RELATIVE CONTRIBUTION OF PHYSICAL-ACTIVITY TO NEONATAL OXYGEN-CONSUMPTION

To explore the relevance of distinguishing between resting and global energy expenditure in newborn infants, oxygen consumption (Vo2) was me asured during extremes of physical activity in 17 parenterally fed new born infants with a large range of body weights (1.0-3.4 kg) and gesta tional ages (28-41 weeks). Under constant nutrient intakes, each infan t served as his/her own control when comparing VO2 during resting cond itions and spontaneous intense physical activity, called exercise. VO2 was significantly correlated with body weight at rest (r = 0.96). But during intense activity, the better predictor of exercise-induced Vo2 was body weight in the smaller infants (< 2.0 kg) and gestational age in the larger infants (> 35 weeks). The difference in Vo2 between bot h levels of activity represented the oxygen cost of exercise, which de creased (P < 0.01) with body weight. For clinical purposes, the physic al activity of low-birth-weight infants does not contribute substantia lly to their energy balance.