Intermittent microclimate cooling during rest increases work capacity and reduces heat stress

Area of Science:

• Environmental Physiology
• Occupational Health
• Protective Equipment

Background:

• Hazardous work environments often require protective gear, increasing thermal burden and fatigue.
• Existing personal cooling systems can be ergonomically impractical for ambulatory tasks.

Purpose of the Study:

• To evaluate the effectiveness of intermittent personal cooling during rest periods for mitigating heat stress.
• To assess the impact of cooling on work capacity and physiological responses in subjects wearing protective ensembles.

Main Methods:

• Eight subjects performed treadmill work (475 W, 40% VO2 max) alternating with 30-min rest periods under three conditions: control, chemical protective ensemble (CPE), and CPE with intermittent microclimate cooling (COOL).
• Environmental conditions were maintained at a Wet Bulb Globe Temperature (WBGT) of 31°C.
• Physiological responses, including rectal temperature (Tre), and fatigue levels were monitored.

Main Results:

• Control conditions showed modest, stable rectal temperature increases.
• Wearing the CPE alone led to progressive rectal temperature rise and early fatigue.
• Intermittent cooling during rest (COOL trial) significantly reduced heat storage, establishing an equilibrated rectal temperature and at least doubling work capacity.
• Subjects reported a significant perceived cooling effect.

Conclusions:

• Intermittent personal cooling during rest periods is an effective strategy to reduce heat strain and fatigue.
• This cooling method enhances work productivity and offers a practical application for military and industrial personnel in hot environments.
• It provides a viable alternative for stress and fatigue reduction when work/rest cycles are utilized.