Oxygen uptake kinetics in treadmill running and cycle ergometry: a comparison

Area of Science:

• Exercise Physiology
• Human Physiology
• Sports Science

Background:

• Understanding oxygen consumption (VO2) kinetics is crucial for assessing exercise efficiency.
• Previous research has explored VO2 responses, but direct comparisons between running and cycling under heavy exercise conditions require further investigation.

Purpose of the Study:

• To comprehensively examine oxygen consumption (VO2) kinetics during running and cycling.
• To compare VO2 responses between moderate and heavy exercise intensities using mathematical modeling.

Main Methods:

• Seven subjects underwent determination of lactate threshold (LT) and maximal oxygen consumption (VO2 max) for both running and cycling.
• Subjects performed "square-wave" rest-to-exercise transitions at intensities relative to LT and VO2 max.
• Breath-by-breath gas exchange data were analyzed using two- or three-phase exponential models.

Main Results:

• VO2 kinetic parameters were largely similar between running and cycling.
• A significantly greater VO2 slow component was observed in cycling compared to running at 50% and 75% of the delta between LT and VO2 max.
• Specific values for the VO2 slow component were 334 +/- 183 and 430 +/- 159 ml/min for cycling versus 205 +/- 84 and 302 +/- 154 ml/min for running at these intensities.

Conclusions:

• Differences in VO2 kinetics between cycling and running, particularly the VO2 slow component, may be attributed to variations in intramuscular tension and eccentric muscle action.
• These factors could lead to greater recruitment of less efficient type II muscle fibers during heavy cycling exercise.