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, s(x) = 0.1; body mass 39.6 kg, s(x) = 1.8; peak VO(2) 2.0 litres . min(-1), s(x) = 0.1) completed an incremental test to exhaustion to determine peak oxygen uptake (peak VO(2)), 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 10 s (140 W, s(x) = 8) was significantly higher than critical power (105 W, s(x) = 6; t = 6.8; P < 0.01), yet the two parameters were strongly correlated (r = 0.74; P < 0.01). After 60 s, there were no further reductions in power output during the 90-s test (P < 0.0001). 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 90 s is not long enough to completely exhaust the anaerobic work capacity in children.