Effect of intermittent sub-maximal exercise on percent body fat using leg-to-leg bioelectrical impedance analysis in children

The purpose of this investigation was to determine the effect of intermittent sub-maximal exercise on percent body fat (%BF) estimated by leg-to-leg bioelectrical impedance analysis (LBIA) in children. Fifty-nine children (29 girls; 30 boys) mean age 9.0 +/- 1.3 years participated in this study. LBIA measured %BF values were obtained immediately before and within five minutes after completing an intermittent exercise protocol consisting of three 8-minute sub-maximal exercise bouts (2.74 km(.)hr(-1), 0% grade; 4.03 km(.)hr(-1), 0% grade; and 5.47 km(.)hr(-1), 0% grade) each separated by a 5-min seated rest period. The three exercise bouts corresponded to 56%, 61% and 71% of maximal heart rate. Significant differences (p < 0.001) were observed for fat mass, fat free mass, total body water, and body weight, post-exercise in both groups. Significant reductions (p < 0.001) in %BF were observed post-exercise in the female (23.1 +/- 9.9 vs. 21.8 +/- 9.9%) and male (23.3 +/- 10.5 vs. 21.8 +/- 10.2%) children when compared to pre-exercise values. However, for the majority of the subjects (females = 86%; males = 73%) the decrease in %BF post-exercise was less than 2.0 %BF. These data indicate that sub-maximal intermittent exercise, that may be representative of daily free-form activities in children, will most likely have a limited impact on %BF estimates when the assessment is performed immediately post-exercise.