Environmental Considerations for Athletic Trainers Thermoregulation

2 Topics related to environmental concerns... Science of temperature regulation Reducing the risk of heat illness Maintaining hydration

3 Heat Illness is Preventable Heat illness can significantly reduce level of performance Heat stroke: the most severe form of heat illness

4 Heat Illness is Preventable Athletic trainers must guard against dehydration & heat illness Comprehensive knowledge is critical

5 Science of Temperature Regulation Heat regulation 1. Hyperthermia 2. Thermoregulation 3. Hypothalamus

The Body’s Thermoregulatory System 6

7 Heat Gain/Loss Metabolic heat production Radiation Conduction Convection Evaporation (sweating)

8 Metabolism Energy & material transformations in living cells Activity increase Heat production Intensity of activity Metabolism Heat production

9 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

10 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

11 Convection Circulating air across the body to gain or loss heat Example –Using a room fan

12 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 13

14 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 …. 16

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 17

18 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 19

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 20

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 periods 21

HUMITURE VHSL RECOMMENDATION º 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 20 to 30 minutes for rehydration.

23 Sweat Rates 2 qt. Sweat/hour = 4 lb. Of body weight

24 Sweating: Good & Bad Natural response for thermoregulation Leads to dehydration Dehydration impairs physiological function Lean athlete = typically 65% H 2 0

25 Importance of Water Helps control temperature of working muscles & vital organs 1. Muscles = 75% H 2 O 2. Blood = 80% H 2 O Essential for cell functioning Medium for nearly all body metabolism

26 Effects of Dehydration Performance is reduced Prolonged training & competition most adversely affected Dehydration + heat intensifies adverse effects * Warm & humid environment > potential for decreased performance

27 Effects of Dehydration in Sports Variable effects on strength & power sports Withholding fluids??

28 Physiological Effects of Dehydration Decreased cardiac function Increased core temperature Reduction in ability to sweat

29 Early Warning Signs of Dehydration Fatigue Loss of appetite Nausea Poor concentration Flushed skin Light headedness Dark urine Muscle cramps

30 Effects of Dehydration Mental performance also affected

Hydration & Rehydration Goal: Match fluids and sodium ingested during activity to fluids and sodium lost during activity. 31

NATA guidelines 1.Establish hydration protocol 2.Fluids should be accessible 3.Begin all exercise well-hydrated 4.Beverage temp: 50° - 59° 32

Hydration Strategies (NATA) 33

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 chart 34

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? 35

36 Clothing Choices Light colored Light weight Porous Avoid 100% cotton Avoid ‘wicking’ clothing Dry shirt slows the cooling process

37 Fluid Loss Increased with Gear

38 Up next… Heat illness Reducing the risk of heat illness Maintaining hydration Altitude problems/illnesses