A2 environmental factors

relationship between cellular metabolism and heat production

• byproduct from aerobically releasing energy, synthesising ATP

• more work we undertake the greater amounts of oxygen and food fuels utilised, the greater production of heat

normal core body temp

37 ± 0.6 degrees celsius

conduction

skin contact with an object of a different temperature e.g. ice packs

convection

moving heat from one place to another by motion of air or water movement e.g. cyclists

radiation

transfer of energy waves sent by one object and absorbed by another e.g. sun, heater

evaporation

heat loss through conversion of water/sweat to vapour

humidity on thermoregulation

sweat cannot evaporate because the air has a decreased capacity to accept more molecules, so this inhibits cooling

• rise in core body temp and potential decrease in performance

wind on thermoregulation

convective heat loss occurs most prominently in the presence of wind

formation and sweat response

• plasma is the source of sweat formation

• sympathetic nervous system activates sweat glands

• amount of sweat depends on: amount sweat gland can produce, amount of sweat glands, individual/exercise int./acclimatisation/hydration

3 physiological response from prolonged exercise in the heat

• cardiovascular responses

• sweating

• energy metabolism

cardiovascular response in heat

cardiovascular drift:

• decreased plasma volume - increased viscosity

• arterial blood pressure is reduced from decreased venous return

• stroke volume decreases

• peripheral blood flow increases to reduce core temperature through sweating

energy metabolism response in heat

increased glycogen breakdown in the muscles

• increased lactate

heat cramps

intermittent spasms, involuntary, earliest symptom of heat-related illness

heat cramps prevention and treatment

• stay hydrated, avoid work or exercise in heat of the day, lower exercise intensity

• stop exercise, rest stretch and apply ice

heat exhaustion

• caused by exertion in heat, high humidity and often dehydration

• does not cause impaired mental function, confusion or loss of consciousness and temperature does not go above 39 degrees

heat exhaustion prevention and treatment

• stay hydrated, avoid working in hottest time of day, lightweight clothing

• soak/immerse in water, remove clothes

heat stroke

body overheats with temperatures of above 40, can have altered mental state and loss of consciousness

heat stroke prevention and treatment

• light clothing, stay hydrated, avoid working in heat of the day

• call emergency services, immerse in cold water and remove clothes

acclimatisation

physiological adaption to changes in climate or environment

how an athlete should acclimatise

• arrive/train in conditions 5-10 days before competition

• reduce exercise intensity initially

physiological adaptations from heat acclimatisation

• increased plasma volume

• increased sweat response

• decreased glycogen stores used

increased plasma volume in heat acclimatisation

occurs as a response to increased stroke volume, accompanied by decrease in heart rate and is temporary

increased sweat response in heat acclimatisation

sweat becomes more diluted and leads to improved regulation of body temperature

decreased muscle glycogen use heat acclimatisation

occurs as cardiac output increases during heat acclimatisation, more O2 is available to save glycogen and use fats

thermoregulation in cold

• shivering

• non-shivering thermogenesis

• peripheral vasoconstriction

shivering

involuntary produces heat as byproduct when chemical energy is used to produce movement

non-shivering thermogenesis

adipose tissue can utilise fuel just to produce without creating ATP

peripheral vasoconstriction

narrowing blood vessels to keep blood from extremities to keep warm blood at core

SA:V on heat loss

• large SA:V increases heat loss

• fat helps slow down heat transfer from inside of body to surface

• tall, heavy have loss SA:V hence less susceptible to hypothermia

• small children large SA:V more difficult to maintain normal body temp in cold

importance of wind chill

chill factor by the increase in the rate of heat loss via convection and conduction caused by wind

problem swimming in cold water

• during swimming effect of cold water on body heat loss is increased because of convective heat loss

• high swimming speeds and high metabolic rates may compensate for heat loss

• water conducts body heat away up to 26 times faster than air

• lose body heat and become hypothermic at a rate proportional to the thermal gradient and duration of exposure

muscle function response to cold

• cold causes muscles to cntract with less force

• fatigue cause less muscle acitivty and less body heat production

• manual dexterity/fine motor skills are greatly impaired

metabolic response to exercise in cold

• muscle glycogen used at a higher rate hence earlier fatigue - shivering, increased adrenalin

• vasoconstriction of blood vessels to fatty tissue

• more energy used exercising in cold than in heat

frostbite

continued cooling and freezing of cells, leading to destruction of cells

• toes, fingers, ears and nose most common sites of frostbite

hypothermia

body temp below 35 degrees that results in decreased respiratory rate and folume

• shivering, slurred speech, shallow breathing, weak pulse, low energy, memory loss, loss of consciousness

precautions when exercising in the cold

• measured in clo

• layer clothing

• cover head

• cover mouth

• stay dry

• keep feet dry

• stay hydrated

• avoid alcohol