Exercise and the Environment

Exercise and the Environment

Altitude Atmospheric Pressure Short-Term Anaerobic Performance Long-Term Aerobic Performance Maximal Aerobic Performance and Altitude Adaptation to High Altitude Training for Competition at Altitude The Quest for Everest Outline • Air Pollution Particulate Matter Ozone Sulfur Dioxide Carbon Monoxide • Heat Hyperthermia • Cold Environmental Factors Insulating Factors Heat Production Descriptive Characteristics Dealing with Hypothermia

Altitude Altitude • Atmospheric pressure • Decreases at higher altitude • Partial pressure • Same percentages of O2, CO2, and N2 in the air • Lower partial pressure of O2, CO2, and N2 • Hypoxia: • Low PO2 (altitude) • Normoxia: • Normal PO2 (sea level) • Hyperoxia: • High PO2

Altitude Effect of Altitude on Performance • Short-term anaerobic performance • Lower PO2 at altitude should have no effect of performance • O2 transport to muscle does not limit performance • Lower air resistance may improve performance • Long-term aerobic performance • Lower PO2 results in poorer aerobic performance • Dependent on oxygen delivery to muscle • Comparison of performances • 1964 Olympics in Tokyo • 1968 Olympics in Mexico City

Altitude Short Races: 1964 and 1968 Olympics

Altitude Long Races: 1964 and 1968 Olympics

Altitude A Closer Look 24.1Jumping Through Thin Air • Bob Beamon set new world record for long jump in 1968 Olympic Games in Mexico City • 29 feet, 2.5 inches • Lower air density at higher altitude • How much was gained at altitude? • Biomechanical calculations indicate only 2.4 cm gained at higher altitude

Altitude In Summary • The atmospheric pressure, PO2, air temperature, and air density decrease with altitude. • The lower air density at altitude offers less resistance to high-speed movement, and sprint performances are either not affected or are improved.

Altitude Maximal Aerobic Power and Altitude • Decreased VO2 max at higher altitude • Primarily due to lower oxygen extraction • Up to moderate altitudes (~4,000m) • Decreased VO2 max due to decreased arterial PO2 • At higher elevations • VO2 max reduction also due to fall in maximum cardiac output • Decreased maximal HR at altitude

Altitude Changes in VO2 Max with Increasing Altitude Figure 24.1

Altitude Effect of Altitude on Submaximal Exercise • Elicits higher heart rate • Due to lower oxygen content of arterial blood • Requires higher ventilation • Due to reduction in number of O2 molecules per liter of air

Altitude Effect of Altitude on the Heart Rate Response to Submaximal Exercise Figure 24.2

Altitude Effect of Altitude on the Ventilation Response to Submaximal Exercise Figure 24.3

Altitude In Summary • Distance-running performances are adversely affected at altitude due to the reduction in the PO2, which causes a decrease in hemoglobin saturation and VO2 max. • Up to moderate altitudes (~4,000 m), the decrease in VO2 max is due primarily to the decrease in arterial oxygen content brought about by the decrease in atmospheric PO2. At higher altitudes, the rate at which VO2 max falls may be increased due to a reduction in maximal cardiac output. • Submaximal performances conducted at altitude require higher heart rate and ventilation responses due to the lower oxygen content of arterial blood and the reduction in the number of oxygen molecules per liter of air, respectively.

Altitude Adaptation to High Altitude • Production of more red blood cells • Higher hemoglobin concentration • Via erythropoietin (EPO) • Counters desaturation caused by lower PO2 • Lifetime altitude residents • Have complete adaptations in arterial oxygen content and VO2 max • In those recently arriving at altitude • Adaptations are less complete

Altitude In Summary • Persons adapt to altitude by producing more red blood cells to counter the desaturation caused by the lower PO2. Altitude residents who spent their growing years at altitude show a rather complete adaptation, as seen in their arterial oxygen content and VO2 max values. Lowlanders who arrive as adults show only a modest adaptation.

Altitude Training for Competition at Altitude • Effect of training at altitude on VO2 max varies among athletes • Due to degree of saturation of hemoglobin • Some athletes can improve VO2 max by training at altitude, others cannot • May be due to training state before arriving at altitude • Some athletes have higher VO2 max upon return to low altitude, while others do not • Could be due to “detraining” effect • Cannot train as intensely at altitude

Altitude Live High, Train Low • Live at high altitude • Elicits an increase in red blood cell mass • Via EPO • Leads to increase in VO2 max • ≥22 hr/day at 2,000–2,500 m required • Or simulated altitude of 2,500–3,000 m for 12–16 hr/day • Intermittent hypobaric hypoxia • For example, 3 hr/day, 5 days/wk at 4,000–5,000 m • Train at low altitude • Maintain high interval training velocity • Some athletes still experience hemoglobin desaturation

Altitude The Winning Edge 24.1Live High, Train Low • Traditionally, increased RBC mass leads to increased VO2 max • Some studies have shown improved VO2 max without increased RBC mass • With intermittent hypoxia • Potential mechanisms: • Improved mitochondrial function • Increased buffering capacity • This is an area of active debate and research

Altitude In Summary • When athletes train at altitude, some experience a greater decline in VO2 max than others. This may be due to differences in the degree to which each athlete experiences a desaturation of hemoglobin. Remember, some athletes experience desaturation during maximal work at sea level. • Some athletes show an increase in VO2 max while training at altitude, whereas others do not. This may be due to the degree to which the athlete was trained before going to altitude.

Altitude In Summary • In addition, some athletes show an improved VO2 max upon return to sea level, whereas others do not. Part of the reason may be the altitude at which they train. Those who train at high altitudes may actually “detrain” due to the fact that the quality of their workouts suffers at the high altitudes. To get around this problem, one can alternate low-altitude and sea-level exposures.

Altitude The Quest for Everest • Mount Everest was first successfully climbed in 1953 • Using supplemental oxygen • Climbed without oxygen in 1978 • Previously thought this would be impossible • VO2 max at summit would be just above rest • Actually, VO2 max estimated at 15 ml•kg–1•min–1 • Due to miscalculation of barometric pressure at summit

Altitude The Highest Altitudes Attained by Climbers in the 20th Century Figure 24.4

Altitude Maximal Oxygen Uptake Measured at a Variety of Altitudes Figure 24.5

Altitude Challenges of High-Altitude Climbing • Successful climbers have great capacity for hyperventilation • Drives down PCO2 and H+ in blood • Allows more O2 to bind with hemoglobin at same PO2 • Climbers must contend with loss of appetite • Weight loss • Reduced type I and type II muscle fiber diameter

Altitude In Summary • Climbers reached the summit of Mount Everest without oxygen in 1978. This surprised scientists who thought VO2 max would be just above resting VO2 at that altitude. They later found that the barometric pressure was higher than they previously had thought and that the estimated VO2 max was about 15 ml•kg–1•min–1 at this altitude. • Those who are successful at these high altitudes have a great capacity to hyperventilate. This drives down the PCO2 and the [H+] in blood, and allows more oxygen to bind at the same arterial PO2.

Altitude In Summary • Finally, those who are successful at climbing to extreme altitudes must contend with the loss of appetite that results in a reduction of body weight and in the cross-sectional area of type I and type II muscle fibers.

Heat Heat • Hyperthermia • Elevated body temperature • Heat-related problems • Heat syncope • Heat cramps • Heat exhaustion • May require medical attention • Heat stroke • Medical emergency • Treatment • Cold water immersion is the most rapid way to lower body temperature

Heat Heat-Related Problems

Heat Factors Related to Heat Injury • Fitness • Higher fitness related to lower risk of heat injury • Tolerate more work in heat • Acclimatize faster • Sweat more • Fit individuals still have risk of heat injury • Acclimatization • Exercise in the heat for 10–14 days • Low intensity, long duration (<50% VO2 max, 60–100 min) • Moderate intensity, short duration (75% VO2 max, 30–35 min) • Lower body temperature and HR response • Best protection against heat stroke and exhaustion

Heat Factors Related to Heat Injury • Hydration • Inadequate hydration increases risk of heat injury • No differences among water, electrolyte drinks, or carbohydrate-electrolyte drinks • Environmental temperature • Convection and radiation dependent on gradient between skin and air temperature • High temperature may result in heat gain • Clothing • Expose as much skin as possible • Chose materials that “wick” sweat away from skin

Heat Factors Related to Heat Injury • Humidity (water vapor pressure) • Evaporation is dependent on gradient between skin and air • Relative humidity is a good index of water vapor pressure • Metabolic rate • Core temperature is proportional to work rate • High work rate increases metabolic heat production • Wind • Wind will increase heat loss by convection and evaporation

Heat Factors Affecting Heat Injury Figure 24.6

Heat Effect of Different Types of Uniforms on Body Temperature Figure 24.7

Heat Implications for Fitness • Know signs/symptoms of heat illness • Cramps, lightheadedness, etc. • Exercise in cooler part of the day • Gradually increase exposure to heat/humidity to acclimatize • Drink water before, during, and after exercise • Wear light clothing • Monitor HR and alter exercise intensity • Stay within target heart rate zone

Heat Implications for Performance • Emphasis on pre-season conditioning • Improve fitness and promote acclimatization • Safety during events in high heat/humidity • Cooler time of day, season of the year • Frequent water stops • Encourage drinking of 150–300 ml water every 15 minutes • Identification of those with heat illness • Coordinate proper treatment • First aid, ambulance services, hospitals • Competitor education • Provide information about heat illness

Heat In Summary • Heat injury is influenced by environmental factors such as temperature, water vapor pressure, acclimatization, hydration, clothing, and metabolic rate. The fitness participant should be educated about the signs and symptoms of heat injury; the importance of drinking water before, during, and after the activity; gradually becoming acclimated to the heat; exercising in the cooler part of the day; dressing appropriately; and checking the HR on a regular basis.

Heat In Summary • Road races conducted in times of elevated heat and humidity need to reflect the coordinated wisdom of the race director and medical director to minimize heat and other injuries. Concerns include running the race at the correct time of the day and season of the year, frequent water stops, traffic control, race monitors to identify and stop those in trouble, and communication between race monitors, medical director, ambulance services, and hospitals. • The heat stress index includes dry bulb, wet bulb, and globe temperatures. The wet bulb temperature, which is a good indicator of the water vapor pressure, is more important than the other two in determining overall heat stress.

Cold Cold • Hypothermia • Core temperature below 35°C (95°F) • 2°C drop associated with maximal shivering • 4°C drop associated with ataxia and apathy • 6°C drop associated with unconsciousness • Further drop associated with ventricular fibrillation, reduced brain blood flow, asystole, death • Heat loss exceeds heat production • Conduction, convection, radiation, evaporation • Important to protect against heat loss • Maintain core temperature

Cold Factors Affecting Hypothermia Figure 24.8

Cold Environmental Factors • Temperature • Gradient for convective heat loss • Vapor pressure • Low water vapor pressure encourages evaporation • Wind • Rate of heat loss influenced by wind speed • Windchill index • “Effective” temperature • Water immersion • Rate of heat loss 25x greater than air of same temperature

Cold Wind Chill Chart

Cold Effect of Water Temperature on Survival Figure 24.9

Cold In Summary • Hypothermia is influenced by natural and added insulation, environmental temperature, vapor pressure, wind, water immersion, and heat production. • The wind chill index describes how the wind lowers the effective temperature at the skin such that convective heat loss is greater than what it would be in calm air at that same temperature. • Water causes heat to be lost by convection twenty-five times faster than it would be by exposure to air of the same temperature.

Cold Insulating Factors • Subcutaneous fat • Especially effective in cold water • Clothing • Clo units • 1 clo is insulation needed to maintain core temperature at rest at 21°C, 50% RH, and 6 m•min–1 wind • Increased clothing required in cold, wet, windy conditions • Dry clothing more effective than wet • Amount of insulation required is lower during exercise

Cold Heat Production • Heat production increases upon exposure to cold • Inverse relationship between VO2 and body fatness • Earlier onset of shivering in lean men • Resting VO2 and core temperature maintained in “fat” men in cold water • Increased VO2 and decreased core temperature in “thin” men • Fuel use • Fat is primary fuel for shivering • Shivering can lead to muscle glycogen depletion

Cold Descriptive Characteristics Influencing Responses to Cold Exposure • Gender • At rest, women show faster reduction in body temperature then men • In cold water, decrease in body temperature similar in men and women • Differences can be explained by body composition and anthropometry • Age • Older (>60 years) less tolerant to cold • Children experience faster fall in body temperature

Cold Changes in Insulation Requirement at Different Temperatures and Activities Figure 24.10

Cold In Summary • Subcutaneous fat is the primary “natural” insulation and is very effective in preventing rapid heat loss when a person is exposed to cold water. • Clothing extends this insulation, and the insulation value of clothing is described in clo units, where a value of 1 describes what is needed to maintain core temperature while sitting in a room set at 21°C and 50% RH with an air movement of 6 m•sec–1.

Cold In Summary • The amount of insulation needed to maintain core temperature is less when one exercises because the metabolic heat production helps maintain the core temperature. Clothing should be worn in layers when exercising so one can shed one insulating layer at a time as body temperature increases. • Heat production increases on exposure to cold, with an inverse relationship between the increase in VO2 and body fatness. Women cool faster than men when exposed to cold water, exhibiting a longer delay in the onset of shivering and a lower VO2, despite a greater stimulus to shiver.

Exercise and the Environment