Association between short sleeping hours and physical activity in boys playing ice hockey.

OBJECTIVES To determine physical activity in healthy boys and how physical activity relates to training and daily awake hours. STUDY DESIGN In 66 boys (5 to 15 years) affiliated with an ice-hockey club, we measured total daily energy expenditure (TDEE, doubly-labeled water) and basal metabolic rate (ventilated-hood method). Physical activity energy expenditure for the whole day (DAEE), during training, and during spontaneous physical activity was measured by accelerometry and activity protocols. Univariate (UA) and multivariate (MA) correlation analysis was applied. RESULTS Physical activity level, DAEE, and TDEE for prepubertal (2.0 and 2.2 Mcal/d) and pubertal (bone age >or=13 years; 1.8 and 2.8 Mcal/d) boys were matched to literature data from normal boys of equal age. In prepubertal boys DAEE correlated positively with awake hours (r(UA) = 0.55, r(MA) = 0.39, P < .01). In pubertal boys this correlation was not significant, the slopes between the 2 groups being significantly different (P = .025). In prepubertal boys spontaneous physical activity expenditure correlated significantly positively with training activity expenditure (r(UA) = 0.72, r(MA) = 0.52, P < .001). CONCLUSION Contrary to findings in adults, where short sleepers had lower physical activity and intensive training was negatively compensated reducing spontaneous physical activity, in physically active prepubertal boys, total daily and spontaneous physical activity relate positively to awake hours and training; suggesting child-specific control of physical activity.