Children's metabolic expenditure during object projection skill performance: new insight for activity intensity relativity

Objective: To examine children’s energy expenditure (EE) during object projection skill performance at three intensity intervals. Methods: Children’s (42, Mage = 8.1) average metabolic equivalents of task (METs) were calculated using a COSMED K4b2 while they repeatedly performed blocks of kicking, throwing (overhand), and striking (two-handed) during 6, 12, and 30-s interval conditions. A repeated-measures analysis of covariance examined differences in METs while controlling for skill level. Results: Data indicated a main effect for interval condition (df = 2, 123, F = 94.36, p <.001, η2 =.605). Post hoc t-tests demonstrated decreasing performance interval times yielded progressively higher METs (p <.001) across the three conditions (30s = 4.5±0.8 METs, 12s = 6.3±1.3, 6s = 8.3±1.6). There also was a main effect for sex (df = 1,120, F = 52.28, p <.001 η2 =.305). Boys demonstrated higher METs at each performance interval (p <.001). Conclusion: Skill practice with a maximum of one trial every 30s resulted in the equivalent of at least moderate physical activity (>4.0 METs) and intervals of 6s demonstrated vigorous physical activity (>7.0 METs). Practicing/performing object projection skills, even at intervals that allow for adequate instruction and feedback (i.e., 1 trial/30s), promotes MVPA in children.