ABSENCE OF RESPIRATORY MUSCLE FATIGUE IN HIGH-INTENSITY CONTINUOUS OR INTERVAL CYCLING EXERCISE

Kurti, SP, Smith, JR, Emerson, SR, Castinado, KM, and Harms, CA. Absence of respiratory muscle fatigue in high-intensity continuous or interval cycling exercise. J Strength Cond Res 29(11): 3171-3176, 2015Respiratory muscle fatigue (RMF) occurs during prolonged exercise (approximate to 15-20 minutes) at >85% V.o(2)max. However, RMF has been reported to occur in approximate to 3-6 minutes in various modes of exercise at a high intensity. It is not known if continuous cycling exercise vs. repeated bouts of high-intensity interval training (HIT) at >85% V.o(2)max will lead to RMF. We hypothesized that RMF would occur after a constant load test and would be present before end exercise in an HIT protocol. Eight moderately active healthy men (21.7 +/- 1.7 years; 181.3 +/- 5.2 cm; 81.3 +/- 2.3 kg) completed a V.o(2)max test on a cycle ergometer. Subjects then completed 2 bouts of HIT (7 x 1 minute, 2-minute recovery between intervals) and 3 bouts of continuous exercise (CE) tests at 90% of peak power (determined from an incremental exercise test to exhaustion). Maximal inspiratory pressure (P-IMAX) and expiratory pressure (P-EMAX) were measured pre- and post-exercise for both HIT and CE and after each interval during HIT. Decreases in postexercise P-IMAX and P-EMAX compared with baseline were used to determine RMF. There were no differences (p > 0.05) in P-IMAX or P-EMAX pre- to post-exercise for HIT (P-IMAX pre: 134 +/- 51, post: 135 +/- 50 cmH(2)O; P-EMAX pre: 143 +/- 41, post: 148 +/- 46 cmH(2)O) or CE (P-IMAX pre: 135 +/- 54, post: 133 +/- 52 cmH(2)O; P-EMAX pre: 146 +/- 46, post: 148 +/- 46 cmH(2)O) indicating RMF was not present following CE and HIT. These data suggest that repeated high-intensity cycling exercise at 90% peak power in a CE or HIT protocol does not lead to RMF.