Heat Acclimation, Hand Cooling Efficacy, and Adaptation Maintenance.

The Effect of Heat Acclimation on Repeated Bouts of Strenuous Heat Stress, Hand Cooling Efficacy, and the Maintenance Thereof.

This study had three aims:

1. To determine the impact of consecutive days of exercise on thermoregulation and cardiovascular strain.
2. To determine the efficacy of a hand cooling device to cool individuals throughout a heat acclimation period.
3. To assess the maintenance of thermoregulatory and cardiovascular adaptations derived from heat acclimation during a 25-day intermittent exercise-heat exposure protocol.

Participants completed 14 days of exercise heat acclimation in either a hot or cool environment, followed by a heat or cool exercise exposure every 5th day for 25 days. Cardiovascular, thermoregulatory, and perceptual strain were measured throughout exercise each day. Hydration assessment and stress response via blood biomarkers were measured before and after exercise. Aerobic capacity was measured before and after heat acclimation as well as after the intermittent exercise-heat exposure. Hand cooling was implemented periodically during exercise-heat stress visits to determine cooling efficacy before and after heat acclimation.

Inclusion Criteria:

• no chronic health problems
• no previous history of exertional heat stroke within the past 3 years
• no history of cardiovascular, metabolic or respiratory disease
• no current musculoskeletal injury that limits physical activity

Exclusion Criteria:

• women
• exercise less than once per week
• VO2max < 45 ml/kg/min