VO2 response profiles in severe intensity exercise.

Area of Science:

• Exercise Physiology
• Human Performance
• Cardiorespiratory Fitness

Background:

• Peak oxygen uptake (VO2peak) is a key indicator of cardiorespiratory fitness.
• The severe intensity domain is characterized by exercise intensities that elicit VO2peak.
• Understanding VO2 kinetics within this domain is crucial for performance.

Purpose of the Study:

• To characterize the oxygen uptake (VO2) response during constant-load exercise in the severe intensity domain.
• To investigate the influence of exercise intensity on VO2 kinetics and VO2peak attainment.
• To determine the relationship between work rate, time to fatigue, and VO2 response characteristics.

Main Methods:

• Participants (n=12) underwent cycle ergometer tests at three intensities selected to elicit VO2peak and cause fatigue at 3, 5, and 7 minutes.
• Work rates were individually determined (267±52 W, 238±45 W, 216±37 W).
• VO2 response was modeled using a three-component system.

Main Results:

• Times to fatigue were 201±16 s, 301±20 s, and 448±51 s for the respective intensities.
• VO2peak was reached faster at higher work rates (154±25 s at highest intensity).
• Primary response speed was intensity-independent (time constant ~23 s), but amplitude was greater at higher intensities; slow component amplitude decreased with intensity.

Conclusions:

• Faster VO2peak attainment at higher intensities is due to a greater primary response amplitude, not an increased response speed.
• A slow component of VO2 response is present across the severe domain.
• At extreme intensities, fatigue may occur before VO2peak is elicited, precluding a slow component.