Progressive changes in energy cost during a three-hour race-walk exercise

Area of Science:

• Exercise Physiology
• Sports Science
• Human Metabolism

Background:

• Understanding metabolic responses during prolonged, high-intensity exercise is crucial for athlete performance and recovery.
• Race walking at speeds of 11.6 km/hr for 3 hours represents a significant physiological challenge.

Purpose of the Study:

• To investigate the metabolic changes, specifically energy expenditure and substrate utilization, in experienced race walkers during extended exercise.
• To assess the utility of the Respiratory Quotient (RQ) as an indicator of recovery following prolonged, severe exercise.

Main Methods:

• Twenty experienced race walkers performed a 3-hour controlled walking exercise at 11.6 km/hr, alternating between treadmill and track.
• Expired air samples were analyzed at 30-minute intervals to determine average Respiratory Quotient (RQ) and energy expenditure.
• Energy cost was calculated in kJ/min and kJ/min/m².

Main Results:

• The Respiratory Quotient (RQ) decreased progressively from 0.92 to 0.66 over the 3-hour exercise period and remained low 30 minutes post-exercise.
• Mean energy expenditure increased from 46.2 to 55.4 kJ/min, and from 24.7 to 29.7 kJ/min/m².
• The observed RQ trend suggests a shift towards increased fat utilization to meet metabolic demands.

Conclusions:

• Experienced race walkers exhibit elevated aerobic activity and increased reliance on fat metabolism during prolonged, high-intensity exercise.
• The Respiratory Quotient (RQ) shows potential as a valuable indicator for assessing recovery status after severe, long-duration exercise bouts.