Acute Immune Responses to Prolonged Exercise in Environmental Extremes

Abstract

This study is to investigate the effect of prolonged exercise with and without a thermal clamp on leukocyte cell, stress hormones, and cytokine responses. Fifteen healthy male volunteers ( means ± SD: age 22 ± 3yr; mass 75.8 ± 3.2kg; maximal oxygen uptake 55 ± 7ml/min/kg) randomly completed four chamber trials of 1 hour each, in different environment and separated by 7 days. Trials were: 1. exercise induced heating (EX‐Heating: temperature/humidity, 38°C/50%); 2. exercise with a thermal clamp (EX‐Cooling: temperature/humidity, 18°C/ 50%); 3. passive heating (PA‐H: temperature/ humidity, 38°C/ 50%); 4. passive cooling (PA‐C: temperature/ humidity, 18°C/50%). EX‐H and EX‐C were composed of 1h treadmill runs at 80% Individual anaerobic threshold (IAT). Blood samples were collected at pre‐post, and 1h post environments exposure. Compared to EX‐H, exercise‐induced increases in core temperature, heart rate, cortisol, human growth hormone, Interleukin‐6, leukocyte and monocyte counts were significantly (p≤0.01) more pronounced after EX‐C. Our results suggest that the additional impact of elevated ambient temperatures on stress responses to endurance exercise in trained subjects seems to affect primarily the hormonal systems and resulting changes in leukocyte number, monocyte and interleukine‐6.This study was supported by the King Saud University