Environment and Exercise

Labs due next week Choose to: –Take book home and write up lab 5 Get marks for labs 1-5 –Submit on the day of your lab Get marks for labs 1-4

Thermoregulation

Body temperature Different temperatures: –Surface / Skin –Core body –Tympanic –Esophogeal –Rectal –oral

Regulation Regulated by hypothalamus to within 1 degree (37 + or – 1) Negative feedback loop  Thermal receptors in the skin  Temperature changes in blood

Mechanisms of Heat Conservation Vascular adjustments –Vasoconstriction of peripheral blood vessels Muscular activity –Voluntary physical activity –Shivering Hormonal output –Increased secretion of E, NE, thyroxine

Mechanisms Facilitating Heat Loss Circulatory adjustments Evaporation Hormonal adjustments

Circulatory Adjustments Two competitive cardiovascular demands exist during exercise in the heat –Oxygen delivery to muscles must increase to sustain exercise energy metabolism –Peripheral blood flow to the skin must increase to transport metabolic heat from exercise for dissipation at the body’s surface

Mechanisms of Heat Loss Radiation –The release of heat via electromagnetic heat waves Conduction –Direct transfer of heat through a liquid, solid, or gas Convection –Facilitates heat loss by conduction by carrying heat away in air currents Evaporation –Provides the major physiologic defense against overheating

Evaporation depends on Surface exposed to environment Temperature and humidity of air Convective air currents

Clothing Cloth traps air next to skin and warms it to provide insulation However if sweat is not absorbed and drawn away from skin to be kept dry, clothing loses 90% insulating property

Exercise in the Heat

Consequences of Dehydration Reduced plasma volume Increased submaximal heart rate Reduced rate of sweating Impaired ability to thermoregulate

Clothing for the heat Cover as little SA as possible Loose fitting to allow convective air currents near skin Wet allows increased evaporation Colour –Dark = absorbs radiant heat –Light – reflects radiant heat

Acclimatisation to heat Physiologic adaptive changes that improve heat tolerance –Lower Heart rate –Lower skin temp –Lower core body temp during exercise

Acclimatisation 2-4 hours each day for 10 days –Efficient blood flow from core  vasodilation  conduction –Sweat Double sweating capacity (volume), Greater area of the body is used for sweating More dilute –Sweat response earlier in exercise session

Factors Affecting Heat Tolerance Acclimatisaton Exercise training Age Gender Body composition Hydration

Exercise in the Cold

Exercise in water in the cold Body loses heat 2 x as fast in cool water as in air the same temperature  Shivering Swimming in 18degrees as opposed to 26 degrees = 500 ml/min

Dry Mouth Air is warmed and humidified by the bronchial tract  27/30 degrees When air is humidified it takes moisture from the respiratory tract Especially during exercise Therefore –Dry mouth –Burning throat –Irritation respiratory passages

Evaluating cold stress Air Temperature Wind Chill Index Tingling & numbness fingers and toes Burning sensation – nose & ears

Acclimatisation to cold Genetic- Eskimo Repeated exposure of extremities to cold  increased peripheral blood flow to reduce possibility of frostbite

Exercise in Pollution Beijing olympics

Pollution Carbon monoxide, sulfur oxides, nitrogen oxides, ozone, peroxyacetyl nitrate, aerosols, soot, dust and smoke Large particles and highly soluble gases are usually filtered out in nasal passages

Amounts Carbon Monoxide (COHb) % Sulfur oxides (Sox), Submax- 1-3 ppm Nitrogen dioxide (NO2) to 4,000 ppm = death Ozone (O3) Submaximal to 0.45 ppm = decrements in pulmonary function and discomfort Ozone has also been associated with eye irritation, general respiratory discomfort and nausea.

Effects Irritation of the upper respiratory tract 30 min submax exercise = smoking a pack of cigarettes? Carbon monoxide - reduces the blood’s capacity to transport oxygen to the tissues. Asthma attacks

Beijing 2008 Pollution levels 2-3 x higher than those deemed safe by WHO Trial to take 1 million cars off the road to see if pollution levels go down

Exercise and Altitude

Exercise at Altitude –Reduced barometric pressure –Reduced partial pressure of oxygen (Po 2 ) –Reduced relative humidity –Reduced ambient temperature

Acclimatisation Adaptive responses to improve one’s tolerance to altitude 2 weeks to adapt to 2300 m Additional 610 m = 1 week

Immediate Adjustments to altitude above 2300 m Hyperventilation –Chemoreceptors detect that not getting enough oxygen –Increase ventilation to compensate –  evaporation fluids respiratory tract Cardiovascular –Increased HR and cardiac output –At rest and during submaximal exercise

Acid-base adjustment -Ambient air at altitude contains very little Co2 -Affects gradient of o2/Co2 volumes -Combined with hyperventilation causes low Co2  increased pH Longer-Term Adjustments

Long term Hematological changes –Reduction in plasma volume –Increase in red blood cell production (Polycythemia) Due to erethropoietin released by the kidney –  increase in blood’s oxygen carrying capacity

Longer-Term Adjustments Cellular adaptations –Peripheral changes that facilitate aerobic metabolism increased capillary density Increased mitochondrial densities- increases ability to store O2 in muscles

Exercise Capacity at Altitude Aerobic capacity –Progressively decreases as altitude increases –1-3.5% reduction Vo2 max every 300m increase from 1500 m –Greater rate decline for trained athletes Circulatory factors –Decreased MHR and SV

Altitude Training Altitude acclimation to altitude improves one’s capacity to exercise at altitude However inability to train at equivalent intensity  no improvement Vo2 max on return to sea level  Live High, Train Low

Summary Environment critical to optimal performance Be aware of environment in case of negative effects Use to your advantage –Heat Humidity –Cool –Pollution –Altitude