Power Reserve at Intolerance in Ramp-Incremental Exercise Is Dependent on Incrementation Rate

Area of Science:

• Exercise Physiology
• Human Performance

Background:

• Exercise intolerance at maximal oxygen uptake (V˙O2max) is not fully understood.
• Standard ramp-incremental (RI) exercise is limited by neuromuscular fatigue.
• It is unknown if slower RI rates alter fatigue mechanisms limiting exercise.

Purpose of the Study:

• To investigate the role of neuromuscular fatigue in exercise intolerance.
• To determine if slower RI rates change the limiting factors of exercise at V˙O2max.

Main Methods:

• Twelve healthy participants performed RI cycling at 50, 25, and 10 W·min-1.
• Maximal voluntary cycling power (Piso) was measured at baseline and exhaustion.
• Pulmonary gas exchange was measured to determine V˙O2peak.

Main Results:

• Tolerable exercise duration increased with slower RI rates.
• Peak power output decreased with slower RI rates.
• A "power reserve" (Piso > RI peak power) was absent at faster RI rates but present at the slowest rate (RI-10).

Conclusions:

• Neuromuscular fatigue limits exercise at faster RI rates (50 and 25 W·min-1) at V˙O2max.
• At slower RI rates (10 W·min-1), neuromuscular fatigue is insufficient to limit exercise, suggesting other factors contribute to intolerance.