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Environment & Exercise Dr. Kyle Coffey

Environment & Exercise Dr. Kyle Coffey. Week 6. Metabolic Rate Duration Type of Work Clothing / Equipment. Environment and Exercise. Modifiers. CLIMATE. EVENT. X. X. Temperature (Heat/ Cold ) Humidity Wind Altitude. Anthropometry Gender* Health Acclimation Aerobic Fitness

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Environment & Exercise Dr. Kyle Coffey

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  1. Environment & ExerciseDr. Kyle Coffey Week 6

  2. Metabolic Rate • Duration • Type of Work • Clothing / Equipment Environment and Exercise Modifiers CLIMATE EVENT X X • Temperature (Heat/Cold) • Humidity • Wind • Altitude • Anthropometry • Gender* • Health • Acclimation • Aerobic Fitness • Hydration

  3. Heat Stress & Temperature Regulation * * * * * * *

  4. Heat Balance Equation S = M – W  C  R – E Where: • S = Heat Storage • M = metabolic heat production (muscle contraction) • W = mechanical work performed • C = convective heat loss or gain • R = radiative heat loss or gain • E = evaporative heat loss

  5. Metabolic Heat Production Mechanical efficiency declines as exercise intensity increases and more energy is liberated as heat (<25% goes toward work) 41 40 39 38 37 Steady-state Core Temperature, C 20 40 60 80 100 % of VO2max Davies et al., 1976

  6. Wet Bulb Globe Temperature (WBGT,C) • Wet Bulb = humidity • Black Globe = solar radiation • Dry Bulb = air temperature Formulas Outdoors : WBGT = 0.7 Wet Bulb + 0.2 Black Globe + 0.1 Dry Bulb Indoors: WBGT = 0.7 Wet Bulb + 0.3 Dry Bulb

  7. Exercise Intensity & Climate Effects on Core Temperature 3 9 . 5 WBGT > 28C is cause to cancel road races ) 3 9 . 0 C ° ( 1 0 0 0 W e r u t 3 8 . 5 a r e P r e s c r i p t i v e p Z o n e m e 3 8 . 0 5 0 0 W T e r 3 5 0 W o C 3 7 . 5 2 0 0 W 3 7 . 0 3 5 3 0 2 5 2 0 1 0 1 5 W B G T ( ° C ) Lind, 1963

  8. CANCEL ZONE DANGER DRY BULB TEMP ZONE °C SAFE ZONE 30 10 20 50 60 70 80 90 100 Climate & Risk of Heat Injury During Exercise 37.8 32.2 26.7 21.1 40 RELATIVE HUMIDITY (%) From: D.R. Lamb, Physiology of Exercise, 1984.

  9. Heat Stress Displaces Blood from Core to Periphery Lower Thermal Strain Higher Thermal Strain  HR  SV  HR  SV Rowell Human Circulation 1986

  10. Exercise Time to Exhaustion Galloway and Maughan, 1997 100 90 80 70 60 50 93 81 81 Time to Exhaustion (min) 51 4 11 21 31 Environmental Temperature (°C)

  11. Heat Stress and Exercise: Impact of Heat Acclimation Acclimatization - Adaptive changes within an organism in response to changes in the natural climate (outdoor) Acclimation - Adaptive changes within an organism in response to experimentally induced climatic factors (indoor/outdoor)

  12. Heat Acclimation • Repeated heat exposure over many days • Heat stress sufficient to increase body temperature and sweating • Duration - 100 min / day • Exposure - 4 to 14 days

  13. Actions of Heat Acclimation Thermal Comfort - Improved Exercise Performance - Improved Core Temperature - Reduced Sweating- Improved Earlier Onset Higher Rate Skin Blood Flow - Increased Earlier Onset Higher Flow Cardiovascular Stability - Improved Heart Rate - Lowered Stroke Volume - Increased Blood Pressure - Better Defended Fluid Balance - Improved Thirst- Improved Electrolyte Loss - Reduced Total Body Water - Increased Plasma Volume - Increased & Better Defended

  14. Participants who did not train during the warmer parts of the day were two and a half times more likely to develop heat exhaustion than those who did attempt to acclimate.

  15. Heat Stress and Exercise: Impact of Fluid Balance • Water intake must equal water output in order to maintain balance, especially during exercise • Sweating increases with exercise intensity and/or time of exercise • Sweating also affected by climate

  16. 3.0 2.5 2.0 1.5 1.0 0.5 0 160 200 240 280 320 10 9 8 7 6 5 Sweating Rate versus Climate and Exercise Intensity HOT & HUMID SWEAT RATE (L / h) COOL & DRY RUNNING SPEED (m/min) RUNNING SPEED (min/ mile) Sawka, MSSE 1992

  17. Dehydration • Increases core temperature • Reduces sweating and skin blood flow during exercise – heat stress • Negates benefits of heat acclimation

  18. Muscle Endurance - Reduced Impact of Dehydration Thermal Strain - Increased CV Strain - Increased Dehydration Heat Stroke Muscle Risk - Strength - Increased Unchanged Aerobic Heat Tolerance - Performance - Reduced Reduced

  19. Quantifying the Adverse Effects of Dehydration What hormone attempts to reduce dehydration? Greenleaf, 1992

  20. Dehydration decreases Exercise Tolerance Time and Performance Sawka et al. JAP, 1992 Armstrong et al. MSSE 1985 ~ 3% 320 300 280 260 240 120 (12 sec) Tolerance Time (min) Running Velocity (m/min) 60 ~ 6% (2 min) 0 5% BWL Normal 1 5 10 Distance (km) NORM DEH (~1-2%)

  21. Fluid Intake Recommendations, ACSM 1996 “During exercise, athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating…”

  22. Fluid Balance in Sport

  23. Fluid Balance in Sport • Typical exercise sweat losses of 0.5 – 2.0 L/hr* are observed in cool and moderate climates • Typical exercise sweat losses of 1.0 – 2.5 L/hr* are observed in hot climates • Athletes (people in general) voluntarily replace 50% or less of sweat losses during exercise

  24. Can we get too much water?? Hyponatremia • Clinically defined as blood sodium < 135 mEq / L • Symptoms are most likely to occur < 130 mEq / L or with rapid dilution of [sodium] • Intra-cranial swelling, headache, confusion, weakness, muscle spasms • Life threatening if sodium < 120 mEq / L • Primary cause is excessive drinking of water

  25. Contributing Factors to Hyponatremia Excessive Loss Excessive Consumption • Prolonged sweating • Not Acclimated • Untrained • Aggressive Rehydration • Misdiagnosis & Treatment Rehydation Increase Total Body Water Hyponatremia Increase Sodium Content Failure to Excrete Excess Volume Inadequate Sodium Intake • Exercise • Heat • AVP • Beverage • Food Montainet.al. ESSR 2001

  26. Altitude and Aerobic Exercise • Altitude is associated with a reduction in barometric pressure and therefore a reduction in air density and the partial pressure of inspired oxygen • How does this change in barometric pressure affect human physiology and exercise performance?

  27. Effect of Altitude on Pulmonary Diffusion Capacity * Assumes gradual ascent to sample altitude at rest (acclimatization) Adapted from: Sutton, 1988 Sea Level: BP = 760 mm Hg PIO2 = 150 mm Hg PAO2 = 100 mm Hg PaO2 = 100 mm Hg PVO2 = 40 mm Hg Gradient = + 60 mm Hg Pike’s Peak: BP ~ 450 mm Hg PIO2 ~ 80 mm Hg PAO2 ~ 56 mm Hg PaO2 ~ 56 PVO2 ~ 30 Gradient ~ + 26 mm Hg Mt. Everest: BP ~ 250 mm Hg PIO2 ~ 52 mm Hg PAO2 ~ 39mm Hg PaO2 ~ 31 PVO2 ~ 24 Gradient ~ + 15 mm Hg

  28. VO2max at Extreme Altitudes Cymerman et al., 1989

  29. Reduced Ability to Sustain a Fixed Work Rate Activity at Altitude 5000 m • Moderate Work Rate • 350 to 450 kcal/hr or • 1.2 to 1.5 L O2/min 4000 m Altitude 3000 m 2000 m Sea Level

  30. Reduction in Climbing Rate with Increasing Altitude* • *Independent of: • altitude illnesses, • grade of ascent • work/rest cycle • environmental • conditions • additional clothing • and equipment From Cymerman and Rock, USARIEM TN 94-2

  31. +45% +37% • 0.25 mile track • Outdoors • n = 8 Pandolf, et al. E.J. Appl. Physiol. 1998

  32. Altitude and Aerobic Exercise: Summary • Altitude adversely affects aerobic performance to a degree directly proportional to the elevation. • The magnitude of the impairment during initial exposure is usually greater than that associated with continued exposure.

  33. Altitude Video • Altitude Training

  34. Altitude and AnaerobicExercise • Altitude improves anaerobic exercise performance to a degree directly proportional to the elevation for events highly dependent on the ATP-PC energy system and lactic acid energy system (throwing, jumping, 100m, 200m, 400m). • For events requiring a mix of aerobic and anaerobic energy systems(800m and above), the benefit of a reduced air resistance becomes outweighed by the reduction in aerobic capacity as altitude increases beyond ~2,500 meters or 8,000 feet.

  35. Effect of Air Resistance on Performance Long Hair 7 6 5 4 3 2 1 0 Loose Cotton Jersey Short Hair Shoes with Exposed Laces Rough Wool % Aerodynamic Drag Crew Socks Hair on Limbs Tight Cotton Jersey Tight Fine Wool No Clothing Adapted from: Kyle and Caiozzo, 1986

  36. To What Extent Might a 2% Reduction in Aerodynamic Drag Improve Performance? Adapted from: Kyle and Caiozzo, 1986

  37. Calm 5 10 15 20 25 30 35 40 a 40 40 37 28 22 18 15 13 11 10 10 10 6 -9 -18 -25 -29 -33 -35 -37 30 30 27 16 9 4 0 -2 -4 -6 0 0 -5 -21 -32 -39 -44 -48 -51 -53 -40 -40 -47 -70 -85 -96 -104 -109 -113 -117 20 20 16 3 -5 -10 -15 -18 -20 -22 -10 -10 -15 -33 -45 -53 -59 -63 -67 -69 -50 -50 -57 -83 -99 -110 -118 -125 -129 -132 50 50 48 40 36 32 30 28 27 26 -20 -20 -26 -46 -58 -67 -74 -79 -82 -85 -30 -30 -36 -58 -72 -82 -89 -94 -98 -101 -60 -60 -68 -95 -112 -124 -133 -140 -145 -148 Equivalent Chill Temperature (°C) Actual Temperature (°F) Wind Speed (Mi/h) Increasing Danger (Exposed flesh may freeze within 1 min.) (Exposed flesh may freeze within 30 s) Little Danger (In less than 5 h with dry skin. Greatest hazard from false sense of security.) a Wind speeds greater than 40 mi/h have little additional effect.

  38. Cold Stress and Exercise: Human Response to Cold • Behavioral • Wear more clothing* • Seek shelter • Use a heat source • Physiological • Shivering* • Vasoconstriction*

  39. Clothing and the Cold • Clothing provides a protective barrier (keeps cold out) • Clothing also keeps heat in – but usually inhibits sweat evaporation • Sweat losses of >1 L/hr are still common in very cold weather when heavily clothed (and therefore, dehydration is still a potential concern)

  40. COMPARISON OF METABOLIC COSTS METS REST 6 MPH JOG SHIVERING 12°C Tsk 35°C core MAX EXERCISE

  41. SHIVERING IS RELATED TO EXERCISE INTENSITY AMBIENT CONDITIONS TEMPERATE COLD OXYGEN UPTAKE ~ 60% VO2max POWER OUTPUT

  42. Alcohol Ingestion Increased Blood [Alcohol] Lower Blood Glucose Skin Blood Flow Lower Heat Production Heat Loss Lower Body Core Temp. Decreased Shivering From Freund et. al, 1994

  43. Cold and Exercise: Summary • At an exercise intensity of ~ 60%VO2max and above, most individuals will be relatively immune to the cooling effects of cold stress • Exercise in the cold produces less cardiovascular strain and thermal strain. Fatigue will be dependent on factors other than cold stress (e.g. training status & glycogen availability) • At an exercise intensity of ~ 30%VO2max or less, a severe thermal challenge will be imposed on inadequately dressed individuals

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