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Lilian F. Wallerstein, Renato Barroso, Valmor Tricoli, Marco T. Mello and Carlos Ugrinowitsch

Ramp isometric contractions determine peak torque (PT) and neuromuscular activation (NA), and ballistic contractions can be used to evaluate rate of torque development (RTD) and electrical mechanical delay (EMD). The purposes of this study were to assess the number of sessions required to stabilize ramp and ballistic PT and to compare PT and NA between contractions in older adults. Thirty-five older men and women (age 63.7 ± 3.7 yr, body mass 64.3 ± 10.7 kg, height 159.2 ± 6.6 cm) performed 4 sessions of unilateral ramp and ballistic isometric knee extension, 48 hr apart. PT significantly increased (main time effect p < .05) from the first to the third session, with no further improvements thereafter. There was a trend toward higher PT in ballistic than in ramp contractions. No difference between contraction types on EMG values was observed. Therefore, the authors suggest that 3 familiarization sessions be performed to correctly assess PT. In addition, PT, NA, RTD, and EMD can be assessed with ballistic contraction in older adults.

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Boris l. Prilutsky

The purpose of this paper is three-fold: (a) to summarize available data on coordination of major two- and one-joint muscles in multijoint tasks and identify basic features of muscle coordination, (b) to demonstrate that there may exist an optimization criterion that predicts essential features of electromyographic activity of individual muscles in a variety of tasks, and (c) to address the functional consequences of the observed muscle coordination and underlying mechanisms of its control. The analysis of the literature revealed that basic features of muscle coordination are similar among different voluntary motor tasks and reflex responses. It is demonstrated that these basic features of coordination of one- and two-joint muscles in two-dimensional tasks are qualitatively predicted by minimizing the sum of muscle stresses cubed. Functional consequences of the observed coordination of one- and two-joint muscles are (a) reduction of muscle force as well as stress, mechanical and metabolic energy expenditure, muscle fatigue, and perceived effort; (b) a spring-like behavior of a multi-joint limb during maintenance of an equilibrium posture; and (c) energy transfer between joints via two-joint muscles. A conceptual scheme of connections between motoneuron pools of one- and two-joint muscles, which accounts for the observed muscle coordination, is proposed. An important part of this scheme is the force-dependent inhibition and excitation from two-joint to one-joint synergists and antagonists, respectively.

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William H. Clark and Jason R. Franz

increases with walking speed and positively correlates with positive work performed about the ankle during push off. 5 , 7 In addition, the profile of k A across the stance phase mirrors that of net ankle moment and triceps surae muscle activation. Together, these findings allude to activation

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Mostafa Yaghoubi, Philip W. Fink, Wyatt H. Page and Sarah P. Shultz

during locomotion ( 27 ) and exhibit increased lower extremity joint moments ( 22 ) and power ( 44 ), ground reaction forces (GRFs) ( 20 ), and muscle activation during gait ( 9 ). In addition, it has been suggested that changes in the locomotor strategy by OW children reduce mechanical efficiency and

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Jay A. Collison, Jason Moran, Inge Zijdewind and Florentina J. Hettinga

defined as a decline in an objective measure of performance over time and can be quantified by reductions in voluntary muscle force or changes in voluntary muscle activation (VA). 5 Performing bouts of resistance exercise induce performance fatigability, and ensuring that performance fatigability is

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Ji-Hyun Lee and Tae-Lim Yoon

). Eventually, patients with CAI experience postural-control deficit, and their functional performance could be damaged (self-reported disability). 7 , 9 Many previous studies introduced various exercises for improving balance and functional performance by improving muscle activation in patients with CAI

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Yi-Fen Shih, Ya-Fang Lee and Wen-Yin Chen

the functions of the shoulder complex. 1 Scapular dyskinesis, or alterations in scapular kinematics and muscle activation, has been shown to occur with SIS in previous studies. 1 , 3 – 5 Kibler and McMullen 6 further suggested that proprioception deficits might play a role in the development of

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Hooman Minoonejad, Mohammad Karimizadeh Ardakani, Reza Rajabi, Erik A. Wikstrom and Ali Sharifnezhad

). **Significant difference between the pretest and posttest collapsed means ( P  < .01). ***Significant difference between the experimental and control group collapsed means ( P  < .02). Table 4 Preparatory Muscle Activation Means, SDs, and Effects Sizes per Group Before and After the Hop Stabilization

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Rebecca L. Krupenevich, William H. Clark, Gregory S. Sawicki and Jason R. Franz

muscle stiffness via changes in triceps surae muscle activation. 6 , 8 Furthermore, this activation-dependent modulation of triceps surae muscle stiffness occurs in response to simulated changes in Achilles tendon stiffness when the task demand requires requisite ankle joint quasi-stiffness to preserve

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Smokey Fermin, Lindsay Larkins, Sarah Beene and David Wetzel

pain and/or ROM deficits, will CE decrease pain and increase ROM? Summary of Search, Best Evidence Appraised, and Key Findings • Ipsilateral muscle activation and muscular strength is significantly increased after performing contralateral maneuvers. • Ipsilateral movement has a significant impact on