Relevance of individual characteristics for human heat stress response is dependent on exercise intensity and climate type

  title={Relevance of individual characteristics for human heat stress response is dependent on exercise intensity and climate type},
  author={George Havenith and Joh. M. Coenen and L. A. Kistemaker and W. Larry Kenney},
  journal={European Journal of Applied Physiology and Occupational Physiology},
Abstract Multiple heterogeneous groups of subjects (both sexes and a wide range of maximal oxygen uptake V˙O2max, body mass, body surface area (AD),% body fat, and AD/mass coefficient) exercised on a cycle ergometer at a relative (%V˙O2max, REL) or an absolute (60 W) exercise intensity in a cool (CO 21°C, 50% relative humidity), warm humid (WH 35°C, 80%) and a hot dry (HD 45°C, 20%) environment. Rectal temperature (Tre) responses were analysed for the influence of the individual's… 

Relevance of individual characteristics for thermoregulation during exercise in a hot-dry environment

A large body size (mass and body surface area) is beneficial to reduce ΔTbody during cycling exercise in the heat, however, subjects with higher absolute heat production (more aerobically fit) accumulate more heat because heat production may exceed potential heat loss (uncompensability).

A Body Characteristic Index to Evaluate the Level of Risk of Heat Strain for a Group of Workers With a Test

2 formulas were developed, which were proved to be better predictors for heat strain responses than each individual characteristic, and more sensitive than body type to describe the distributions of individual characteristics and distinguish the differences in physiological responses to heat.

Individualized model of human thermoregulation for the simulation of heat stress response.

In conclusion, individualization of the model allows improved prediction of heat strain, although a substantial error remains.

Power Relative to Body Mass Best Predicts Change in Core Temperature During Exercise-Heat Stress

Prescription of exercise under heat stress using power (W·kg−1 or %Powermax) has the strongest relationship with the rate of change in Trec with no additional requirement to correct for body composition within a normal range, and Practitioners should prescribe exercise intensity using relative power during isothermic HA training to increase Trec efficiently and maximize adaptation.

Individual Responses to Heat Stress: Implications for Hyperthermia and Physical Work Capacity

Understanding how individual factors impact responses to heat stress is necessary for the prediction of heat wave impacts on occupational health and work capacity.

Core Temperature and Sweating in Men and Women During a 15-km Race in Cool Conditions.

WBSR was associated with heat production, irrespective of sex, during a self-paced 15-km running race in cool environmental conditions, and men had a higher ΔCBT than women.

Responses to mild cold stress are predicted by different individual characteristics in young and older subjects.

It is suggested that the relative influence of individual characteristics changes with aging, as shown in the chart below.

Sex differences in response to exercise heat stress in the context of the military environment.

More work is required to fully understand sex differences to exercise heat stress in a GCC context and there is often lower reported heat illness incidence in women, although the extent to which this is influenced by behavioural factors or historic differences in role allocation is unclear.

Explained variance in the thermoregulatory responses to exercise: the independent roles of biophysical and fitness/fatness-related factors.

Biophysical parameters related to Hprod, Ereq, and body size explain 54-71% of the individual variability in ΔTre, WBSL, and LSRss, and only 1-4% of additional variance is explained by factors related to fitness or fatness.



The relative influence of body characteristics on humid heat stress response

Total body sweat loss was highly dependent on body size (AD or mass) with regular activity level having a quarter of the effect of body size on sweat loss, and the widely accepted concept, that body core temperature is determined by exercise intensity expressed as % O2max and sweat loss by absolute heat load, was only partially supported by the results.

Thermoregulatory responses of middle-aged and young men during dry-heat acclimation.

Thermoregulatory responses during heat acclimation were compared between nine young and nine middle-aged men who were matched (P greater than 0.05) for body weight, surface area,surface area-to-weight ratio, percent body fat, and maximal aerobic power.

Heat stress and age: Skin blood flow and body temperature

Sex Differences in Human Thermoregulatory Response to Heat and Cold Stress

Proportionately fewer women than men can be successfully heat acclimated and have a relatively greater risk of cold injury.

A review of comparative responses of men and women to heat stress.

Physiological responses of physically fit men and women to acclimation to humid heat.

It was concluded that aerobic capacity is an important factor to be considered when men and women are compared in the heat, and when fitness levels are similar, except for sweating, the previously reported sex-related differences in response to heat seem to disappear.

Physiological responses of men and women to humid and dry heat.

Under wet conditions, whether mild or hot, females tolerated the heat better than males, and displayed lower deep body and skin temperatures, and therefore lower heat storage, while demonstrating lower sweat rates and subsequently less dehydration than males.

Effects on heat tolerance of physical training in water and on land.

It was concluded that PT can improve the cardiovascular response to dry heat without affecting thermoregulatory capacity and appears to enhance heat tolerance only if Tc is permitted to rise during exercise, thus stimulating the temperature-regulating center for heat dissipation.

Evaluation of tolerance limits for humans under heat stress and the problems involved.

The probability of reaching the potentially critical rectal temperature of 39 degrees C was calculated according to data of Wyndham & Heyns and the 37.6 degrees C isotherm might be taken into consideration as a limit.

Heat tolerance and aging.

Observations generally support the importance of aerobic fitness and other morphological factors to middle-aged and elderly individuals working or performing recreational activities in hot environments.