Lecture 20: Heat and hydration Flashcards
as atmospheric temperature –, the temperature gradient between air and the body –
increases
decreases
over 27c the body–
absorbs heat
exercise in the heat
- heat is generated by endogenous sources
- when an athlete exercises in a hot environment they sweat to dissipate heat
risk of exertional heat injury
- we must take the humidity into consideration
- substantial humidity, even at low temperatures can be dangerous
external heat stroke (EHS)
- 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.
signs of exertional heat stroke
- 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
heat exhaustion
- 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
sings and symptoms of heat exhaustion
- 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
management of exertional heat injury (mild patients)
- 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
management of exertional heat injuries (severe patients)
- 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!
intrinsic risk factors for EHS
- lack of acclimatization
- fever
- overweight/obesity
- dehydration
- recent alcohol use
- sunburn
extrinsic risk factors for EHS
- 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
concepts for combatting heat injuries
- get an accurate temperature
- keep them/get them cool
- allow time for acclimatization
get an accurate temperature
- 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
keep them/get them cool
- 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
allow time for acclimatization
- 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
acclimatization
- 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
train coaches and players on the signs of EHS
- 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
hypo hydrated
no hydrated enough
keep them hydrated!
- 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
– fluid loss, there will be – systemic compromise
increase
increase
physiological implications of dehydration
- it affects core temperature, cardiac output, heart rate,
sample question: what are 3 intrinsic and extrinsic factors that contribute to the risk of hypo hydration or rehydration?
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
tracking hydration changes
- acute hydration changes can be measured by taking nude body mass before and after exercise
- check urine concentration/ colour in morning
- thirst- first morning thirst is correlated with hypo hydration
rehydration concepts
- 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
hydration bottom line
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
hydration plans
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)
