Critical velocity during continuous and intermittent exercises in children

The purpose of this study was to apply the "critical velocity" concept to short intermittent high-intensity running exercises in prepubescent girls and boys, and to compare running performances obtained either by intermittent or continuous exercise runs. Eleven 8 to 11-year- old children underwent a maximal graded field test to determine peak oxygen uptake (peakVO2) and maximal aerobic velocity (MAV). During the six following sessions, they randomly performed three continuous runs (90%, 100%, and 110% of MAV) and three intermittent runs (120%, 130%, and 140% of MAV) until exhaustion. Intermittent exercises consisted of repeated 15-s runs each one separated by a 15-s passive recovery interval. For continuous as well as for intermittent exercises, distance versus time to exhaustion (TTE) relationships were calculated to determine continuous (CVc) and intermittent (CVi) critical-1 -1 -1 velocities. Values for peakVO2, and MAV were 45.8±5.3 ml.kg .min and 10.5±1.0 km.h ,respectively. For the whole population, a significant relationship was found between distance to exhaustion and TTE for continuous (r2=0.99, p<0.05) and intermittent exercises (r2=0.99, p<0.05). Significant relationships were found between peakVO2 and both CVc (r2=0.60, p<0.01) and CVi (r2=0.47, p