The Relationship between Inspiratory Muscle Strength and Cycling Performance: Insights from Hypoxia and Inspiratory Muscle Warm-Up.

Hypoxia increases inspiratory muscle work and consequently contributes to a reduction in exercise performance. We evaluate the effects of inspiratory muscle warm-up (IMW) on a 10 km cycling time trial in normoxia (NOR) and hypoxia (HYP). Eight cyclists performed four time trial sessions, two in HYP (FiO ₂ : 0.145) and two in NOR (FiO ₂ : 0.209), of which one was with IMW (set at 40% of maximal inspiratory pressure-MIP) and the other was with the placebo effect (PLA: set at 15% MIP). Time trials were unchanged by IMW (NOR _IMW : 893.8 ± 31.5 vs. NOR _PLA : 925.5 ± 51.0 s; HYP _IMW : 976.8 ± 34.2 vs. HYP _PLA : 1008.3 ± 56.0 s; p > 0.05), while ventilation was higher in HYP _IMW (107.7 ± 18.3) than HYP _PLA (100.1 ± 18.9 L.min ^-1 ; p ≤ 0.05), and SpO ₂ was lower (HYP _IMW : 73 ± 6 vs. HYP _PLA : 76 ± 6%; p ≤ 0.05). A post-exercise-induced reduction in inspiratory strength was correlated with exercise elapsed time during IMW sessions (HYP _IMW : r = -0.79; p ≤ 0.05; NOR _IMW : r = -0.70; p ≤ 0.05). IMW did not improve the 10 km time trial performance under normoxia and hypoxia.