The Effects of Exhaustive Exercise on Thermoregulatory Fatigue During Cold Exposure
Abstract
Two experiments were conducted to examine whether acute (one-hour) or chronic exertional fatigue (3-7 days) would impair the thermoregulatory response during subsequent cold exposure thereby leading to an accentuated core temperature reduction compared to when the same individual was exposed to cold in a rested condition. In Study 1, ten men rested for 2 hours during a standardized cold air test (CAT, 4.6 deg C) following 2 treatments: (1) 60 min of cycle exercise (EX) at 55% VO2(sub peak), and (2) passive heating (HEAT). EX was performed during a 35 deg C water immersion (WI) and HEAT was conducted during a 38.2 deg C WI. The duration of HEAT was individually adjusted (mean = 53 min) so that rectal temperature (T(sub re)) was similar at the end of WI in both EX (38.2 deg C) and HEAT (38.1 deg C). During CAT following EX, relative to HEAT: (1) T(sub re) was lower (P < 0.05) from min 40-120, (2) mean weighted heat flow was higher (P < 0.05), (3) insulation was lower (P < 0.05), and (4) metabolic heat production was not different. In Study 2, thirteen men (10 experimental and 3 Control subjects) performed a cold-wet walk (CW) for up to 6 h (6 rest-work cycles, each cycle one h in duration) in 5 deg C air on three occasions. One cycle of CW consisted of 10 min standing in the rain (5.4 cm/hr) followed by 45 min walking (1.34 m/s, 5.4 m/s wind). Clothing was saturated at the start of each walking period (0.75 clo vs. 1.1 clo when dry). The initial CW trial (Day 0, D0) was performed (afternoon) with subjects rested before initiating exercise-cold exposure. During the next 7 days, 4 h of exhaustive exercise (aerobic, anaerobic, resistive) was performed each morning. The subsequent two CW trials were performed on the afternoon of days 3 (D3) and 7 (D7), ^ 2.5 h after the cessation of fatiguing exercise. For the Control group, no exhaustive exercise was performed on any day.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 2002
- Accession Number
- ADP012430
Entities
People
- Andrew J Young
- John W Castellani
- Michael N. Sawka
Organizations
- United States Army Research Institute of Environmental Medicine