Heterogeneity of Muscle Oxygen Consumption and Muscle Oxygenated Hemoglobin/Myoglobin Content in Thigh during Incremental Cycling Exercise

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The purpose of this study was to evaluate the heterogeneity of muscle oxygen consumption (VO2mus) and muscle oxygenated hemoglobin/myoglobin content (Hb/MbO2) in the right thigh during stepwise incremental cycling exercise in supine position. Subjects were five healthy male volunteers (30±2 yrs., height 175.0±1.9 cm, weight: 67.3±3.1 kg). Muscle oxygenation in the right thigh was measured using multi-channel near infrared continuous wave spectroscopy (multi-NIRcws). In order to reduce the influence of the hydrostatic pressure within multi-NIRcws measurement sites, the subjects performed the stepwise incremental cycling exercise while lying on a bed in a supine position. The exercise load was started at 30 watts and increased by 30 watts every 4 minutes until the subjects reached exhaustion. We evaluated VO2mus and Hb/MbO2 at rest and during each exercise load. VO2mus increased and Hb/MbO2 decreased with the increase exercise load in all measurement sites. VO2mus at high intensity exercise load was significantly larger in the proximal positions than in the distal positions (p<0.05). Hb/MbO2 showed no significant differences in all measurement sites at rest and during all exercise loads. These results indicated the heterogeneity of VO2mus and oxygen supply toward a longitudinal direction between proximal and distal positions at high intensity exercise load.