Association between muscle oxygenation dynamics and cardiac workload and ventilation during exercise.

BACKGROUND

Although high muscle oxygenation dynamics in active muscles are expected to decrease cardiac workload and ventilation associated with carbon dioxide excretion at an exercise at equivalent peak oxygen uptake (VO<inf>2</inf>) loads in the whole body, these relationships remain unclear. The aim of this study was to investigate whether high muscle oxygenation dynamics contribute to reduced cardiac workload and ventilation during exercise.

METHODS

Twenty-three healthy young males were enrolled in this cross-sectional study and divided into two groups: the low muscle oxygenation dynamics group (N.=11) and the high muscle oxygenation dynamics group (N.=12), based on the change in muscle oxygen saturation (SmO<inf>2</inf>) in the right vastus lateralis from rest to peak VO<inf>2</inf>. All participants underwent cardiopulmonary exercise testing to assess the double product, cardiac workload, carbon dioxide production (VCO<inf>2</inf>), and expiratory minute volume as ventilation parameters associated with carbon dioxide excretion.

RESULTS

Linear mixed-effect models with double product, VCO<inf>2</inf>/body mass or expiratory minute volume/body mass as the dependent variable, individual as random effects, and the group and metabolic equivalents (METs) as fixed effects revealed significant interactions between the group and METs (all P<0.001). Multiple comparison results demonstrated that the double product, VCO<inf>2</inf>/body mass at 5-8 METs, and expiratory minute volume/body mass at 6-8 METs were significantly lower in the group with high muscle oxygenation dynamics than in the group with low muscle oxygenation dynamics.

CONCLUSIONS

High muscle oxygenation dynamics contribute to reduced cardiac workload and ventilation associated with carbon dioxide excretion during exercise.