2ObjectivesDescribe 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 decreases at altitude.Draw a graph to show effect of altitude on VO2 max and list the reasons for this response.Graphically describe effect of altitude on the heart rate and ventilation responses to submaximal work, and explain why these changes are appropriate.
3ObjectivesDescribe 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 VO2 max upon exposure to altitude, the degree of improvement in VO2 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.
4ObjectivesExplain the circumstances that caused physiologists to reevaluate their conclusions that humans could not climb Mount Everest without oxygen.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.
5ObjectivesDescribe the three elements in the heat stress index, and explain why one is more important than the other two.List the factors influencing hypothermia.Explain what the wind chill 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.
6ObjectivesDescribe the role of subcutaneous fat and heat 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.
7Outline Altitude Heat Air Pollution Cold Atmospheric Pressure Short-Term Anaerobic PerformanceLong-Term Aerobic PerformanceMaximal Aerobic Performance and AltitudeAdaptation to High AltitudeTraining for Competition at AltitudeThe Quest for EverestHeatHyperthermiaColdEnvironmental FactorsInsulating FactorsHeat ProductionDescriptive CharacteristicsDealing with HypothermiaAir PollutionParticulate MatterOzoneSulfur DioxideCarbon Monoxide
8Altitude Atmospheric pressure Decreases at higher altitude Partial pressureSame percentages of O2, CO2, and N2 in the airLower partial pressure of O2, CO2, and N2Hypoxia:Low PO2 (altitude)Normoxia:Normal PO2 (sea level)Hyperoxia:High PO2
9Effect of Altitude on Performance Short-term anaerobic performanceLower PO2 at altitude should have no effect of performanceO2 transport to muscle does not limit performanceLower air resistance may improve performanceLong-term aerobic performanceLower PO2 results in poorer aerobic performanceDependent on oxygen delivery to muscleComparison of performances1964 Olympics in Tokyo1968 Olympics in Mexico City
10Short Races: 1964 and 1968 Olympics AltitudeShort Races: 1964 and 1968 Olympics
11Long Races: 1964 and 1968 Olympics AltitudeLong Races: 1964 and 1968 Olympics
12A Closer Look 24.1 Jumping Through Thin Air AltitudeA Closer Look 24.1 Jumping Through Thin AirBob Beamon set new world record for long jump in 1968 Olympic Games in Mexico City29 feet, 2.5 inchesLower air density at higher altitudeHow much was gained at altitude?Biomechanical calculations indicate only 2.4 cm gained at higher altitude
13AltitudeIn SummaryThe 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.
14Maximal Aerobic Power and Altitude Decreased VO2 max at higher altitudePrimarily due to lower oxygen extractionUp to moderate altitudes (~4,000m)Decreased VO2 max due to decreased arterial PO2At higher elevationsVO2 max reduction also due to fall in maximum cardiac outputDecreased maximal HR at altitude
15Changes in VO2 Max with Increasing Altitude Figure 24.1
16Effect of Altitude on Submaximal Exercise Elicits higher heart rateDue to lower oxygen content of arterial bloodRequires higher ventilationDue to reduction in number of O2 molecules per liter of air
17Effect of Altitude on the Heart Rate Response to Submaximal Exercise Figure 24.2
18Effect of Altitude on the Ventilation Response to Submaximal Exercise Figure 24.3
19AltitudeIn SummaryDistance-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.
20Adaptation to High Altitude Production of more red blood cellsHigher hemoglobin concentrationVia erythropoietin (EPO)Counters desaturation caused by lower PO2Lifetime altitude residentsHave complete adaptations in arterial oxygen content and VO2 maxIn those recently arriving at altitudeAdaptations are less complete
21AltitudeIn SummaryPersons 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.
22Training for Competition at Altitude Effect of training at altitude on VO2 max varies among athletesDue to degree of saturation of hemoglobinSome athletes can improve VO2 max by training at altitude, others cannotMay be due to training state before arriving at altitudeSome athletes have higher VO2 max upon return to low altitude, while others do notCould be due to “detraining” effectCannot train as intensely at altitude
23The Winning Edge 24.1 Live High, Train Low AltitudeThe Winning Edge 24.1 Live High, Train LowLive at high altitudeElicits an increase in red blood cell massVia EPOLeads to increase in VO2 max≥22 hr/day at 2,000–2,500 m requiredOr simulated altitude of 2,500–3,000 m for 12–16 hr/dayIntermittent hypobaric hypoxiaFor example, 3 hr/day, 5 days/wk at 4,000–5,000 mTrain at low altitudeMaintain high interval training velocitySome athletes still experience hemoglobin desaturation
24The Winning Edge 24.1 Live High, Train Low AltitudeThe Winning Edge 24.1 Live High, Train LowTraditionally, increased RBC mass leads to increased VO2 maxSome studies have shown improved VO2 max without increased RBC massWith intermittent hypoxiaPotential mechanisms:Improved mitochondrial functionIncreased buffering capacityThis is an area of active debate and research
25AltitudeIn SummaryWhen 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.
26AltitudeIn SummaryIn 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.
27AltitudeThe Quest for EverestMount Everest was first successfully climbed in 1953Using supplemental oxygenClimbed without oxygen in 1978Previously thought this would be impossibleVO2 max at summit would be just above restActually, VO2 max estimated at 15 ml•kg–1•min–1Due to miscalculation of barometric pressure at summit
28The Highest Altitudes Attained by Climbers in the 20th Century Figure 24.4
29Maximal Oxygen Uptake Measured at a Variety of Altitudes Figure 24.5
30Challenges of High-Altitude Climbing Successful climbers have great capacity for hyperventilationDrives down PCO2 and H+ in bloodAllows more O2 to bind with hemoglobin at same PO2Climbers must contend with loss of appetiteWeight lossReduced type I and type II muscle fiber diameter
31A Closer Look 24.3 The Lactate Paradox AltitudeA Closer Look 24.3 The Lactate ParadoxUpon exposure to altitudeHigher HR, ventilation, and lactate during exerciseDue to hypoxiaAfter acclimatizationLactate response is reducedDespite continued hypoxiaCauses of the lactate paradoxLower plasma epinephrineMay also be due to muscle adaptationsGreat debate about this topicCauses of the lactate paradox?Does it even exist?Some studies do not observe this phenomenon
32AltitudeIn SummaryClimbers reached the summit of Mount Everest without oxygen in 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.
33AltitudeIn SummaryFinally, 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.
34Heat Hyperthermia Elevated body temperature Heat-related problems Heat syncopeHeat crampsHeat exhaustionMay require medical attentionHeat strokeMedical emergencyTreatmentCold water immersion is the most rapid way to lower body temperature
36Factors Related to Heat Injury FitnessHigher fitness related to lower risk of heat injuryTolerate more work in heatAcclimatize fasterSweat moreFit individuals still have risk of heat injuryAcclimatizationExercise in the heat for 10–14 daysLow intensity, long duration (<50% VO2 max, 60–100 min)Moderate intensity, short duration (75% VO2 max, 30–35 min)Lower body temperature and HR responseBest protection against heat stroke and exhaustion
37Factors Related to Heat Injury HydrationInadequate hydration increases risk of heat injuryNo differences among water, electrolyte drinks, or carbohydrate-electrolyte drinksEnvironmental temperatureConvection and radiation dependent on gradient between skin and air temperatureHigh temperature may result in heat gainClothingExpose as much skin as possibleChose materials that “wick” sweat away from skin
38Factors Related to Heat Injury Humidity (water vapor pressure)Evaporation is dependent on gradient between skin and airRelative humidity is a good index of water vapor pressureMetabolic rateCore temperature is proportional to work rateHigh work rate increases metabolic heat productionWindWind will increase heat loss by convection and evaporation
40Effect of Different Types of Uniforms on Body Temperature HeatEffect of Different Types of Uniforms on Body TemperatureFigure 24.7
41Implications for Fitness HeatImplications for FitnessKnow signs/symptoms of heat illnessCramps, lightheadedness, etc.Exercise in cooler part of the dayGradually increase exposure to heat/humidity to acclimatizeDrink water before, during, and after exerciseWear light clothingMonitor HR and alter exercise intensityStay within target heart rate zone
42Implications for Performance HeatImplications for PerformanceEmphasis on pre-season conditioningImprove fitness and promote acclimatizationSafety during events in high heat/humidityCooler time of day, season of the yearFrequent water stopsEncourage drinking of 150–300 ml water every 15 minutesIdentification of those with heat illnessCoordinate proper treatmentFirst aid, ambulance services, hospitalsCompetitor educationProvide information about heat illness
43Environmental Heat Stress Wet bulb globe temperature (WBGT)Dry bulb temperature (Tdb)Air temperature in shadeBlack globe temperature (Tg)Radiant heat load in direct sunlightWet bulb temperature (Twb)Index of ability to wick sweatMost important in determining overall heat stressRisk of heat stress depends on WBGTWBGT = 0.7Twb + 0.2Tg + 0.1Tdb
44Risk of Exercise-Related Heat Stroke (EHS) WBGT ≤50.0°F (≤10.0°C)Risk of hypothermia; EHS can occurWBGT 50.0–65.0°F (10.0–18.3°C)Low risk of hypo- and hyperthermia; EHS can occurWBGT 65.1–72.0°F (18.4–22.2°C)Caution: moderate risk of heat illnessWBGT 72.1–78.0°F (22.3–25.6°C)Extreme caution: risk of hyperthermia increased for allWBGT 78.1–82.0°F (25.7–27.8°C)Extreme caution: high risk for unfit, non-acclimatizedWBGT >82.0°F (>18.3°C)Extreme risk of hyperthermia; cancel or postpone event
45HeatIn SummaryHeat 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.
46HeatIn SummaryRoad 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.
47Cold Hypothermia Core temperature below 35°C (95°F) 2°C drop associated with maximal shivering4°C drop associated with ataxia and apathy6°C drop associated with unconsciousnessFurther drop associated with ventricular fibrillation, reduced brain blood flow, asystole, deathHeat loss exceeds heat productionConduction, convection, radiation, evaporationImportant to protect against heat lossMaintain core temperature
49Environmental Factors ColdEnvironmental FactorsTemperatureGradient for convective heat lossVapor pressureLow water vapor pressure encourages evaporationWindRate of heat loss influenced by wind speedWindchill index“Effective” temperatureWater immersionRate of heat loss 25x greater than air of same temperature
51Effect of Water Temperature on Survival ColdEffect of Water Temperature on SurvivalFigure 24.9
52ColdIn SummaryHypothermia 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.
53Insulating Factors Subcutaneous fat Especially effective in cold water ClothingClo units1 clo is insulation needed to maintain core temperature at rest at 21°C, 50% RH, and 6 m•min–1 windIncreased clothing required in cold, wet, windy conditionsDry clothing more effective than wetAmount of insulation required is lower during exercise
54Heat Production Heat production increases upon exposure to cold Inverse relationship between VO2 and body fatnessEarlier onset of shivering in lean menResting VO2 and core temperature maintained in “fat” men in cold waterIncreased VO2 and decreased core temperature in “thin” menFuel useFat is primary fuel for shiveringShivering can lead to muscle glycogen depletion
55Descriptive Characteristics Influencing Responses to Cold Exposure GenderAt rest, women show faster reduction in body temperature then menIn cold water, decrease in body temperature similar in men and womenDifferences can be explained by body composition and anthropometryAgeOlder (>60 years) less tolerant to coldChildren experience faster fall in body temperature
56ColdChanges in Insulation Requirement at Different Temperatures and ActivitiesFigure 24.10
57ColdIn SummarySubcutaneous 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.
58ColdIn SummaryThe 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.
59Dealing with Hypothermia ColdDealing with HypothermiaEffects of hypothermiaReduced coordinationSlurred speechImpaired judgmentTreatment of hypothermiaGet person out of cold, wind, and rainRemove all wet clothingProvide warm drinks and dry clothingPut person into sleeping bagWith another person, if semiconsciousFind a source of heat
60ColdIn SummaryIf a person becomes hypothermic, get the person out of the wind, rain, and cold; remove wet clothing and put on dry clothing; use a sleeping bag for warmth; and if it is an extreme case, remove clothing from the person and have another person in the sleeping bag to provide warmth; finally, provide some source of heat.
61Air Pollution Variety of gases and particulates Have detrimental effect on health and performanceDecrease capacity to transport oxygenIncrease airway resistanceAlter perception of effortPhysiological response depends on:Amount or “dose” receivedConcentration in airDuration of exposureVolume of air inhaledIncreases during exercise
62Air Pollution Particulate matter Promote pulmonary infection Elevate blood pressure, reduce fibrinolysis, reduce vasodilationCause oxidative stress and DNA damageOzoneDecreases VO2 max and respiratory functionSulfur dioxideCauses bronchoconstriction in asthmaticsCarbon monoxideBinds to hemoglobin and reduces oxygen transportAffects submaximal exercise and VO2 max
63Effect of Carbon Monoxide on VO2 Max Air PollutionEffect of Carbon Monoxide on VO2 MaxFigure 24.11
64Preventing Air Pollution Problems Reduce exposure timeEffects are dose-dependentStay away from “bolus” amounts of pollutantsSmoking areas, high-traffic areas, urban areasDo not exercise during most polluted parts of day7–10 a.m., 4–7 p.m.Monitor the air quality index (AQI)Measure of five pollutantsOzone, particulate matter, CO, SO2, and NO2AQI scale runs from 0–500
66Air PollutionIn SummaryAir pollution can affect performance. Exposure to ozone decreases VO2 max and respiratory function, while sulfur dioxide causes bronchoconstriction in asthmatics.Carbon dioxide binds to hemoglobin and reduces oxygen transport in much the same way that altitude does.To prevent problems associated with pollution of any type, reduce exposure time; stay away from “bolus” amounts of the pollutant; and schedule activity at the least polluted part of the day.The Air Quality Index should be monitored to determine if conditions are safe for exercising outdoors.
67Study QuestionsDescribe the changes in barometric pressure, PO2, and air density with increasing altitude.Why is sprint performance not affected by altitude?Explain why maximal aerobic power decreases at altitude and what effect this has on performance in long-distance races.Graphically describe the effect of altitude on the HR and ventilation responses to submaximal work, and provide recommendations for fitness participants who occasionally exercise at altitude.Describe the process by which an individual adapts to altitude, and contrast the adaptation of the permanent residents of high altitude with that of the lowlander who arrives there as an adult.
68Study QuestionsWhile training at altitude can be beneficial, how could someone “detrain”? How can you work around this problem?It was formerly believed that a person could not climb Mount Everest without oxygen because the estimated VO2 max at altitude was close to basal metabolic rate. When two climbers accomplished the feat in 1978, scientists had to determine how this was possible. What were the primary reasons allowing the climb to take place without oxygen?List and describe the factors related to heat injury.What is the heat stress index, and why is the wet bulb globe temperature weighed so heavily in the formula?List the factors related to hypothermia.
69Study QuestionsExplain what the wind chill index is relative to convective heat loss.What is a clo unit, and why is the insulation requirement less when you exercise?What would you do if a person had hypothermia?Explain how carbon monoxide can influence VO2 max and endurance performance.What steps would you follow to minimize the effect of pollution on performance?