PHYSIOLOGICAL RESPONSES TO HIGH-INTENSITY INTERVAL EXERCISE DIFFERING IN INTERVAL DURATION

Tucker, WJ, Sawyer, BJ, Jarrett, CL, Bhammar, DM, and Gaesser, GA. Physiological responses to high- intensity interval exercise differing in interval duration. J Strength Cond Res 29( 12): 3326-3335, 2015-We determined the oxygen uptake ( VO2), heart rate ( HR), and blood lactate responses to 2 high- intensity interval exercise protocols differing in interval length. On separate days, 14 recreationally active males performed a 4 3 4 ( four 4-minute intervals at 90-95% HRpeak, separated by 3-minute recovery at 50 W) and 16 x 1 ( sixteen 1- minute intervals at 90-95% HRpeak, separated by 1- minute recovery at 50 W) protocol on a cycle ergometer. The 4 3 4 elicited a higher mean VO2 ( 2.44 +/- 0.4 vs. 2.36 +/- 0.4 L center dot min(-1)) and " peak" VO2 (90-99% vs. 7685% VO2peak) and HR ( 95-98% HRpeak vs. 81-95% HRpeak) during the high- intensity intervals. Average power maintained was higher for the 16 3 1 ( 241 6 45 vs. 204 6 37 W), and recovery interval VO2 and HR were higher during the 16 3 1. No differences were observed for blood lactate concentrations at the midpoint ( 12.1 +/- 2.2 vs. 10.8 +/- 3.1 mmol center dot L-1) and end ( 10.6 +/- 1.5 vs. 10.6 +/- 2.4 mmol center dot L-1) of the protocols or ratings of perceived exertion ( 7.0 +/- 1.6 vs. 7.0 +/- 1.4) and Physical Activity Enjoyment Scale scores ( 91 6 15 vs. 93 6 12). Despite a 4-fold difference in interval duration that produced greater between- interval transitions in VO2 and HR and slightly higher mean VO2 during the 4 x 4, mean HR during each protocol was the same, and b doth protocols were rated similarly for perceived exertion and enjoyment. The major difference was that power output had to be reduced during the 4 x 4 protocol to maintain the desired HR.