Reduced heart rate variability during recovery from exertional vs. passive heat stress
Abstract
Acute exposure to high ambient temperatures (Ta), leading to increased core body temperature (Tc), can adversely affect physiological function. In this study we tested the hypothesis that the addition of exercise can further increase cellular stress and injury, which can subsequently translate to functional damage at a systemic level. Rats were exposed to an Ta of 39°C while resting (HS‐C) or exercising on a running wheel (HS‐EX). Once Tc reached 41.5°C the exercise protocol was stopped in HS‐EX and Ta was reduced to 25°C in both groups. Tc and blood pressure (BP) were recorded telemetrically throughout the protocol and recovery period of 24 h. Tc increased to 41.5°C within ~1.5 h in HS‐EX and within ~3 h in HS‐C. BP and heart rate (HR) increased similarly in both groups to ~180 mmHg and ~450 bpm. During recovery, Tc and BP returned to baseline levels with no significant time‐course difference. However, during the night hours of the recovery period, HR was 30‐50 bpm lower in HS‐EX than in HS‐C. In addition, LF and HF spectral powers of HR variability were reduced in HS‐EX vs. HS‐C during recovery, which may indicate greater cardiovascular impairment in HS‐EX. In conclusion, the combination of heat stress and exercise causes greater cardiovascular impairment than heat stress alone, even with the same increase in Tc and shorter overall exposure to heat stress. (Supported by USAMRMC; author views not official US Army or DoD policy)
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2009
- Source ID
- 10.1096/fasebj.23.1_supplement.788.5
Entities
People
- Harald Stauss
- Kevin Kregel
- Lauren Liaboe
- Lisa Leon
Organizations
- United States Army Medical Research and Development Command
- University of Iowa