Effect of high-intensity interval training on the profile of muscle deoxygenation heterogeneity during incremental exercise

This study examines the effect of high-intensity interval training (HIT) on the spatial distribution of muscle deoxygenation during incremental exercise. Young untrained male adults (n = 11) performed an incremental bicycle exercise before and after a running HIT of 6 weeks. Muscle deoxygenation (HHb) and blood volume (Hb_tot) were monitored continuously by near-infrared spectroscopy at eight sites in the vastus lateralis. The rise in HHb during incremental exercise was significantly higher after training, in comparison with before training (P = 0.020), whereas the rise in Hb_tot was not affected by training. The standard deviation of HHb and the relative dispersion of HHb at the eight sites were not significantly different irrespective of the intensity of exercise between pre- and post-training. After training, the standard deviation of HHb was greater at 60, 70, and 80 % of \( \dot{V}{\text{O}}_{ 2} { \max } \) than at rest. Finally, training significantly increased the standard deviation of Hb_tot (P = 0.036). These results indicate that HIT changes the muscle deoxygenation profile during incremental exercise, suggesting an improvement in the O₂ extraction with training. HIT did not reduce the spatial heterogeneity of muscle deoxygenation and blood volume during incremental exercise. This indicates that the intra-muscular distribution of the VO₂/O₂ delivery ratio was not improved by 6 weeks HIT.