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

<p><b><i>Aim:</i></b>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. <i>High Alt Med Biol.</i> 21:370–377, 2020.</p> <p><b><i>Materials and Methods:</i></b> Eighteen cyclists (<i>V̇</i>O_2peak: 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%, <i>n</i> = 9) or interval training in normoxia (NORM; FiO₂ = 20.6% ± 0.3%, <i>n</i> = 9). Cyclists completed twice weekly interval training (8 × 1 minutes: ∼120% <i>V̇</i>O_2peak, 5 minutes recovery: ∼50% <i>V̇</i>O_2peak) 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.</p> <p><b><i>Results:</i></b> 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 VO_2peak was unchanged (IHT: 1% ± 6%; NORM: 1% ± 4%). However, within-group analysis shows that supramaximal work performed improved with IHT (14% ± 13%; <i>p</i> = 0.02; <i>d</i> = 0.42) but not NORM (1% ± 22%), and peak aerobic power output increased with IHT (5% ± 7%; <i>p</i> = 0.04; <i>d</i> = 0.32) but not NORM (2% ± 4%).</p> <p><b><i>Conclusion:</i></b> 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.</p>