Symptoms at Exhaustion from Uncompensable Exercise-Heat Stress
Abstract
Exhaustion occurs over a broad range of core temperatures during uncompensable exercise-heat stress. This study examined the symptoms at heat exhaustion and whether they differed among individuals terminating exercise at low vs. high core temperatures. Forty-seven healthy, heat-acclimated volunteers exercised to exhaustion during uncompensable heat stress on one or more occasions for a total of 133 trials. Mean core temperature (+/- sd) at exhaustion was 38.7 +/- 0.5 deg C (range 37.4 to 39.8 deg C) and was generally consistent within an individual. Volunteers stopped primarily due to ataxia/dizziness (42%), followed by physical exhaustion (25%), headache/nausea (17%), dyspnea (12%) and muscle cramps (4%). Volunteers who terminated at lower core temperatures (<- 38.4 deg C) were limited by physical exhaustion at a rate similar to those stopping at higher (>- 39.0 deg C) core temperatures. However, those who stopped at lower core temperatures had a higher incidence of dyspnea and lower incidence of both ataxia/dizziness and headache/nausea when compared to volunteers terminating exercise at higher core temperatures (X(sup 2) - 10.6; P < 0.05). Therefore, heat intolerant persons were more likely to develop respiratory distress while heat tolerant persons were able to continue until cardiovascular and illness symptoms limited further effort. These data suggest that different physiological mechanisms contribute to the inter-subject variability in tolerance to uncompensable exercise-heat stress.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2002
- Accession Number
- ADP012448
Entities
People
- B. S. Cadarette
- L. Levine
- Michael N. Sawka
- S. J. Montain
- W. A. Latzka
Organizations
- United States Army Research Institute of Environmental Medicine