Critical power is not attained at the end of an isokinetic 90-second all-out test in children

The purpose of this study was to establish whether critical power, as traditionally determined from the performance of three constant-load tests to exhaustion, is attained at the end of a 90-s all-out test in children. Sixteen healthy children (eight males and eight females; mean age 12.3 years, sx=0.1; body mass 39.6kg, sx=1.8; peak VO2 2.0 litresmin-1, sx=0.1) completed an incremental test to exhaustion to determine peak oxygen uptake (peak VO2), three separate constant-load tests to exhaustion to calculate critical power, and an isokinetic 90-s all-out test. The end power of the 90-s test averaged over the last 10s (140W, sx=8) was significantly higher than critical power (105W, sx=6; t=6.8; P0.01), yet the two parameters were strongly correlated (r=0.74; P0.01). After 60s, there were no further reductions in power output during the 90-s test (P0.0001). In conclusion, at the end of a 90-s all-out test, children are able to produce power outputs well above critical power. This suggests that 90s is not long enough to completely exhaust the anaerobic work capacity in children.