Environmental Considerations

for Athletic Trainers

Thermoregulation

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Topics related to environmental

concerns...

• Science of temperature regulation

• Reducing the risk of heat illness

• Maintaining hydration

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Heat Illness is Preventable

• Heat illness can significantly reduce level of performance

• Heat stroke: the most severe form of heat illness

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Heat Illness is Preventable

• Athletic trainers must guard against dehydration & heat illness

• Comprehensive knowledge is critical

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Science of Temperature Regulation

• Heat regulation

1. Hyperthermia

2. Thermoregulation

3. Hypothalamus

The Body’s Thermoregulatory System

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Heat Gain/Loss

• Metabolic heat production

• Radiation

• Conduction

• Convection

• Evaporation (sweating)

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Metabolism

• Energy & material transformations in living cells

• Activity increase

• Heat production

Intensity of activity

Metabolism

Heat production

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Radiation

• Objects emit heat (infrared radiation)

• Body loses heat to environment

• Body can also gain heat through radiation

– Warm environment

• Sauna

• Hot day

• Effective when skin temp > environment

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Conduction

• Body can gain or lose heat when it is in contact with an object that is warmer or cooler than itself

• Examples

– Hot pack

– Ice pack

• Heat transfer between solids or solids & liquids

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Convection

• Circulating air across the body to gain or loss heat

• Example

– Using a room fan

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Evaporation

• The MOST important mechanism for losing heat

• Most effective means

• Sweating can provide more than 80% of heat loss

• Warmer environment > dependence on evaporative heat loss, thus on sweating

Blood Flow & Heat Exchange

• Proportion of heat lost via radiation, conduction, convection, and evaporation depends on:– Intensity of exercise

– Relative humidity

• Ratio between the amount of water vapor in the air and the actual amount of water the air could potentially hold based on the current temperature

– Ambient temperature

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Evaporation

• Sweating does NOT cause heat loss

• Evaporation must occur

• Role of humidity??

• Limits of efficient evaporation?

Ambient Temperature Influence

• Until 95°F or the relative humidity (RH) reaches 75%, sweating and evaporation account for more of heat loss

• For every 5°F in air temperature, the % that RH raises the risk of heat illness by 10% – Example: 70°F the humidity danger zone = 80% RH– Example: 90°F the humidity danger zone = 50% RH– If RH = 100% and the air and body temp are the same, the

body CANNOT lose heat to the environment

= DANGER ZONE!15

During Exercise ….During Exercise ….

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Sweating Mechanism

• Sweating reduces the body’s internal temperature (evaporation)

• Sweat is not pure water; its also electrolytes– Body’s ability to sustain activity is related to

the replacement of water and electrolytes

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Sweat Rates Determined by:

• Athlete’s size

• Acclimitization

• Fitness

• Hydration status

• Environment

• Clothing

• Type of exercise

• Heredity????

Acclimatization

– Physical adaptations that occur in a natural environment

– Gradual exposure to the environmental conditions over several days

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practice guidelines

• Days 1-5 – One practice/day– Days 1 & 2: helmets only– Days 3 & 4: helmets & shoulder pads– Day 5: full pads

• After day 5: two/day every other day

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VHSL guidelines

• Days 1- 6: only one full practice /day– No session, should exceed 3 hours – Total time /day = no more than 5 hours

• Equipment restrictions– Day 1-3 helmets only;

– Day 4-5 helmets and shoulder pads;

– Day 6 + full pads.

• Also required recovery periods21

HUMITURE VHSL RECOMMENDATION

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105º and up: Recommend no outside activities.95º to 104º: Recommend no equipment (helmets, pads, etc) be

used during activity.90º to 94º: Recommend equipment be removed as often as

possible (during rest breaks, on sideline,etc). Careful monitoring of all athletes for signs of heat problems.

Below 89º: Recommend adequate water supply at all practices and competitions with breaks every 20to 30 minutes for rehydration.

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Sweat Rates

• 2 qt. Sweat/hour =

4 lb. Of body weight

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Sweating: Good & Bad

• Natural response for thermoregulation

• Leads to dehydration

• Dehydration impairs physiological function

• Lean athlete = typically 65% H20

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Importance of Water

• Helps control temperature of working muscles & vital organs

1. Muscles = 75% H2O

2. Blood = 80% H2O

• Essential for cell functioning

• Medium for nearly all body metabolism

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Effects of Dehydration

• Performance is reduced

• Prolonged training & competition most adversely affected

• Dehydration + heat intensifies adverse effects

* Warm & humid environment > potential for decreased performance

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Effects of Dehydration in Sports

• Variable effects on strength & power sports

• Withholding fluids??

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Physiological Effects of Dehydration

• Decreased cardiac function

• Increased core temperature

• Reduction in ability to sweat

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Early Warning Signs of Dehydration

• Fatigue

• Loss of appetite

• Nausea

• Poor concentration

• Flushed skin

• Light headedness

• Dark urine

• Muscle cramps

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Effects of Dehydration

• Mental performance also affected

Hydration & Rehydration

• Goal: Match fluids and sodium ingested during activity to fluids and sodium lost during activity.

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NATA guidelines

1. Establish hydration protocol

2. Fluids should be accessible

3. Begin all exercise well-hydrated

4. Beverage temp: 50° - 59°

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Hydration Strategies (NATA)

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Each athlete weighs “in” before practice and weighs “out” afterward. In the example, the athlete should have been restricted from practice on day 4 because of a 5 percent loss of body weight.

Weight chartWeight chart

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Exertional Hyponatremia

• Sodium level drops below 130 – 135 mmol/L• Excessive fluid consumption and inappropriate fluid retention• If untreated can lead to death

– Refer immediately– Do not give fluids

• Signs– Altered mental/cognitive state/headache– Vomiting & nausea– Swelling of the extremities– Seizures– Unconsciousness

Can you drink too much?

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Clothing Choices

• Light colored• Light weight• Porous• Avoid 100% cotton• Avoid ‘wicking’ clothing• Dry shirt slows the

cooling process

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Fluid Loss Increased with Gear

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Up next…

• Heat illness

• Reducing the risk of heat illness

• Maintaining hydration

• Altitude problems/illnesses