Physiological responses during moderate exercise in thermo-neutral and hot environment for normal weight

Background: Recent research has shown that climatic stress has the ability to cause changes in exercise performance. The purpose of this study was to investigate whether the current exercise prescription guidelines remain appropriate or should be modified, given rise of summer temperatures in the United Kingdom, and to what effect the prescription guidelines had on individuals with different body weights. Subjects and Methods: Twenty healthy normal weight adult males with a body mass index (BMI) 23±1.9, and waist to hip ratio (WHR) 0.89±0.04, age 24±1.4 year were randomly assigned to either cycling for 30 min in a climate chamber at either at 18°C (thermo-neutral) or 30°C (hot environment) (T18, T30), with 24-h between trials. The third trial was performed at 30°C with an adjusted workload (T30a) to determine whether workload adjustment was necessary in order to reduce HR to approximately that of T18 levels 24-h after the second trial. Heart rate (HR), RPE, VO2, CHO and fat utilization; energy expenditure in calorie KCAL (kcal.min^-1) and RER were determined. Results: HR at T30 was significantly higher than the HR at T18 and at T30a. Carbohydrate (CHO) and fat utilization; energy expenditure in calorie KCAL (kcal.min^-1) and Respiratory Exchange Ration (RER) HR at T30a dropped to a level close to the HR level of T18. No statistical differences were found for KCAL, VO2, RER, CHO and fat between the three trials. Conclusion: Exercising moderately for 30min in a hot environment of 30°C, compared to 18°C, raises the HR and the RPE for normal weight men. Adjusting workload is not required to reduce HR whilst exercising moderately in 30°C.

Key-words:

Hot Temperature - Thermo-neutral - Moderate Intensity - Physical Activity - Energy Expenditure

Publication History

Received: 27 December 2013

Accepted: 06 October 2014

Article published online:
07 July 2022