Running when temperatures are high forces the body to work harder to maintain normal temperature. Physical activity that generates heat from within the body, combined with external heat, can increase the risk of fluid loss and heat-related illness.
According to the Ministry of Health, running in scorching heat without adequate fluid intake can increase the risk of dehydration, heat exhaustion, and heatstroke. The ministry warns the public to reduce outdoor activities during very hot weather and keep the body hydrated, while choosing cooler times for exercise.
During running, the body naturally generates heat and cools itself through sweating. When air temperature is high and humidity is also high, the evaporation of sweat becomes less effective. At the same time, running causes the body to lose fluid through sweat that is not adequately replaced, resulting in dehydration. The Ministry of Health identifies this condition and heatstroke as risks requiring vigilance, with symptoms including fatigue, skin feeling hot and dry, rapid heartbeat, cramps, nausea, vomiting, dizziness, and dark-coloured urine.
Hot weather does not mean running must stop completely, but the choice of timing, duration, intensity, and the body's ability to adapt need to be considered. One simple way is to choose exercise times with lower temperatures, such as early morning or late afternoon when heat exposure is reduced. The Ministry of Health advises the public to seek shade or stay indoors as much as possible around 11.00 to 15.00 when it is hot, although these times may vary depending on local conditions.
Hydration is key when running in hot weather. The Ministry of Health recommends that the public drink adequate water before running, during the activity, and afterwards, without waiting until feeling thirsty. Choosing light, loose clothing that allows air circulation is also important, as is the use of a hat or other equipment to reduce direct sun exposure. If the body begins to feel heavy or symptoms of health problems appear, it is advisable to immediately reduce intensity, walk for a while, or stop the activity and move to a cooler location.
