ch 14/15 Flashcards
Heat loss mechanisms
Radiation
Conduction
Convection
Evaporation
Radiation
about 60% of our heat loss
electromagnetic waves give off heat
Conduction
direct contact with something (including the air) that results in heat loss in the body
heat always flows from the warmer to colder object
Heat conduction in water is — times greater than in air
25
Convection
The transfer of heat between the surface of the body and the air/water because of circulation of air/water molecules next to the skin
Evaporation
heat transfer from the body surface through change of liquid water on the skin to water vapour
no evaporation can occur if air is 100% saturated with water
normal core temp
–> and what range can we tolerate
normal= 36.5-37.5 degrees C
tolerate a temp decrease of 10 deg C
Increase of 6 deg C
Why can we tolerate lower core temp better?
less cell death
–> lower core temp= slower processes/cells
Higher core temp= heat speeds rxns up
How do we generate heat?
Basal metabolic rate
Exercise
Shivering
The digestion of food
The reference temperature
the thermoregulatory system maintains a core temp of 37 deg C
When we exercises, reference temp rises. This is beneficial because it allows
-increased rate of metabolic rxns
-increased rate of diffuction of gases across membranes
-decreased viscosity of blood/body fluids
Which receptors sense the increase in body temp?
- Central receptors (in hypothalamus) which are sensitive to temp of arterial blood
- Peripheral receptors (on skin) which are sensitive to hot or cold
The regulatory centre controls…
the two receptors that sense change in body temp
they initiate vol/invol regulation through effectors
Temp regulation: Skeletal muscles
shivering/voluntary physical activity
Temp regulation: smooth muscles
they are around the arterioles supplying blood to the skin
–> constrict the arteriole= reduced blood flow (to gain heat)
–> relax= enhance blood flow (to loose heat)
Temp regulation: glands
Sweat glands: loose heat through evaporation
Certain endocrine glands: secrete hormones that increase basal metabolic rate
Sweat loss also reduces..
blood volume and stroke volume
–> HR will be higher and stroke volume will be lower in a hot envmnt
Factors of heat illness risk
heat exposure
loss of water and salt
heat storage
why are athletes susceptible because
they ignore discomfort
clothing/equipment
coach may deny water
How to prevent heat disorders
acclimitization
shade
schedule (time of day)
gear/equipment
colours (black/white)
expose skin/remove
clothing
How to monitor fluid loss?
weigh athletes before/after competition
colour of urine
Greater than …. of mass of fluid loss is considered dehydration
2%
Acclimation
physiologically adopting to the heat in an artificially induced envmnt
Acclimatization
physiologically adapting to heat by going to a naturally hot environment
to quantify envmntal heat stress, you need to combine the effects of
ambient temp
envmntal radiation
humidity levels
Heat index table
is used if heat is an issue in a race
it is a combination of temp and relative humidity
fluid replacement
goal= maintain plasma volume (blood is 50-55% plasma)–> which is 90% water
200-800mL/hour of vigorous exercise
at least 5 clear urinations per day
Sweat is —- to body fluids
hypotonic
(concentration of particles in sweat is lower than in the body’s fluids)
–> it is usually more important to replace water than ions
— fluid has concentrations of particles that are higher than the body’s fluids
hypertonic
–> that is why gatorade is more effective than hypertonic beverages
Recommended ratio of glucose to fructose
2:1
CHO consumption per hour during exercise
30/60g
ideal range for fructose-glucose blends of CHO per hour
68-88g
Fluid replacement guidelines
-hydrate b4 exercise
-drink frequently
-maintain less than 2% loss of body weight in sweat
-cool beverages are better absorbed than warm
-replenish fluids at rate of 0.5L for every 0.5kg of body weight lost after workout
Hyponatremia
deficiency of sodium in the blood
–> from inadequate sodium intake, excessive water ingestion/retention, or excessive sweating
Dipsomania
=over-hydration can cause the body and the brain to swell
“water intoxication”
the pressure of the brain against the skull can increase, leading to convulsions, heart failure, and cessation of breathing
how are hyponatremia and dipsomania related??
dispomania can cause hyponatremia but they are not directly related
dipsomania is the uncontrolable urge to consume fluids= overhydration
Neuroendocrine system
composed of endocrine glands
the nervous system controls the release of hormones from these glands
The neuroendocrine system is responsible for
-maintaining homeostasis and commanding responses to exercise and diet
-how we respond/adapt to training stimulus
-depends on quality and quantity of exercise
we are usually dominated by — (which component of nervous system)?
PNS unless we are under a lot of mental stress
sympathetic nervous system (SNS) main effect
prepares body for physical activity
The PNS controls
responses during relaxation
“rest and digest”
Hormone mechanisms
ex. High GI foods
ex. Lack of sleep
High GI foods–> insulin increase–> increased fat storage
Lack of sleep–> increased ghrelin and decreased leptin
Differences in rates of signals: endocrine and nervous system
endocrine= slow to initiate, prolonged response
nervous= fast signalling, short-lived responses
What controls the secretion of hormones??
the brain (CNS)
catabolism
the metabolic pathways that break down molecules to release energy
anabolism
construct molecules from smaller units
Anabolic rxns require
energy
therefore anabolism is powered by catabolism
Immediate catabolic response to acute exercise (sudden onset of exercise)
fight or flight response triggers neural sympathetic response
–> secretion of ACTH
–> releases neurotransmitters epinephrine and norepinephrine
–> produces cortisol
–> increases BP and respiration
–> more O2 delivered to muscles
–> liver converts proteins to glucose
–> aids in metabolism of fat and carbs
Cortisol negative effects
can suppress the immune system and repair functions and decrease bone formation
chronically high cortisol levels can
cause insulin resistance and diabetes
can stimulate visceral adipose tissue to store fat
psychological stress= main factor in high rates of obesity and coronary heart disease and has been linked to pain syndromes
High level performance equation
Performance= Fitness - Fatigue
-must balance work and recovery
-inadequate rest lowers testosterone levels
-joint pain= warning sign of overtraining
Acute inflammation
normal and beneficial
–> increase blood plasma and WBC move into injured tissues causing pain
–> anti-inflammatory drugs block production of extra prostaglandins
Chronic inflammation
leads to progressive shift in the type of cells present at the site of inflammation
–> simultaneous destruction of damaged cells and initiation of tissue repair
–> NEVER repair tissues/cells
athlerosclerosis, rheumatoid arthriris…..
DOMS
peaks 24-72 hours after exercise
-indicates complex metabolic and hormonal processes involved in creating the symptoms of muscle soremess
-loss of coordination and strength and decreased ROM
–> much greater for ECCENTRIC muscle contractions
DOMS mechanism
- mechanical damage to ultrastructure and accumulation of calcium (myofibril and membrane breakdown)
- acute inflammatory response increases swelling=pain
- high mechanical tension, muscle strain and elevated muscle soreness peaked 24-48 hours after exercise
Causes of chronic inflammation
Excessive exercise without recovery
Diet
Inability to cope w persistent psychological stress
Environmental stressors
Is there an acute anabolic repsponce during exercise???
NO
-need catabolic first
–> need breakdown of substrates to produce ATP
anabolic happens after exercise
Anabolic response after exercise
post-exercise insulin will help replenish glycogen
other key anabolic hormones
testosterone, human growth hormone, and inlusin like growth factors (IGF)
Which exercises increase the secretion of GH, IGF-1, and testosterone
compound, multi-joint exercise at high intensities
Ideal time to exercise based on hormones?
whenever you feel best/have most energy
testosterone levels highest in the morning but does not mean that you need to exercise at that time
Hormonal effects of diet
High GI= elevated cortisol can cause pancreas to become insulin resistant==> obesity, diabetes etc.
Psychological aspect
Vitamin D= increases receptors for IGF which impacts growth of all cells
Sleeping and Naps
Insufficient sleep= linked to cancers, heart disease and diabetes and low testosterone levels
Napping is beneficial, especially if person is sleep deprived
Ideal time for a nap
10-20 min
beyond 20 min= sleep inertia= groggy feeling
if you sweat more are you more fit or less fit?
well-conditioned people will sweat more, with more volume and less salt in their sweat
–> well-conditioned= will respond more efficiently to heat stress
are hypotonic or hypertonic beverages good for hydration?
hypotonic is easily absorbed!!
hypertonic= sugary drinks, need to be diluted in the stomach first (because it has a higher concentration of particles than our body fluid does)
how does our diet impact our hormones?
the quality and the quantity of the foods we consume
hyperinsulinemia
chronically high levels of insulin which leads to T2D
decreased sleep and obesity
decreased sleep leads to weight gain
decrease leptin, increase ghrelin, and compromises insulin sensitivity
testosterone and cortisol relationship
increased cortisol lowers testosterone
inadequate work-rest balance lowers testosterone
