The influence of resistance training on the critical power function & time to fatigue at critical power

The present study examined whether a six-week resistance training program would influence the critical power (CP) function, time to exhaustion (TE) at CP and/or peak oxygen uptake (VO2 peak). The CP function is believed to provide an index of endurance ability (CP given by the slope), and anaerobic work capacity (the y-intercept). Eight healthy, untrained males undertook lower-body resistance training (90 min/day, 3-4 times/wk) for six weeks; eight controls refrained from resistance or endurance training for the same period. Before and immediately following the training period, subjects completed three trials to determine their CP function, a test of VO2 peak, a one-repetition maximum (1-RM) leg press test and TE at their CP. Training significantly increased both 1-RM leg press (28.6\%, P < 0.05) and the y-intercept (34.9\%, P < 0.05) while no changes in CP, VO2 peak or TE (p > 0.05) were found. Changes in the y-intercept following resistance training were negatively correlated with changes in the CP (r = -0.94, p < 0.05, N = 8). The present data show that the y-intercept of the CP function is sensitive to, and modified by, six weeks of resistance training. Given that resistance training had no significant influence on CP, TE at CP or VO2 peak, the present study has also shown that six weeks of resistance training will not alter indices of endurance ability. The negative relationship between changes in the y-intercept and CP exposes a potential limitation of the linear CP function when evaluating changes in endurance ability following an intervention which significantly alters the y-intercept.