The influence of physical activity on lean mass accrual during adolescence: a longitudinal analysis

Abstract

Baxter-Jones AD, Eisenmann JC, Mirwald RL, Faulkner RA, Bailey DA. The influence of physical activity on lean mass accrual during adolescence: a longitudinal analysis. J Appl Physiol 105: 734-741, 2008. First published May 8, 2008 doi:10.1152/japplphysiol.00869.2007.-During childhood, physical activity is likely the most important modifiable factor for the development of lean mass. However, the effects of normal growth and maturation must be controlled. To distinguish effects of physical activity from normal growth, longitudinal data are required. One hundred nine boys and one hundred thirteen girls, participating in the Saskatchewan Pediatric Bone Mineral Accrual Study, were repeatedly assessed for 6 yr. Age at entry was 8 -15 yr. Stature, body mass, and physical activity were assessed biannually. Body composition was assessed annually by dual-energy X-ray absorptiometry. Physical activity was determined using the physical activity questionnaires for children and adolescence. Biological age was defined as years from age of peak height velocity. Data were analyzed using multilevel random-effects models. In boys, it was found that physical activity had a significant time-dependent effect on lean mass accrual of the total body (484.7 Ϯ 157.1 g), arms (69.6 Ϯ 27.2 g), legs (197.7 Ϯ 60.5 g), and trunk (249.1 Ϯ 91.4 g) (P Ͻ 0.05). Although the physical activity effects were similar in the girls (total body: 306.9 Ϯ 96.6 g, arms: 31.4 Ϯ 15.5 g, legs: 162.9 Ϯ 40.0 g, and trunk: 119.6 Ϯ 58.2 g; P Ͻ 0.05), boys for the same level of activity accrued, depending on the site, between 21 and 120% more absolute lean mass (g). In conclusion, habitual physical activity had a significant independent influence on the growth of lean body mass during adolescence, once biological maturity and stature were controlled. growth and development; exercise; longitudinal studies SEVERAL FACTORS INFLUENCE the normal biological growth and maturation of the child and adolescent. Although genes, nutrients, and hormones are viewed as the chief determinants, the level of habitual physical activity (PA) is thought to be one of several ancillary factors contributing to the growth and maturation of body size and composition (11,51). Recently, concern has been expressed regarding the low levels of habitual PA and associated negative health outcomes among contemporary youth (49).Most of the previous studies examining the influence of PA on body composition of children and adolescents have focused on either adiposity (4) or bone accrual (2), given the concern of obesity and osteoporosis, respectively. In contrast, few studies have considered the influence of PA on lean body mass (LBM) in children and/or adolescents. LBM is often considered a surrogate for skeletal muscle mass, which is an important predictor of several physiological capacities expressed in absolute terms (e.g., maximal oxygen uptake, neuromuscular strength, anaerobic capacity, etc.) (1, 54) and health indicators (e.g., bone mass, insulin resistance, and obesity) (18,56). Previous stud...

Association of physical activity with muscular strength and fat-free mass in adolescents: the HELENA study

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Do neuromuscular adaptations occur in endurance-trained boys and men?

“…In adults, both morphological and neurological adaptations explain the increase in strength (Aagaard 2003;Aagaard et al 2002). In children, recent studies demonstrate that increased general physical activity (12 months to 6 years) results in enhanced total lean body mass (Baxter-Jones et al 2008;Stenevi-Lundgren et al 2009). However, resistance training (up to 20 weeks) has not been shown to result in muscle hypertrophy.…”

Postexercise protein ingestion increases whole body net protein balance in healthy children

“…protein synthesis; lean body mass; youth; physical activity; protein requirements PHYSICAL ACTIVITY is an essential component for the optimal growth and development of the musculoskeletal system in children. Greater levels of physical activity, especially those which are weight bearing and of higher intensity, have been associated with higher bone mineral density, lean mass, and strength in children (5,18,43). The net gain in lean mass with physical activity would require alterations in whole body protein turnover that would favor the net synthesis of body proteins, or, in other words, protein synthesis would be chronically elevated above protein breakdown.…”