How to prevent heatstroke

Two major physiological changes occurring when we stay in an environment with a high temperature for a long time are the dilatation of skin blood vessel and sweating. The former increases skin temperature via an increase in its blood flow and the latter increases the dissipation of the evaporation heat. Both contribute to keep our body temperature, especially those of internal organs, stable.

It must be noted that we may suffer from heatstroke even when we are in a shaded area such as a gym or classroom, or on a relatively cool day. Heatstroke occurs due to failures of the thermoregulation mechanisms above mentioned, but it is preventable as far as we have proper knowledge. Furthermore, it is good idea for us to know how to give first aid for patients suffering from heatstroke.

Preventing heatstroke

　 　
Source：Ministry of Health, Labour and Welfare

1. Beware not just of heat but also of humidity

Heatstroke occurs even at temperatures below 30℃when humidity levels are high. There is a greater risk of heatstroke in highly humid environments owing to the body's decreased ability to cool itself down from poor evaporation of sweat. In principle, you should refrain from all exercise at temperatures of 30℃accompanied by humidity levels in excess of 80%; while at temperatures of 30℃accompanied by humidity levels in excess of 30% and even at temperatures of 26℃when accompanied by humidity levels in excess of 60%, vigorous exercise must be avoided.

2. Rehydrate regularly

Rehydrate with liquids by taking amounts appropriate to perspiration levels (around 50～100cc every 30 minutes). As sweat also contains salts, you should ideally rehydrate with drinks which contain over 40mg of sodium per 100ml.

3. Habituate yourself to the heat

Heatstroke often occurs when persons are not used to the heat such as on days when it gets suddenly hot, on the first days of training camps, following exam breaks, among new club members, etc. Warm-up well before activities to allow yourself to gradually get used to the heat.

4. Wear clothing and headwear which are moisture absorbent and permeable

Select clothing which is moisture absorbent and permeable, and avoid direct sunlight using headwear. During sports which involve wearing protective gear, take this off during rest times to recuperate from the heat.

5. Physical conditioning

Individual body types have a great bearing on the incidence of heatstroke. Persons with cold symptoms (fever, diarrhea, stuffiness); those who have consumed large volumes of alcohol the previous day; have skipped breakfast: are lacking sleep; or have an underlying health condition (obesity, diabetes, high blood pressure, mental/nervous disorder) are particularly susceptible to heatstroke and should be especially vigilant.

【First Aid】

Have the patient carried to cool and shaded area, elevate his/her feet, and hydrate with a "sports drink" or water which is rich in minerals, if they are available. If the patient has difficulty to drink due to nausea, or if the person exhibits symptoms such as confusion or coma, notify emergency services immediately. Cool the person's body while waiting for the ambulance. Remove outer clothing, spray the body with water, or wrap in a wet towel. Place ice packs or a wet towel under armpits and around groin, neck and ankles, as these areas are close to large blood vessels. Massage hands and feet upward, toward the heart, to promote circulation. The key to lifesaving in case of heatstroke is to reduce body temperature.