Chapter 14

Question 1

Muscles turn chemical
energy into mechanical
work and into ____ as
well.

Answer 1

heat

Question 2

There are 4 mechanisms of heat exchange, what are they?

Answer 2

• radiation
• conduction
• convection
• evaporation

Question 3

Explain the mechanism of heat exchange: radiation

Answer 3

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

Question 4

Explain the mechanism of heat exchange: conduction

Answer 4

transfer of heat between two objects of different temperatures that are in direct contact with each other.

Question 5

Explain the mechanism of heat exchange: convection

Answer 5

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)

Question 6

Explain the mechanism of heat exchange: evaporation

Answer 6

The transfer of heat from the body surface through
the change of liquid water on the skin to a gaseous
water vapour.

Question 7

In hot weather, is it better to cycle or run?

Answer 7

Cycling is better than running in hot weather

because of convection.

Question 8

What is the humans’ major physiological defence

against overheating? In very hot environments this may be the only method of heat loss.

Answer 8

evaporation

Question 9

What are 4 ways we generate heat?

Answer 9

• basal metabolic rate (heat production at rest)
• exercise
• shivering
• thermogenic effect of food (digestion of food raises metabolic rate above fasting level)

Question 10

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?

Answer 10

• increased rate of metabolic reactions
• Increased rate of diffusion of gases and metabolites across membranes
• Decreased viscosity of blood and other body fluids

Question 11

How does the brain help us regulate temperature?

Answer 11

• 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

Question 12

How does this tissue/ gland impact the process of temperature regulation?: skeletal muscles

Answer 12

We can shiver or voluntarily perform physical

activity to generate heat.

Question 13

How does this tissue/ gland impact the process of temperature regulation?: smooth muscles

Answer 13

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.

Question 14

How does this tissue/ gland impact the process of temperature regulation?: sweat glands

Answer 14

To lose heat through evaporation, we sweat

Question 15

How does this tissue/ gland impact the process of temperature regulation?: certain endocrine glands

Answer 15

These are glands such as the thyroid and adrenal medulla. They secrete hormones that can increase
the basal metabolic rate.

Question 16

How does exercising in hot environments impact:

• the circulatory system
• blood volume and stroke volume
• heart rate

Answer 16

- 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.

Question 17

List the heat illnesses (3) that athletes can suffer from. List them in order of increasing severity

Answer 17

• heat cramps
• heat exhaustion
• heat stroke

Question 18

What are the factors (3) that can impact the onset of heat disorders?

Answer 18

• Heat exposure
• Loss of water and salt
• Heat storage (reflected by high core temp)

Question 19

What makes athletes more susceptible to heat disorders (things they DO) (3).

Answer 19

• ignore discomfort
• wearing restrictive clothing + equipment
• coach may deny water to train mental toughness

Question 20

Fluid loss varies from person to person. A loss of ____ in mass is considered dehydration.

Answer 20

> 2%

Question 21

What are 6 ways to prevent heat disorders?

Answer 21

• acclimatization
• shade
• schedule
• gear/ equipment
• colors
• expose skin/ remove clothing

Question 22

Explain: heat acclimatization; How long does it take to acclimatize?

Answer 22

• 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

Question 23

Do you understand the relationship between acclimatisation adaptations and the physiological effects it has on the body listed on table 14.1?

Answer 23

• see google doc

Question 24

How do we assess environmental heat stress?

Answer 24

• 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

Question 25

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?

Answer 25

- Goal is to maintain plasma volume | - 200-800mL/ hour of vigorous exercise

Question 26

State the fluid replacement guidelines – prior, during, and after exercise

Answer 26

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

Question 27

Explain the impacts of water vs hypotonic (gatorade) drinks vs hypertonic drinks (sugary soft drinks) for rehydration/ fluid replacement

Answer 27

- 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.

Question 28

define: hyponatremia - when can it occur - symptoms

Answer 28

- 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

Question 29

define: dipsomania; How does this definition apply to our understanding of exercise physiology?

Answer 29

``` - “Uncontrollable desire for drink, especially alcohol.” - Drinking water constantly, at every station even when intensity is low – might not be necessary ```

Question 30

``` 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 ```

Answer 30

D) conduction

Question 31

``` 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 ```

Answer 31

A) evaporation

Question 32

``` 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 ```

Answer 32

D) Reduced blood flow to the periphery