Abstract
The aim of this study was to evaluate the impact on muscle strength, aerobic fitness and body composition, of replacing the physical education (PE) class of Colombian adolescents with resistance or aerobic training. 120 tanner stage 3 adolescents attending a state school were randomized to resistance training, aerobic training, or a control group who continued to attend a weekly 2- hour PE class for 16 weeks. The resistance training and aerobic training groups participated in twice weekly supervised after-school exercise sessions of < 1 hour instead of their PE class. Sum of skinfolds, lean body mass (bioelectrical impedance analysis), muscular strength (6 repetition maximum (RM)) bench press, lateral pulldown and leg press) and estimated cardiorespiratory fitness (multistage 20 meter shuttle run) were assessed at pre and post intervention. Complete data were available for n = 40 of the resistance training group, n = 40 of the aerobic training group and n = 30 PE (controls). Resistance training attenuated increases in sum of skinfolds compared with controls (d = 0.27, [0.09–0.36]). We found no significant effect on lean body mass. Resistance training produced a positive effect on muscle strength compared with both controls (d = 0.66 [.49-.86]) and aerobic training (d = 0.55[0.28–0.67]). There was a positive effect of resistance training on cardiorespiratory fitness compared with controls (d = 0.04 [-0.10–0.12]) but not compared with aerobic training (d = 0.24 [0.10–0.36]). Replacing a 2-hour PE class with two 1 hour resistance training sessions attenuated gains in subcutaneous adiposity, and enhanced muscle strength and aerobic fitness development in Colombian youth, based on a median attendance of approximately 1 session a week. Further research to assess whether adequate stimuli for the development of muscular fitness exists within current physical education provision is warranted.
Highlights
International guidelines recommend that youth should partake in at least 60 min of moderateto-vigorous physical activity each day incorporating three bouts of muscle strengthening activities [1]
We compared resistance training with a simultaneous isotemporal aerobic training program in order to control for the potential effect of supervision and isolate resistance training-specific effects
Resistance training led to similar improvement in cardiorespiratory fitness and attenuation of adiposity gains as that observed in the aerobic training group, but to greater strength development
Summary
International guidelines recommend that youth should partake in at least 60 min of moderateto-vigorous physical activity each day incorporating three bouts of muscle strengthening activities [1]. Strength activities are an intrinsic element of current physical activity guidelines for adults older adults and young people [1], based on growing evidence that muscular strength is associated with better cardiometabolic health throughout the lifecycle [2,3,4,5]. From a public health perspective, muscle strength is lower in adults living in low-middle income countries compared to high-income country populations [8]. This low-middle income country “strength deficit” appears to have its origins in earlier life as strength tracks from childhood [9] and lower birthweight, an indicator of poorer in uterine nutrition and more common in low-middle income countries, are associated with lower muscle strength throughout life [10]. We have reported that children in Colombia (a middle-income country), those from low-to-middle socio-economic households [11, 12], have lower muscle strength compared with that reported in high-income countries [13]
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