Physical activity related heat stress risk

Physical activity has many health benefits, it reduces the risk for many chronic diseases, premature mortality and is associated with increased well-being. With climate change the frequency and intensity of hot days is increasing. Doing physical activity, such as walking and running, under heat exposure can heighten the risk for heat stress. Therefore, public health recommendations for physical activity should reflect the heightened risk for heat stress during physical activity.

Method description for calculating the risk hours for physical activity risk classification 1 (walking) and 3 (jogging, cycling):

• Heat stress risk is stratified into four categories – low, moderate, high and extreme, in accordance with the Sports Medicine Australia Extreme Heat Policy.  Sports and activities are classifying into five risk groups. This analysis covers Risk Classification 1, which we term “low intensity”(such as leisurely walking) and Risk Classification 3, which we term “moderate intensity” (such as jogging, cycling). For each grid cell, the number of daylight hours in each grid cell were counted, where the combination of recorded temperature and humidity exceeded at least the “moderate”, “high” and “extreme” threshold  for Risk Classifications 1 and 3.
• The total number of sunlight hours per year were then weighted by population and  summed across all grid cells in a given country for each year. These hours were divided by the total population of the country  that year, giving  the number of hours per person exceeding each threshold for each Risk Classification group.

Interpretation of results:

In Europe, during 2015-2024 the total person hours of at least moderate or higher heat stress risk during walking and running, has increased by 114% and 90.5%, respectively, compared to the baseline period of 1991-2000.

Caveats

Heat stress risk for each exercise intensity classification may differ among people due to various risk factors (e.g. age, health status and clothing). There is a risk that heat stress during spring and autumn is overestimated, since the Sports Medicine of Australia policy assumes summertime strength of solar radiation.