Abder Amokrane from Stand 21 and Dr. Terry Trammell |
Heat related illness in motorsports usually goes under-recognized. Not only can it degrade your performance, but it can cause illness or even death. Heat stress is simply heat production (metabolic) and accumulation (metabolic + environmental) in the body- if your body fails to dissipate the heat load, there is an increase in your core temperature (98.6F).
Environmental heat load:
- ambient temperature
- relative humidity
- radiant heat (direct heat, engine & drivetrain)
- air flow
- clothing (color, texture, fabric, layers)
Exercising at your maximum level requires 20x more muscular energy than at rest. 75% of the energy is heat, only 25% is work. Racing is a physical activity requiring 200W/m2 (50W to drive a car).
We dissipate heat by:
- radiation; blood flow to the skin (red face)
- conduction; bringing areas of body with large surface area (head, palms & soles) into contact with cooler surfaces
- convection; heat lost in expired air (fogs your visor).
- and evaporation; sweating
Humidity has an effect on sweating. At less than 75% humidity, 85% of heat is lost by sweating. As the temperature and humidity increase, evaporation is less efficient. At 90% humidity or greater, sweat will NOT evaporate. Beware of some 'waterproof' sunscreens - these can actually block sweat causing you to overheat.
Water is 60% of the body weight on an average male. You need a mminimum of 2300ml a day (2.4 qts). You'll lose 1100ml/d with urination and 900-1200ml/d through other insensible losses. Exercise will lose 1000-2000ml per hour of exercise.
You cannot 'hyper-hydrate' the day of a race - your body will not store it. You should begin to hydrate 2-3 days before an event. Your fingers and feet will slightly swell when you're at maximum H20 levels. The best rule of thumb is that you should be urinating every 2 hours, and it should be crystal clear. You are then properly hydrated.
As you become hotter, your performance can suffer:
- 2% loss = 3 pints
- minimal impairment of body temp thermo-regulation
- 3% loss = 4.5 pints
- Reduced muscular endurance strength and time
- Risk of heat related illness
- 4% loss = 6 pints
- Heat cramps and heat syncope (fainting)
- 8% loss = 1.5 gallons!
- Heat exhaustion
- Heat Stroke
- Coma and death
Stay safe and cool this season!
Learn more by watching the Stand21 video below:
Learn more by watching the Stand21 video below:
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