A Physiological Strain Index (PSI) to Evaluate Heat Stress

Although there are many heat strain indices, we found that they were valid only under certain and specific conditions. The present study suggests a simple valid physiological strain index PSI to evaluate heat stress either on-line or when data analysis is applied. This index should be easier to interpret and use than other indices available, and includes the ability to depict rest and recovery periods. PSI is capable of overcoming the limits of previous indices, while providing the potential to be widely accepted and used universally. However, further investigation is required to possibly adjust this index for different age groups. The PSI successfully evaluated the heat stress in subjects who exercised in a warm environment at different exercise intensities combined with different levels of hypohydration. This index overcame the individual limits of the physiological parameters Tre, Tes and HR in assessing heat stress for this study, and continues to provide the potential to be accepted universally. The PSI also successfully evaluated heat stress and gender when exercising at different intensities in different climates. We have also extended the applicability of PSI in the present study to consider sweat rate and relative exercise intensity as a function of climate. Therefore, PSI applicability was further extended for exercised heat stress and gender at different combinations of exercise intensity and climate, and continues to show potential to be widely accepted.