THIS IS AN OFFICIAL IAAF MEDICAL ADVISORY POSTED FOR COMPETITORS IN OSAKA.
WASN’T SURE WHERE TO POST THIS ON THE FORUM, BUT THE NEWS SECTION IS PROBABLY WHERE IT WILL BE NOTICED. THIS INFO, PASSED ON TO OSAKA ATHLETES, MAY HELP THEM HAVE A BETTER MEET, OR AT LEAST AVOID A POOR ONE.
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ADVISORY NOTE
with special thanks to
David E. Martin, PhD, FACSM, Atlanta, Georgia, USA
Athletes must be very careful when competing in Osaka. The climatic heat stress
of Osaka’s semi-tropical summer will make conditions quite difficult, particularly
in distance events.
Osaka’s present summertime weather has a morning start time temperature
averaging 23.5º C (74ºF), with high humidity (70 to 90%). Compare this with the
ideal racing conditions for a marathon (12ºC or 54ºF and 40% humidity).
Why are hot, humid conditions so stressful?
The answer is fairly simple. When
we metabolise food for energy, only about 30% of this energy is available for
movement. The other 70% of the energy produced is in the form of heat. The
faster the pace, the greater the heat production.
A runner’s resting body temperature is around 37ºC (98ºF). Enzymes for
metabolism work best at about 39ºC (102ºF), and this explains why runners
warm up before they start racing.
Beyond 40.5ºC (105ºF), however, enzyme
activity starts to deteriorate.
Thus, the temperature margin between optimum
cellular function and death from hyperthermia is very narrow, and the body
cannot accumulate heat.
On a cool or cold day, this heat is easily dissipated because the temperature gradient between body and surrounding air is large.
The higher the outside temperature and the greater the humidity, the slower this
heat will be dissipated, and it can start to accumulate. This cannot be tolerated.
The most successful athletes will run just fast enough that they will not
accumulate heat – any faster and they will risk heat injury: nausea, dizziness,
blurred vision, and possible collapse.
Practical recommendations regarding weather conditions during the 2007 IAAF World Championships in Osakaഊ2
The body’s primary mechanism for heat loss is through evaporation of sweat.
Runners can easily lose one liter of sweat per hour (or more!), and this must be
replaced as it is lost.
Practical recommendations
Acclimatisation, i.e. offering our body the opportunity to progressively adapt to
hot and humid conditions, is of utmost importance.
Acclimatisation takes 1-2
weeks: the first days it is recommended to train at rather low intensity and not too
long a duration in the hot and humid conditions.
High-intensity training sessions
and recovery should take place in cooler conditions. Heat dissipation and sweat
losses will progressively adapt to the changing conditions.
After a few days / 1 week of acclimatisation: practice, in training, at what you
think is your race pace in Osaka-type weather.
Determine for yourself whether
you have judged correctly.
Weigh yourself before and after your training runs so you’ll know how much fluid you will need to replace while racing.
Make sure you are well hydrated before the race starts
During Marathon and Walk Races Osaka
organisers will have plenty of
energy/electrolyte drinks at the feeding stations; be sure to drink at each station.
Pure water will also be available to pour onto the head for cooling by conduction.
Be sure to wear small thin socks that won’t soak up water and become heavy.
Also, ensure that these thin socks fit perfectly and do not cause blisters when
wet. Learn what works best on your training runs.
Do not get sunburn while training, because sunburned skin does not
thermoregulate.
Finally, do not apply sunscreen just before your race, as this will cause the sweat
to bead and quickly roll off the skin surface without contributing to cooling.
Have a great race!
During the World Championships, weather information will be provided at the
Technical Information Centers (TIC).
A coloured panel showing the heat stroke
risk in four levels will be placed in the LOC Physio Room at the Warm-Up Area’s.
Colour Heat index Risk
Black 28°C and more Extreme
Red 23 – 28°C High
Yellow 18 – 23°C Moderate
Green Lower than 18°C Low