Critical Power (PCRIT) is the greatest power that a person can sustain for prolonged periods of time while maintaining steady-state, submaximal aerobic conditions. Work-prime (W’) is the amount of work that can be tolerated when exercising in non-steady-state conditions above PCRIT. PURPOSE: Compare the effect of equal amounts of moderate intensity continuous training (MICT) and high intensity interval training (HIIT) on PCRIT and W’. METHODS: Twenty-two (10 female) untrained, young adults completed 8 weeks of cycling training (40 minutes, 3x per week) administered as either MICT (44% max power achieved during a graded exercise test; PGXT) or HIIT (4 bouts at 80% PGXT for 4 minutes with recovery intervals between). PCRIT, W’ and other physiological variables were determined before and after training. RESULTS: PCRIT significantly increased in both groups, but to a greater extent in the HIIT group (MICT: 15.7 ± 3.1% vs. HIIT: 27.5 ± 4.3%; P=0.04). W’ was not consistently impacted by training (P=0.76). The training-induced change in PCRIT was not significantly related to the training-induced change in V̇O2MAX. The training-induced increase in PCRIT was related to how intense the training was relative to PCRIT, with those performing the same workout at a greater % PCRIT exhibiting greater training-induced increases in PCRIT (R2=0.49, PCONCLUSION: HIIT elicits approximately twice the increase in PCRIT than an equal amount of MICT in untrained young adults. Training-induced increases in PCRIT are not dependent upon changes in V̇O2MAX. Exercise may be more effectively prescribed and described relative to PCRIT, rather than V̇O2MAX or PGXT.



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