Muscle Deoxygenation and Its Heterogeneity Changes After Endurance Training

Area of Science:

• Exercise Physiology
• Sports Science
• Muscle Physiology

Background:

• Endurance training enhances aerobic capacity (VO2peak).
• Understanding muscle oxygenation changes during training is crucial for optimizing performance.
• Near-infrared spectroscopy (NIRS) allows non-invasive assessment of muscle tissue oxygen saturation (SmO2).

Purpose of the Study:

• To investigate the time course of muscle deoxygenation and its heterogeneity during endurance training.
• To correlate changes in VO2peak with muscle oxygen saturation (SmO2) during exercise.

Main Methods:

• Nine healthy untrained males underwent 6 weeks of supervised endurance training.
• VO2peak and vastus lateralis muscle SmO2 were measured using ramp incremental cycle tests and multi-channel near-infrared spatially resolved spectroscopy before and after 3 and 6 weeks of training.
• Exercise was performed at 60% of VO2peak for 30 minutes, 3 times per week.

Main Results:

• VO2peak significantly increased after 3 and 6 weeks of training, with further gains at 6 weeks compared to 3 weeks.
• Mean SmO2 at VO2peak decreased significantly after 3 and 6 weeks of training compared to pre-training, but no significant difference was observed between 3 and 6 weeks.
• Muscle SmO2 heterogeneity during exercise did not change significantly with training.
• A negative correlation between changes in VO2 and SmO2 was observed after the first 3 weeks, but not after the subsequent 3 weeks.

Conclusions:

• Enhanced muscle oxygen availability appears to be a key factor in the initial improvements in VO2peak during the first 3 weeks of endurance training.
• The relationship between oxygen consumption and muscle deoxygenation shifts as training progresses.
• Further research is needed to fully understand the complex interplay between muscle oxygenation and aerobic adaptations to training.