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Christopher Napier, Christopher L. MacLean, Jessica Maurer, Jack E. Taunton and Michael A. Hunt

all-cause mortality. 1 However, injury rates are high and have not decreased appreciably in the decades since monitoring began. 2 – 4 While the etiology of running injuries is multifactorial, 5 biomechanical factors—primarily kinetic factors associated with the loading phase of running—have been

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Aaron Nelson, Nathan Koslakiewicz and Thomas Gus Almonroeder

second injury involves the previously uninjured knee. It appears that there is an urgent need to improve rehabilitation following ACL reconstruction. Athletes who have undergone an ACL reconstruction often demonstrate greater interlimb knee joint kinetic (ie, joint moments and power) asymmetry during

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Joseph M. Hart, Jamie L. Leonard and Christopher D. Ingersoll

Context:

Despite recent findings regarding lower extremity function after cryotherapy, little is known of the neuromuscular, kinetic, and kinematic changes that might occur during functional tasks.

Objective:

To evaluate changes in ground-reaction forces, muscle activity, and knee-joint flexion during single-leg landings after 20-minute knee-joint cryotherapy.

Design:

1 × 4 repeated-measures, time-series design.

Setting:

Research laboratory.

Patients or Other Participants:

20 healthy male and female subjects.

Intervention:

Subjects performed 5 single-leg landings before, immediately after, and 15 and 30 minutes after knee-joint cryo-therapy.

Main Outcome Measures:

Ground-reaction force, knee-joint flexion, and muscle activity of the gastrocnemius, hamstrings, quadriceps, and gluteus medius.

Results:

Cryotherapy did not significantly (P > .05) change maximum knee-joint flexion, vertical ground-reaction force, or average muscle activity during a single-leg landing.

Conclusion:

Knee-joint cryotherapy might not place the lower extremity at risk for injury during landing.

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Sahar Boozari, Ali Ashraf Jamshidi, Mohammad Ali Sanjari and Hassan Jafari

Context:

Flat foot is one of the lower extremity deformities that might change kinetic variables of gait. Fatigue is one of the factors that can alter the vertical ground-reaction force (GRF). The effect of a fatiguing condition on vertical GRF has not been documented in individuals with flat feet.

Objective:

To examine the fatigue effect on vertical GRF in individuals with flat feet compared with a normal group during barefoot walking.

Design:

Repeated-measure ANOVA for the effects of fatigue on individuals with flat feet and normal feet.

Setting:

Biomechanics laboratory.

Participants:

17 subjects with flat feet and 17 normal subjects (recruited according to their arch-height ratio).

Main Outcome Measures:

Three vertical GRF measures (F1, the first peak force; F2, minimum force; and F3, the second peak force) were extracted before and after a functional fatigue protocol.

Results:

No significant interaction between fatigue and group was observed for the 3 vertical GRF measures. For F2, fatigue and group effects were significant (P = .001 and P = .02, respectively). Furthermore, F2 was higher in the flat-feet group than in the normal group; F2 also increased after fatigue. For F3, only a significant fatigue effect was observed (P = .004). F3 decreased after fatigue in both groups.

Conclusions:

In the flat-feet group, a decrease in the variation of vertical GRF might be due to more flexible foot joints. After fatigue, muscles might lose their ability to control the foot joints and cause higher F2 in the flat-feet group.

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Dustin J. Oranchuk, Eric J. Drinkwater, Riki S. Lindsay, Eric R. Helms, Eric T. Harbour and Adam G. Storey

direction tasks. 3 , 4 Weightlifting movements are therefore commonplace in strength and conditioning settings, 5 due to the kinetic and kinematic similarities with propulsive athletic movements and their ability to improve key kinetic and kinematic variables. 6 – 8 For example, Hoffman et al 7 compared

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John R. Harry, Max R. Paquette, Brian K. Schilling, Leland A. Barker, C. Roger James and Janet S. Dufek

energy to be converted to downward kinetic energy and then elastic strain energy. 1 , 9 Accordingly, it has been suggested that the countermovement phase be divided into “unloading,” “eccentric,” and “concentric” subphases (Figure  1 ). 1 The eccentric and concentric subphases have been directly

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Andrzej Kochanowicz, Bartłomiej Niespodziński, Jan Mieszkowski, Stanisław Sawczyn, Paweł Cięszczyk and Kazimierz Kochanowicz

the overall effects of several years of gymnastic training and were limited to cross-sectional comparisons of athletes and untrained groups. Little remains known on torque kinetic and neuromuscular changes over a specific period of explosive strength training in children. Based on the current

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Toshimasa Yanai, Akifumi Matsuo, Akira Maeda, Hiroki Nakamoto, Mirai Mizutani, Hiroaki Kanehisa and Tetsuo Fukunaga

body forward and generate rotation around the center of mass (CM), ground reaction forces (GRFs) are important in initiating the kinetic sequencing of pitching. Despite this importance, no study has measured GRFs during pitching performed on a soil-filled mound. To remove this deficiency, we have

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Anis Rostami, Amir Letafatkar, Alli Gokeler and Mehdi Khaleghi Tazji

with the purpose of improving jump/landing maneuver and performance in volleyball athletes. So, our study is the first one focused on evaluation the effect of the EF instructions on performance and kinetic variables associated with lower-extremity injury risk in landing after volleyball blocks. The

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Natalia Romero-Franco, Juan Antonio Montaño-Munuera, Juan Carlos Fernández-Domínguez and Pedro Jiménez-Reyes

in closed kinetic chain (CKC). As then, the evaluation of JPS with inclinometer has been used to describe the effects of fatiguing exercise, such as repeated series of 300-meter springs, which demonstrated that higher proprioceptive errors are shown in CKC knee movement when athletes are fatigued. 11