Effect of arm cranking on the NIRS-determined blood volume and oxygenation of human inactive and exercising vastus lateralis muscle

Abstract.

In this study, the effects of arm cranking on total (HbT) and oxygenated haemoglobin concentrations (HbO₂) of inactive and exercising vastus lateralis muscles were investigated using near-infrared spectrometry (NIRS). Four exercise protocols were performed, 6-min arm cranking at intensities of 30% and 50% of peak oxygen uptake ($\dot V{\rm O}_{{\rm 2peak}}$ , recorded during incremental arm exercise; AE₃₀ and AE₅₀, respectively), and 6 min of combined exercise in which AE₃₀ or AE₅₀ was added to on-going leg cycling at an intensity of 40% $\dot V{\rm O}_{{\rm 2peak}}$ (LE₄₀: AE₃₀LE₄₀ and AE₅₀LE₄₀, respectively). During AE₃₀ in the inactive vastus lateralis, neither HbT nor HbO₂ changed from the control values, whereas they both decreased during AE₅₀. The decrease in HbT was observed from the 1st to the 5th min of exercise, whereas the decrease in HbO₂ was observed from the 3rd to the 6th min of exercise. In the exercising vastus lateralis, neither HbT nor HbO₂ changed from the control value during AE₃₀LE₄₀. In addition, HbO₂ did not change during AE₅₀LE₄₀. During AE₅₀LE₄₀, however, although HbT did not change from the 1st to the 4th min of exercise, it increased from the 4th to the 6th min. These results indicate that although in the inactive vastus lateralis both HbT and HbO₂ decrease during moderate arm exercise, these decreases are suppressed in the exercising vastus lateralis muscle.