Early fall football, cross country, soccer and field hockey
practices are conducted in very hot and humid weather in many parts of the
United States. Due to the equipment and uniform needed in football, most of the
heat problems have been associated with football. From 1995 through the
2000 football season there have been 14 high school heat stroke deaths in
football. This is not acceptable. There are no excuses for heatstroke
deaths, if the proper precautions are taken. During hot weather conditions the
athlete is subject to the following:
HEAT CRAMPS Painful cramps involving
abdominal muscles and extremities caused by intense, prolonged exercise in the
heat and depletion of salt and water due to profuse sweating.
HEAT SYNCOPE Weakness fatigue and
fainting due to loss of salt and water in sweat and exercise in the heat.
Predisposes to heat stroke.
HEAT EXHAUSTION (WATER DEPLETION) Excessive weight loss, reduced sweating,
elevated skin and core body temperature, excessive thirst, weakness, headache
and sometimes unconsciousness.
HEAT EXHAUSTION (SALT
DEPLETION) Exhaustion,
nausea, vomiting, muscle cramps, and dizziness due to profuse sweating and
inadequate replacement of body salts.
HEAT STROKE An acute medical emergency
related to thermoregulatory failure. Associated with nausea, seizures,
disorientation, and possible unconsciousness or coma. It may occur suddenly
without being preceded by any other clinical signs. The individual is usually
unconscious with a high body temperature and a hot dry skin (heat stroke
victims, contrary to popular belief, may sweat profusely).
It is believed that the
above-mentioned heat stress problems can be controlled provided certain
precautions are taken. According to the American Academy of Pediatrics
Committee on Sports Medicine, heat related illnesses are all preventable.(
Sports Medicine: Health Care for Young Athletes, American Academy of
Pediatrics, July 2000). The following practices and precautions are
recommended:
1.
Each athlete
should have a physical examination with a medical history when first entering a
program and an annual health history update. History of previous heat illness
and type of training activities before organized practice begins should be
included. State High School Associations recommendations should be followed.
2.
It is clear that top physical performance can only be achieved
by an athlete who is in top physical condition. Lack of physical fitness
impairs the performance of an athlete who participates in high temperatures.
Coaches should know the PHYSICAL CONDITION of their athletes and set
practice schedules accordingly.
3.
Along with
physical conditioning the factor of acclimatization to heat is important.
Acclimatization is the process of becoming adjusted to heat and it is essential
to provide for GRADUAL ACCLIMATIZATION TO HOT WEATHER. It is necessary
for an athlete to exercise in the heat if he/she is to become acclimatized to
it. It is suggested that a graduated physical conditioning program be used and
that 80% acclimatization can be expected to occur after the first 7-10 days.
Final stages of acclimatization to heat are marked by increased sweating and
reduced salt concentration in the sweat.
4. The old idea that water should be withheld from athletes during workouts has NO SCIENTIFIC FOUNDATION. The most important safeguard to the health of the athlete is the replacement of water. Water must be on the field and readily available to the athletes at all times. It is recommended that a minimum 10-minute water break be scheduled for every half hour of heavy exercise in the heat. Athletes should rest in a shaded area during the break. WATER SHOULD BE AVAILABLE IN UNLIMITED QUANTITIES. Check and be sure athletes are drinking the water. Cold water is preferable. Drinking ample water before practice or games has also been found to aid performance in the heat.
5. Salt should be replaced daily. Modest salting of foods after practice or games will accomplish this prupose. Salt tablets are not recommended. ATTENTION MUST BE DIRECTED TO REPLACING WATERFLUID REPLACEMENT IS ESSENTIAL.
6. Know both the TEMPERATURE and HUMIDITY. The greater the humidity, the more difficult it is for the body to cool itself. Test the air prior to practice or game using a wet bulb, globe, temperature index (WBGT index) which is based on the combined effects of air temperature, relative humidity, radiant heat and air movement. The following precautions are recommended when using the WBGT Index: (ACSM's Guidelines for the Team Physician, 1991)
Below 64 Unlimited activity
65-72 Moderate risk
74-82 High risk
82 plus Very high risk
There is also a weather
guide for activities that last 30 minutes or more (Fox and Mathews, 1981) which
involves know the relative humidity and air temperature:
|
AIR TEMP |
DANGER ZONE |
CRITICAL ZONE |
|
70 F |
80% RH |
100% RH |
|
75 F |
70% RH |
100% RH |
|
80 F |
50% RH |
80% RH |
|
85 F |
40% RH |
68% RH |
|
90 F |
30% RH |
55% RH |
|
95 F |
20% RH |
40%
RH |
|
100 F |
10% RH |
30% RH |
RH = RELATIVE HUMIDITY
One other method of
measuring the relative humidity is the use of a sling psychrometer, which
measures wet bulb temperature. The wet bulb temperature should be measured
prior to practice and the intensity and duration of practice adjusted
accordingly. Recommendations are as follows:
Under 60 F
. Safe
but always observe athletes
61-65 F
.. Observe
players carefully
66-70 F
.. Caution
71-75 F
.. Shorter
practice sessions and more frequent water
and rest breaks
75 plus F
Danger
level and extreme caution
7.
Cooling by
evaporation is proportional to the area of the skin exposed. In extremely hot
and humid weather reduce the amount of clothing covering the body as much as
possible. NEVER USE RUBBERIZED CLOTHING.
8. Athletes should weigh each day before and after practice and WEIGHT CHARTS CHECKED. Generally a 3 percent weight loss through sweating is safe and over a 3 percent weight loss is in the danger zone. Over a 3 percent weight loss the athlete should not be allowed to practice in hot and humid conditions. Observe the athletes closely under all conditions. Do not allow athletes to practice until they have adequately replaced their weight.
9. Observe athletes carefully for signs of trouble, particularly
athletes who lose significant weight and the eager athlete who constantly
competes at his/her capacity. Some trouble signs are nausea, incoherence,
fatigue, weakness, vomiting, cramps, weak rapid pulse, visual disturbance and
unsteadiness.
10.
Teams that
encounter hot weather during the season through travel or following an
unseasonably cool period, should be physically fit but will not be
environmentally fit. Coaches in this situation should follow the above
recommendations and substitute more frequently during games.
11.
Know what to
do in case of an emergency and have your emergency plans written with copies to
all your staff. Be familiar with immediate first aid practice and prearranged
procedures for obtaining medical care, including ambulance service.
HEAT STROKE THIS
IS A MEDICAL EMERGENCY DELAY COULD BE FATAL. Immediately cool body
while waiting for transfer to a hospital. Remove clothing and place ice bags on
the neck, in the axilla (armpit), and on the groin areas. Fan athlete and spray
with cold water to enhance evaporation.
HEAT EXHAUSTION OBTAIN
MEDICAL CARE AT ONCE. Cool body as you would for heat stroke while waiting for
transfer to hospital. Give fluids if athlete is able to swallow and is
conscious.
SUMMARY The main problem associated
with exercising in the hot weather is water loss through sweating. Water loss
is best replaced by allowing the athlete unrestricted access to water. Water
breaks two or three times every hour are better than one break an hour.
Probably the best method is to have water available at all times and to allow
the athlete to drink water whenever he/she needs it. Never restrict the amount
of water an athlete drinks, and be sure the athletes are drinking the water.
The small amount of salt lost in sweat is adequately replaced by salting food
at meals. Talk to your medical personnel concerning emergency treatment plans.