Lecture 20 - Heat and Hydration

Question 1

what is the number one rule of sports issues in heat?

Answer 1

• when it starts to go poorly, it progresses fast
• you cannot beat physiology

Question 2

how does atmospheric temperature affect body temperature?

Answer 2

• as the atmospheric temperature increases, the gradient decreases
• Tbody > Tenvironment = lose heat via radiation
• over 27 C = the body absorbs heat (hard to dissipate it)
• heat loss is from evaporation (sweat) only

Question 3

how is heat generated during exercise?

Answer 3

• by endogenous sources (muscle activity and metabolism)
• by exogenous sources (heat transfer when air is > 27 C, or hotter than the body)

Question 4

how does humidity affect body temperature?

Answer 4

• increased humidity = decreased vapour gradient = less evaporation
• more humid = less sweat loss = hotter temperature
• increased body temp due to decreased sweat evaporation
• substantial humidity even at low temperatures can be dangerous

Question 5

what is exertional heat stroke?

Answer 5

• exertion-related hyperthermia
• temperature over 40 C
• CNS disturbance and organ system damage

Question 6

what are the symptoms of exertional heat stroke?

Answer 6

• dizziness
• weakness
• nausea
• fast pulse and respiration
• mental confusion
• potential unconsciousness/collapse
• may stop sweating (hot, dry skin) –> red flag

Question 7

what is heat exhaustion?

Answer 7

• inability to continue functioning in the heat
• without evidence of EHS
• a precursor to heat stroke

Question 8

what are the symptoms of heat exhaustion?

Answer 8

• heavy sweating
• pale, moist, cool skin
• headache
• weakness
• dizziness
• nausea (with or without vomiting)

Question 9

how do you manage heat exhaustion?

Answer 9

• up to 2L of fluid for up to 1 hour (sideline)
• rest in the shade, cooling, rehydration, frequent vital signs and mental status assessment (every 5-10 mins)
• if not recovering, send to the ER asap

Question 10

how do you manage heat stroke?

Answer 10

• cool first, transport second
• aggressive cooling within first 1/2 hour
• remove gear
• ice/water submersion (unless risk of drowning) –> armpits and groin under
• rehydration (IV if they can’t drink)
• frequent vital signs and mental status assessment every 5-10 mins
• go to the ER asap
• require immediate evaluation

Question 11

what are the intrinsic risk factors of heat stroke?

Answer 11

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

Question 12

what are the extrinsic risk factors of heat stroke?

Answer 12

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

Question 13

what are the 5 concepts for combatting heat illness?

Answer 13

1. get an accurate temperature
2. keep them/get them cool
3. allow time for acclimatization
4. train coaches and players on the signs
5. keep them hydrated

Question 14

how can you get an accurate temperature?

Answer 14

• do not trust forehead/ear temperatures
• rectal is the only accurate (which will not be done on field)
• if the temperature is slightly lower, and symptoms are present, assume EHS

Question 15

how can you keep/get athletes cool?

Answer 15

• gradually add more equipment as practices start back up (summer)
• use cold water/ice submersion to cool temp fast (armpits under)
• use cold packs on groin and armpits only when submersion is not possible

Question 16

how can you allow time for acclimatization?

Answer 16

• improve cooling mostly through increased sweating/evaporation
• less effective in high humidity
• may need to add electrolytes (not just water)
• progressive and prolonged elevation of the body’s temperature
• does not work if the athlete isn’t exercising
• takes 1-3 weeks for exercise-heat exposure before effective

Question 17

how can you train coaches and players on signs?

Answer 17

• inform coaches of the risks so they don’t push athletes past their point of stop/rest/rehydration
• do not use exercise as a punishment
• teach them to remove players when signs or symptoms arise
• medical team must educate staff and players
• follow EAPs (completed, understood and followed)

Question 18

how can you keep athletes hydrated?

Answer 18

• don’t let them arrive at training dehydrated
• calculate specific individual water recommendations
• prevent excessive dehydration (>2% body weight loss from water deficit)
• balance electrolytes
• will reduce cardiovascular strain (decreased SV and increased HR if dehydrated)

Question 19

what are the 5 risks of hypohydration?

Answer 19

1. intrinsic factors (sex, body size, acclimatization)
2. exercise structure (duration, intensity, frequency)
3. availability of fluids (water breaks, stations, fluids available, temperature of fluids)
4. environmental conditions (altitude, humidity, clothing/equipment, air flow)
5. sport-specific factors (weight loss, appearance-based sports)

Question 20

how do you track hydration changes?

Answer 20

1. nude body mass before and after exercise (>2% change = dehydration)
2. check urine concentration/colour in the morning (yellow = bad)
3. thirst in the morning = dehydration (if you are thirsty, it is probably too late)

Question 21

how much fluid is needed to rehydrate?

Answer 21

• ~50% more intake than sweat loss (compensate for urine)
• 2-3 glasses per lb of body weight lost
• eat regularly (will supply ~ 1L water from a balanced diet)

Question 22

how to avoid dehydration: pre-exercise

Answer 22

• start hydrated

Question 23

how to avoid dehydration: during exercise

Answer 23

• maintain water levels (drink early and often)
• use CHO if exercising for >1hr
• optimal concentration = 4% (5% = diarrhea if dehydrated)

Question 24

how to avoid dehydration: post-exercise

Answer 24

• correct fluid loss ASAP
• general nutrition and H2O
• add CHO and electrolytes

Question 25

what is hyponatremia? (aka water intoxication)

Answer 25

• when an athlete drinks water without electrolytes and dilutes their body
• may occur in heavy sweaters or salty sweaters
• risk if working out for more than 4 hours with excessive rehydration
• very rare