Effect of pedaling cadence on muscle oxygenation during high-intensity cycling until exhaustion: a comparison between untrained subjects and triathletes

Purpose: The aim of this study was to compare the muscle oxygenation between trained and untrained subjects during heavy exercise until exhaustion at two extreme pedaling cadences using a NIRS system. Methods: Nine untrained male subjects and nine male competitive triathletes cycled until exhaustion at an intensity corresponding to 90 % of the power output achieved at peak oxygen uptake at 40 and 100 rpm. Gas exchanges were measured breath-by-breath during each exercise. Muscle (de) oxygenation was monitored continuously by near-infrared spectroscopy on the Vastus Lateralis. Results: Muscle deoxygenation (Delta deoxy[Hb + Mb], i.e., O-2 extraction) and Delta total[Hb + Mb] were significantly higher at 40 rpm compared to 100 rpm during the exercise in untrained subjects but not in triathletes (p < 0.05). The time performed until exhaustion was significantly higher at 40 than at 100 rpm in untrained subjects (373 +/- 55 vs. 234 +/- 37 s, respectively) but not in triathletes (339 +/- 69 vs. 325 +/- 66 s). Conclusions: These results indicate that high aerobic fitness (1) allows for better regulation between (V) over dotO(2M) and (Q) over dot O-2M following the change in pedaling cadence, and (2) is the most important factor in the relationship between pedaling cadence and performance