# ExPhys exam 4

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1. Means by which heat can be produced and gained by the body
• Voluntary
• -Exercise = 70–80% energy expenditure appears as heat
• Involuntary
• -Shivering = Increases heat production by ~5x
• -Action of hormones
• Thyroxine
• Catecholamines
• Called nonshivering thermogenesis
2. Means of heat loss
• Radiation
• Transfer of heat via infrared rays
• Like a grill
• 60% heat loss at rest
• Can be a method of heat gain
• Conduction
• Heat loss due to contact with another surface
• Example: cold towel
• Convection
• Heat transferred to air or water
• Heated molecules are moved away
• Example: a fan pushing air past skin
• Evaporation
• Heat from skin converts water (sweat) to water vapor
• Requires vapor pressure gradient between skin and air
3. Explain role of temp and humidity on sweat evaporation
• Sweat evaporation requires a vapor pressure gradient between skin and air
• Evaporation rate depends on:
• - Temp and relative humidity
• -conductive currents around the body
• -amount of skin surface exposed
• 25% of heat loss at rest
4. How much heat is lost through sweat evaporation
• 0.58 kcal heat / ml of sweat evaporated
• 1L sweat = loss of 580 kcal
• 1L = 1 Kilogram
5. Describe the changes in HR and blood flow during prolonged constant load exercise in hot/humid environment
• a. constant work rate,
• prolonged exercise
• (1) CO maintained (CO = HR x SV)
• (2) SV decreases but HR increases to compensate
• (3) cardiovascular drift - due to rising body temperature
• (a) due to skin vasodilation & dehydration
• (b) both decrease venous return which reduces SV
• if hot/humid environments - response is exaggerated
6. hypothalamus and response to temperature
• Anterior hypothalamus
• -Responds to increased core temperature
• -Commencement of sweating
• -=Increased evaporative heat loss
• -Increased skin blood flow
• -=Allows increased heat loss
• Posterior hypothalamus
• -Responds to decreased core temperature
• -Shivering and increased norepinephrine release
• -=Increased heat production
• -Decreased skin blood flow
• -=Decreased heat loss
7. Acclimitization to cold
• more heat, less shivering
• • increase thyroid hormone, moresensitive to NE, uncoupled ox-phos
• • more leptin, increase SNS activity
• • more adipose tissue (insulation)
• • less heat loss in hands in feet
• • intermittent peripheral vasodilation
• • habituation (more pain tolerance)
• • better sleep
8. Acclimitization to heat
• Plasma Volume
• Earlier onset of sweating
• Osmolality of sweat
• Muscle glycogenolysis
9. cross sectional vs. longitudinal training studies
• Cross-sectional Studies
• Compare groups (sedentary vs runners) that differ in physical activity level on some variable (VO2max, CO, HR, strength).
• Looks at differences.

• Longitudinal Training Studies
• Examines the changes that occur over the
• course of a training program.
• Looks at changes, and rate of change
• Problems: cost/length. attrition. age-period confound
10. symptoms of overt-training 6
• decrease in performance
• loss of body weight
• chronic fatigue
• increased number of infections
• psychological staleness
• elevated heart rate and blood lactate levels during exercise
11. go over aerobic training effects
 Author: dvdromm ID: 290504 Card Set: ExPhys exam 4 Updated: 2014-12-03 21:31:40 Tags: ExPhys exam Folders: ExPhys exam 4 Description: ExPhys exam 4 Show Answers: