Lecture 19 Flashcards
Cold Stress
three factors that lead to cold stress
cold, wet, wind
4 problems that can arise from cold stress for exercise
- impaired performance
- discomfort
- glycogen depletion
- injury / illness
how can exercise performance be impaired by cold stress
- power
- strength
- dexterity
- aerobic capacity
- early fatigue
what injury / illnesses can arise from exercise in cold stress
- hypothermia
- non freezing tissue
- frostbite
- soft tissue strains
what determines the net level of cold stress
the balance between heat gain and heat loss
4 ways heat is lost from the body
evaporation
radiation
convection
conduction
heat will be lost if air temperature is less than skin temperature, in which ways
- radiation
- convection
- conduction
what is the optimal environment for exercise (compared to rest) and why
optimal environment for exercise is cooler than at rest, more so as intensity increases
because heat itself is a stressful
what is the biggest method heat loss from the body when exercising in the cold and how does this happen
convection
- heat lost to the environment, when the environment is cooler than the body temperatire
example of behavioural response to cold
clothing
when is behavioural responses not the most effective to combating the cold
- cognitively impaired by hypothermia (and alcohol)
- cold-impaired strength, dexterity or coordination
- injured
- competitive exercise and behaviour choices
when is exercise not effective response to cold
- cool / cold water (but can still be best option)
- fatigued (decreased production, increased loss of heat)
what are the 2 major physiological responses to cold
- vasoconstriction of skin and muscle
- allows both of them to be insulators - shivering
what other processes are affected by shivering
movement increases heat loss if in water - boundary layer
dilates blood vessels muscle (decreases its insulation)
what are the two minor physiological responses to cold
counter-current heat exchange in limbs
non shivering thermogenesis
what is the boundary layer that occurs when we are in water and what can disturb this
thin layer of water that is in direct contact with the skin,
this layer can be warmer than the surrounding water as it is in contact with the body
shivering can disturb it
what is the resting comfort skin temperature
33 degrees
what type of drive occurs in the cooling defence zone and what is it driving
provides feedforward drive for vasoconstriction, also contributes to drive for shivering
what occurs at a core temperature of 36
moderate shivering, reduced strength, power and dexterity
what occurs at a core temperature of 35
hypothermia
- maximal shivering and decreased performance
how quickly will you develop hypothermia
depends on many factors, especially temperature but it still takes a reasonably long time to develop
what occurs at a core temperature of 33
cardiac arrhythmias; highly variable inter individual responses
what happens at a core temperature of 29
severe cardiac arrhythmias and unconsciousness common
what happens to sensory and motor functions due to decreased peripheral temperature (skin, muscle and nerves) due to cold
decreased sensory and motor functions
what are hand and foot temperatures governed by (3)
- if body is in +ve heat balance overall
- clothing coverage
- local muscle activity
what does not help prevent hypothermia
- ectomorphy
what is ectomorphy
this is having a thin body build
who is most at risk during exercise in cold conditions
- small, ectomorphic body shape
- young
- elderly
who can be at risk during exercise in cold conditions but it depends
sedentary people
males + females
why does it depend is sedentary people are at risk during exercise in the cold
typically they have a higher body mass, but aerobic fitness plays against them
so depends on balance between these if they are at risk or not
will a fit or unfit person maintain their core body temperature better in the cold
fit person
humans do not adapt cold defence with repeated cold stress, instead what happens ? and what is this called
we cool faster while feeling more comfortable
- habituation
how much faster does water conduct heat than air
25x faster
is convection increased or decreased in water compared to air
convection is increased in water
how long does the cold shock response typically last
1.5 - 3 minutes
if the initial gasp response that occurs in cold shock was to occur under water what could happen
drowning as it is a large breath
how rapidly can we adapt to the cold shock response
rapidly = only takes a few immersions
what is incapacitation (over the first few minutes) of immersion into cold water
- difficulty breathing and muscle contraction
- strain on the heart
why is there strain on the heart in incapacitation
severe sympathetic drive on the heart but also parasympathetic drive = dual activation on SA node
what temperature is beneficial to exercise in water in terms of maintaining heat balance
28 degrees
what temperature is detrimental to exercise in water
10 degrees
implications that can occur exercising in the cold if you have had prior exercise or heat stress and why
- cool faster during cold stress
- cause skin vasodilated so as soon as we enter cold heat will be removed - can decrease energy capacity
- due to decreased insulative capacity
symptoms of hypothermia
- cold and shivering
- disorientation
- obvious alteration in mood, lethargy
- muscle weakness
- symptoms variable
what should you attempt to warm first when treating someone with hypothermia
warm their torso and core
