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Ursula Barrett and Drew Harrison

This study examined the force-velocity and power-velocity relationships of the quadriceps muscles of children and adults. Measurements of muscle function were collected using the Con-Trex isokinetic dynamometer. Twenty adults and twenty children performed maximal effort knee extensions at nine different velocities. The mean force-velocity curves of children and adults revealed obvious differences between the groups. The curves remained different following corrections of torque for CSA and velocity for length. ANOVA revealed significant differences in the uncorrected values of power between the two groups. When power values were corrected for lean thigh muscle volume, no significant differences were found between the groups. These findings suggest that differences in muscle strength between children and adults are a function of muscle size and imply that muscle function remains relatively unchanged from childhood to early adulthood.

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Yuya Watanabe, Michiya Tanimoto, Akane Ohgane, Kiyoshi Sanada, Motohiko Miyachi and Naokata Ishii

The authors investigated the effects of low-intensity resistance training on muscle size and strength in older men and women. Thirty-five participants (age 59–76 yr) were randomly assigned to 2 groups and performed low-intensity (50% of 1-repetition maximum) knee-extension and -flexion exercises with either slow movement and tonic force generation (LST; 3-s eccentric, 3-s concentric, and 1-s isometric actions with no rest between repetitions) or normal speed (LN; 1-s concentric and 1-s eccentric actions with 1-s rests between repetitions) twice a week for 12 wk (2-wk preparation and 10-wk intervention). The LST significantly increased thigh-muscle thickness, as well as isometric knee-extension and -flexion strength. The LN significantly improved strength, but its hypertrophic effect was limited. These results indicate that even for older individuals, the LST can be an effective method for gaining muscle mass and strength.

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Madoka Ogawa, Naotoshi Mitsukawa, Michael G. Bemben and Takashi Abe

Context:

Previous studies investigated the relationship between ultrasound-derived anatomical muscle thickness (MTH) and individual muscle cross-sectional area (CSA) and muscle volume in several limb and trunk muscles; however, the adductor muscle that contributes to hip adduction and pelvic stabilization, as well as balance ability, has not been studied.

Objective:

To examine the relationship between MTH of the lower, middle, and upper thigh measured by B-mode ultrasound and the muscle CSA and volume of adductor muscle obtained by magnetic resonance imaging (MRI) to confirm the possibility of predicting adductor muscle CSA/volume using ultrasound-derived MTH.

Setting:

University research laboratory.

Subjects:

10 men and 10 women (20–41 y old) volunteered to participate in this study.

Main Outcome Measures:

A series of continuous muscle CSAs along the thigh were measured by MRI scans (1.5-T scanner, GE Signa). In each slice, the anatomical CSA of the adductors was analyzed, and the muscle volume was calculated by multiplying muscle CSA by slice thickness. Thigh MTH was measured by B-mode ultrasound (Aloka SSD-500) at 5 sites (anterior 30%, 50%, and 70% and posterior 50% and 70% of thigh length).

Results:

A strong correlation was observed between anterior 30% MTH and 30% adductor CSA in men (r = .845, P < .002) and women (r = .952, P < .001) and in both groups combined (r = .922, P < .001). Anterior 30% MTH was also strongly correlated to adductor muscle volume when combined with thigh length (n = 20, r = .949, P < .001). However, there were moderate or nonsignificant correlations between anterior and posterior 50% and 70% MTH and adductor muscle CSA/volume.

Conclusions:

The results suggest that MTH in the upper portion of anterior thigh best reflects adductor muscle CSA or muscle volume, while the lower portions of the anterior and posterior sites are least likely to predict adductor muscle size.

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Wayne W. Campbell, Lyndon J.O. Joseph, Richard A. Anderson, Stephanie L. Davey, Jeremy Hinton and William J. Evans

This study assessed the effect of resistive training (RT), with or without high-dose chromium picolinate (Cr-pic) supplementation, on body composition and skeletal muscle size of older women. Seventeen sedentary women, age range 54-71 years. BMI 28.8±2.4 kg/m2. were randomly assigned (double-blind) to groups (Cr-pic. n = 9; Placebo, n = 8) that consumed either 924 μg Cr/d as Cr-pic or a low-Cr placebo (<0.2 μg Cr/d) during a 12-week RT program (2 day/ week, 3 sets · exercise−1 · d1,80% of 1 repetition maximum). Urinary chromium excretion was 60-fold higher in the Cr-pic group, compared to the Placebo group (p < .001), during the intervention. Resistive training increased maximal strength of the muscle groups trained by 8 to 34% (p < .001), and these responses were not influenced by Cr-pic supplementation. Percent body fat and fat-free mass were unchanged with RT in these weight-stable women, independent of Cr-pic supplementation. Type I and type II muscle fiber areas of the m. vastus lateralis were not changed over time and were not influenced by Cr-pic supplementation. These data demonstrate that high-dose Cr-pic supplementation did not increase maximal strength above that of resistive training alone in older women. Further, these data show that, under these experimental conditions, whole body composition and skeletal muscle size were not significantly changed due to resistive training and were not influenced by supplemental chromium picolinate.

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Alon Eliakim, Mark Y. Moromisato, David Y. Moromisato and Dan M. Cooper

In this study, the hypothesis that improvements in functional and structural measures could be detected in the young, female rat with only 5 days of moderate treadmill training was tested. Eight-week-old female Sprague-Dawley rats were divided randomly into control (n = 10) and training groups (n = 11). Over the 5-day period, running duration and treadmill speed increased progressively. Maximal running time and gas exchange were measured on Day 6. In trained compared with control rats, maximal running time was 54% greater (p < .005), right hindlimb muscle was 16% heavier (p < .01), and end-exercise respiratory exchange ratio (RER) was 17% lower (p < .05). Substantial metabolic and structural adaptations occurred in young female rats after only 5 days of treadmill training. This protocol may be useful in discovering the initiating mechanisms of the training response in the young organism.

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Louise E. Wood, Sharon Dixon, Chris Grant and Neil Armstrong

The aim of this study was to examine elbow flexion torque, muscle cross-sectional area (CSA), and leverage in boys and girls. Thirty-eight prepubertal children (9.6 ± 0.3 years) volunteered to participate. All performed isometric flexion actions at 10°, 50°, and 90° of elbow flexion. Magnetic resonance imaging was used to assess elbow flexor (EF) muscle CSA and brachialis moment arm lengths. No significant gender differences were observed for any of the variables studied. EF CSA was directly proportional to isometric torque at 50° and 90°. CSA explained between 47% and 57% of torque variance. Moment arm estimates explained 19% of the variance in isometric torque at 90°. These baseline data contribute to our understanding of factors influencing strength variation during childhood.

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Leila Ghamkhar, Somayeh Amiri Arimi and Amir H. Kahlaee

increased JRE, smaller extensor muscles size, and reduced extensor endurance in comparison with the control group and (2) JRE, extensor muscles size, and cervical endurance are associated with the chronic nonspecific NP odds ratio. Methods Participants A total of 60 subjects aged 20–55 years volunteered to

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Conall F. Murtagh, Christopher Nulty, Jos Vanrenterghem, Andrew O’Boyle, Ryland Morgans, Barry Drust and Robert M. Erskine

. Therefore, the present soccer talent selection models are limited. Subsequently, the aims of this study were to (1) investigate the differences in muscle strength, size, architecture, and activation between elite and nonelite soccer players and (2) determine the contribution of muscle size, architecture

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Robert S. Thiebaud, Takashi Abe, Jeremy P. Loenneke, Tyler Garcia, Yohan Shirazi and Ross McArthur

Muscle strength and size are associated with various indicators of overall health and well-being. 1 A practical solution to developing strength and muscle size in individuals who may not be able to lift heavy loads is known as “blood flow restriction (BFR)” or “vascular occlusion” exercise. This

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Kevin R. Short and K. Sreekumaran Nair

Loss of muscle mass, strength, and oxidative capacity accompanies normal aging in humans. The mechanisms responsible for these changes remain to be clearly defined. Muscle protein mass and function depend on protein turnover. Synthesis rate of the major muscle contractile protein, myosin heavy chain (MHC), and transcript levels of fast MHC isoforms decrease in association with strength reductions, while mitochondrial protein synthesis rate declines in parallel with activities of mitochondrial enzymes and maximal oxidative capacity (V̇O2max). Resistance exercise training increases the synthesis rate of MHC and transcript levels of the slow MHC isoform in older humans, along with increasing muscle strength. The relationship between the synthesis of muscle proteins, and muscle size and function, with aging and exercise training are discussed in this review.