et al., 2002; Naylor et al., 2008). Increases in handgrip strength were associated with reductions in systolic blood pressure in normal-weight boys and girls aged 10-15 (Janz et al., 2002), and gains in a combined measure of bench press and leg press strength were associated with improvements in systolic blood pressure and markers of heart function (i.e., peak transmitral velocity of flow, diastolic myocardial velocity, and left atrial pressure) in obese boys and girls aged 12-13 (Naylor et al., 2008). Likewise, only two studies examined the relationship between muscle strength and power measures and measures of mental/cognitive health. Velez and colleagues (2010) report a positive association between measures of upper-body (i.e., shoulder press), trunk (i.e., bench press, seated row), and lower-body (i.e., squat) strength and power and self-esteem in normal-weight and overweight/obese adolescent boys and girls aged 14-18, whereas Lubans and colleagues (2010) provide direct evidence of a link between bench press and leg press strength and physical self-worth in normal-weight boys and girls aged 14-15.
Resistance Training Programs and Health Outcomes
Paralleling the adult literature, there is growing acceptance that appropriately prescribed and administered resistance training programs can improve muscle strength, endurance, and power in youth (Blimkie and Bar-Or, 2008; Faigenbaum et al., 2009; Malina, 2006). However, the health-related risks and benefits of this type of training and the relationship between improvements in musculoskeletal fitness and changes in health outcomes have not been as systematically investigated for youth. Effective resistance training programs may (1) reduce the risk of joint injury in adolescent athletes, (2) improve body composition specifically among children and adolescents who are obese or at risk of obesity, (3) improve insulin sensitivity in both normal-weight peripubertal children and obese adolescents, (4) reduce blood pressure in hypertensive adolescents, and (5) improve blood lipid profiles in both children and adolescents (Blimkie, 1993; Faigenbaum et al., 2009). The relationship between resistance training and improvements in musculoskeletal fitness and bone health in youth are controversial, mainly because of the complex manner and time frame in which bone responds to physical activities. In addition to very high forces on bone, bone adaptation may be regulated by other parameters of the activity (e.g., the loading rate) and muscle mass (Beck, 2009). Based on the limited number of good prospective controlled experimental studies, the link between improved musculoskeletal fitness and bone health remains tenuous in youth. Also paralleling the adult literature, the relationship between improved musculoskeletal fitness following resistance training and psychological health outcomes in youth is relatively weak (Faigenbaum et al., 2009).