VO L U M E N o. 6 - D E C E M B E R

Transcription

1 PUBBLICAZIONE PERIODICA BIIMESTRALE - POSTE ITALIANE S.P.A. - SPED. IN A. P. D.L. 353/2003 (CONV. IN L. 27/02/2004 N 46) ART. 1, COMMA 1, DCB/CN - ISSN TAXE PERÇUE VO L U M E N o. 6 - D E C E M B E R

2 J SPORTS MED PHYS FITNESS 2014;54:691-9 Traditional and ankle-specific vertical jumps as strength-power indicators for maximal sprint acceleration R. NAGAHARA 1, H. NAITO 1, K. MIYASHIRO 1, J.-B. MORIN 2, K. ZUSHI 1 Aim. This study aimed to determine the demand of strengthpower capabilities represented by traditional and ankle-specific vertical jump modalities squat jump (SJ), counter-movement jump (CMJ), rebound-continuous jump (RJ), rebound-continuous ankle jump (AJ) relative to sprint acceleration ability during the entire acceleration phase of maximal sprint. Methods. Nineteen male sprinters performed a 60-m maximal sprint and various vertical jumps. Correlation coefficients among the vertical jump performances and between those and the 60-m sprint time and sprint acceleration at each step were calculated. Results. There were significant relationships between the 60-m sprint time and SJ height, CMJ height, AJ height, and AJ index. AJ height and index had no correlation with any other jump variables. Acceleration was significantly correlated with SJ height from the 6th to the 10th steps (r= ) and with CMJ height from the 5th to the 11th steps (r= ). Acceleration was also correlated with the AJ index from the 14th to the 19th steps (r= ). Acceleration had no correlation with the RJ index at any step. Conclusion. The results suggest that the AJ allows assessment of different reactive strengths compared with traditional jump modalities. To accelerate effectively, the explosive strengths of the SJ and CMJ are important during the early stage of acceleration (from 6.6±0.4 to 17.5±0.8 m), and the reactive strength represented by the AJ is necessary during the later stage of acceleration (from 23.4±1.0 to 33.7±1.4 m). Sprinters and coaches should be aware of the different demands of strength-power capability for effective acceleration. Key words: Running - Muscle strength - Visual field test. Sprint running performance is one of the most important abilities for athletes in many sports. Maximal speed during a 100-m race highly corre- Corresponding author: R. Nagahara, MSc, Faculty of Health and Sport Sciences, University of Tsukuba, Tennoudai, Tsukuba, Ibaraki , Japan. nagahara.r@gmail.com 1Faculty of Health and Sport Sciences University of Tsukuba, Tsukuba, Japan 2Laboratory of Exercise Physiology University of Lyon, Saint Etienne, France lates with race time, 1 and the time to accelerate with maximal effort is limited to 5 to 7 s. 2 Accordingly, acceleration ability is the critical factor for 100-m race performance. 3 There is a concept whereby the entire acceleration phase is divided into sections, 1, 4, 5 and this concept is of practical importance for better performance in the 100-m race. 6 The characteristics of sprinting during the different stages of acceleration can be shown as follows. For successful acceleration, sprinters should not shorten the support time and should exert a large amount of horizontal forward impulse while extending the three major joints of the lower extremity during the early stage of acceleration. 7, 8 During the later stage of acceleration and at maximal speed, sprinters should shorten the support time while exerting a large vertical force, and stiff leg behaviour is needed to achieve higher running speed These characteristics indicate that different strength-power capabilities are required to accelerate effectively during the different stages of the entire acceleration. Running speed can be expressed as a product of step-length and step-frequency. Although some studies which were conducted with relatively homogeneous participants groups showed contradictory results (the relative importance of high step-frequency and no systematic relative importance of step-length or step-frequency), 12, 13 a large number of studies Vol No. 6 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 691

3 NAGAHARA Traditional and ankle-specific vertical jumps as strength-power indicators which were conducted with a large extent of the participants performance level presented the relative importance of long step-length for better sprinting performance. 1, 5, 14, 15 Although many factors, such as neuromuscular function and morphological features, affect maximal effort sprinting performance, the force and power production capability of the lower extremities is one of the critical factors for better sprint performance through developing the long step-length. 16 There are various tests for assessing strength-power capability. Laboratory tests using an isokinetic dynamometer can strictly evaluate the strength-power capability at the respective joints. However, this test is not easily employed for everyday training, and the device does not reflect actual sprinting movement because sprinting is a quick multi-joint movement. In contrast, a field test using several jump modalities is advantageous because it is easy to perform. Additionally, the movement of the jumps resembles that of sprinting in some respects: That is, these jump tests are performed with multi-joint participation, are of relatively high movement velocity using the athlete s own body weight, and produce a large amount of force. Jump tests, including the squat jump (SJ), counter-movement jump (CMJ), drop jump (DJ), and rebound-continuous jump (RJ), have been commonly employed to indirectly assess the muscular determinants of sprint ability. 9, These jump modalities are able to assess different strength-power capabilities. The SJ is conducted from a semi-squatting position with no preceding flexion of the joints and no eccentric loading, and is thus considered a pure concentric jump. 21 The performance of the CMJ is enhanced by preceding eccentric loading with flexion of the lower limb joints from an initial upright standing position. 21, 22 The DJ and RJ are able to impose greater amounts of preceding eccentric loading and, accordingly, have the potential to further increase power production by the lower extremity muscles. 23 According to the difference in neuromuscular recruitment among these jump modalities, these vertical jumps have been used to assess the different phases of the sprint. 9, 16-18, 20 For instance, the SJ and CMJ height may be able to predict the earlier stage of sprint performance, 9, 18 and by contrast, the DJ height and stiffness during the RJ are possibly better predictors during the later stage of acceleration. 9, 17 The aforementioned jump modalities are conducted with the extensor and plantar flexor muscles of the hip, knee, and ankle joints. Although the amount of work done by the ankle plantar flexors during these jumps is not small (35% to 43% of the sum of the work done by the muscles of the three joints), a large amount of power (25% of the work done by the ankle plantar flexors) is transferred from the knee joint to the ankle joint via the gastrocnemius muscles during jumping. 25, 26 Moreover, it has been shown that the CMJ height is significantly correlated with the maximal isometric force of the hip and knee extensors and without that of the ankle plantar flexor. 27 Consequently, the performance of these jump tests mainly depends on the power exerted by the hip and knee extensors, and might not precisely reflect the capacity to exert power at the ankle joint. 28 During the later stage of acceleration, when approaching maximal speed, the ankle plantar flexors play an important role in achieving high sprint performance by producing a large vertical force. 29, 30 The anklespecific jump, which can directly assess the ability of the ankle plantar flexors to exert force, has been used. 31, 32 Therefore, the ankle-specific jump would improve the assessment of acceleration ability in addition to traditional jump modalities. Because the running speed after the first step is affected by the changes in speeds of previous steps, running speed or time, which were previously used as performance indicators, 18, 20 in the remaining acceleration stage cannot directly assesses the sprint acceleration ability at that spot. Moreover, although sprint motion, force production, and body posture change gradually and step to step, 33 previous studies have used sprint time or mean speed of every 10-m section from the start or the same variables in rougher sections as indicators of sprint performance. 9, 18 These variables may not be sensitive enough to provide a detailed relationship between sprint performance and strength-power capabilities. Consequently, the relationship between the acceleration ability of each step and the performance of jump modalities should be investigated for a better understanding of the association between sprint performance and strength-power capabilities. Clarifying the relationship between sprint acceleration and strength-power capability would allow sprinters and coaches to assess acceleration ability at specific phases of acceleration during training 692 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS December 2014

4 Traditional and ankle-specific vertical jumps as strength-power indicators NAGAHARA After performing the sprint test and resting for 30 minutes for full recovery, participants performed vertical jump tests in the order of SJ, CMJ, RJ, and rebound-continuous ankle jump (AJ) with resting for 3 minutes between each jump modality (Figure 1). These jump tests were used as usual training in the above-mentioned order (non-randomized) by all participants, and each jump test was not an exhausting exercise. Thus, the influence of fatigue was negligible. All jumps were performed without armsessions, thereby improving the quality of training programs according to the specific need for strength training. This study aimed to determine the demand of strength-power capabilities represented by traditional and ankle-specific vertical jump modalities relative to the sprint acceleration ability during the entire acceleration phase of maximal sprint. Participants Materials and methods Nineteen male sprinters who had no physical injuries volunteered for this study (mean±sd: age, 20.1±1.2 y; stature, 1.75±0.04 m; body mass, 66.1±4.0 kg; personal best record of 100-m race, 11.19±0.34 s, ranging from to s). All participants specialized in sprint events. They were fully informed about the experimental procedures, purpose, and risks involved before they gave their written informed consent to participate in this study. The investigation was conducted with the approval of the ethics committee of the institute and in accordance with the ethical standards of the Helsinki Declaration. Sprint test The experiment was conducted in October, after the competition season. Participants performed a 60-m maximal sprint using a starting block after warming up. To eliminate the influence of fatigue for the following jump tests, the participants performed this sprint once. All participants wore their own spiked shoes. The time of the 60-m sprint was measured using a photocell system (Sprint System; Brower Timing Systems, Draper, UT, USA). Participants were videotaped throughout the 60-m sprint with six panning cameras (EX-F1, 300 fps; Casio, Tokyo, Japan). The cameras were placed every 10 m from the 5- to 55-m marks. All cameras were placed on the right side of the 45-m mark from the centre of the running lane. Reference markers were placed every metre on both sides of the running lane from 1 m behind the start line to the 60-m mark. Foot-strike during the sprint was determined three times at 10-day intervals by visual identification. Matched pairs of the instants of the foot-strikes were used for analysis. Approximately 97% of the instants of foot-strike matched completely, and all of the mismatched instants were within one frame (0.33%). We calculated the step-frequency using the time taken for each foot-strike. Toe coordinates were digitized with a Frame-DIAS system (DKH Co., Tokyo, Japan) for the duration of time the foot was on the ground at each step. In the same frame, coordinates of four reference markers that were placed closest to the digitized toe were also digitized. The coordinates of the toe were converted into real 2D coordinates using the four reference marker coordinates. Before the experiment, we assessed the precision of the calculation of the foot position. The coordinates of 10 markers randomly placed over a 10-m section were calculated. The error ranged from less than 1 to 9 mm (less than 0.09%). The step-length was the difference between the coordinates of two series of steps. The running speed was calculated as the product of step-length and step-frequency. To avoid the influence of any left and right differences and random noise caused by human variability, we approximated the running speed against the time axis using a fourth-order polynomial equation. 34 Acceleration as a function of time was calculated as the first derivative of the approximated running speed. Peculiar changes in running speed were observed in the last few steps because of the finishing motion; thus, the running speed of the last three steps was excluded from the approximation. The minimal number of approximated steps of the sprinter with the longest step-length in the 60-m sprint was 25. Therefore, the values of acceleration from the 1st to the 25th steps of all participants were used in the statistical analysis. Vertical jump tests Vol No. 6 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 693

5 NAGAHARA Traditional and ankle-specific vertical jumps as strength-power indicators Figure 1. Examples of vertical jump modalities. (a) SJ: squat jump; (b) CMJ: counter-movement jump; (c) RJ: rebound-continuous jump; (d) AJ: rebound-continuous ankle jump. swinging action. The SJ and CMJ were performed twice with 1 minute of rest between jumps, and the best trial was used for the statistical analysis. The participants were instructed to jump as high as possible and land with an extended position. The RJ is a repeated jump and was performed with six jumps. For the RJ, the participants were instructed to jump as high as possible and push against the ground as quickly as possible. The jump with the highest index (explained below), excluding the first and last jumps, was chosen for statistical analysis. The AJ was performed only with plantar flexion, without any other joint movement with reference to previous studies, 31, 32 although we used continuous jumps. To perform the AJ, the participants stood with their legs straight and began jumping with only plantar flexion. Before touching the ground, the participants tried to keep their bodies straight without flexing their knees or hips, and attempted to push off the ground with only ankle and metatarsophalangeal (MTP) plantar flexion. The AJ comprised six jumps, and the jump with the highest index, excluding the first and last jumps, was chosen for statistical analysis. For the AJ, the participants were instructed to jump as high as possible, to keep their lower limbs fully straight, and to push against the ground as quickly as possible with only the ankle and MTP joints. The researchers checked whether the jumps were performed correctly by visual assessment. In the case of the AJ, the jump was checked immediately after the trial using the high-speed camera that was used in the sprint test. For this procedure, an observer judged particularly whether the knee straightened during the support phase. If a participant performed a jump incorrectly, he was required to perform it again. The jump heights and contact times were measured using a contact mat system (Multi Jump Tester; DKH Co., Tokyo, Japan). The contact mat system read the ON and OFF signals during foot contact on the ground and the flight of the body in milliseconds. The jump height was calculated using Bosco s theory. 35 All participants had performed jumping exercises for training and testing in their training program and were therefore familiar with all jumping tests used in our study with the exception of the AJ. All participants had performed the AJ at least five times before the experiment to familiarize themselves with it. The researchers confirmed that the participants were able to conduct the AJ correctly. The SJ and CMJ were measured only for height. The RJ and AJ were measured for jump height, contact time, and jump index; i.e., the ratio of the jump height (m) divided by the contact time (s). 19 This index was used as an indicator of the athlete s ability to overcome stretch loads during stretch-shortening cycle activities. 19 The intraclass correlation coefficients for the jump test variables ranged from 0.91 to 0.97 (P<0.01). Statistical analysis The means and standard deviations were calculated. Pearson s correlation test was used to analyse the relationship between two variables and the relationships between acceleration and jump performances at every step. The significance level was set at 5% for all tests. Results Table I shows the means and standard deviations of the 60-m sprint time and jump performances as well as the correlation coefficients among those variables. The SJ (r= 0.55), CMJ (r= 0.52), AJ index (r= 0.49), and AJ height (r= 0.53) were signifi- 694 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS December 2014

6 Traditional and ankle-specific vertical jumps as strength-power indicators NAGAHARA Table I. Means±SD of sprint and jump test variables and correlation coefficients among the variables (n=19). Variables Mean ± SD Correlation coefficients Sprint SJ CMJ RJI RJCT RJH AJI AJCT 60 m sprint time (Sprint) [s] 7.54±0.27 SJ [m] 0.44± * CMJ [m] 0.50± * 0.83* Index (RJI) [ms -1 ] 2.634± RJ Contact time (RJCT) [s] 0.149± * Height (RJH) [m] 0.39± * 0.56* 0.88* Index (AJI) [ms -1 ] 1.132± * AJ Contact time (AJCT) [s] 0.132± * Height (AJH) [m] 0.15± * * 0.05 *P<0.05 cantly correlated with the 60-m sprint time. RJ variables and AJ contact time were not correlated with the 60-m sprint time. The correlations of SJ with CMJ (r=0.83) and of SJ (r=0.53) and CMJ (r=0.56) with RJ height were significant. The RJ index correlated with both RJ contact time (r= 0.56) and height (r=0.88). The correlation of the AJ index with AJ height was significant (r=0.97). There was a significant positive correlation between RJ and AJ contact times (r=0.52). Figure 2 shows the means and standard deviations of running speed and acceleration. Running speed reached maximal speed (9.52±0.41 ms 1 ) at the 24th step. Figure 3 shows the correlation coef- Figure 2. Mean±SD of approximated running speed and acceleration. Black and grey lines show running speed and acceleration, respectively. Figure 3. Changes in the correlation coefficients between acceleration and (a) SJ, (b) CMJ, (c) RJ, and (d) AJ for each step. Dotted horizontal lines show the significance level as P<0.05 (N.=19). Vol No. 6 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 695

7 NAGAHARA Traditional and ankle-specific vertical jumps as strength-power indicators as the distance increased, and it was pointed out that the SJ and CMJ are more predictive of performance during the early stage of the 100-m sprint. However, in those studies, significant correlations were actually found between the SJ and CMJ and the mean running speed from the start to 10 m, 10 to 30 m, and 30 to 60 m. In contrast, we used step-to-step acceleration to assess the sprint performance, and found significant correlations only during the earlier stage of acceleration. Accordingly, the use of step-to-step acceleration to assess sprint acceleration performance appropriately at the spot is more advantageous than the use of running speed. During the early stage of acceleration, the support time is longer than that during the later stage, and the posture at the time of foot-strike is characterized by a deeply flexed hip and knee and a forward-leaning trunk. 33 Likewise, the durations of force production in the SJ and CMJ are longer than those for the RJ or AJ, 22 and the lowest positions in the SJ and CMJ involve a deeply flexed hip and knee and forwardleaning trunk (Figure 1). Moreover, both sprinting during the early stage of acceleration and the SJ and CMJ are accomplished with explosive extension and plantar flexion of the three major lower extremity joints. 7, 22 Therefore, these similarities in joint behaviour and characteristics of force production are probably responsible for the relationship between sprint acceleration ability during the earlier stage and SJ and CMJ performance. Although significant correlations between the RJ and sprint performance in male sprinters have been reported, 16, 18 we found no significant correlation between the RJ and sprint variables (Table I, Figure 3). This is possibly because the RJ procedure in our study differed from that used in previous studies. In our study, the RJ comprised six jumps with instructions to jump as high as possible and push against the ground as quickly as possible, whereas the RJ in previous studies comprised 60 s of continuous jumps 16 or 15 s of continuous jumps with instructions to bend the knees in a 90 position during jumping. 18 A jump procedure used by Maulder et al. 36 was similar to the procedure used for our RJ, and they found no significant correlation between jump variables, including the height and contact time, and a 10-m sprint test. Despite the different distances between studies, our results are consistent with those of Maulder et al. 36 Whereas further research using the same RJ proceficients between the jump variables (jump heights of SJ and CMJ and indices of RJ and AJ) and sprint acceleration at each step. The SJ was significantly correlated with acceleration from the 6th to the 10th steps (r=0.48/0.51). CMJ significantly correlated with acceleration from the 5th to the 11th steps (r=0.46/0.54). No significant correlation was found between the RJ index and acceleration at every step. The AJ index significantly correlated with acceleration from the 14th to the 19th steps (r= ). Discussion This study primarily aimed to determine the demand of the strength-power capability relative to the sprint acceleration ability by investigating the association between vertical jump performances and acceleration at each step during maximal sprint acceleration. In the present study, participants performed only one 60-m sprint, and the time of the 60-m sprint was relatively low (7.54±0.27 s, ranging from 7.11 to 7.84 s). However, the correlation coefficient between the 60-m sprint time in the experiment and the best record of the 100-m race was high (r=0.75). Moreover, Mackala 1 showed that the average maximal speed of average-level sprinters, whose average best record for a 100-m race was s, in an experimental 100-m sprint was 9.66 ms 1. Although the maximal speed achieved in our study (9.52±0.41 ms 1 ) was slightly low compared with Mackala s results, the difference is within a tolerable range. Therefore, the 60-m sprint trial in this study appropriately reflected the participants sprinting performance. The present findings are similar to those of previous studies in that significant correlations were found between the 60-m sprint time and the SJ and CMJ (Table I). 16, 18, 20 Significant correlations of acceleration with the SJ from the 6th (8.3±0.4-m mark) to the 10th steps (15.5±0.7-m mark) and with the CMJ from the 5th (6.6±0.4-m mark) to the 11th steps (17.5±0.8-m mark) were also found (Figure 3). Accordingly, explosive strength represented by the SJ and CMJ is important for acceleration during the earlier stage (approximately 7 to 18 m from the start line) of the sprint. In previous studies, 9, 18 the correlation coefficients of the SJ and CMJ with velocity variables decreased 696 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS December 2014

8 Traditional and ankle-specific vertical jumps as strength-power indicators NAGAHARA dure would be needed to verify this concept, reactive strength represented by the RJ consequently may not be important for sprint ability. The AJ index and AJ height were significantly correlated with the time of the 60-m sprint (Table I), and significant correlations between acceleration and the AJ index from the 14th (23.4±1.0-m mark) to the 19th steps (33.7±1.4-m mark) were found (Figure 3). To the best of our knowledge, this is the first study to investigate the relationship between the AJ and sprint performance, and it is thus impossible to make any comparisons with results in the literature. Although the SJ, CMJ, and AJ variables showed significant correlations with the 60-m time, the AJ index had significant correlations with acceleration at different stage of acceleration (Figure 3). The AJ index and AJ height had no significant relationship with the variables of other jump modalities (Table I). Whereas the AJ contact time significantly correlated with the RJ contact time, it had no significant correlation with either the 60-m time or the AJ index (Table I). Moreover, the AJ was performed with only plantar flexion of the ankle and MTP joints and without work done by the knee and hip joints. Consequently, the AJ allows assessment of reactive strengths different from those assessed with traditional jump modalities, and the reactive strength represented by AJ presumably influences the acceleration ability during a later stage (approximately 23 to 34 m from the start line) of the entire sprint acceleration. It has been pointed out that higher-level sprinters show greater peak negative plantar flexor power than do lower-level sprinters during maximal-speed sprint 37 and that the performance of the ankle plantar flexors may limit the maximal running speed. 29 These previous studies support our results. The erect body posture in the AJ and during sprinting when approaching maximal speed is a common feature. The AJ contact time (0.132±0.008 s) is longer than that during maximal-speed sprinting (less than 0.1 s); 33 however, the contact time in the AJ was shorter than that in the other jump modalities. 22, 23 Knee extension during sprinting results in powertransferring actions by the gastrocnemius from the knee to the ankle that contribute to the work done during plantar flexion. 25 During high-speed sprinting, faster sprinters showed smaller amounts of knee extension at toe-off than did slower collegiate sprinters, 12 and thus extending the knee joint with transfer- ring power via the bi-articular muscles is probably less important to achieve higher sprint performance during the later stage of acceleration. The AJ also had no influence on power transfer from the knee. Accordingly, the significant correlation between the AJ index and the later stage of acceleration is probably attributed to those common features. During the initial and last parts of acceleration in our study, there was no significant correlation of acceleration with any jump performance (Figure 3). The step-frequency of sprinters at the fourth step (4.38±0.24 Hz) was 97% of the peak value (4.54±0.20 Hz at the 20th step), and the step-length at the fourth step (1.51±0.07 m) was 72% of the peak value (2.11±0.09 m at the 25th step). These results indicate that acceleration to the fourth step was associated with an increase in step-frequency, while after that the contribution was relatively small. 1 Jump performance in our study is not a measure of the ability to move the legs with high frequency. Therefore, it seems that the association of acceleration with an increase in step-frequency caused no significant correlation of acceleration ability with jump variables during the initial phase. Although there were no significant correlations during the last part of acceleration, the running speed at the 20th step was almost maximal (99.4% of maximal speed). Therefore, the running speed almost reached its maximum at that spot. The jump modalities used in our study are easy to perform during a typical training session. Therefore, by using the SJ, CMJ, and AJ as practical field tests to quantify associated strength-power capability, sprinters and coaches could better identify the strengths and weaknesses of the earlier (approximately 7 to 18 m from the start line) and later stages (approximately 23 to 34 m from the start line) of acceleration. Moreover, the entire acceleration phase can be divided into two sections approximately 20 m from the start line (middle of the earlier and later stages of acceleration), which is in line with the concept of a previous study, 1 according to the different demand of the strength-power capability. Because different strength-power capabilities are needed for the earlier and later stages of acceleration, as we showed, training tasks for improving specific sprint performance could be selected. Although the RJ in our study was conducted with the instruction to push against the ground as quickly as possible, the con- Vol No. 6 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 697

9 NAGAHARA Traditional and ankle-specific vertical jumps as strength-power indicators tact times in the RJ were longer than those in the AJ. In addition, acceleration was only significantly correlated with the AJ index and not with the RJ index. In a typical sprint training program, sprinters perform the rebound-continuous jump, drop jump, hurdle jump, and etc. as reactive-strength training; these are similar to the RJ in our study and may have longer contact times than our AJ. Consequently, to develop strength-power capabilities for improving sprint performance in the later stage of acceleration, sprinters may need to adopt training methods with shorter force production durations than those of traditional jumps. In our study, participants abilities were not of an international standard. There is the possibility that the results may differ when examining world-class sprinters. In addition, we investigated the relationship between the acceleration ability and strength-power capability of various jump modalities. It is important that future investigations examine step-to-step acceleration ability during the entire acceleration phase in relation to the kinetics of the sprint. Such information would be of practical benefit for sprinters. Conclusions This study demonstrated the demand of strengthpower capabilities for acceleration abilities. For effective sprint acceleration, the strength-power capabilities of the SJ and CMJ were needed during the earlier stage of acceleration (approximately 7 to 18 m from the start line), and the strength-power capability of the AJ was required to reach higher maximal speed during the later stage of acceleration (approximately 23 to 34 m from the start line). Because jump tests are easy to perform, sprinters are able to indirectly assess their acceleration ability during different stages of sprint acceleration. Sprinters and coaches should be aware of the different demands of strength-power capability for effective acceleration. References 1. Mackala K. Optimisation of performance through kinematic analysis of the different phases of the 100 metres. N Stud Athletics 2007;22: Hirvonen J, Rehunen S, Rusko H, Harkonen M. Breakdown of high-energy phosphate compounds and lactate accumulation dur- ing short supramaximal exercise. Eur J Appl Physiol Occup Physiol 1987;56: Doolittle D, Tellez T. Sprinting - from start to finish. Track Field Q Rev 1984;84: Delecluse CH, van Coppenolle H, Willems E, Diels R, Goris M, van Leemputte M, Vuylsteke M. Analysis of 100 meter sprint performance as a multi-dimensional skill. J Hum Mov Stud 1995;28: Gajer B, Thepaut-Mathieu C, Lehenaff D. Evolution of stride and amplitude during course of the 100 m event in athletics. N Stud Athletics 1999;14: Dick FW. Developing sprinting speed. Athletics Coach 1987;21: Baumann W. Kinematic and dynamic characteristics of the sprint start. In: Komi PV editor. Biomechanics V-B. Baltimore: University Park Press; p Kugler F, Janshen L. Body position determines propulsive forces in accelerated running. J Biomech 2010;43: Bret C, Rahmani A, Dufour AB, Messonnier L, Lacour JR. Leg strength and stiffness as ability factors in 100 m sprint running. J Sports Med Phys Fitness 2002;42: Mero A, Komi PV. Force-, EMG-, and elasticity-velocity relationships at submaximal, maximal and supramaximal running speeds in sprinters. Eur J Appl Physiol Occup Physiol 1986;55: Weyand PG, Sternlight DB, Bellizzi MJ, Wright S. Faster top running speeds are achieved with greater ground forces not more rapid leg movements. J Appl Physiol 2000;89: Mann R, Herman J. Kinematic analysis of olympic sprint performance: Men s 200 meters. Int J Sport Biomech 1985;1: Salo AI, Bezodis IN, Batterham AM, Kerwin DG. Elite sprinting: are athletes individually step-frequency or step-length reliant? Med Sci Sports Exerc 2011;43: Dillman CJ. Kinematic analyses of running. Exerc Sport Sci Rev 1975;3: Ito A, Fukuda K, Kijima K. Mid-phase movements of Tyson Gay and Asafa Powell in the 100 metres at the 2007 World Championships in Athletics. N Stud Athletics 2008;23: Kale M, Asci A, Bayrak C, Acikada C. Relationships among jumping performances and sprint parameters during maximum speed phase in sprinters. J Strength Cond Res 2009;23: Bissas AI, Havenetidis K. The use of various strength-power tests as predictors of sprint running performance. J Sports Med Phys Fitness 2008;48: Smirniotou A, Katsikas C, Paradisis G, Argeitaki P, Zacharogiannis E, Tziortzis S. Strength-power parameters as predictors of sprinting performance. J Sports Med Phys Fitness 2008;48: Young W. Laboratory strength assessment of athletes. N Stud Athletics 1995;10: Young W, McLean B, Ardagna J. Relationship between strength qualities and sprinting performance. J Sports Med Phys Fitness 1995;35: Komi PV, Bosco C. Utilization of stored elastic energy in leg extensor muscles by men and women. Med Sci Sports 1978;10: Fukashiro S, Komi PV. Joint moment and mechanical power flow of the lower limb during vertical jump. Int J Sports Med 1987;8(Suppl 1): Bobbert MF, Mackay M, Schinkelshoek D, Huijing PA, van Ingen Schenau GJ. Biomechanical analysis of drop and countermovement jumps. Eur J Appl Physiol Occup Physiol 1986;54: Bobbert MF, Huijing PA, van Ingen Schenau GJ. Drop jumping. II. The influence of dropping height on the biomechanics of drop jumping. Med Sci Sports Exerc 1987;19: Jacobs R, Bobbert MF, van Ingen Schenau GJ. Mechanical output from individual muscles during explosive leg extensions: the role of biarticular muscles. J Biomech 1996;29: Bobbert MF, Huijing PA, van Ingen Schenau GJ. An estimation of power output and work done by the human triceps surae muscletendon complex in jumping. J Biomech 1986;19: THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS December 2014

10 This document is protected by international copyright laws. No additional reproduction is authorized. It is permitted for personal use to download and save only one file and print only one copy of this Article. It is not permitted to make additional copies (either sporadically or systematically, either printed or electronic) of the Article for any purpose. It is not permitted to distribute the electronic copy of the article through online internet and/or intranet file sharing systems, electronic mailing or any other means which may allow access to the Article. The use of all or any part of the Article for any Commercial Use is not permitted. The creation of derivative works from the Article is not permitted. The production of reprints for personal or commercial use is not permitted. It is not permitted to remove, cover, overlay, obscure, block, or change any copyright notices or terms of use which the Publisher may post on the Article. It is not permitted to frame or use framing techniques to enclose any trademark, logo, or other proprietary information of the Publisher. Traditional and ankle-specific VERTICAL jumps as strength-power indicators 27. Jaric S, Ristanovic D, Corcos DM. The relationship between muscle kinetic parameters and kinematic variables in a complex movement. Eur J Appl Physiol Occup Physiol 1989;59: Horita T, Komi PV, Nicol C, Kyrolainen H. Interaction between prelanding activities and stiffness regulation of the knee joint musculoskeletal system in the drop jump: implications to performance. Eur J Appl Physiol 2002;88: Dorn TW, Schache AG, Pandy MG. Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance. J Exp Biol 2012;215: Stefanyshyn DJ, Nigg BM. Dynamic angular stiffness of the ankle joint during running and sprinting. J Appl Biomech 1998;14: Bosco C, Tarkka I, Komi PV. Effect of elastic energy and myoelectrical potentiation of triceps surae during stretch-shortening cycle exercise. Int J Sports Med 1982;3: Fukashiro S, Kurokawa S, Hay DC, Nagano A. Comparison of muscle-tendon interaction of human M. Gastrocnemius between ankleand drop-jumping. Int J Sport Health Sci 2005;3: Bosch F, Klomp R. Running: Biomechanics and Exercise Physiology Applied in Practice. (Boer-Stallman DW, Trans.). Philadelphia: Elsevier (Original work published 2001); De Smet K, Segers V, Lenoir M, De Clercq D. Spatiotemporal characteristics of spontaneous overground walk-to-run transition. Gait Posture 2009;29: Bosco C, Luhtanen P, Komi PV. A simple method for measurement NAGAHARA of mechanical power in jumping. Eur J Appl Physiol Occup Physiol 1983;50: Maulder PS, Bradshaw EJ, Keogh J. Jump kinetic determinants of sprint acceleration performance from starting blocks in male sprinters. J Sports Sci Med 2006;5: Bezodis IN, Kerwin DG, Salo AI. Lower-limb mechanics during the support phase of maximum-velocity sprint running. Med Sci Sports Exerc 2008;40: Presented at the European College of Sports Science (July 8, 2011; Liverpool, UK). Funding. Naito has received a research grant from the Kozuki Foundation for Sports and Education in Japan. Conflicts of interest. The authors certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript. Acknowledgements. The authors thank Dr. Satoru Tanigawa for allowing track club members to participate in this study. This study was partially supported by a research grant from Kozuki Foundation for Sports and Education. Received on January 10, Accepted for publication on February 9, Epub ahead of print on April 16, Vol No. 6 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 699