Variability in protein consumption may influence muscle mass changes induced by resistance exercise training (RET). We sought to administer a post-exercise protein supplement and determine if daily protein intake variability affected variability in muscle mass gains. Men (N = 22) and women (N = 30) ranging in age from 60 to 69 y participated in a 12-wk RET program. At each RET session, participants consumed a post-exercise drink (0.4 g/kg lean mass protein). RET resulted in significant increases in lean mass (1.1 ±1.5 kg), similar between sexes (P > 0.05). Variability in mean daily protein intake was not associated with change in lean mass (r < 0.10, P > 0.05). The group with the highest protein intake (1.35 g · kg−1 · d−1, n = 8) had similar (P > 0.05) changes in lean mass as the group with the lowest daily protein intake (0.72 g · kg−1 · d−1, n = 9). These data suggest that variability in total daily protein intake does not affect variability in lean mass gains with RET in the context of post-exercise protein supplementation.
Ryan D. Andrews, David A. MacLean and Steven E. Riechman
Brittney Bernardoni, Tamara A. Scerpella, Paula F. Rosenbaum, Jill A. Kanaley, Lindsay N. Raab, Quefeng Li, Sijian Wang and Jodi N. Dowthwaite
We prospectively evaluated adolescent organized physical activity (PA) as a factor in adult female bone traits. Annual DXA scans accompanied semiannual records of anthropometry, maturity, and PA for 42 participants in this preliminary analysis (criteria: appropriately timed DXA scans at ~1 year premenarche [predictor] and ~5 years postmenarche [dependent variable]). Regression analysis evaluated total adolescent interscan PA and PA over 3 maturity subphases as predictors of young adult bone outcomes: 1) bone mineral content (BMC), geometry, and strength indices at nondominant distal radius and femoral neck; 2) subhead BMC; 3) lumbar spine BMC. Analyses accounted for baseline gynecological age (years pre- or postmenarche), baseline bone status, adult body size and interscan body size change. Gymnastics training was evaluated as a potentially independent predictor, but did not improve models for any outcomes (p < .07). Premenarcheal bone traits were strong predictors of most adult outcomes (semipartial r 2 = .21-0.59, p < .001). Adult 1/3 radius and subhead BMC were predicted by both total PA and PA 1-3 years postmenarche (p < .03). PA 3-5 years postmenarche predicted femoral narrow neck width, endosteal diameter, and buckling ratio (p < .05). Thus, participation in organized physical activity programs throughout middle and high school may reduce lifetime fracture risk in females.
Peter N. Wiebe, Cameron J. R. Blimkie, Nathalie Farpour-Lambert, Julie Briody, Damian Marsh, Allan Kemp, Chris Cowell and Robert Howman-Giles
Few studies have explored osteogenic potential of prepubertal populations. We conducted a 28-week school-based exercise trial of single-leg drop-landing exercise with 42 prepubertal girls (6 to 10 yrs) randomly assigned to control (C), low-drop (LD) or high-drop (HD) exercise groups. The latter two groups performed single-leg drop-landings (3 sessions/wk−1 and 50 landings/session−1) from 14cm(LD) and 28cm(HD) using the nondominant leg. Osteogenic responses were assessed using Dual Energy X-ray Absorptiometry (DXA). Single-leg peak ground-reaction impact forces (PGRIF) in a subsample ranged from 2.5 to 4.4 × body-weight (BW). No differences (p > .05) were observed among groups at baseline for age, stature, lean tissue mass (LTM), leisure time physical activity, or average daily calcium intake. After adjusting for covariates of body mass, fat mass and LTM, no differences were found in bone mineral measures or site-specific bone mineral density (BMD) at the hip and lower leg among exercise or control groups. Combining data from both exercise groups failed to produce differences in bone properties when compared with the control group. No changes were apparent for between-leg differences from baseline to posttraining. In contrast to some reports, our findings suggest that strictly controlled unimodal, unidirectional single-leg drop-landing exercises involving low-moderate peak ground-reaction impact forces are not osteogenic in the developing prepubertal female skeleton.
Lauren A. Burt, David A. Greene and Geraldine A. Naughton
QUS can provide structural information in addition to density ( 28 ), something that standard DXA analysis does not provide. With advancing 3-dimensional imaging modalities such as pQCT and HR-pQCT, examining peripheral skeletal sites closer to impact loading locations such as the wrist and ankle are
Ahmed Ismaeel, Michael Holmes, Evlampia Papoutsi, Lynn Panton and Panagiotis Koutakis
oxygen uptake or greater) or has an eccentric component like down-hill running ( Gomez-Cabrera et al., 2008 ). Generally, because of the extreme plasticity of skeletal muscle, the physiological stress applied through exercise induces adaptations that improve the muscle’s ability to cope with similar
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
Hellen C.G. Nabuco, Crisieli M. Tomeleri, Rodrigo R. Fernandes, Paulo Sugihara Junior, Edilaine F. Cavalcante, Danielle Venturini, Décio S. Barbosa, Analiza M. Silva, Luís B. Sardinha and Edilson S. Cyrino
kilograms divided by the square of the height in meters. Body Composition A spectral bioelectrical impedance device (Xitron Hydra; Xitron, San Diego, CA) was used to estimate the total body water, body fat (%), resistance ( R ), and reactance ( X c). The skeletal muscle mass (SMM) was estimated by the
Maria À. Cebrià i Iranzo, Mercè Balasch-Bernat, María Á. Tortosa-Chuliá and Sebastià Balasch-Parisi
even higher in Spain (37%) ( Salvà et al., 2016 ). The European Working Group on Sarcopenia in Older People (EWGSOP) defines this syndrome as a gradual and widespread loss of skeletal muscle mass and strength. As a result, mobility disorders appear, such as an increased risk of falls and fractures
Amy J. Hector and Stuart M. Phillips
accompanying loss of lean body mass (LBM) during caloric restriction that can comprise roughly 25% of the total weight lost ( Weinheimer et al., 2010 ). Lean body mass, a significant proportion of which is skeletal muscle, is critical for good metabolic function (i.e., site of postprandial glucose disposal
Andrew M. Holwerda, Freek G. Bouwman, Miranda Nabben, Ping Wang, Janneau van Kranenburg, Annemie P. Gijsen, Jatin G. Burniston, Edwin C.M. Mariman and Luc J.C. van Loon
Skeletal muscle adaptation is regulated by the balance between protein synthesis and protein breakdown rates. Muscle protein fractional synthesis rates (FSRs) can be determined by administration of stable isotope labeled amino acids and the subsequent measurement of their incorporation into muscle