Effects of eight interval training sessions in hypoxia on anaerobic, aerobic, and high intensity work capacity in endurance cyclists

This study aimed to determine if eight sessions of supramaximal but steady-state, set duration interval training in hypoxia enhanced measured anaerobic capacity and work performed during high intensity exercise. Materials and Methods: Eighteen cyclists (V̇O2peak: 57 ± 7 ml·kg−1·min−1) were pair-matched for anaerobic capacity determined by maximal accumulated oxygen deficit (MAOD) and allocated to a 4-week interval training in hypoxia (IHT; FiO2 = 14.7% ± 0.5%, n = 9) or interval training in normoxia (NORM; FiO2 = 20.6% ± 0.3%, n = 9). Cyclists completed twice weekly interval training (8 × 1 minutes: ∼120% V̇O2peak, 5 minutes recovery: ∼50% V̇O2peak) in addition to their habitual training. Before and after the intervention, a constant work rate supramaximal time to fatigue and a graded exercise test were used to determine changes in anaerobic capacity/supramaximal work performed and aerobic capacity/peak aerobic power output, respectively. Results: No interaction or main effects were observed. Using indirect calorimetry, anaerobic capacity was not significantly different in either group pre- to postintervention using MAOD (IHT: 4% ± 15%; NORM: −5% ± 12%) or gross efficiency methods (IHT: 7% ± 14%; NORM: −2% ± 9%), and VO2peak was unchanged (IHT: 1% ± 6%; NORM: 1% ± 4%). However, within-group analysis shows that supramaximal work performed improved with IHT (14% ± 13%; p = 0.02; d = 0.42) but not NORM (1% ± 22%), and peak aerobic power output increased with IHT (5% ± 7%; p = 0.04; d = 0.32) but not NORM (2% ± 4%). Conclusion: Steady-state, set duration supramaximal interval training in hypoxia appears to provide a small beneficial effect on work capacity during supramaximal and high intensity exercise.