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Warren Young, Stuart Cormack, and Michael Crichton

Purpose:

The main purpose of this study was to determine the relationships between countermovement jump (CMJ) variables and acceleration and maximum speed performance.

Methods:

Twenty-three elite Australian football players were tested on a CMJ, which yielded several kinematic and kinetic variables describing leg muscle function. A 40 m sprint was also conducted to assess acceleration (10 m time) and an estimate of maximum speed (fying 20 m time). Players from one Australian Football League (AFL) club were tested and Pearson correlations for CMJ variables and sprint performance were calculated.

Results:

Jump height, peak velocity, peak force, and peak power had less than 50% common variance, and therefore represented independent expressions of CMJ performance. Generally, the correlations between CMJ variables and sprinting performance were stronger for maximum speed (small to large effect sizes) than for acceleration (trivial to moderate sizes). The variable that produced the strongest correlation with acceleration was jump height (r = -0.430, P = .041) and with maximum speed was peak power/weight (r = -0.649, P = .001).

Conclusions:

The results indicate that if an integrated system comprising a position transducer and a force platform is available for CMJ assessment, jump height and peak power/weight are useful variables to describe leg muscle explosive function for athletes who perform sprints.

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Davide Ferioli, Ermanno Rampinini, Andrea Bosio, Antonio La Torre, and Nicola A. Maffiuletti

Peripheral Muscle Function of Knee Extensors Measured During the Multistage Change-of-Direction Exercise Division I, n = 27 Division II, n = 25 Division III, n = 32 Division VI, n = 27 PT max , N·m 73.1 (17.4) 71.5 (12.7) 65.0 (12.2) 61.1 (8.3) Fatigue, % 10.5 (8.3) 13.5 (12.2) 15.7 (16.8) 28.7 (23.9) MP max

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Jaqueline M. Porto, Sállua B. Spilla, Luciana M. Cangussu-Oliveira, Renato C. Freire Júnior, Ana Paula M. Nakaishi, and Daniela C.C. de Abreu

the association of trunk muscle strength with falls ( Granacher et al., 2013 ; Kasukawa et al., 2010 ; Pfeifer et al., 2001 ). In addition, we detected no studies investigating the influence of other trunk muscle function parameters, such as the rate of torque development (RTD) and torque steadiness

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D.G.E. Robertson, Jean-Marie J. Wilson, and Taunya A. St. Pierre

The purpose of this research was to determine the functions of the gluteus maximus, biceps femoris, semitendinosus, rectus femoris, vastus lateralis, soleus, gastrocnemius, and tibialis anterior muscles about their associated joints during full (deep-knee) squats. Muscle function was determined from joint kinematics, inverse dynamics, electromyography, and muscle length changes. The subjects were six experienced, male weight lifters. Analyses revealed that the prime movers during ascent were the monoarticular gluteus maximus and vasti muscles (as exemplified by vastus lateralis) and to a lesser extent the soleus muscles. The biarticular muscles functioned mainly as stabilizers of the ankle, knee, and hip joints by working eccentrically to control descent or transferring energy among the segments during ascent. During the ascent phase, the hip extensor moments of force produced the largest powers followed by the ankle plantar flexors and then the knee extensors. The hip and knee extensors provided the initial bursts of power during ascent with the ankle extensors and especially a second burst from the hip extensors adding power during the latter half of the ascent.

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Francesco V. Ferraro, James P. Gavin, Thomas W. Wainwright, and Alison K. McConnell

significant decline in inspiratory muscle function ( Britto et al., 2009 ) and an increase in pulmonary inflammation, known as senile emphysema ( Janssens et al., 1999 ). These progressive declines may impair the inspiratory muscles’ contribution to their secondary role in balance stabilization, as evident in

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Matthew A. Wyon, Roger Wolman, Nicolas Kolokythas, Karen Sheriff, Shaun Galloway, and Adam Mattiussi

to examine whether vitamin D supplementation can improve muscle function and injury incidence in adolescent elite dancers. Materials and Methods Experimental Design The study implemented a randomized double-blind methodology. Supplementation was organized by an independent researcher who prepared the

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Will Abbott, Callum Brashill, Adam Brett, and Tom Clifford

of the subsequent inflammatory response remains debated, 3 , 4 there is evidence to suggest that it might contribute to the delayed recovery of muscle function typically observed in the days following strenuous exercise. 5 – 7 This has led to growing interest in the use and efficacy of anti

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Amy K. Hegarty, Max J. Kurz, Wayne Stuberg, and Anne K. Silverman

The goal of this pilot study was to characterize the effects of gait training on the capacity of muscles to produce body accelerations and relate these changes to mobility improvements seen in children with cerebral palsy (CP). Five children (14 years ± 3 y; GMFCS I-II) with spastic diplegic CP participated in a 6-week gait training program. Changes in 10-m fast-as-possible walking speed and 6-minute walking endurance were used to assess changes in mobility. In addition, musculoskeletal modeling was used to determine the potential of lower-limb muscles to accelerate the body’s center of mass vertically and forward during stance. The mobility changes after the training were mixed, with some children demonstrating vast improvements, while others appeared to be minimal. However, the musculoskeletal results revealed unique responses for each child. The most common changes occurred in the capacity for the hip and knee extensors to produce body support and the hip flexors to produce body propulsion. These results cannot yet be generalized to the broad population of children with CP, but demonstrate that therapy protocols may be enhanced by modeling analyses. The pilot study results provide motivation for gait training emphasizing upright leg posture, mediolateral balance, and ankle push-off.

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Debra G. George-Reichley and Jill S. Higginson

The understanding of individual muscle impairments that affect swing phase in stroke gait will lead to better rehabilitation strategies for this population. We used induced acceleration analysis to evaluate the potential each muscle has to accelerate the hip and knee joints of the swing limb, using kinematics from three stroke subjects and five healthy subjects. To determine the influence of altered limb position on muscle function, we augmented hip extension by 10° in swing phase for all subjects. We found that in early swing, healthy subjects had greater potential to accelerate the knee into flexion than stroke subjects, whereas stroke subjects had greater potential to accelerate the hip into flexion. Perturbing the hip flexion angle into greater extension increased the potential of biarticular muscles to flex the knee in swing phase. The potential of muscles to improve swing phase dynamics depends on the initial posture of the limb and highlights the importance of subject-specific evaluations in the design of appropriate therapeutic interventions.

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Lothar Stein, Constanze Pacht, Sibylle Junge, Tobias S. Kaeding, Momme Kück, Norbert Maassen, Torge Wittke, and Vladimir Shushakov

Purpose:

Defects in the gene encoding the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) cause CF. Absence of the CFTR may result in skeletal muscle dysfunction. Here, we tested skeletal muscle function in male adolescent patients with CF.

Methods:

Ten CF and 10 control participants (age: 16.8 ± 0.6 years) performed 7 repetitive sets of maximum voluntary contractions (MVCs) and underwent an isometric fatigue test of the knee extensors. Electromyography (EMG) activity was recorded from the m. vastus lateralis (VL) and m. vastus medialis (VM).

Results:

In CF, the MVC torque was lower and correlated with the predicted forced expiratory volume in one second (r = .73, p = .012, n = 10). The M-wave in the VL was shorter in CF than in controls (18.6 ± 0.5 vs. 20.3 ± 0.5 ms, p < .028). In the VM, both the M-wave (4.96 ± 0.61 vs. 7.97 ± 0.60 mV, p = .001) and the EMG (0.29 ± 0.04 vs. 0.47 ± 0.04 mV, p = .004) amplitudes were smaller in CF.

Conclusion:

The differences in the VL and VM EMG signals between the groups indicate that the lower MVC torque in CF did not result from the direct impact of a CFTR defect on the sarcolemmal excitability; the differences more likely resulted from the less developed musculature in the patients with CF.