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.
Serge Beliaeff, Danielle R. Bouchard, Christophe Hautier, Martin Brochu and Isabelle J. Dionne
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
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.
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.
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.
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.
Kosuke Kojima, Christopher L. Brammer, Tyler D. Sossong, Takashi Abe and Joel M. Stager
thickness at 9 sites of the body; Experience, competitive swimming experience; %Fat, percentage of body fat; MTT sum , sum of muscle tissue thickness at 9 sites; SMM, skeletal muscle mass. *Significant difference between weeks 0 and 11 ( P < .05). Anthropometric, Body Composition, and Muscle Size and Mass
Krissy D. Weisgarber, Darren G. Candow and Emelie S. M. Vogt
To determine the effects of whey protein before and during resistance exercise (RE) on body composition and strength in young adults.
Participants were randomized to ingest whey protein (PRO; 0.3 g/kg protein; n = 9, 24.58 ± 1.8 yr, 88.3 ± 17.1 kg, 172.5 ± 8.0 cm) or placebo (PLA; 0.2 g/kg cornstarch maltodextrin + 0.1 g/kg sucrose; n = 8, 23.6 ± 4.4 yr, 82.6 ± 16.1 kg, 169.4 ± 9.2 cm) during RE (3 sets of 6–10 repetitions for 9 whole-body exercises), which was performed 4 d/wk for 8 wk. PRO and PLA were mixed with water (600 ml); 50% of the solution containing 0.15 g/kg of PRO or PLA was consumed immediately before the start of exercise, and ~1.9% of the remaining solution containing ~0.006 g/kg of PRO or PLA was consumed immediately after each training set. Before and after the study, measures were taken for leantissue mass (dual-energy X-ray absorptiometry), muscle size of the elbow and knee flexors and extensors and ankle dorsiflexors and plantar flexors (ultrasound), and muscle strength (1-repetition-maximum chest press).
There was a significant increase (p < .05) in muscle size of the knee extensors (PRO 0.6 ± 0.4 cm, PLA 0.1 ± 0.5 cm), knee flexors (PRO 0.4 ± 0.6 cm, PLA 0.5 ± 0.7 cm) and ankle plantar flexors (PRO 0.6 ± 0.7 cm, PLA 0.8 ± 1.4 cm) and chest-press strength (PRO 16.6 ± 11.1 kg, PLA 9.1 ± 14.6 kg) over time, with no differences between groups.
The ingestion of whey protein immediately before the start of exercise and again after each training set has no effect on muscle mass and strength in untrained young adults.
Øyvind Sandbakk, Guro Strøm Solli and Hans-Christer Holmberg
differences in the established sexual dimorphisms in skeletal-muscle mass and potential for producing metabolic power, more recent investigations have shown relatively steady sex differences in performance over the past couple of decades. 4 – 6 Accordingly, an updated overview of sex differences in
Chantal A. Vella, Erin D. Michos, Dorothy D. Sears, Mary Cushman, Rachel B. Van Hollebeke, Michelle M. Wiest and Matthew A. Allison
, type 2 diabetes, functional disability, and premature death. 1 Skeletal muscle accounts for 40% of total body mass and is the main determinant of energy expenditure among sedentary individuals. Although regular physical activity is fundamental for preserving skeletal muscle mass, strength and function