A2 - environmental factors and physical performance

explain the relationship between cellular metabolism and the production of heat in the human body

the energy released when glucose reacts with oxygen is sued to produce ATP, however, only a fraction of the released energy goes into the high energy bonds of ATP.

• overall reaction is termed exergonic and some energy is lost as heat

therefore, the more work we undertake, the greater amount of oxygen and food fuels are utilised, the greater the production of heat.

what is cellular metabolism

energy produced aerobically

state the normal physiological range for core body temperature

resting adult human being is stated to be at 37+ or - 0.6 degrees celsius.

what are some factors that may cause variation in core temperature

• time of day/temp

• body location of measurement

• metabolism rate → the faster it is, the higher the normal body temp is

outline how the body thermoregulates in hot and cold environments

conduction - involves skin contact with an object of a different temperature

• body will lose temp when in contact with colder surfaces e.g. the snow and vice versa

convection - involves moving heat from one place to another by motion of air/water movement

• e.g. the fan making someone cool, wind in the snow etc

radiation - transfer of energy waves (sun, fireplace, radiator) sent by one object and absorbed by another

• if atmosphere is cooler than the body, the body will lose heat, vice versa

• e.g. an air conditioned room, the sauna or a desert

evaporation - heat loss through the conversion of water/sweat to vapour

• important to the body to regulate heat

• as sweat evaporates from the skin, a cooling effect is achieved, thus releasing heat from the body.

what is homeostasis

the maintenance of a constant internal bodily environment despite possible changes in external conditions.

discuss the significance of humidity in relation to body heat loss

• in hot weather, sweating in primary mehtod for staying cool

• if the air is humd (full of moisture), sweat cant evaporate because air has a decreased capcity to accpet more molecules, so this inhibits cooling.

• this leads to a rise in core body temp qand links to a potential decrease in performacne.

discuss the significance of wind in relation to body heat loss

convective heat loss occurs in the presence of wind

• in higher wind, air passes over the skin at a greater sped, thereby increasing the rate t which heat can be transferred to the atmosphere

• if wind is cold and body is wet, the cooling affect is amplified, therefore wind chill can become a factor and lead to hypothermia

describe the formation of sweat and the sweat resposne

formation

• muscular activity increases body heat

• heat stimulates hypothalamus

• hypothalamus stimulates sweat glands to secrete fluid

• evaporation of fluid cools body.

sweat produced by the sweat glands is converted from liquid to vapour by heat from the skin and is transported away (evaporates), therefore cooling the skin.

• plasma is the source of sweat formation

• sympathetic nervous system activates sweat glands

discuss the 3 physiological responses that occur during prolonged exercising in the heat

cardiovascular responses

• cardiovascular drift

  • plasma volume decreases during exercise du to water being drawn from the blood plasma and out of the body as sweat

  • hemo-concentration occurs → plasma is lost, resulting in higher concentration of red blood cells resulting higher viscosity of blood

  • arterial blood pressure is reduced as a result of the decreased venous return

  • stroke volume decreases due to reduced venous return → results in an increased HR to maintain cardiac output

  • peripheral blood floe increases to reduce core temp through sweating

sweating

• exercise increases core temp → causes the hypothalamus to stimulate the production of greater volumes of sweat

• sweating during exercise is a sign of an efficient cooler

  • an athlete who has adapted to keep the body core cool during exercise will shunt blood to the skins surface more quickly and release heat from the body quicker.

  • the swat glands increase their output and thus cool the body during sweat evaporation

energy metabolism

• reduced muscle blood flow in high temp results in increased glycogen breakdown in the muscle and higher levels of muscles and blood lactate in comparison to the sam exercise performed in cooler environments.

what are the health risks are associated with exercising in the heat

cramps, heat exhaustion, heat stroke

discuss heat cramps

• intermittent spasms that can affect a person doing intense physical activity in hot and humid environments.

symptoms

• cramping pains in the abdomen, arms and legs

• clammy, pale skin

• nausea

prevention

• stay hydrated

• do not drink alcohol or coffee before or during exercise

• avoid exercise during the heat of the day

• find rest in shaded area when outdoors

treatment

• drink frequent small amounts of cool water, waiting for any nausea to pass first

• cease all activity

• apply ice packs

• rest in a cool shaded area.

discuss heat exhaustion

caused by exertion accompanies by heat, high humidity and often dehydration. Internal body temp doesn’t go above 39 degrees celsius

symptoms

• irratable behaivour

• rapid, shallow breathing

• dizziness

• headache

prevention

• stay hydrated to prevent dehydration

• avoid caffeine and alcohol

• wear lightweight clothing

treatment

• strip off clothing and move to cooler surrounds

• soak with water

• fan vigorously and mist with cold water

• call 000 if there is no improvement in 10 mins

discuss heat stroke

a condition where the body ovrheats itself. Core temperatures go above 40.6 degrees → known as core temperature emergency

symptoms

• high body temp → 40.6

• lack of sweating

• heart racing

• rapid and shallow breathing

prevention

• wear lightweight clothing

• stay well hydrated

• avoid hot area exposed to the sun

treatment

• strip of clothing and more to cooler surrounds

• soak with water

• fan vigorously and mist with cool water

• call 000 but only when first aid cooling has ben implemented

what are general steps to prevent heat-related disorders

acclimatise

tapering - reduce intensity/duration of training leading up to competition

war lightweight clothing

stop exercising

hydration

avoid direct sunlight

describe how an athlete should acclimatise to heat stress

• performing training sessions in similar environmental conditions (heat and humidity) for 5-10 days results in almost total heat acclimatisation

• initially the intensity of training should be reduced to avoid heat related problems in these conditions

  • e.g. national team sports choose to acclimatise to conditions of a host country during a major international sporting comp

will follow progression

• training volume and intensity are reduced on the athletes first exposure to the hot environment

• both volume and intensity are increased as athlete begins to adapt

• body mass, hydration rates and other physical indicators must be monitored through heat training phase

what is acclimatisation

the physiological adaptation to changes in climate and environment

discuss the 3 physiological adaptation that occur with heat acclimatisation

increased plasma volume - a responses to increased stroke volume

• expansion resulting from increased plasma ranges from +3 to +27% and is accompanied by a 15-25% decrease in HR

• reduces rate of perceived exertion

increased sweat response - as sweat become more diluted → leads to an improved regulation of body temo during exercise in the heat

• thermoregulatory adaptation results in a decreased core body temp → maximised after 5-8 days of heat acclimatisation

decreased rate of muscle glycogen usage

• occurs as cardiac output increases during hat acclimatisation

• there is more O2 available to be used to glycogen spare so glycogen usage can decrease at a given intensity

outline the 3 principal means by which the body maintains core body temp in cold environments

shivering

• produces heat because heat is a by product when chemical energy is used to produce movement in the muscles

non-shivering thermogenesis

• adipose tissue has the ability to utilise fuel to produce heat, without creating ATP

• this is due to increasing cellular metabolic rates

• when it is triggered into activity, it causes the warming of the blood and then the warm blood can be circulates throughout the body to spread this heat

• can be done when exposed to cold to raise body temp

peripheral vasoconstriction

• the narrowing of blood vessels resulting from contraction of the muscular wall of vessels

• prevents blood flow to extremities of the body and keeps the heat towards the body’s core

what is thermogenesis

the process of heat production in organisms

• temperature creation

explain why the body surface area to body mass ratio is important in terms of heat preservation

people with greater amounts of body fat can retain more body heat

• larger surface area to body mass ratio makes heat loss easier → great for warm settings, bad for cold settings

• tall, heavy individuals have a small body surface area to body mass ratio, which makes them less susceptible to hypothermia

• small children tend to have a large body surface area to body mass ratio compared to adults, makes it more difficult for them to maintain normal body temp in the cold

outline the importance of wind-chill in relation to body heat loss

often called the wind chill factor, is the apparent temp felt on exposed skin due to wind

• the degree depends on both air temp and wind speed

• wind chill temp is usually lower than the air temp since the air temp is usually lower than the human body temp

e.g. if the air temp is 0 degrees, but the wind blows at 24mph, the temperature will feel liked -9

what is wind chill

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

explain why swimming in cold water represents a particular challenge to the body’s ability to thermoregulate

• water conducts body heat away up to 26 degrees times faster than air of the same temp

• body generally loses heat 4 times faster in water than it does in air of the same temp

• the colder the water, the faster the rate of heat loss, whilst the longer the time spent exposed to the water, the greater the overall heat loss

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

discuss the 2 physiological responses to exercise in the cold

muscle function

• cooling causes muscles to contract with less force → less blood flow

  • muscle shortening, velocity and power decrease significantly

  • as fatigue sets in and muscle activity decreases, body hear production also decreases.

    • therefore long sloe distance activities such as cycling and running may be dangerous in the cold as energy stores deplete and intensity decreases, potentially leading to hypothermia.

metabolic response

• muscle glycogen is used at a higher rate in the cold and would therefore lead to an earlier fatigue

• caused by shivering and increased levels of adrenalin

• the cold stimulates vasoconstriction of blood vessels

• people use more energy exercising in the cold than in the heat

describe the 2 health risks of exercising in the cold, including cold water

frostbite

• the continued cooling and freezing of the cells, leading the destruction of cells

• superficial

  • complete thickness of skin is frozen

  • white, wax looking skin

  • skin is firm but tissue beneath is soft

  • may feel pain before numbness sets in

• deep frostbite

  • sin including tissue beneath are frozen

  • a greyish-blue skin tone

  • skin feels cold and firm

  • no feeling in the area

hypothermia

• a low body temp below 35 degrees

• results in decrease in respiratory rat and volume

• mild → 32-35 degrees

• moderate → 28-32 degrees

• profound hypothermia → <25 degrees

• symtoms

  • shivering

  • weak pulse

  • shallow breathing

  • confusion

  • loss of consciousness

discuss the precautions that should be taken when exercising in the cold

the principal barrier to hypothermia is clothing

• the amount of insulation offered by clothing is measured in a unit called clo

  • zero clo → corresponds to a naked person

  • one clo → corresponds to a person wearing a typical business suit

• insulating effect of clothing is reduced when it becomes wet

• overdressing during exercise also enhances heat loss, wearing too many layers increase heat production and sweating

  • as the sweat soaks through the clothing and evaporates, heat is lost

• layer clothing - several thin layers are warmer than one heavy layer

  • layers are also easier to add or remove and thus, better regulate your core temp

  • goal is to keep body warm and minimise sweating and shivering

other precaution can include

• covering your head - head and neck heat loss can account for as much as 50% of total heat being lsot from body

• stay hydrated

• cover your mouth - to warm the air before you breathe in

  • cover with scarf to prevent chest pain and respiratory problems

what is ‘clo’

the amount of insulation offered by clothing