It has been reported that exercise under hypoxic conditions induces reduced muscle oxygenation, which could be related to enhanced activity on electromyography (EMG). Although it has been demonstrated that exercise under conditions of voluntary hypoventilation (VH) evokes muscle deoxygenation, it is unclear whether VH during exercise impacts EMG. Seven men performed bicycle exercise for 5 min at 65 % of peak oxygen uptake with normal breathing (NB) and VH. Muscle oxygenation; concentration changes in oxyhemoglobin (Oxy-Hb), deoxyhemoglobin (Deoxy-Hb) and total hemoglobin (Total-Hb); and surface EMG in the vastus lateralis muscle were simultaneously measured. In the VH condition, Oxy-Hb was significantly lower and Deoxy-Hb was significantly higher compared to those in the NB condition (P < 0.05 for both), whereas there was no significant difference in Total-Hb between the two conditions. We observed significantly higher values (P < 0.05) on integrated EMG during exercise under VH conditions compared to those under NB conditions. This study suggests that VH during exercise augments EMG activity.

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In sports sciences, blood lactate is commonly measured for performance testing or setting exercise intensity. Differences in measuring lactate concentration over time and across sampling sites during constant exercise are unknown. We aimed to compare blood lactate concentration across sampling sites during constant exercise. Eight participants performed three bouts of 20-min steady-state cycle exercise, consisting of 45, 60, and 75% of peak oxygen uptake (V ． O 2peak). Blood lactate levels were measured simultaneously from the fingertip and earlobe every 5 min during exercise. The time course analysis revealed that lactate level in the fingertip was significantly higher than in the earlobe at either work intensity (P < 0.05). A significant interaction effect (site x time) was observed at 60% V ． O 2peak (P < 0.001), which indicated that the difference in samples across sampling sites decreased over time. The levels in the fingertip samples were higher at 5 min (P < 0.05); this difference was not noted after 10 min. Similarly, the fingertip values were significantly higher until 10 min (P < 0.05), but not after 15 min at 75% V ． O 2peak. These findings suggest that the sampling site may affect the time course of change in lactate value under a constant workload.

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