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Chiharu Iwasaka, Tsubasa Mitsutake and Etsuo Horikawa

The loss of skeletal muscle mass in older adults is related to functional impairment, disability, and mortality ( Balogun et al., 2017 ; Baumgartner et al., 1998 ; Janssen, Heymsfield, & Ross, 2002 ). Evidence from sarcopenia-related research has increased, focusing on maintaining and improving

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Élvio R. Gouveia, Andreas Ihle, Bruna R. Gouveia, Matthias Kliegel, Adilson Marques and Duarte L. Freitas

between ankle MS and limits of stability. In spite of the ample evidence about the relationship between MS and balance, there is a paucity and inconsistency of evidence concerning the relationship between muscle mass (MM) and balance ( Bijlsma et al., 2013 ; Muehlbauer, Gollhofer, & Granacher, 2015

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Erik Sesbreno, Gary Slater, Margo Mountjoy and Stuart D.R. Galloway

model to estimate body composition ( Drinkwater & Ross, 1980 ). The Drinkwater four-way fractionation model uses the unisex phantom model to partition total body mass into four compartments—FM, skeletal muscle mass (SMM; intramuscular adipose tissue included), bone mass, and residual mass ( Drinkwater

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Alex S. Ribeiro, Ademar Avelar, Witalo Kassiano, João Pedro Nunes, Brad J. Schoenfeld, Andreo F. Aguiar, Michele C.C. Trindade, Analiza M. Silva, Luís B. Sardinha and Edilson S. Cyrino

Muscle hypertrophy is one of the main morphological adaptations resulting from resistance training (RT). Due to the trainability principle, trained individuals exhibit a lesser magnitude of gains in muscle mass than novice or detrained subjects ( Ahtiainen et al., 2003 ; Kraemer & Ratamess, 2004

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Serge Beliaeff, Danielle R. Bouchard, Christophe Hautier, Martin Brochu and Isabelle J. Dionne

This cross-sectional study examined the relationship between arm and leg muscle mass and isometric muscle strength in 465 well-functioning women and 439 well-functioning men from the NuAge cohort, age 67–84 years. Leg and arm muscle mass and body fat were measured by dual-X-ray absorptiometry. Maximum voluntary isometric strength of knee extensors and elbow flexors was measured using the belt-resisted method and a handheld dynamometer, respectively. The regression model including leg muscle mass, physical activity level, age, height, and body fat explained 14% of the variance in quadriceps strength in men and 11% in women (p < .001), whereas the model including arm muscle mass and the same covariates elucidated 40% and 28%, respectively, of the variance in biceps strength (p < .001). These results suggest that muscle mass does not play a crucial role in the variations of isometric muscle strength in well-functioning elderly.

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Paulo Sugihara Junior, Alex S. Ribeiro, Hellen C.G. Nabuco, Rodrigo R. Fernandes, Crisieli M. Tomeleri, Paolo M. Cunha, Danielle Venturini, Décio S. Barbosa, Brad J. Schoenfeld and Edilson S. Cyrino

Biological aging is associated with a progressive reduction in strength and skeletal muscle mass (SMM), a condition commonly known as sarcopenia, and these alterations show a negative correlation with health, quality of life, and survival in older women ( Brady et al., 2014 ; Clark & Manini, 2010

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Leonard S. Jefferson and Scot R. Kimball

Gain or loss of skeletal muscle mass is due largely to the establishment of an imbalance between rates of protein synthesis and degradation. A key determinant of the rate of protein synthesis is translation initiation, a process regulated in part through binding of initiator methionyl-tRNA (met-tRNAi) and messenger RNA (mRNA) to a 40S ribosomal subunit. Either the met-tRNAi or mRNA binding step can become limiting for protein synthesis. Furthermore, the mRNA binding step can modulate translation of specific mRNAs with or without changes in the overall rate of protein synthesis. This report highlights molecular mechanisms involved in mediating control of the mRNA binding step in translation initiation. Particular attention is given to the effect of exercise on this step and to how the branched-chain amino acid leucine stimulates muscle protein synthesis after exercise. Potential mechanisms for exercise induced increase in muscle mass are discussed.

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Terry J. Housh, Jeffrey R. Stout, Dona J. Housh and Glen O. Johnson

The purpose of this investigation was to examine the covariate influence of estimated muscle mass on age-related increases in isokinetic peak torque for flexion and extension of the forearm and leg in high school wrestlers. One hundred thirteen high school wrestlers volunteered to be measured for strength at 30, 180, and 300°·s−1. Underwater weighing was performed to determine body composition characteristics, and the anthropometric equation of Martin et al. (10) was used to estimate total skeletal muscle mass (MM). There were significant (p < .05) relationships (r = .19 to .37) for age versus peak torque covaried independently for fat-free weight (FFW) and MM for forearm flexion at 30, 180, and 300°·s−1; forearm extension at 180 and 300°·s−1; and leg extension at 30, 180 and 300°·s−1. The results of this study indicated that there was no increase across age in MM per unit of FFW, and the age-related increases in peak torque in high school wrestlers could not be fully accounted for by changes in MM.

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Janne Sallinen, Arto Pakarinen, Mikael Fogelholm, Elina Sillanpää, Markku Alen, Jeff S. Volek, William J. Kraemer and Keijo Häkkinen

This study examined the effects of strength training and diet on serum basal hormone concentrations and muscle mass in aging women. Fifty-one women age 49 to 74 y were divided into two groups: strength training and nutritional counseling (n = 25), and strength training (n = 26). Both groups performed strength training twice a week for 21 wk. Nutritional counseling was given to attain sufficient energy and protein intake and recommended intake of fat and fiber. We found that the cross-sectional area of the quadriceps femoris increased by 9.5 ± 4.1% in the nutritional counseling group versus 6.8 ± 3.5% in the strength training only group after training (P < 0.052). Nutritional counseling evoked dietary changes such as increases in the proportion of energy from protein and the ratio of poly-unsaturated and saturated fatty acids. Strength training increased testosterone and testosterone/sex hormone-binding globulin ratio after the first half of training, but these returned to baseline values at the end of the entire training period. Changes in serum basal hormone concentrations did not differ between the groups. Our results support the conclusion that nutritional counseling can contribute to the increase in the muscle cross-sectional area during prolonged strength training in aging women.

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Iñigo Mujika, Bent R. Rønnestad and David T. Martin

Despite early and ongoing debate among athletes, coaches, and sport scientists, it is likely that resistance training for endurance cyclists can be tolerated, promotes desired adaptations that support training, and can directly improve performance. Lower-body heavy strength training performed in addition to endurance-cycling training can improve both short- and long-term endurance performance. Strength-maintenance training is essential to retain strength gains during the competition season. Competitive female cyclists with greater lower-body lean mass (LBLM) tend to have ~4–9% higher maximum mean power per kg LBLM over 1 s to 10 min. Such relationships enable optimal body composition to be modeled. Resistance training off the bike may be particularly useful for modifying LBLM, whereas more cycling-specific training strategies like eccentric cycling and single-leg cycling with a counterweight have not been thoughtfully investigated in well-trained cyclists. Potential mechanisms for improved endurance include postponed activation of less efficient type II muscle fibers, conversion of type IIX fibers into more fatigue-resistant IIa fibers, and increased muscle mass and rate of force development.