Supra-maximal cycling efficiency assessed in humans by using a new protocol

Area of Science:

• Exercise Physiology
• Sports Science
• Biomechanics

Background:

• Assessing exercise efficiency is crucial for understanding human performance.
• Previous methods for calculating efficiency were limited to sub-maximal exercise intensities.
• Maximal aerobic power (MAP) represents a key threshold in exercise physiology.

Purpose of the Study:

• To propose and validate a non-invasive method for determining gross efficiency (GE), net efficiency (NE), and work efficiency (WE) during cycling.
• To investigate the relationship between these efficiency indices and power output, specifically at intensities above MAP.
• To confirm if efficiency-power output relationships observed at sub-maximal levels persist at supra-maximal intensities.

Main Methods:

• Twelve male subjects performed cycling protocols at 50%, 63%, and 130% of their MAP.
• Oxygen uptake was continuously measured throughout the exercise bouts.
• Gross efficiency (GE), net efficiency (NE), and work efficiency (WE) were calculated using different baseline correction methods.

Main Results:

• Gross efficiency (GE) and net efficiency (NE) increased with power output (P < 0.001).
• Work efficiency (WE) decreased with increasing power output (P < 0.001).
• Efficiency indices showed consistent relationships across sub-maximal and supra-maximal intensities.

Conclusions:

• The proposed non-invasive method accurately determines cycling efficiency at intensities exceeding MAP.
• Efficiency-power output relationships are maintained at supra-maximal exercise intensities.
• Findings support the extension of established efficiency models to higher exercise loads.