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Kajetan J. Słomka, Slobodan Jaric, Grzegorz Sobota, Ryszard Litkowycz, Tomasz Skowronek, Marian Rzepko and Grzegorz Juras

output as an index of the maximal capacity of the leg muscles to produce force and power. However, the most frequently recorded variable observed from the vertical jump tests is maximum jump height, which is typically interpreted as an index of the capacity of a muscle to produce either a high force or

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Christina A. Geithner, Claire E. Molenaar, Tommy Henriksson, Anncristine Fjellman-Wiklund and Kajsa Gilenstam

1 SD after. Maturity-associated differences, or differences among early, average, and late maturers, are present in body size (height and weight), body composition, and fitness in both sexes. Early-maturing individuals are taller and heavier relative to their average- and late-maturing peers early

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Olaf Prieske, Helmi Chaabene, Christian Puta, David G. Behm, Dirk Büsch and Urs Granacher

, standing long jump [SLJ]), drop jumps (DJ) represent one of the most frequently applied jump exercises. 3 During reactive strength training protocols, drop-height is considered the key variable for practitioners to modulate training intensity of the DJ exercise. 4 In fact, previous studies revealed that

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Anthony Birat, David Sebillaud, Pierre Bourdier, Eric Doré, Pascale Duché, Anthony J. Blazevich, Dimitrios Patikas and Sébastien Ratel

landing phase of a jump. The onset of adolescence (ie, around the peak height velocity [PHV]) is a particularly critical period for injuries because of (1) imbalances within muscle-tendon units of young athletes, (2) strength imbalances between the hamstrings and quadriceps, particularly in post

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Rienk M.A. van der Slikke, Annemarie M.H. de Witte, Monique A.M. Berger, Daan J.J. Bregman and Dirk Jan H.E.J. Veeger

detailed insight into the relationship between key settings, such as seat height/position and performance, could support athletes and wheelchair experts in their decision making. Often, there is not a single performance target, but decisions have to be made on the trade-off; for example, between desirable

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Maury L. Hull and Hiroko K. Gonzalez

Using a five-bar linkage model of the leg/bicycle system in conjunction with experimental kinematic and pedal force data, the inverse dynamics problem is solved to yield the intersegmental moments. Among the input data that affect the problem solution is the height of the pedal platform. This variable is isolated and its effects on the total joint moments are studied as it assumes values over a ±4-cm range. Platform height variation affects the total joint moment peak values by up to 13%. Relying on a cost function derived from the hip and knee moments, it is found that the platform height that minimizes the cost function is +2 cm. The sensitivity of the cost function to the platform height variable is low; over the variable range the cost function increases 2% above the minimum. These results hold for a pedaling rate of 90 rpm. As pedaling rate is varied above and below 90 rpm, the sensitivity of the cost function increases. The platform heights that minimize the cost function are the lower and upper limits for 60 and 120 rpm, respectively. Thus the platform height variable interacts with pedaling rate, requiring a compromise in platform height adjustment. The compromise height depends on the individual’s preferred pedaling rate range.

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Mark A. King, Cassie Wilson and Maurice R. Yeadon

This study used an optimization procedure to evaluate an 8-segment torque-driven subject-specific computer simulation model of the takeoff phase in running jumps for height. Kinetic and kinematic data were obtained on a running jump performed by an elite male high jumper. Torque generator activation timings were varied to minimize the difference between simulation and performance in terms of kinematic and kinetic variables subject to constraints on the joint angles at takeoff to ensure that joints remained within their anatomical ranges of motion. A percentage difference of 6.6% between simulation and recorded performance was obtained. Maximizing the height reached by the mass center during the flight phase by varying torque generator activation timings resulted in a credible height increase of 90 mm compared with the matching simulation. These two results imply that the model is sufficiently complex and has appropriate strength parameters to give realistic simulations of running jumps for height.

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Riley C. Sheehan and Jinger S. Gottschall

In a previous study, we found that participants modified how they transitioned onto and off of ramp configurations depending upon the incline. While the transition strategies were originally attributed to ramp angles, it is possible that the plateau influenced the strategies since the final surface height also differed. Ultimately, for the current study, we hypothesized that an individual’s transition strategies would have significant main effects for ramp angle, but not plateau height. Twelve healthy, young adults transitioned onto 3 distinct ramp configurations, a 2.4-m ramp angled at 12.5° ending at a plateau height of 53 cm, a 1.2-m ramp angled at 23.5° ending at a plateau height of 53 cm, and a 2.4-m ramp angled at 23.5° ending at a plateau height of 99.5 cm. Kinematics, kinetics, and muscle activity were measured during the stance phase before contacting the ramp. In support of our hypothesis, impact peak, active peak, and all of the muscle activity variables had a significant main effect for ramp angle, with greater vertical force peaks and muscle activity on steeper ramp transitions. These findings support our previous interpretation that individuals use estimations of ramp angle, not plateau height, to determine their transition strategies.

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Basilio Pueo, Patrycja Lipinska, José M. Jiménez-Olmedo, Piotr Zmijewski and Will G. Hopkins

Vertical-jump tests are commonly used to evaluate lower-limb power of athletes and nonathletes. Several types of equipment are available for this purpose.

Purpose:

To compare the error of measurement of 2 jump-mat systems (Chronojump-Boscosystem and Globus Ergo Tester) with that of a motion-capture system as a criterion and to determine the modifying effect of foot length on jump height.

Methods:

Thirty-one young adult men alternated 4 countermovement jumps with 4 squat jumps. Mean jump height and standard deviations representing technical error of measurement arising from each device and variability arising from the subjects themselves were estimated with a novel mixed model and evaluated via standardization and magnitude-based inference.

Results:

The jump-mat systems produced nearly identical measures of jump height (differences in means and in technical errors of measurement ≤1 mm). Countermovement and squat-jump height were both 13.6 cm higher with motion capture (90% confidence limits ±0.3 cm), but this very large difference was reduced to small unclear differences when adjusted to a foot length of zero. Variability in countermovement and squat-jump height arising from the subjects was small (1.1 and 1.5 cm, respectively, 90% confidence limits ±0.3 cm); technical error of motion capture was similar in magnitude (1.7 and 1.6 cm, ±0.3 and ±0.4 cm), and that of the jump mats was similar or smaller (1.2 and 0.3 cm, ±0.5 and ±0.9 cm).

Conclusions:

The jump-mat systems provide trustworthy measurements for monitoring changes in jump height. Foot length can explain the substantially higher jump height observed with motion capture.

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Loren Z.F. Chiu and George J. Salem

Sacral marker and pelvis reconstruction methods have been proposed to approximate total body center of mass during relatively low intensity gait and hopping tasks, but not during a maximum effort vertical jumping task. In this study, center of mass displacement was calculated using the pelvic kinematic method and compared with center of mass displacement using the ground-reaction force-impulse method, in experienced athletes (n = 13) performing restricted countermovement vertical jumps. Maximal vertical jumps were performed in a biomechanics laboratory, with data collected using an 8-camera motion analysis system and two force platforms. The pelvis center of mass was reconstructed from retro-reflective markers placed on the pelvis. Jump height was determined from the peak height of the pelvis center of mass minus the standing height. Strong linear relationships were observed between the pelvic kinematic and impulse methods (R 2 = .86; p < .01). The pelvic kinematic method underestimated jump height versus the impulse method, however, the difference was small (CV = 4.34%). This investigation demonstrates concurrent validity for the pelvic kinematic method to determine vertical jump height.