Chapter 24: Exercise and the Environment EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 5 th edition Scott K. Powers & Edward T. Howley Presentation revised and updated by TK Koesterer, Ph.D., ATC Humboldt State University

Objectives Describe the changes in atmospheric pressure, air temperature, and air density with increasing altitude Describe how altitude affects sprint performances and explain why that is the case Explain why distance running performance decrease at altitude Draw a graph to show effect of altitude on VO 2 MAX and list reasons for this response Graphically describe effect of altitude on the HR and ventilation responses to submaximal work, and explain why these changes are appropriate

Objectives Describe the process of adaptation to altitude, and the degree to which this adaptation can be complete Explain why such variability exists among athletes in the decrease in VO 2 MAX upon exposure to altitude, the degree of improvement in VO 2 MAX at altitude, and the gains made upon return to sea level Describe potential problems associated with training at high altitude and how one might deal with them Explain the circumstances that caused physiologists to reevaluate their conclusions that humans could not climb Mount Everest without oxygen

Objectives Explain the role that hyperventilation plays in helping to maintain a high oxygen-hemoglobin saturation at extreme altitudes List and describe the factors influencing the risk of heat injury Provide suggestions for the fitness participant to follow to minimize the likelihood of heat injury Describe in general terms the guidelines suggested for running road races in the heat Describe three elements in the heat stress index, and explain why one is more important than the other two

Objectives List the factors influencing hypothermia Explain what Windchill Index is relative to heat loss Explain why exposure to cold water is more dangerous than exposure to air of the same temperature Describe what the “clo” unit is and how recommendations for insulation change when one does exercise

Objectives Describe the role of subcutaneous fat and energy production in the development of hypothermia List the steps to follow to deal with hypothermia Explain how carbon monoxide can influence performance, and list the steps that should be taken to reduce the impact of pollution on performance

Altitude Atmospheric pressure –Decreases at higher altitude Partial pressure –Same percentages of O 2, CO 2, and N 2 in the air –Lower partial pressure of O 2, CO 2, and N 2 –Hypoxia: low PO 2 (altitude) –Normoxia: normal PO 2 (sea level) –Hyperoxia: high PO 2

Effect of Altitude on Performance Short-term anaerobic performance –Lower PO 2 at altitude should have no effect of performance –Lower air resistance may improve performance Long-term aerobic performance –Lower PO 2 results in poorer aerobic performance

Effect of Altitude on VO 2max Decreased VO 2max at higher altitude Up to moderate altitudes (~4,000m) –Decreased VO 2max due to decreased arterial PO 2 At higher elevations –Rate of VO 2max reduction also due to fall in maximum cardiac output

Changes in VO 2max With Increasing Altitude Fig 24.1

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 O 2 molecules per liter of air

Effect of Altitude on Submaximal Heart Rate Response Fig 24.2

Effect of Altitude on Submaximal Ventilation Response Fig 24.3

Adaptation to High Altitude Production of more red blood cells –Counter desaturation caused by lower PO 2 In those who grew up at altitude –Have complete adaptations in arterial oxygen content and VO 2max In those recently arriving at altitude – Adaptations are less complete

Training for Competition at Altitude Effect of training at altitude on VO 2max varies between athletes –Due to degree of saturation of hemoglobin Some athletes can improve VO 2max by training at altitude, others cannot – May be due to training state before arriving at altitude Some athletes have higher VO 2max upon return to low altitude, while others do not –Could be due to “detraining” effect Cannot train as intensely at altitude

The Quest for Everest Mount Everest was climbed without oxygen in 1978 –Previously thought that VO 2max at summit would be just above rest –Actually, VO 2max estimated at 15 mlkg -1 min -1 Due to miscalculation of barometric pressure at summit

Challenges of High Altitude Climbing Successful climbers have great capacity for hyperventilation –Drives down PCO 2 and H + in blood –Allows more O 2 to bind with hemoglobin at same PO 2 Climbers must contend with loss of appetite –Results in loss of weight –Reduction muscle fiber diameter

Heat Hyperthermia –Elevated body temperature Heat-related problems –Heat syncope –Heat cramps –Heat exhaustion May require medical attention –Heat stroke Medical emergency

Factors Affecting Heat Injury Fig 24.6

Consideration for Exercise Know signs/symptoms of heat illness Exercise in cooler part of the day Gradually increase exposure to heat to acclimatize Drink water before, during, and after exercise Wear light clothing Alter exercise intensity to stay within THR zone

Implications for Performance Safety during events in high heat/humidity –Time of day, season of the year –Frequent water stops –Traffic control –Identification of those with heat illness –Coordinate proper treatment First aid, ambulance services, hospitals

Environmental Heat Stress Wet bulb globe temperature (WBGT) –Dry bulb temperature (T db ) Air temperature in shade –Black globe temperature (T g ) Radiant heat in direct sunlight –Wet bulb temperature (T wb ) Index of ability to wick sweat WBGT = 0.7T wb + 0.2T g + 0.1T db

Cold Important to protect against heat loss –Maintain core temperature The windchill index –Describes how wind lowers the effective temperature at the skin Water –Causes heat loss by convection 25 times greater than in air

Hypothermia Insulating factors –Subcutaneous fat –Clothing –Amount of insulation required is lower during exercise Environmental factors –Temperature –Vapor pressure –Wind –Water immersion –Energy production

Insulation in the Cold Insulation –Subcutaneous fat –Clothing –Amount of insulation needed is lower during exercise Energy production increases upon exposure to cold –Inverse relationship between VO 2 and body fatness –Women cool faster than men

Factors Affecting Hypothermia Fig 24.9

Effect of Water Temperature on Survival Fig 24.9

Changes in Insulation Requirement at Different Temperatures and Activities Fig 24.10

Air Pollution Ozone –Decreases VO 2max and respiratory function Sulfur dioxide –Causes bronchoconstriction in asthmatics Carbon monoxide –Binds to hemoglobin and reduces oxygen transport Prevention of problems –Reduce exposure time –Stay away from “bolus” amounts of pollutants –Exercise during least polluted part of day

Effect of Carbon Monoxide on VO 2max Fig 24.11