Key result
The decrease in oxygenation in inactive arm muscle is closely coupled with an increase in the amount of hyperventilation during leg cycling (r = -0.72, p<0.001).
Decrease in oxygenation in inactive arm muscle during leg cycling is closely coupled with an increase in hyperventilation rather than a decrease in PaCO2.
May refine models of exercise hyperventilation; leaves open clinical relevance and causal mechanisms in cardiopulmonary disease.
Inactive forearm muscle oxygenation has been reported to begin decreasing from the respiratory compensation point (RCP) during ramp leg cycling. From the RCP, hyperventilation occurs with a decrease in arterial CO2 pressure (PaCO2). The aim of this study was to determine which of these two factors, hyperventilation or decrease in PaCO2, is related to a decrease in inactive biceps brachii muscle oxygenation during leg cycling. Each subject (n = 7) performed a 6-min two-step leg cycling. The exercise intensity in the first step (3 min) was halfway between the ventilatory threshold and RCP (170+/-21 watts), while that in the second step (3 min) was halfway between the RCP and peak oxygen uptake (240+/-28 watts). The amount of hyperventilation and PaCO2 were calculated from gas parameters. The average cross correlation function in seven subjects between inactive muscle oxygenation and amount of hyperventilation showed a negative peak at the time shift of zero (r = -0.72, p<0.001), while that between inactive muscle oxygenation and calculated PaCO2 showed no peak near the time shift of zero. Thus, we concluded that decrease in oxygenation in inactive arm muscle is closely coupled with increase in the amount of hyperventilation.
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Ogata et al. (2007) studied Healthy (n=7). Two-step leg cycling exercise vs. Rest was evaluated on Cross correlation between inactive muscle oxygenation and amount of hyperventilation (r = -0.72, p=<0.001). The decrease in oxygenation in inactive arm muscle is closely coupled with an increase in the amount of hyperventilation during leg cycling (r = -0.72, p<0.001).
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