Hot and Cold Temperatures
Around the world, our events take place across a hugely diverse range of climates, and at some times of the year, we can see over 60 degrees centigrade difference between our hottest and coldest events. In parts of Australia and South Africa, for example, we experience temperatures of over 30 degrees centigrade, and at the same time in parts of Canada and Poland, we experience temperatures as low as -30 degrees centigrade.
Importantly, people who live in extreme climates tend to cope very well and, in fact, we see most temperature-related issues where parkrunners aren’t used to the temperatures they are participating in, or where a lack of experience leads them to make inappropriate decisions, for example wearing unsuitable clothing in the cold or over-exerting themselves in the heat.
Hot conditions and heat stress
Heat stress during or immediately after exercise is usually the result of a combination of two factors:
- An increased rate of heat production, resulting from high-intensity exercise (e.g. overexertion for a period of time).
- Impeded heat loss (and/or heat gain from the environment) as a result of high ambient temperature, high relative humidity, radiant heat gain in direct sunlight, or inappropriate clothing.
It should be noted that very high ambient temperature is not a prerequisite for heat stress, particularly if the humidity is high and the event takes place in direct sunlight with little natural shade on the course.
Although the most serious form of heat illness (exertional heat stroke) is a very unlikely scenario at parkrun events, heat exhaustion (a milder, but still potentially serious situation) may occur during hot weather, particularly where participants are not acclimatised.
Signs & symptoms of heat exhaustion
The most common symptoms of heat exhaustion are:
- Staggering gait
- Muscle or abdominal cramps
- Nausea, vomiting or diarrhoea
- Profuse sweating: skin is ‘cool and clammy’
- Rapid, weak pulse
- Rapid, shallow breathing
In the parkrun setting, these signs and symptoms are most likely to be observed in a participant at, or close to, the finish of the event.
Treatment of heat exhaustion
If anyone suspects that a participant is suffering from heat exhaustion, the first priority is to remove the casualty from the heat if possible and to actively cool them. Dehydration, if present at all, is likely to be mild in the context of a parkrun event, and therefore rehydrating the casualty is not a priority under these circumstances.
Methods of cooling
- Move the casualty indoors (if this is practical, and assuming that the temperature indoors is lower than the temperature outside, which may not be the case if a shelter is a tent positioned in direct sunlight).
- Failing this, move the casualty into the shade and ensure that they are exposed to any breeze/air movement as this will increase the rate of heat loss.
- Placing the casualty on a grass surface is preferable to placing them on tarmac/concrete as these surfaces may be hotter than the ambient temperature and may result in further heat gain.
- Whilst respecting privacy and decency, expose as much skin to the air as possible (roll-up sleeves, leggings, remove their cap, etc.)
- Lie the casualty on their back (provided that they are conscious and not retching or vomiting), and elevate the legs.
- The casualty must be monitored continuously and placed in the recovery position if consciousness is lost, or retching/vomiting starts.
- Immerse the hands and wrists in a bucket of cold/cool water (add ice, if available). This method is only practical with a casualty who is conscious and able to support themselves in a kneeling position.
- Drench exposed skin and/or non-waterproof clothing with cold/cool water. Avoid pouring cold water directly onto the face, as this may provoke counterproductive (and potentially dangerous) reflex falls in heart rate and blood pressure
- Fan the casualty using towels, blankets, etc. or, preferably, an electric fan
If at any point the casualty loses consciousness, emergency services should be called, the casualty placed in the recovery position and both pulse and respiration monitored. At this point, our critical incident protocol should be followed.
Cold conditions and hypothermia
Hypothermia is a risk at all events that experience colder than usual temperatures. Should an event proceed, the event team should monitor participants for the following symptoms:
- Slurred speech or mumbling
- Slow, shallow breathing
- Weak pulse
- Clumsiness or lack of coordination
- Drowsiness or very low energy
- Confusion or memory loss
- Loss of consciousness