Thermoregulation

Thermal Balance Hypothalamus Heat Stress Cold Stress

Mechanism for Temperature Regulation -Cold

Decreases heat loss-vasoconstriction Increases in heat production-Shivering

and increased voluntary activity Increased thyroxin and epinephrine

secretion

Mechanism for Temperature Regulation-Heat

Increased heat loss-Vasodilatation Decreases heat production-

Decreased muscle tone and voluntary activity

Decreased secretion of thyroxin and epinephrine

Heat Loss

Radiation Conduction Convection Evaporation

Complications

Heat Cramps-Spasms in exercising muscles

Heat Exhaustion-weak and rapid pulse,low BP,HA,dizzy,weakness

Heat Stroke-excessive core temp,no sweat,altered mental status,life threatening

ACSM Recommendations

Above 82 degrees-very high risk-postpone

73-82 degrees-high risk-Heat sensitive individuals should not compete

65-73 degrees-mod risk Below 65-low risk

Exercising -Heat Vascular adjustments-Blood flow to

skin increases,compromising blood to working muscles and other vital organs

SV decreases,AC and CO also decrease because of fluid deficit

Attempts to maintain BP Core Temp Increases

Water Fluid loss .5-1.0 L for mod exercise in 1 hour 3 L loss for intense exercise Must constantly replenish fluids.Must exceed

25-50% above sweat loss(urine loss) Water replacement is more important than

mineral replacement Electrolyte replacement and water is

optimal

Clothing-Warm Weather

Cotton or linen Light colors Changing into a dry shirt from a

wet one while exercising will negatively affects the cooling process

Exercising in the Cold

Peripheral vasoconstriction can lead to tingling and numbness

Burning sensation in nose and ears Tissue damage-Frostbite Surgical removal of damaged

tissue

Cold Weather-Clothing Numerous layers is better than a single

bulky layer Moisture must be allowed to pass to

outer layers Wools and synthetics insulate and dry

fast Wear a hat(30-40% Heat loss by Head) Wet clothing loses 90% of it’s insulating

properties