Chapter 14 Flashcards
Muscles turn chemical
energy into mechanical
work and into ____ as
well.
heat
There are 4 mechanisms of heat exchange, what are they?
- radiation
- conduction
- convection
- evaporation
Explain the mechanism of heat exchange: radiation
accounts for about 60 percent of the heat
loss from a nude person resting quietly in a room
at 21oF. explains how dark colours allow us to absorb heat from the sun
Explain the mechanism of heat exchange: conduction
transfer of heat between two objects of different temperatures that are in direct contact with each other.
Explain the mechanism of heat exchange: convection
the transfer of heat between the surface of the
body and the air (or water, if one is swimming)
because of the circulation of air or water molecules
next to the skin. (Wind Chill Index)
Explain the mechanism of heat exchange: evaporation
The transfer of heat from the body surface through
the change of liquid water on the skin to a gaseous
water vapour.
In hot weather, is it better to cycle or run?
Cycling is better than running in hot weather
because of convection.
What is the humans’ major physiological defence
against overheating? In very hot environments this may be the only method of heat loss.
evaporation
What are 4 ways we generate heat?
- basal metabolic rate (heat production at rest)
- exercise
- shivering
- thermogenic effect of food (digestion of food raises metabolic rate above fasting level)
The thermoregulatory system maintains a relatively
constant internal body temperature. At rest this is
around 37oC. This is the reference temperature. In exercise, this reference temperature is increased. Why is this beneficial?
- increased rate of metabolic reactions
- Increased rate of diffusion of gases and metabolites across membranes
- Decreased viscosity of blood and other body fluids
How does the brain help us regulate temperature?
- hypothalamus acts like a thermostat allowing us to increase or decrease temp in body
- example: In exercise, the setting of the body’s thermostat is
elevated. Heat dissipation mechanisms don’t
begin until the body core has warmed up to a level
closely related to the relative exercise intensity
How does this tissue/ gland impact the process of temperature regulation?: skeletal muscles
We can shiver or voluntarily perform physical
activity to generate heat.
How does this tissue/ gland impact the process of temperature regulation?: smooth muscles
They encircle the arterioles supplying blood to
the skin. Can contract to constrict the arteriole and reduce blood flow, or they can relax to enhance blood flow. When the body wants to conserve heat, it will reduce blood flow to the
periphery; when it wants to lose heat, it will increase blood flow to the skin.
How does this tissue/ gland impact the process of temperature regulation?: sweat glands
To lose heat through evaporation, we sweat
How does this tissue/ gland impact the process of temperature regulation?: certain endocrine glands
These are glands such as the thyroid and adrenal medulla. They secrete hormones that can increase
the basal metabolic rate.
How does exercising in hot environments impact:
- the circulatory system
- blood volume and stroke volume
- heart rate
- Puts stress on the circulatory system – blood has to go to the muscle and the skin - Sweat loss reduces blood volume and thus stroke volume - Heart rate for the same workloads increases.
List the heat illnesses (3) that athletes can suffer from. List them in order of increasing severity
- heat cramps
- heat exhaustion
- heat stroke
What are the factors (3) that can impact the onset of heat disorders?
- Heat exposure
- Loss of water and salt
- Heat storage (reflected by high core temp)
What makes athletes more susceptible to heat disorders (things they DO) (3).
- ignore discomfort
- wearing restrictive clothing + equipment
- coach may deny water to train mental toughness
Fluid loss varies from person to person. A loss of ____ in mass is considered dehydration.
> 2%
What are 6 ways to prevent heat disorders?
- acclimatization
- shade
- schedule
- gear/ equipment
- colors
- expose skin/ remove clothing
Explain: heat acclimatization; How long does it take to acclimatize?
- Acclimatization is the physiological adaptation which a person makes with repeated exposures to a set of thermal conditions. Improves general tolerance to the heat and change in HR response noted.
- It usually takes 7–10 days, with at least 2–4 hours of daily exposure of exercise periods
Do you understand the relationship between acclimatisation adaptations and the physiological effects it has on the body listed on table 14.1?
- see google doc
How do we assess environmental heat stress?
- Wet- Bulb Globe Temperature (WBGT): combines ambient temperature, environmental
radiation and humidity levels. - heat index: index that takes into account temperature and humidity; in short: add 6 deg if wearing clothing and 6 deg if in direct sunlight
What is the goal of fluid replacement during exercise? What is the general numerical guideline (ml/hr during vigorous exercise) for hydration during vigorous exercise?
- Goal is to maintain plasma volume
- 200-800mL/ hour of vigorous exercise
State the fluid replacement guidelines – prior, during, and after exercise
prior:
- hydrate properly before prolonged exercise, especially in a hot and/or humid environment.
during:
- replace fluid to maintain less than a 2% loss of body weight in sweat;
- drink frequently; keep them readily available
- drink cool beverages as they are better absorbed than warm drinks and can help reduce body heat
after:
- replenish fluids at a rate of around 0.5 L for
every 0.5 kg of body weight lost
Explain the impacts of water vs hypotonic (gatorade) drinks vs hypertonic drinks (sugary soft drinks) for rehydration/ fluid replacement
- water: usually adequate as a fluid replacement. The addition of modest amounts of salt in fluid or food can promote rehydration more effectively than plain water when significant weight has been lost through sweating
- hypotonic drinks (Gatorade): replenish electrolytes if excessive sweating and prolonged exercise
- hypertonic drinks (sugary soda): not ideal and can be dangerous in situations where dehydration is potentially severe.
define: hyponatremia
- when can it occur
- symptoms
- deficiency of sodium in the blood
- It can occur as a result of inadequate sodium intake, as in a sodium-restricted diet, excessive water ingestion or retention, or excessive sweating
- symptoms: muscular weakness and twitching, progressing to convulsions if unrelieved; alterations in level of consciousness; mental
confusion; and anxiety
define: dipsomania; How does this definition apply to our understanding of exercise physiology?
- “Uncontrollable desire for drink, especially alcohol.” - Drinking water constantly, at every station even when intensity is low – might not be necessary
Quiz yourself: The transfer of heat via direct contact with an object is called: A. evaporation B. radiation C. convection D. conduction E. the wind chill index
D) conduction
Quiz yourself: When exercising in very hot conditions, which of these mechanisms is the major (and sometimes only) avenue of heat loss: A. evaporation B. radiation C. convection D. conduction E. the wind chill index
A) evaporation
Quiz yourself: Which of these mechanisms does not increase energy production above resting metabolism?: A. Exercise B. Shivering C. Eating food D. Reduced blood flow to the periphery
D) Reduced blood flow to the periphery
