Increases in the incremental exercise mean response time across the steady state domain: Implications for exercise...

Area of Science:

• Exercise Physiology
• Cardiorespiratory Fitness

Background:

• Oxygen uptake (V̇O2) kinetics reflect the efficiency of cardiorespiratory adaptation to exercise.
• Understanding the mean response time (MRT) is crucial for assessing exercise tolerance and metabolic responses.

Purpose of the Study:

• To investigate if slowed oxygen uptake (V̇O2) kinetics during transitions to higher power outputs (PO) increase the mean response time (MRT) with increasing exercise intensity.
• To determine if a single incremental MRT (iMRT) exists or if it varies with exercise intensity.

Main Methods:

• Fourteen highly trained cyclists performed a ramp incremental cycling test and 6-min steady-state (SS) cycling bouts at 30%, 45%, 65%, and 75% of peak PO.
• MRT was calculated from SS trial data using mono-exponential and linear curve fitting.
• Incremental MRT (iMRT) was quantified by converting PO to time during the ramp test.

Main Results:

• Slope analyses revealed significant differences in V̇O2 responses between SS and incremental exercise below the gas exchange threshold (GET).
• Significant differences were observed in steady-state V̇O2 (ssV̇O2) and iMRT between 45% and 30% Wpeak.
• Specifically, ssV̇O2 was higher at 45% Wpeak compared to 30% Wpeak, and iMRT was longer for 45% Wpeak compared to 30% Wpeak.

Conclusions:

• The findings suggest that there is no single iMRT, as it varies with exercise intensity.
• This variability is consistent with slowed V̇O2 kinetics and an increasing V̇O2 deficit at higher exercise intensities within the steady-state domain.
• These results have implications for understanding exercise tolerance and metabolic responses in trained individuals.