High-intensity Interval Training in the Boundaries of the Severe Domain: Effects on Sprint and Endurance Performance

In order to compare the effects of two 4-week interval training programs performed at the lower (Critical Power, CP) or at the higher (The highest intensity at which V˙O₂max is attained, I_HIGH) intensities of the severe exercise domain on sprint and endurance cycling performance, 21 recreationally trained cyclists performed the Wingate Anaerobic Test (WAnT) and a 250-kJ time trial. Accumulated oxygen deficit (AOD), surface electromyography (RMS), and blood lactate kinetics were measured during the WAnT. Subjects were assigned to 105% CP or I_HIGH groups. During the WAnT, significantly greater improvements in peak (Mean ±95%CI) (5.7±2.3% vs. 0.2±2.2%), mean power output (MPO) (3.7±2.0% vs. 0.5±1.8%), and RMS (17.8±7.4% vs. -15.7±7.9%) were observed in the I_HIGH group (P<0.05). Higher and lower AOD, respectively, at the start and during the second half of the WAnT were observed after I_HIGH training. The changes in RMS and MPO induced by the training were significantly correlated (r=0.584). The 2 interventions induced improvements in the 250-kJ time trial. In conclusion, although the improvements in endurance performance were similar, training at I_HIGH led to higher gains in WAnT performance than training at 105%CP.