ENS 304 Slides

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And now a contest

Why women live longer than men.
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6th place
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5th place
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4th place
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3rd place
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2nd place
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And the winner is
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...and now, a close runner up
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EUROPEAN HUSBAND OF THE YEAR AWARDS
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3rd Place goes to Greece
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2nd Place goes to Serbia
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and the winner of the husband of the year
is         Ireland...........

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Thermoregulation

• 60-65 of total energy expenditure lost as heat
• Transfer of heat from body
• conduction transfer through direct contact
• convection transfer through air flow
• radiation heat given off as IR rays
• evaporation (1º) assisted by heat of
  vaporization

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Effects of exercise intensity on sweat rate
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Effects of Exercise in Heat
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Effect of exercise in heat on central (thoracic)
blood flow (CBV) and other CV dynamics. Figure
on right shows data of 4 exercise intensities.
Decreased CBV and SV suggests a redistribution of
blood from core to periphery, which contributed
to decreased CO.
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Physiological responses to heat accumulation

• surface blood flow is increased at expense to
  other tissues
• ? EPI release
• HR upward drift
• ? glycogen use
• ? blood volume
• ? cardiac efficiency (? SV, ? HR)
• ? fatigue

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Effect of Dehydration on HR
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Dehydration and Performance
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Fluid balance

• dehydration impairs endurance performance,
• minimal effect on power and speed events
• ? blood volume will ? skin blood flow and heat
  dissipation
• thirst mechanism doesnt keep up with dehydration
• need for water replacement gt than electrolyte
  replacement

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Maintaining fluid balance

• fluid intake during exercise will
• minimize dehydration
• minimize rise in body temperature
• reduce CV stress
• CHO gt 6-8 slows absorption from gut

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Sport Nutrition Sport Drinks

• CHO affects fluid absorption rate in gut
• Gatorade 6
• Exceed 7.2
• Coca-Cola 11
• Sprite 10.2
• cranberry juice 15
• orange juice 11.8

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ACSM Fluid Replacement Recommendations

• Before exercise, drink
• 500 ml 2 hr before exercise
• During exercise, drink
• early and at regular intervals
• to replace lost fluids (if tolerated)
• over-hydration can result in hyponatremia
• After exercise, drink
• excess of that lost during exercise

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Thermal distress

• wet-bulb temperature single temperature reading
  to account for all atmospheric conditions
• heat cramps least serious
• heat exhaustion caused by insufficient blood
  flow
• heat stroke failure of thermoregulatory system,
  is life threatening

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Acclimatization to exercise in heat

• ? body fluids/blood volume (w/in 3-5 d)
• ? skin blood flow
• ? rate of sweating (may take up to 10 d)
• ? electrolyte loss
• ? heat tolerance
• Achieving heat acclimatization
• normal workouts in heat for 5-10 d

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Heat acclimatization
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Suggested Readings(available at gssiweb.com
under Sport Science Exchange)

• Murray, R. Fluid replacement The American
  College of Sports Medicine Position Stand. GSSE
  9(4) SSE53, 1996.
• http//www.gssiweb.com
• Maughan, R.J. and S.M. Shirreff. Preparing
  athletes for competition in the heat developing
  an effective acclimatization strategy. GSSE 10(2)
  SSE65, 1997.
• http//www.gssiweb.com

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• The primary mode of heat dissipation during
  exercise is
• convection
• radiation
• conduction
• sweat evaporation

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• What likely is the primary cause of HR drift
  during moderate-intensity exercise in heat?
• ? plasma volume leading to ? SV
• ? Epi release
• ? temperature
• ? sweating
• ? body weight

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• Which of the following fluids would best maintain
  hydration during exercise in heat?
• water
• orange juice
• Coke
• Coke without carbonation
• fruit juice