Effect of Fitness Level on Thermoregulatory Variables in Healthy Males After Cold Exposure

Abstract

INTRODUCTION: Previous research has elucidated that training status or fitness level may influence the thermoregulatory response during acute cold exposure (ACE). However, it is uncertain whether fitness level has a similar response during re-warming (ACE-REC). PURPOSE: To determine the effect of fitness level on the thermoregulatory response during a two hour recovery period from exposure to 10oC cold air. METHODS: Ten males (25.6 ± 1.6 y) underwent pre-experimental testing to determine VO2max and body composition. Subjects were then randomly divided into low-fit (LF: VO2 = 36.6 ± 0.9 ml.kg-1.min-1; %BF = 22.9 ± 0.8 %) and high fit (HF: VO2 = 52.0 ± 1.2 ml.kg-1.min-1; %BF = 15.5 ± 1.2) groups. Each subject underwent 2 trials which consisted of 120 min of exposure to 10oC air and 120 min of recovery in 25oC air. Maximal oxygen consumption (VO2), mean skin temperature (Tsk), and core temperature (Tre) were measured continuously. RESULTS: Percent body fat was significantly different between the HF and LF subjects (p=0.007). ANOVA did not reveal a main effect for fitness for Tre (p=0.856) and Tsk (p= 0.223). However, VO2 was significantly different (p= 0. 013) between high-fit and low-fit subjects during ACE-REC. CONCLUSION: Based on these data, fitness level demonstrated a differential response with regard to VO2 during the recovery period following ACE. Since high-fit individuals tend to have a reduced resistor to heat exchange, i.e. percent body fat, they were able to maintain Tre via an increase in metabolic heat production.