Effects of high-intensity interval training on the VO2 response during severe exercise

This study examined the effect of high-intensity interval training on the VO2 response during severe, constant-load exercise. Prior to, and following training, 10 females (VO2peak 37.4 +/- 6.0 mL kg(-1) min(-1)) performed a graded exercise test to determine VO2peak and lactate threshold (LT) and a 6 min cycle test the pre-training VO2peak intensity. Training involved high-intensity intervals min work, 1 min rest) performed 3x week for 8 weeks. Breath-by-breath data from 0 to 6 min during the CT were smoothed using 5 s averages and fit to a biexponential model starting from 20 s. Training resulted in significant improvements in VO2max (2.34 +/- 0.37-2.78 +/- 0.30 L min(-1)), power at VO2max (170 +/- 26-204 +/- 25 W) and power at LT (113 +/- 17-136 +/- 20 W) (p < 0.05). Following training, the VO2 response showed a significant increase in the amplitude of the primary phase (A,) (1396 +/- 103-1695 +/- 100 mL min(-1); p < 0.05) and end-exercise VO2 (VO2EE), with no difference (p > 0.05) in the time constants of either phase or the amplitude of the slow component (318 +/- 67-380 +/- 48 mL; p = 0.15). In conjunction, accumulated oxygen deficit (AOD) (43.7 +/- 9.8-17.2 +/- 2.8 mL O-2 eq kg(-1)) and anaerobic contribution to the CT (19.4 +/- 4.4-7.2 +/- 1.2%) were significantly reduced. In contrast to previous moderate-intensity research, a high-intensity interval training program increased A, and VO2EE for the same absolute exercise intensity, decreasing the AOD during a severe-intensity CT (c) 2006 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.