A2: Environmental factors affecting physical performance

Question 1

A.2.1 - Explain the relationship between cellular metabolism and the production of heat in the human body.

Answer 1

-Cellular metabolism breaks down nutrients To produce energy (ATP).

-Some energy released during metabolism is converted into heat.

-Heat production regulates body temperature (thermoregulation).

-Heat is generated during muscle contraction.

-Metabolic rate influences heat production.
Heat is involved in digestion and absorption of nutrients.

Question 2

A.2.2 - State the normal core body temperature at rest

Answer 2

36°C to 38°C

Question 3

A.2.3 - Outline how the body thermoregulates in hot and cold environments

Answer 3

4 main ways
- conduction
-convection
-Radiation
-Evaporation

• Vasoconstriction
• Vasodilation

Question 4

A.2.4 - Discuss the significance of humidity and wind in relation to body heat loss

Answer 4

Surfaces exposed to the environment - As humidity increases, no more water can evaporate.

In hot conditions, sweat evaporates slower, which causes the body to overheat. In low humidity, sweat evaporates quickly, which may cause dehydration.

With wind: convection involves moving heat from one place to another by the motion of air.

more wind, more convection so more heat is lossed.

Question 5

A.2.5 - Describe how an athlete forms sweat in order to maintain body temperature during exercise

Answer 5

• Hypothalamus/brain detect rise in body temperature\
• sympathetic nervous system activates sweat glands
• plasma is the source of sweat formation
• sweat passes through the (uncoiled) duct/pores of the gland onto the skin surface
• amount of sweat formed depends on the individual / exercise intensity/ acclimatization/hydration status.

Question 6

A.2.6 - Physiological responses to prolonged exercise in the heat

Answer 6

• Muscular exercise increases metabolism by 5 to 15 times
• Depending on the type of exercise, 70 to 100 percent of the metabolism is released as heat and needs to be dissipated in order to maintain body heat balance
• The reduced muscle blood flow in high temperatures results in increased glycogen breakdown in the muscle and higher levels of muscle and blood lactate in comparison to the same exercise performed in a cooler environment.

IB syllabus:
Performing training sessions in similar
environmental conditions (heat and humidity)
for 5 to 10 days results in almost total heat
acclimatization. Initially, the intensity of training
should be reduced to avoid heat-related problems in these conditions.

Question 7

A.2.10 - Discuss the physiological and metabolic adaptations that occur with heat acclimatization

Answer 7

Long Term Adaptations
-Thirst is regulated to meet the needs of the body
-Total body water increases (up to 5%)
-Increased plasma volume
-Earlier onset of sweating (and at a lower temp)
-more dilute sweat (electrolyte loss reduced)
-Reduced rate of muscle glycogen use
- Deceased psychological perception of effort.

Example: Heat stress during a single bout of exercise increases the body’s metabolic rate. This leads to increased glycogen use. When you acclimatize to hot environments, your body’s metabolic rate decreases which means a reduced rate of muscle glycogen use. Therefore the muscle glycogen stores last longer allowing the athlete to perform for longer (improved endurance). In addition, a lower metabolic rate means less heat production and removal.

Question 8

A.2.7 - Discuss the health risks associated with exercising in the heat.

Answer 8

• Hyperthermia,
• heat stroke
• heat exhaustion

Having a higher level of aerobic fitness can protect an athlete from heat stress/illness (similar to acclimatization)

Question 9

A.2.8 - Prevention of health risks with exercising in the heat.

Answer 9

Heat stroke - Immediate whole body cooling, Acclimatize, Adapt to climatic constraints.

Heat exhaustion - Remove subject to shaded area/air-conditioned area, Hydrate before and during exercise,
Acclimatize

Heat Cramps - Stop exercise; rehydrate Massage/Light stretching

Question 10

A.2.9 - Describe how an athlete should acclimatize to heat stress.

Answer 10

• Preforming training sessions in similar environmental conditions
• for 5 to 10 days result in almost total heat acclimatization
• Initially, the intensity of training should be reduced to avoid heath related problems in these conditions.

Question 11

2.2.11 Outline the principal means by which the body maintains core temperature in cold environments.

Answer 11

cold exposure decreased skin and core temp, which stimulates the hypothalamus.

• Shivering, The body shivers to produce heat from the repeated muscular contractions. Shivering, however, uses up extra oxygen and glucose / glycogen stores.

Peripheral vasoconstriction:
Constriction of blood vessels close to the skin and skeletal muscles meaning more blood remains near the core. This keeps the core temp elevates and decreases the heat transferred to the environment.

non shivering thermogenesis
Increase in metabolic process where excess calories are used to produce heat rather than stored as fat

Question 12

A.2.15 -Discuss the physiological responses to exercise in the cold.

Answer 12

Decrease in muscle contractility
- Decrease in the power and velocity of muscle contraction
-change in the pattern of muscle fiber recruitment.
- Prolonged exercise in the cold depletes glycogen stores and can lead to an inability to maintain blood glucose.

• cold -> decreases HR -> increase in stroke volume.

Question 13

A.2.12 - Explain why the body surface area to body mass ratio is important for heat preservation

Answer 13

A large surface area to body mass ratio = increased heat loss

A lower area to body mass ratio = decreased heat loss.

Tall heavy individuals have a small body surface to body mass ratio compared to kids with a higher body surface to body mass ratio, losing heat faster.

Question 14

A.2.13 Outline the importance of wind chill in relation to body heat loss.

Answer 14

Wind influences the rate of heat loss via convection and conduction

Windproof clothing or strenuous exercise in wind reduces wind chill effects.

Question 15

A.2.16 - Describe the health risks of exercising in the cold, including cold water.

Answer 15

hypothermia - condition in which the bodies’ temperature drops below that required for normal metabolism and body functions. This, generally considered to be less than 35 Celsius

Frostbite - The continued cooling and frezzing of cells. Can lead to cell death.

Question 16

A.2.17 Discuss the precautions that should be taken when exercising in the cold.

Answer 16

clothing, the amount of insulation offered by which is meaured in a unit called a clo.

Increased hydration: exercise in cold results in increased breathing treated, increased heat production and therefore increased potential to dehydration.

Decrease amount of skin in contact with environment in high wind chill: decrease the amount of heat loss through convection.

Provide insulation for feet hands, ears: most prone to frost bite,

Increases in carbohydrate intake: Account for increases in glucose/glycogen use during exercise in the cold.

Question 17

A.2.14 - Explain why swimming in cold water represents a particular challenge to the body’s ability to thermoregulate.

Answer 17

Heat loss occurs even more when water moment is strong convection.

The colder the water and the faster the movement, the greater the rate of heat loss

However, at high swimming speeds, the metabolic rate of the swimmer may compensate for the increased heat loss