Friday, May 16, 2014

STAND21 Safety Seminar: Stay hydrated and fight off heat illness

Here's another excerpt from the Stand21 Safety Seminar we attended at the 2014 Long Beach Grand Prix.  This topic was presented by Dr. Terry Trammell, one of the founders of the International Council of Motorsports Sciences, and the former Director of Medical Services for CART.   I thought his presentation could be of use to a lot of our gentlemen racers/ weekend warriors who spend time at the track.  With summer approaching, we need to consider how heat affects our bodies.

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)
Metabolic heat load is when muscular work produces heat.  When a human does work, the muscles supply the energy.  The energy comes from chemical reactions at the cellular level.  This energy is incompletely converted to work, with heat as a secondary product.

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:

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