VO2 responses to running speeds above VO2max

Area of Science:

• Exercise Physiology
• Sports Science
• Cardiovascular Response

Background:

• Understanding physiological responses to high-intensity running is crucial for optimizing training in middle-distance runners.
• The relationship between exercise intensity above VO2max, cardiodynamic kinetics, and neuromuscular activity requires further investigation.

Purpose of the Study:

• To compare oxygen uptake (VO2), heart rate (HR), and electromyographic (iEMG) responses between 100% and 110% of the velocity associated with VO2max (v-VO2max).
• To examine the influence of running faster than v-VO2max on time to fatigue and cardiodynamic response kinetics.

Main Methods:

• Eight male middle-distance runners underwent a graded exercise test to determine VO2max and v-VO2max.
• Participants completed fatiguing runs at 100% and 110% v-VO2max.
• Continuous monitoring of VO2 and HR, with pre- and post-run lactate ([La (-)]) measurements and iEMG of rectus femoris and vastus lateralis.

Main Results:

• Time to fatigue was longer at 100% v-VO2max compared to 110% v-VO2max.
• No significant differences were found in VO2 or HR amplitudes, or post-run [La (-)] between conditions.
• Faster VO2 and HR response kinetics (tau values) were observed at 110% v-VO2max, with increased rectus femoris iEMG in the initial phase of the faster run.

Conclusions:

• Running at 110% v-VO2max elicits faster cardiodynamic responses compared to 100% v-VO2max, potentially due to increased muscle fiber recruitment.
• Despite faster kinetics, there was no significant difference in the amplitude of VO2 or HR, nor in time to fatigue, suggesting a decoupling between response speed and endurance at these intensities.
• The study highlights that while faster running speeds accelerate physiological adjustments, they do not necessarily enhance endurance performance or maximal oxygen utilization.