Subjective thermal strain impairs endurance performance in a temperate environment

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Sports Science

Background:

• Endurance performance is often impaired in hot environments.
• Physiological strain, such as increased heart rate and body temperature, is typically associated with this decline.
• The role of subjective thermal perception as an independent factor has been less understood.

Purpose of the Study:

• To investigate if subjective thermal strain can reduce endurance performance independently of general physiological strain.
• To differentiate the effects of perceived heat discomfort from physiological heat stress on exercise capacity.

Main Methods:

• 12 endurance-trained athletes completed a time to exhaustion (TTE) cycling test at 70% VO2max.
• Two conditions were used: a heat pad (HP) to induce subjective thermal strain and a control (CON) condition.
• Cardiorespiratory, metabolic, thermoregulatory, and perceptual responses were measured.

Main Results:

• Time to exhaustion (TTE) was significantly reduced by 9% in the heat pad condition compared to control.
• Subjects reported significantly higher thermal discomfort and thermal sensation in the heat pad condition.
• No significant differences in measured cardiorespiratory, metabolic, or thermoregulatory variables were observed between conditions.

Conclusions:

• Localized heat application can induce subjective thermal strain and impair endurance performance.
• This impairment occurs without significant changes in physiological strain markers.
• Subjective thermal strain is an important and independent mediator of reduced endurance performance, even in temperate conditions.