Muscle and cerebral oxygenation during exercise performance after short-term respiratory work

The purpose of the study was to investigate the effect of 30-min voluntary hyperpnoea on cerebral, respiratory and leg muscle balance between O2 delivery and utilization during a subsequent constant-power test. Eight males performed a V˙O2max test, and two exercise tests at 85% of peak power output: (a) a control constant-power test (CPT), and (b) a constant-power test after a respiratory maneuver (CPTRM). Oxygenated (Δ[O2Hb]), deoxygenated (Δ[HHb]) and total (Δ[tHb]) hemoglobin in cerebral, intercostal and vastus lateralis were monitored with near-infrared spectroscopy. The performance time dropped ∼15% in CPTRM (6:55 ± 2:52 min) compared to CPT (8:03 ± 2:33 min), but the difference was not statistically significant. The vastus lateralis and intercostal Δ[tHb] and Δ[HHb] were lower in CPTRM than in CPT (P ≤ 0.05). There were no differences in cerebral oxygenation between the trials. Thus, respiratory work prior to an exercise test influences the oxygenation during exercise in the leg and respiratory muscles, but not in the frontal cortex.