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 degrees-high risk-Heat sensitive individuals should not compete 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 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