Abstract
Introduction: The VO2 excess (VO2e) observed after the ventilatory anaerobic threshold (VAT) has been considered as a consequence to an increase in respiratory muscles work during maximal incremental exercise (MIE).
Aims: to assess respiratory muscles performance (RMP) and their deoxyhemoglobin (HHb) kinetic performed by NIRS during MIE and thereafter to study the relationships between the VO2e, the HHb and the RMP.
Methods: Ten male cyclists performed a MIE on a cycle ergometer with maximal inspiratory (MIP) and expiratory (MEP) pressures measurement assessed both before and after MIE. The HHb kinetic was monitored by NIRS in the seventh intercostal space. The VO2e represent the difference between VO2max measured by portable gas analyzer (Cosmed K4b2) and VO2max calculated using linear equation before VAT (VO2= a x Power + b; at VO2max, Power = Maximal Aerobic Power (MAP)).
Results: MIP and MEP decrease respectively by 7.8% and 12.6% (p<0.01) after MIE. HHb remains unchanged from the start to 60% MAP, then increase significantly until the end (40 µM and 53 µM respectively between 60-80% and 80-100% MAP (p<0.05)). Above VAT, a correlation has been shown between HHb and VO2e (r=0.62, p<0.05). However, VO2e and the decline of RMP was not related.
Conclusions: The increase in work of respiratory muscles contributes to VO2e and might limit their performance during MIE. This result highlighted the importance of respiratory muscles training incorporation in rehabilitation protocols to improve independency and quality of life in cardiorespiratory patients.
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