Chapter 6 Flashcards
How does environmental stress effect performance?
can adversely impact performance and pose serious health threats
What are the environmental areas of concern?
Hyperthermia
Hypothermia
Altitude
Exposure to the sun
Lightning storms
Air pollution
Circadian dysrhythmia
What causes hyperthermia?
heat stress
Who is most susceptible to heat stress?
Young athletes and the elderly
When can heat stress occur in the cold?
Heat stress can also be a factor when competing in the cold if heat dissipation is limited and dehydration occurs
Metabolic heat production
Normal metabolic function results in production of heat (will increase with intensity of exercise)
Conductive heat exchange
Physical contact with objects will result in heat loss or gain
Convective heat exchange
Body heat can be lost or gained depending on temperature of circulating medium
Radiant heat exchange
Radiant heat from sunshine will cause increase in temperature
Evaporative heat loss
Sweat glands allow transport of water to surface
Evaporation of water removes heat
When radiant heat and environment temperature are higher than body temperature, loss of heat through evaporation is key
Lose 1 quart of water per hour for up to 2 hours
Air must be relatively water free for evaporation to occur
Relative humidity of
65% =
impairs evaporation
Relative humidity of
75% =
stops evaporation
Hydration recommendations for athletes
17–20 fluid ounces of water or sports drink 2–3 hours prior to activity and an additional 7–10 fluid ounces 10–20 minutes before exercise
Dehydration
Mild dehydration occurs when 2% of body weight is lost in fluid
Will impair cardiovascular and thermoregulatory responses
Must move individual to cool environment and begin rehydration
Fluid and Electrolyte Replacement
Body requires 2.5L of water daily when engaged in minimal activity
Adult will typically lose ~1.5L per hour
1–2% drop in body weight (due to dehydration) results in thirst
If thirst is ignored, dehydration results in:
- Nausea, vomiting, fainting, and increased risk for heat illness
- only 50% of fluid is ever replaced and should therefore be replaced before, during, and after exercise
Using sports drinks
More effective than just replacing fluids with water
Flavoring results in increased desire to consume
Replaces fluids and electrolytes
Small amounts of sodium help in retention of water
Optimal carbohydrate level is 14g per 8 ounces of water
Gradual Acclimatization
Most effective method of avoiding heat stress
Involves becoming accustomed to heat and exercising in heat
Early pre-season training and graded intensity changes are recommended with progressive exposure over 7-day period
80% of acclimatization can be achieved during first 5–6 days with two–hour morning and afternoon practice sessions
Heat Stress: Susceptible Individuals
Athletes with large muscle mass
Overweight athletes (Due to increased metabolic rate)
Death from heat stroke increases 4:1 as body weight increases
Women are physiologically more efficient with regard to body temperature regulation
Others that are susceptible include those with poor fitness, history of heat illness, or febrile condition, the young, and the elderly
Weight Records
Keep track of before and after measures for first two weeks
If increase in temperature and humidity occurs during the season, weights should again be recorded
Greater than 2% loss of body weight could be a health threat and should be removed from practice until normal weight is achieved
Wetbulb globe temperature index (WBGT)
provides objective measure for determining precautions concerning participation in hot
What are the different WGBT thermometer readings?
Dry bulb
Wet bulb
Black bulb
- Formula yields WBGT index
Dry bulb
standard mercury temperature
Wet bulb
thermometer with wet gauze that is swung around in air