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Educating the Student Body
energy expenditure. Resistance training may be particularly useful for rais-
ing metabolic rate in overweight and obese children without the risk associ-
ated with higher-impact activities (Watts et al., 2005; Benson et al., 2007).
Flexibility Flexibility has been operationally defined as “the intrinsic 
property of body tissues, including muscle and connective tissues, that 
determines the range of motion achievable without injury at a joint or 
group of joints” (IOM, 2012b, p. 190). At all ages, girls demonstrate 
greater flexibility than boys, and the difference is greatest during the adoles-
cent growth spurt and sexual maturation. Perhaps the most common field 
measure of flexibility in children and youth is the sit-and-reach test (IOM, 
2012b) of low-back flexibility. Low-back flexibility as measured by this 
test is stable in girls from age 5 to 11 and increases until late adolescence. 
In boys, low-back flexibility declines linearly starting at age 5, reaching its 
nadir at about age 12, and then increases into late adolescence. The unique 
pattern of age- and sex-associated variation is related to the growth of 
the lower extremities and the trunk during adolescence. In boys the nadir 
in low-back flexibility coincides with the adolescent growth spurt in leg 
length. In both boys and girls, the increase during adolescence coincides 
with the growth spurt in trunk length and arm length, which influences 
reach. Flexibility in both males and females tends to decline after age 17, in