Characterization of the cortisol response to incremental exercise in physically active young men

Area of Science:

• Exercise Physiology
• Endocrinology
• Sports Science

Background:

• Cortisol, a stress hormone, plays a role in the body's response to physical exertion.
• The relationship between cortisol levels and exercise intensity, particularly at lower intensities, requires further clarification.
• Previous understanding suggested a linear correlation between cortisol response and exercise workload.

Purpose of the Study:

• To investigate the cortisol response to low-intensity incremental exercise.
• To determine if blood cortisol levels increase at exercise intensities below 60% of peak oxygen uptake (VO2).
• To ascertain whether the cortisol response to increasing exercise workloads is linear or follows a different pattern.

Main Methods:

• Healthy, physically active young men (n=11) underwent incremental exercise tests.
• Exercise involved progressive 3-minute workload stages to determine peak VO2.
• Blood samples were collected at rest and after each stage for cortisol analysis.

Main Results:

• Cortisol levels significantly increased from resting levels at the first exercise stage (80 W; 41.9% peak VO2).
• Cortisol remained elevated throughout the exercise, with further significant increases during the final two stages (exceeding lactate threshold).
• A sigmoidal (third-order polynomial) curve, rather than a linear model, best characterized the cortisol response to incremental exercise.

Conclusions:

• Low-intensity exercise (<60% peak VO2) demonstrably provokes a significant increase in blood cortisol levels.
• The cortisol response to incremental exercise is not strictly linear but is better described by a sigmoidal relationship.
• These findings challenge the notion that only high-intensity exercise significantly impacts cortisol levels.