Lecture 20: Heat and hydration

Question 1

as atmospheric temperature –, the temperature gradient between air and the body –

Answer 1

increases
decreases

Question 1

over 27c the body–

Answer 1

absorbs heat

Question 2

exercise in the heat

Answer 2

• heat is generated by endogenous sources
• when an athlete exercises in a hot environment they sweat to dissipate heat

Question 3

risk of exertional heat injury

Answer 3

• we must take the humidity into consideration
• substantial humidity, even at low temperatures can be dangerous

Question 4

external heat stroke (EHS)

Answer 4

• occurs when the patient presents with exertion-related hyperthermia (core body temperature > 40c) and associated central nervous system disturbance or evidence of other end organ system damage.

Question 5

signs of exertional heat stroke

Answer 5

• they may experience dizziness, weakness nausea, fast pulse and respiration, and mental confusion
• they may collapse and suddenly become unconscious.
• the individual may stop sweating (hot, dry skin), but this is unreliable

Question 6

heat exhaustion

Answer 6

• is characterized by an inability to continue functioning in the heat WITHOUT evidence supporting the diagnosis of EHS.
• i.e. no temperature greater than 40c
• their bodies are trying to cool off itself

Question 7

sings and symptoms of heat exhaustion

Answer 7

• it various, but may include - heavy sweating with pale, moist, cool skin; headache, weakness, dizziness, nausea (with or without vomiting).
• happens right before heat stroke

Question 8

management of exertional heat injury (mild patients)

Answer 8

• alert with appropriate behaviour, near-normal/stable vital signs and able to drink fluids
• care on side-line for up to 1 hour with up to 2 liters of fluids
• should cool patient down as much as possible
• come up with a plan if things get worse

Question 9

management of exertional heat injuries (severe patients)

Answer 9

• COOL FIRST - TRANSPORT SECOND
• care on side-lines in cludes aggressive cooling with golded first 30 minutes
• remove gear
• ice/water submersion (best) or on core starting with armpits and groin) / fanning
• rehydration
• quickly arranging evacuation to an emergency room
• this is life threatening!

Question 10

intrinsic risk factors for EHS

Answer 10

• lack of acclimatization
• fever
• overweight/obesity
• dehydration
• recent alcohol use
• sunburn

Question 11

extrinsic risk factors for EHS

Answer 11

• hot, humid environment
• exercise intensity
• inappropriate work-to-rest ratios
• equipment/clothing
• education (athletes, coaches, and medical staff)
• lack of emergency plans to identify and treat EHS
• lack of proper infrastructure (heat acclimatization)
• access to fluids
• access to preventative cooling strategies

Question 12

concepts for combatting heat injuries

Answer 12

1. get an accurate temperature
2. keep them/get them cool
3. allow time for acclimatization

Question 13

get an accurate temperature

Answer 13

• know what you are dealing with
• devices to measure “core body temperature” via direct contact with the forehead, or radiation from the ear canal may not be accurate and/or validated in controlled experiments involving athletes and are potentially dangerous!
• the patent will only display EHS if they have a temperature higher than 40C

Question 14

keep them/get them cool

Answer 14

• ease the athletes into the environment to allow time to climatize things
• modifying duration and equipment to help athletes climatize
• cold water and ice water immersion provide superior cooling rates

Question 15

allow time for acclimatization

Answer 15

• most EHS deaths occur among non-acclimatized players during the initial 3 days of summer practices
• acclimatization improves cooling mostly through increases sweating (evaporation)
• less effective in high humidity
• may need to add electrolytes

Question 16

acclimatization

Answer 16

• physiological adaptations will occur during 1-3 weeks of exercise-heat exposure. these include: reduced rectal temperature, cardiovascular strain, and perceived exertion, as well as increased plasma volume
• you have to be in the environment, it will take 2-3 weeks in that environment

Question 17

train coaches and players on the signs of EHS

Answer 17

• coaching need to know the risks of over pushing their athletes
• coaches/trainers are responsible for removing a player from practice when he or she exhibits signs and symptoms of EHS
• some coaches do not understand or accept this responsibility!
• the medical team must educate staff and players on sings and symptoms and ensure ESPs are completed, understood and followed

Question 18

hypo hydrated

Answer 18

no hydrated enough

Question 19

keep them hydrated!

Answer 19

• specific individual recommendations are calculated based on sweat rates, activity, equipment and dynamics, as well as individual tolerance
• the goal of drinking during exercise is to prevent ecessive (>2% body weight loss from water deficit) dehydration and excessive changes in electrolyte balance to avert compromised performance

Question 20

– fluid loss, there will be – systemic compromise

Answer 20

increase
increase

Question 21

physiological implications of dehydration

Answer 21

• it affects core temperature, cardiac output, heart rate,

Question 22

sample question: what are 3 intrinsic and extrinsic factors that contribute to the risk of hypo hydration or rehydration?

Answer 22

extrinsic: environmental conditions (humidity), availability of fluids (water stations), sports specific factors (weight loss in weight divisions for boxing)

intrinsics: sex, thirst drive, body size and composition, acclimatization status

Question 23

tracking hydration changes

Answer 23

1. acute hydration changes can be measured by taking nude body mass before and after exercise
2. check urine concentration/ colour in morning
3. thirst- first morning thirst is correlated with hypo hydration

Question 24

rehydration concepts

Answer 24

- the primary goal is the immediate return of physiologic function - compensate for urine losses by drinking approx 50% more than sweat losses to assure optimal hydration, if recovery time is less than 4 hours - if you give them a big gallon it will run through them, but if you give them smaller amounts more frequently it will help them more

Question 25

hydration bottom line

Answer 25

individal rehydration planning is important and should be reassessed and altered as needed pre-exercise: - need to start exercise in a state of euhydration - body water within its optimal range during exercise: - try to maintain water levels.. drink early and often - use CHO drink if exercising for periods greater than 1 hour - optimal concentration is between 3-8 percent - those over 5% may slow gastic emptying post-exercise: - need to correct fluid loss ASAP. much of this through general nutrition and H2O - may need to add CHO and electrolytes

Question 26

hydration plans

Answer 26

need to be individualized and consider many factors an athlete who exercises for more than 4 hours and hydrates excessively (well beyond sweat loss) only with water or low-solute beverages may be susceptible to a relatively rare condition known as Hyponatremia (also known as water intoxication)