As we go into the hottest part of the year it’s a great time to think about how we can help our body keep cool. Our resting body temperature lies between 36.5˚ and 37.5˚ Celsius. During exercise heat is produced because of the chemical reactions that cause our muscles to contract. It is not uncommon during exercise for the core temperature to climb to nearly 40˚ Celsius. In normal circumstances the body adjusts to keep our core temperature from rising above 40˚ Celsius.
Blood vessels under the skin dilate, allowing more blood to be near the surface of the skin. At the same time heat from the muscles dissipates into the blood and is carried from the core to the skin. When the air temperature is cool the skin will be at a lower temperature than the blood and so heat will be lost to the environment. This lowers the temperature of the blood and the body. When the air is moving against the skin – as in windy conditions, cooling is increased as the warmed air is constantly being replaced by cooler air.
Another method the body uses to control body temperature is by sweating. The nervous system opens sweat glands – releasing sweat and making the skin moist. The sweat on the skin absorbs heat and as it evaporates the skin is cooled.
What Could Go Wrong? – Risk Factors
The more we use our muscles the more heat we produce. The reverse is also true – less activity will cool us down. The first line of defence against heating up is simply to reduce our activity level and ‘slow down’. It is sometimes hard for athletes ‘in the heat of battle’ to make this decision for themselves so coaches may need to step in if they feel the athlete is overheating.
When exercising in direct sun or high temperatures the skin may become hotter than your blood. Blood sent to the extremities to be cooled may actually be heated up. Exercising outdoors for long durations in high temperatures places you at risk.
High Relative Humidity
In humid conditions the sweat produced by the body will not evaporate. It will simply drip off the body resulting in no cooling effect. Exercising outdoors in humid conditions or indoors where there is poor ventilation places you at risk.
Signs and Symptoms
Hyperthermia occurs when the body’s core temperature rises in an uncontrolled fashion outside of its normal range. Symptoms of hyperthermia include: dizziness, headache, nausea, diarrhoea, vomiting, lack of co-ordination, fatigue, decreased athletic performance (Armstrong, 2007). The person may also sweat profusely. If sweating has stopped entirely this is extremely serious and may indicate ‘heat stroke’. In these circumstances the individual may suffer permanent organ damage or even death so cooling the person down should take priority over transportation to hospital (Armstrong, 2007).
What to do when we overheat
If you suspect someone is suffering from hyperthermia the most effective treatment method is immersing the person in ice-water (Armstrong et al, 2007; McDermott et al, 2009; Roberts, 2007). If this is not possible an alternative is to rotate ice cold towels to the areas of the head, trunk, groin, and under the arms while wetting the patient and fanning them with a towel (Armstrong et al, 2007) (McDermott et al, 2009) (Roberts, 2007). Hyperthermia and dehydration frequently go hand in hand so rehydration with an electrolyte-based drink is advisable. In extreme cases hospitalisation and observation will be necessary.
Preventing hyperthermia is always better than cure. Try to avoid exercising in the heat of the day. If you must exercise in hot or humid conditions ensure you are hydrated well and wear loose, breathable clothing to maximise the opportunity for cooling. Start drinking at least half an hour before commencing exercise. Don’t wait until you feel thirsty to start drinking – by this time you are already dehydrated. If you need to exercise and it is hot outside why not come and enjoy the air-conditioning at Warwick Workout!
by Marcus Lewenhoff-Jones, Fitness Manager, Warwick Workout.
Armstrong, L., Casa, D., Millard-Stafford, M., Moran, D., Pyne, S., & Roberts, W. (2007). Exertional Heat Illness during Training and Competition. Medicine & Science In Sports & Exercise, 39(3), 556-572.
McDermott, B., Casa, D., Ganio, M., Lopez, R., Yeargin, S., Armstrong, L., & Maresh, C. (2009). Acute Whole-Body Cooling for Exercise-Induced Hyperthermia: A Systematic Review. Journal Of Athletic Training, 44(1), 84-93.
Roberts, W. (2007). Exercise-Associated Collapse Care Matrix in the Marathon. Sports Medicine, 37(4), 431-433.
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