how often it was experienced: never, seldom, sometimes, often or always). The results concerning perceived discomfort and pain were grouped into two categories, (a) no pain or discomfort (never, seldom) and (b) pain or discomfort (sometimes, often or always). A total of 206 (189 male, 17 female) international kitesurfers answered the web questionnaire. Their mean age was 30.8 (16-62) years, and the mean period they had practised the sport was 4.1 (1-10) years. 144

4 2.4. Interviews The interviews were used to gather complimentary information from another sample of participants (Kaulio and Karlsson 1998, Sandelowski 2000). The interviews was constructed as open questions related to the purpose of the survey, thus related to the interviewees experiences of kitesurfing with regard to musculoskeletal stress and pain, their performance, and the injuries sustained (Kvale 1996). Interviews were conducted with 17 Swedish kitesurfers (16 males and 1 female), with a mean age of 30.1 (20-50) years. The interviews were carried out during the kitesurfing season (April to November 2009), individually by self-confrontation as proposed by other authors (Hauw et al. 2008, Kvale 1996, Poizat et al. 2010). We did not use any video recordings during the interviews. The interview questions covered the same issues as the questionnaire (regarding their practice of the sport, physical training, perceived musculoskeletal stress, pain and discomfort), in a semi-structured manner. The data were analysed by categorising quotations from the interviews into a series of systematically labelled answers (Hauw et al. 2008) Statistical analysis For statistical analysis of the questionnaire data, frequencies were analysed and presented as the number or percentage of respondents. To determine whether the level of performance was statistically related to any specific region of pain or musculoskeletal stress, Pearson s chi-square test, χ 2 (df), was used, and p < 0.05 was regarded as statistically significant. The statistical analyses were performed using SPSS version 17.0 (Statistical Packages for Social Sciences). 3. Results 3.1. Movement patterns of kitesurfing elements The elements identified while kitesurfing were crossing and different kinds of jumps. These elements are described in terms of the general characteristics of the phase, body position and subjective descriptions of the musculoskeletal stress in Tables 1-4. The crossing element (Figure 1) is performed as sideways transportation, sometimes slightly upwind and sometimes downwind. The body position is mainly static, with forward rotation of the upper body. The hip and knee joints compensate for small waves through flexion/extension movements. Before take-off for a jump or trick, the hip angle decreases, as do the angle between the subject and the surface of the water. Figure 1. The body position while crossing (left). Before take-off (right), the hip angle is decreased as is the angle between the water surface and the kitesurfer. 145

5 Tricks can be performed in different ways, such as jumps with the kite (Figure 2) and pop tricks (Figure 3). Figure 2. Photo illustrating the sequence of a jump. The participant steers the kite upwards during take-off and is pulled out of the water. Prior to landing, the kite is steered forward in the wind direction. (Photo: Ricard Rinaldo) Figure 3. Photo illustrating the sequence of a pop trick. The kitesurfer edges away from the water with the kite at a constant height, performs a 540 rotation in the air, and lands with the board pointing downwind. (Photo: Daniel Gustavsson) Jumping is achieved using the lift of the kite by steering it upwards at the same time as edging the board, causing the participant to lift from the water surface more vertically than horizontally, as described in more detailed in Table 2. A pop trick is performed by edging the board towards the water surface using the tension in the lines and keeping the kite at a constant height from the horizontal, causing the participant to lift from the water surface with a high forward speed. Pop tricks can be performed both unhooked and hooked into the harness, in the latter case, the force exerted by the kite is borne by the upper extremities instead of the harness around the lumbar region of torso. These elements are described in Tables 3 & 4. The movement pattern for the unhooked pop trick differs mainly during airtime, because it allows a wider range of spinning and air movements, such as the most commonly observed unhooked trick railey (extended body, flying after the kite). This movement is performed with a hyperextended trunk and hip, with knee joints slightly flexed and the shoulder joint at 180 flexion (Figure 4). 146

6 Figure 4. Body position during the unhooked trick railey. (Photo: Sofia Lennartsson) Sometimes, when performing unhooked tricks, the force of the kite is applied to the upper extremities in a position close to maximum flexion, or extension, combined with rotation of the shoulder joint. The ideal landing position is similar for all kinds of jumps and tricks, with knees and upper body aligned above the board pointing in the direction of the wind. Table 1. Description of crossing based on observations. Crossing Control using kite Control by edging board General description Crossing performed in Steering and control of Pointing board slightly both directions bilateral depowering with upper upwind or downwind and movement pattern. extremities (UE). compensating for Compensation for waves/choppy water. waves/choppy water. Body position Static position: leaning backwards towards water surface. Slight hip flexion, upper body (UB) forward rotated, rear knee flexed, rear shoulder protracted. Compensation for choppy water/waves by knee and hip joint flexion/extension. Steering with UE. Hands holding the bar with power grip, with the lower arm in pronation. Push and pull movements of the bar to steer and control depowering flexion and extension of shoulder and elbow. Using different degrees of edging the board to change body position. More edge, increased leaning back towards the water surface, and increased hip flexion. The same pattern was also observed when braking or travelling upwind. Subjective description (observers perceptions) musculoskeletal stress of Constant muscle use to maintain body position and absorb thrusts from waves/choppy water. Weight bearing in harness. UE use the bar for steering and sheeting (to change the shape of the kite). Low forces are required, but performed during the total time of riding. Velocity controlled by edging the board. Muscular stress appeared to depend on wind speed. 147

7 Table 2. Descriptions of jumps performed by steering the kite upwards, based on observations Take-off Air time Landing General description Build-up of speed prior to being pulled out of water by steering the kite upwards and edging the board. Hanging in the harness. In some cases spinning or grabbing the board. Horizontal velocity transformed into almost vertical velocity by steering the kite into the wind direction. Absorbing the force of landing. Body position Increased hip flexion before take-off, lowering centre of mass. Subjective description (observers perceptions) of musculoskeletal stress Force from the kite applied to harness around waist. At least the participants own body weight must be supported when leaving the water. Different body positions possible during air-time, e.g. extended body or certain parts flexed to spin or grab the board. Action by arms to steer the kite while jumping. Push and pull movements. Before landing, the board is positioned horizontally in the downwind direction. Hip and knee joints were extended before landing and flexed while decelerating body in vertical direction. Absorption of the force of the vertical velocity. With lower vertical velocity (greater horizontal velocity), less deceleration was needed, hence lower compressive force. 148

8 Table 3. Description of hooked-in pop tricks based on observations Take-off Air-time Landing General description Build-up of speed and edging the board prior to being pulled out of the water by the recoil of the kite. Body position Increased hip flexion before take-off, lowering centre of mass. Subjective description (observers perceptions) musculoskeletal stress of Force from the kite applied to harness around the waist. The force at take-off was sufficient to pull the kitesurfer out of the water at, at least the same forward velocity as the movement of the kite. Pulled in the harness. Direction (height of the trick) dependent on the take-off (e.g. velocity, edge of board, technique, power) and angle of the kite. Tricks performed hooked-in were mainly spins. Spinning or rotational movements initiated by UE or lower extremities (LE). High-velocity air movement exposed the trunk to loads during the acceleration phase. Absorption of the force of vertical deceleration. Before landing, the board was aligned horizontally in the downwind direction and the body was recomposed above the board. Hip and knee joints were almost extended to allow for flexion while decelerating body in vertical direction. When vertical velocity was high, greater deceleration was required, hence stress on LE. Low risk of injury when landing with LE joints in well-aligned position above the board. 149

9 Table 4. Description of unhooked pop tricks based on observations Take-off Air time Landing General description Build-up of speed, unhooking the bar and edging the board prior to be pulled out of the water by the recoil from the kite. Body position Increased hip flexion before take-off, lowering centre of mass. Subjective description (observers perception) of musculoskeletal stress Force from the kite applied to UE. The tension force was high enough to pull the kitesurfer out of the water at, at least, the same forward velocity as the movement of the kite. The bar held by UE. Direction (height of the trick) dependent on take-off (e.g. velocity, edge of board, technique, power) and angle of the kite. Most common trick observed was railey (extended body, flying after the kite). Other tricks were spins and handle passes (passing the bar behind the body). The railey required hyperextended trunk and hips, with knee joints flexed and shoulder joints at 180 flexion. Handle passes required the shoulder joints to be hyperextended and medially rotated. High-velocity air movement exposed UE to high loads during the acceleration phase. Absorption of the force from vertical deceleration. Moving along the wind direction to hook into the harness again. Before landing, the board was aligned horizontally in the downwind direction and the body was recomposed above the board. Hip and knee joints were almost extended to allow for flexion while decelerating body in vertical direction. When vertical velocity was high, greater deceleration was required, hence stress on LE. Low risk of injury when landing with LE joints in well-aligned position Perceived musculoskeletal stress Questionnaire: The arm muscles were the part of the body most frequently perceived as being moderately or highly stressed while kitesurfing (reported by 85% of the respondents), followed by the abdomen (77%) and lower back (74%) (Table 5). When considering only perceptions of high musculoskeletal stress the abdominal muscles were reported by 34% of the respondents, lower back by 32%, thighs by 28% and arms by 24%. The element of kitesurfing most frequently associated with high musculoskeletal stress was performing jumps and tricks, (reported by 61% of the respondents), followed by crossing in high winds. 150

10 Table 5. Perceived level of musculoskeletal stress rated as low, moderate or high, in various parts of the body Body segment Low (n) Percentage (%) Moderate (n) Percentage (%) High (n) Percentage (%) Upper back Shoulder Arms Abdomen Lower back Thighs (front) Thighs (back) Calves Feet Total number of respondents (n) was 206. Interviews: Most interviewees (14 out of 17) reported high activation of the abdominal muscles during kitesurfing. The feeling of tiredness in the abdominal region was most noticeable during or after many jumps. It was also reported that muscle soreness could occur in the abdominal region after a session, especially if it was the first session after a long break, or contained many jumps. The lower back was not frequently brought up as an area perceived to be exposed to high musculoskeletal stress among the interviewees, and very few associated kitesurfing with back problems or back pain. Some of the interviewees (n=3) had slight back problems, but these were mainly due to other sporting activities that they had participated in before kitesurfing. However, two of these experienced worsening of their back problems after kitesurfing, and one interviewee said; I d like to think that I m getting stronger thanks to exercise of the abdominal muscles. The lower extremities, or more precisely the thighs, were perceived as being stressed while kitesurfing, and as a site at which tiredness could be felt when kitesurfing for a long time or in strong winds Perceived pain and discomfort Questionnaire: Pain and discomfort were experienced in the knees (38%), lower back (38%), shoulders (29%), feet/ankles (26%), and elbows (23%). The results are summarized in Table 6. Pain in the shoulders was related to the variable of being able to perform unhooked tricks (χ 2 (1) = 8.4, p < 0.01). No statistically significant relations were found between other region and any performance variable. Of the respondents, 12 specifically described elbow pain as tennis elbow, or lateral epicondylitis. Upper and lower extremities (including both muscles and joints) were the body regions most frequently associated with other forms of pain and discomfort, e.g. muscle soreness, minor sprains, muscle strain, bruises, rashes or cramp. The causes of discomfort were reported to be crashes, pressure from the harness, a hard pull from the kite, long sessions or colliding with equipment. 151

11 Table 6. Experienced pain related to the body region. Body Region Pain (n=206) Percentage (%) Upper back Lower back Shoulders Elbows Wrists/Hands Hips Knees Feet/Ankles Interviews: Some of the interviewees (5 of 17) stated that they sometimes or more often felt pain in their knees or feet while kitesurfing. Most of them associated this with landing tricks or while crossing for a long time in strong winds. Just before landing a jump at high speed, the description; Well, you tense all the muscles in your whole body just to compensate for the smash that s coming... was given by one of the interviewees. Participants who were able to perform unhooked tricks often stated that arms and shoulders were areas where high loads were experienced, and a small number (n=3) also described their pain as tennis elbow. The shoulders were reported as being susceptible to injury, especially in unhooked jumps. The explanation given was that this situation requires the kitesurfer to bear all the tension from the kite with their arms, while trying to make spins, or landing on the blind side (backwards). As one interviewee expressed it;...it s like you catch yourself for a second. 4. Discussion This study describes the performance of kitesurfing and the participants own experiences of musculoskeletal stress during kitesurfing. The results can be used to relate some of the problems and stress experienced to a specific element of kitesurfing or to a certain movement pattern in the sport Analysis of the results The abdominal muscles were most frequently perceived as being highly stressed in the questionnaires and interviews. While crossing, the body position was observed to be leaning back with upper body rotation and protracted shoulders. The force from the kite is transferred to the trunk or lumbar back, which forces the abdominal muscles to counteract increased lumbar lordosis. This could be one reason why many respondents claimed to experience pain in lower back, and high stress and frequent muscle soreness in the abdominal region. Another reason given for tiredness in the abdominal muscles was jumping, when the kite pulls the rider out of the water within a fraction of a second. When jumping hooked-in, the force is transmitted through the harness, which results in most of the tension from the kite being applied to the lumbar region of the back. As for crossing, the abdominal muscles play an important role in preventing this force from increasing lumbar lordosis or shear in the spinal column. The abdominal muscles are reasonably also used to recompose the body before landing unhooked pop tricks, as for example the trick 152

12 railey with a hyperextended position described in Table 4. The cause of muscle soreness reported to arise from this element is probably due to the eccentric movement required to counterbalance the fully or hyperextended position of the hip and lumbar region. Landing from pop tricks generally seemed to be performed with more speed compared to the jumps, leading to greater shock absorption upon contact with the water. Many respondents and interviewees reported experiencing musculoskeletal stress or pain in the lower extremities, especially when kitesurfing for a long time or in strong winds. Choppy water or waves create an intermittent load that has to be compensated for by movement of the lower extremities. Moreover, the force upon landing jumps and tricks is absorbed by the lower extremities. Some interviewees identified their shoulders as highly stressed parts of the body, and in most cases referred to the movements involved in performing unhooked tricks especially with rotation or handle passes (passing the bar behind the back). During these tricks the force of the kite is borne by the arms only, and in some cases by one arm in an extreme position (outside the range of motion of daily activities). Although kitesurfers have the choice of releasing the bar in these situations, they do not always do so. Pain and musculoskeletal stress in the arms, which some respondents and interviewees specifically described as pain in the elbow, can be partly explained by the constant push and pull movement of the arm in the pronate position required for steering, powering and depowering the kite. The force, sometimes called bar pressure, arising from this movement cannot be very high since the force from the kite is usually transmitted through the harness. However, the time spent on the water during a session can be up to several hours. When unhooking from the harness to perform a trick, all the force is borne by the arms for a short period, which could explain why most of the respondents who performed unhooked tricks experienced pain in their elbows Implications of the results Some elements of kitesurfing can be assumed to place considerable mechanical stress on the musculoskeletal system. Such continuous stress, which creates pain or discomfort, can also affect the performance of the participant. The interviewees indicated that good condition and different levels of strength in various muscles in the trunk, thighs and arms, are required to perform different elements of the sport, and that specific physical training could enhance their capacity. A movement identified while kitesurfing was the railey trick, involving hyperextension of the lumbar spine. This stretches the abdominal muscles and implies a close-packed position of the facet joints, which should only be adopted in a controlled manner (Standaert et al. 2003). It is possible that the abdominal muscles must have a minimum functional strength to withstand the physical requirements of the sport and to avoid placing too high loads on the spinal ligaments and other tissues. Also high-speed motion, as was seen in some tricks, is more likely to lead to unfavourable positions of the extremities and joints (Hagins et al. 2007). Since unsuccessful landings were considered one of the main reasons for discomfort or risk of injury, it is important for the kitesurfer to have sufficient technique, awareness of the task and the physical strength to perform safe landings. 153

13 Both shoulder problems and pain in the elbow, also known as lateral epicondylitis or tennis elbow, have been reported by respondents in other sports such as wakeboarding, golf and tennis (Cabri et al. 2009, Marx et al. 2001). This could be due to the action of grasping a handle, which is required, and may indicate that the upper extremities have an important function for the performance of all of these sports. The findings of this study can be used as the basis for further observations and measurements of the musculoskeletal load that occur while kitesurfing. They can also serve as input for further studies on comfort and safety issues regarding the development of new equipment and training methods aimed at improving participants ability to handle the biomechanical loads involved in the sport Methodological considerations Surveys consisting of multiple methods, including questionnaires, interviews and observations, are commonly used in qualitative scientific studies, and are recommended to reduce the errors in the study (Kaulio and Karlsson 1998, Coromina and Coenders 2006, Rudd and Johnson 2010, Sandelowski 2000). The information acquired by the two observers in this study was mainly used for the description of movement patterns, whereas the other two survey methods provided information on the perceptions of participants of the sport. The questionnaire study was performed first to identify issues related to kitesurfing, which were then addressed in more detail in the interviews. This study confirms that the information gathered from the participants regarding the sport is useful, as reported by other authors (Holm et al. 2003, Joksimovic et al. 2002, Yeung et al. 2002). The reliability of the observations was investigated by comparing the independent descriptions of the video recordings by two analysts using the same protocol. Both these analysts were familiar with the sport, and agreed in their descriptions of the movements. As always when respondents are asked questions, the interpretation of terminology can differ. Problems associated with the interpretation of the subjective measures used in this study were avoided by giving examples or descriptions of the measures. Discomfort was exemplified as: muscle soreness, minor sprains, muscle strain, bruises, rashes or cramp, and was graded in terms of how often they occurred. Pain was described as a feeling of discomfort that you do not usually have, resulting from, or restraining your practicing of kitesurfing, and was reported in relation to the joints affected and how often it occurred. Musculoskeletal stress was described as the requirement of physical effort in various parts of the body, and was graded in terms of low, moderate or high. The questions were expanded in the interview to gain information on how, when and why. A web-based questionnaire was chosen instead of a printed form mainly because it offers the possibility of gathering data worldwide at a reasonable cost, despite the uncertainty of non-response bias. The questionnaire was designed to be easy and fast to answer, which is an important factor when gathering a comprehensive amount of reliable data (Couper 2000, Couper et al. 2001). According to many studies of the methodology employing web-based questionnaires, lack of internet availability is one of the major biases for open web surveys (Couper 2000, Fleming and Bowden 2009, Marta-Pedroso et al. 2007, Berrens et al. 2003, Jones et al. 2008). However, this target group (kitesurfers) was expected to consist of 154

14 experienced and frequent users of the internet, since the nature of the sport requires both a certain financial status (necessary to purchase equipment) and the ability to check coming events and weather forecasts, etc. online. In all study groups, kitesurfing competence ranged from intermediate to competitive. It is therefore likely that the participants have different experiences of musculoskeletal stress and muscle soreness from kitesurfing since the movement patterns, and hence, the physical requirements differ depending on the level of performance. However, all the subjects were required to be able to perform crossing and jumping. We believe that the mismatch in terms of gender is representative of kitesurfing participants, as the same pattern, with very few females, has been found in other studies, e.g. that by Nickel et al. (2004), which included only ten females out of a total of 235 participants. 5. Conclusions The following conclusions can be drawn from this study. The movement patterns of kitesurfing are specific to each element of the sport (crossing and acrobatic moves) and are influenced by the body position and dynamic environment. A kitesurfer experiences high, dynamic musculoskeletal stress for short times during a session (resulting from jumps, tricks and strong winds), and lower, static musculoskeletal stress over a longer time (due to crossing). The performance of jumps and tricks was associated with musculoskeletal stress in the abdominal muscles (take-off), upper extremities (unhooked spinning) and lower extremities (landing). Lower musculoskeletal stress was experienced during crossing, but the abdominal muscles, thigh muscles and lower back were generally perceived as being highly stressed, especially in strong winds. Knees and feet were frequently reported as the site of pain and discomfort when landing jumps at high speed. The pronate arm position and the grip used while steering, depowering and holding the kite while crossing for a long time, and performing unhooked tricks caused pain and discomfort in the shoulders and elbows. This study provides new information about the movement patterns and perceived musculoskeletal stress, pain and discomfort related to kitesurfing, which can be used to develop training methods and equipment for safe and comfortable performance in aquatic board sports. 6. References Berrens, R. P., Bohara, A. K., Jenkins-Smith, H., Silva, C. and Weimer, D. L. (2003) 'The advent of Internet surveys for political research: A comparison of telephone and Internet samples', Political Analysis, 11(1),

15 Bryja, J. (2008) 'Kiteboarding statistics: Worldwide participation and sales statistics', SBC Kiteboard [online], available: [accessed April, 2009]. Buchanan, M., Cunningham, P., Dyson, R. J., Hurrion, P.D. (1996) 'Electromyographic activity of beating and reaching during simulated boardsailing', Journal of Sport Science, 14(2), Cabri, J., Sousa, J. O. P., Kots, M. and Barreiros, J. O. (2009) 'Golf-related injuries: A systematic review', European Journal of Sport Science, 9(6), Carson, W. G. (2004) 'Wakeboarding Injuries', The American Journal of Sports Medicine, 32(1), Coromina, L. and Coenders, G. (2006) 'Reliability and validity of egocentered network data collected via web - A meta-analysis of multilevel multitrait, multimethod studies', Social Networks, 28(3), Couper, M. P. (2000) 'Web surveys - A review of issues and approaches', Public Opinion Quarterly, 64(4), Couper, M. P., Traugott, M. W. and Lamias, M. J. (2001) 'Web survey design and administration', Public Opinion Quarterly, 65(2), Delorme, S., Tavoularis, S. and Lamontagne, M. (2005) 'Kinematics of the ankle joint complex in snowboarding', Journal of Applied Biomechanics, 21(4), Dyson, R. J., Buchanan, M., Farrington, T. A., Hurrion, P. D. (1996) 'Electromyographic activity during windsurfing', Journal of Sport Sciences, 14(2), Fleming, C. M. and Bowden, M. (2009) 'Web-based surveys as an alternative to traditional mail methods', Journal of Environmental Management, 90(1), Funk, J. R., Srinivasan, S. C. and Crandall, J. R. (2003) 'Snowboarder's talus fractures experimentally produced by eversion and dorsiflexion', American Journal of Sports Medicine, 31(6), Hagins, M., Pappas, E., Kremenic, I., Orishimo, K. F. and Rundle, A. (2007) 'The effect of an inclined landing surface on biomechanical variables during a jumping task', Clinical Biomechanics (Bristol, Avon), 22(9), Hauw, D. and Durand, M. (2005) 'How do elite athletes interact with the environment in competition? A situated analysis of trampolinists' activity', Revue Européenne de Psychologie Appliquée/European Review of Applied Psychology, 55(3), Hauw, D., Renault, G. and Durand, M. (2008) 'How do aerial freestyler skiers land on their feet? A situated analysis of athletes' activity related to new forms of acrobatic performance', Journal of Science and Medicine in Sport, 11(5), Hincapié, C. A., Morton, E. J. and Cassidy, J. D. (2008) 'Musculoskeletal Injuries and Pain in Dancers: A Systematic Review', Archives of Physical Medicine and Rehabilitation, 89(9), e6. Hogan, K. A. and Gross, R. H. (2003) 'Overuse injuries in pediatric athletes', Orthopedic Clinics of North America, 34(3), Holm, I., Friis, A., Storheim, K. and Brox, J. I. (2003) 'Measuring Self-Reported Functional Status and Pain in Patients with Chronic Low Back Pain by Postal Questionnaires: A Reliability Study', Spine, 28(8), Joksimovic, L., Starke, D., v.d. Knesebeck, O. and Siegrist, J. (2002) 'Perceived work stress, overcommitment, and self-reported musculoskeletal pain: Across-sectional investigation', International Journal of Behavioural Medicine, 9(2),

16 Jones, S., Murphy, F., Edwards, M. and James, J. (2008) 'Doing things differently: advantages and disadvantages of Web questionnaires', Nurse Research, 15(4), Kaulio, M. A. and Karlsson, M. (1998) 'Triangulation strategies in user requirements investigations: A case study on the development of an IT-mediated service', Behaviour & Information Technology, 17(2), Kirkpatrick, D. P., Hunter, R. E., Janes, P. C., Mastrangelo, J. and Nicholas, R. A. (1998) 'The snowboarder's foot and ankle', American Journal of Sports Medicine, 26(2), Krüger, A. and Edelmann-Nusser, J. (2009) 'Biomechanical analysis in freestyle snowboarding: application of a full-body inertial measurement system and a bilateral insole measurement system', Sports Technology, 2(1-2), Kvale, S. (1996) InterViews: An Introduction to Qualitative Research Interviewing, Sage Publications. LaPorte, R. E., Montoye, H. J. and Caspersen, C. J. (1985) 'Assessment of physical activity in epidemiologic research: problems and prospects', Public health reports, 100(2), Marta-Pedroso, C., Freitas, H. and Domingos, T. (2007) 'Testing for the survey mode effect on contingent valuation data quality: A case study of web based versus in-person interviews', Ecological Economics, 62(3-4), Marx, R. G., Sperling, J. W. and Cordasco, F. A. (2001) 'Overuse injuries of the upper extremity in tennis players', Clinics in Sports Medicine, 20(3), Nickel, C., Zernial, O., Musahl, V., Hansen, U., Zantop, T. and Petersen, W. (2004) 'A Prospective Study of Kitesurfing Injuries', The American Journal of Sports Medicine, 32(4), Patel, D. R. and Baker, R. J. (2006) 'Musculoskeletal Injuries in Sports', Primary Care: Clinics in Office Practice, 33(2), Petersen, W., Nickel, C., Zantop, T., Zernial, O. (2005) 'Verletzungen beim Kitesurfen', Der Orthopäde, 34(5), Poizat, G., Adé, D., Seifert, L., Toussaint, H. and Gal-Petitfaux, N. (2010) 'Evaluation of the Measuring Active Drag system usability: An important step for its integration into training sessions', International Journal of Performance Analysis in Sport, 10, Rudd, A. and Johnson, R. B. (2010) 'A call for more mixed methods in sport management research', Sport Management Review, 13(1), Sandelowski, M. (2000) 'Combining qualitative and quantitative sampling, data collection, and analysis techniques in mixed-method studies', Research in nursing & health, 23(3), Slanger, E. and Rudestam, K. E. (1997) 'Motivation and disinhibition in high risk sports: Sensation seeking and self-efficacy', Journal of Research in Personality, 31(3), Spanjersberg, W. R. and Schipper, I. B. (2007) 'Kitesurfing: when fun turns to trauma-the dangers of a new extreme sport', Journal of Trauma, 63(3), E Standaert, C. J., Herring, S. A., Cole, A. J. and Stratton, S. A. (2003) 'The Lumbar Spine and Sports' in Low Back Pain Handbook, Second Edition, (Edited by Cole, A.J., Herring, S.A.), Philadelphia: Hanley & Belfus,

17 Stanton, N. A. (2006) 'Hierarchical task analysis: developments, applications, and extensions', Applied ergonomics, 37(1), Stränger, J., Hommel, B., Wolfgang, P. and Bruce, B. (1996) 'Chapter 11 The perception of action and movement' in Handbook of Perception and Action, Vol. 1, Edited by Prinz W., Bridgeman B., Academic Press, Takahashi, T., Kawazoe, T., Yamamoto, H. and Kondo, K. (2004) 'Mechanism of combined injuries of the posterior cruciate ligament and the posterolateral ligament while wake boarding', Archives of Orthopaedic Trauma Surgery, 124(9), Vercruyssen, F., Blin, N., L'Huillier, D. and Brisswalter, J. (2009) 'Assessment of physiological demand in kitesurfing', European Journal of Applied Physiology, 105(1), Yeung, S. S., Genaidy, A., Deddens, J., Alhemood, A. and Leung, P. C. (2002) 'Prevalence of Musculoskeletal Symptoms in Single and Multiple Body Regions and Effects of Perceived Risk of Injury Among Manual Handling Workers', Spine, 27(19), Ziegler, M., Lockemann, U. and Püschel, K. (2009) 'Tödlicher Unfall beim Kitesurfingunterricht', Rechtsmedizin, 19(3), Corresponding author: Lina Lundgren Centre for Research on Welfare, Sport & Health and Biological & Environmental Systems, Halmstad University, SE Halmstad, Sweden. (L. Lundgren) Tel: +46 (0) , Fax: +46 (0)