Critical power in adolescents: physiological bases and assessment using all-out exercise

This study examined whether critical power (CP) in adolescents: (1) provides a landmark for maximal steady-state exercise; and (2) can be determined using ‘all-out’ exercise. Nine active 14–15 year olds (6 females, 3 males) performed five cycling tests: (1) a ramp test to determine \( \dot{V}{\text{O}}_{{2\,{\text{peak}}}} \); (2) up to four constant power output tests to determine CP; (3–4) constant power output exercise 10% above and 10% below CP; and (5) a 3 min all-out cycle test to establish the end power (EP) at 90 and 180 s of exercise. All participants completed 30 min of exercise below CP and were characterized by steady-state blood lactate and \( {\dot{V}\text{O}}_{2} \) profiles. In contrast, time to exhaustion during exercise above CP was 15.0 ± 7.0 min and characterized by an inexorable rise in blood lactate and a rise, stabilization (~91% \( {\dot{V}\text{O}}_{{2\,{\text{peak}}}} \)) and fall in \( {\dot{V}\text{O}}_{2} \) (~82% \( {\dot{V}\text{O}}_{{2\,{\text{peak}}}} \)) prior to exhaustion. Eight out of nine participants completed the 3 min test and their EPs at 90 s (148 ± 29 W) and 180 s (146 ± 30 W) were not different from CP (146 ± 27 W) (P = 0.98). The typical error of estimates for establishing CP using EP at 90 s or 180 s of the 3 min test were 25 W (19.7% CV) and 25 W (19.6% CV), respectively. CP in active adolescence provides a valid landmark for maximal steady-state exercise, although its estimation on an individual level using the 3 min all-out test may be of limited value.