Learning Outcomes• Define thermoregulation and thebody’s four methods ofthermoregulation.• Explain the importance of the bodymaintaining its temperature.
Thermoregulation• What will the man below be experiencing?
Thermoregulation• As with anything the body is affected bythe heat of the environment andanything else surrounding it.• The body is able to adjust its owntemperature constantly to keep it in asafe zone.• This is called being homeothermic.
Thermoregulation• Body temp fluctuatesfrom hour to hour byroughly 1.0 C.• The normal zone forthe body is 36.1 -37.8 C.• Only extreme cold,heat, illness orexercise takes thebody out of this ‘safezone’.
HEAT GAIN HEAT LOSSMETABOLICHEATENVIRONMENTALHEAT/SOLARRADIATIONRADIATIONCONDUCTIONCONVECTIONEVAPORATIONTHE SCALES OF BODY TEMPERATURESHIVERINGEXERCISE
Convection• As the air is constantly moving around us,the colder molecules in the air ‘sweep away’the warm molecules next to our skin.• This also occurs when the skin is submergedin water.• Conduction and Convection together willaccount for 10-20% of heat loss.• This is 26 times more when you’re in water.
Conduction• Conduction is the passing of heat fromone tissue into another it is in contactwith.• For example, from the muscle to theskin, from the skin to your clothes orthe air.• If the air next to the skin is warm aswell, then less of the heat can beconducted from the skin.
Radiation• The body is constantly giving off heat in theform of infrared rays.• At normal room temperature, the nude bodywill lose 60% of it’s natural heat in thismanner.• The body gains the most heat in the sameway. If the environment is warmer than yourskin, your body absorbs the heat.• If the environment is much colder, the bodyloses heat much quicker.
Evaporation• What happenswhen you startrunning?
Evaporation• The body moves waterto the surface of theskin where it canevaporate and carry theheat off the body.• At rest – 20%• Active – 80%• If the water doesn’tevaporate, very littleheat is lost and most isreabsorbed.• Don’t remove sweatwith a towel!
Humidity• Which of the four methods ofthermoregulation allows the most heatto be removed from the body?• Evaporation.• The more water molecules that arealready in the air, the less moisture canevaporate.
Humidity• Where are youlikely to feel themost sweaty??• The Dubai orSingapore?• 2 minutes
Humidity• The dry hot air of Dubai would allow thesweat to evaporate almost immediately,whereas the moist air of the Singaporewould not allow much heat to be lostthrough evaporation, causing the bodyto continue sweating.• What problems could both of thesesituations cause?
Thermoregulation in Sport• The harder the muscles are working,the more heat is generated.• The more energy that is beingprocessed by the body the more heat isbeing generated.• If the environment is warmer than thebody, no heat can be removed from thebody.• Think Vasodilation/constriction
Thermoregulation in Sport• At the same time, if the environment is toocold, then heat will be lost too quickly.• Due to increased or decreased temperatureeffects the flow of blood, the contractions ofall the muscles (including the heart) and thefunctions of the nervous system.• Clothing will play a large role in this, as we’llsee in our experiment next session!
Key terms• Hyperthermia – a condition in whichbody temperature is elevated to a veryhigh level• Hypothermia – a condition in whichbody temperature is lowered to a verylow level• Hypohydration – a condition in whichthere are very low levels of fluid in thebody
Surface Area to mass ratio• Small children lose temp quicker thanlarge people• Gymnasts, distance runners, jockeys• V• Weight lifters, sumo wrestling,throwers, rugby players
What happens in the body?• Thermoregulatory centre is situated inthe hypothalamus – in the brain• Receives signals from central andperipheral receptors• But what can the body do…..
Reactions...in addition to sweat• Vasoconstriction/dilation• Exercise in warm climate– Cardiac output shared between muscles & skin– Can cause a reduction in cardiac return and asa consequence SV – effects performance• Increase in heart rate (Cardiac drift) – but hasa limited effect on performance•
Effect of temp• Ability to run/cycle for long periodsreduces as temperature increases 11oCto 21oC to 31oC• Dehydration – big risk at warm and coldtemps (lost through respiratory systembut also sweat if wearing thick clothing)– leads to fatigue• Fluid intake essential - hypohydration
Effects of Differing BodyTemperature• 37 C – Normal Temp.• 39 C – Severe sweating, fast heart rateand breathlessness• 41 C – Fainting, vomiting,hallucinations• 43 C – Possible death, serious braindamage.• 44 C – Almost certain death
Effects of Differing BodyTemperature• 36 C – Moderate shivering – sleeptemp.• 34 C – Hypothermia• 32 C – Hallucinations, extremesleepiness and comatose• 27 C – Approaching death• 25 C – Death due to irregular heart rate
But........• You do need to be warmer than normalduring sport for the followingadvantages......
Effects of Heat Increase• Higher V02 MAX• Higher heart rate and quicker increaseof heart rate• But• Increased blood lactate and quickerbuild of lactate.
Task• Alan is a long distance runner who isused to training in Berkshire. He istaking part in a race in the south ofSpain in July.• Explain what will be happening to hisbody during the race due to his body’sactivity, the environment and the typeof clothing he’ll be wearing.• 10 minutes
Next Session• Bring your kit, we’ll be in the gym.• And you will probably need showerstuff!
Learning Outcomes• Define and discuss the different typesof body composition methods.• Explain who these methods would beuseful for.