unit 2 ex phys

• Direct calorimetry


  1. 40% of energy is released as ATP, 60% as heat

  2. Use a chamber to measure the amount of heat put out as body temperature increases
• Indirect calorimetry


  1. Estimation of total energy expenditure by measuring how much O2 is used and CO2 produced

  2. Measure VO2 and VCO2, use Haldane transformation to figure out expiration
• Respiratory exchange rate (RER)


  • VCO2/VO2
  • Palmitic acid: 16/23 = 0.7
  • Glucose is 6/6= 1
  • It is .80 at rest
• As exercise increases


  RER may exceed 1.1 due to excess CO2 production
• VO2 at rest

  0.25 L
• BMR (basal metabolic rate)


  After 12 h of fasting and 8 h of sleep, minimum energy requirement for life
• RMR (resting metabolic rate)


  No stringent standardized conditions, total daily metabolic activity
• Metabolic rate


  Increases with exercise intensity
• VO2 drift


  Occurs at submaximal intensities, increased VO2 consumption
• VO2 max


  Maximal amount of oxygen inspired and used, cannot take any more in, best predictor of aerobic fitness, training allows for an athlete to perform for longer before maxing out
• At rest, ATP is produced by aerobic metabolism
• Oxygen deficit


  Lag in oxygen at the beginning of exercise, smooth transition between anaerobic to aerobic systems
• EPOC (excess post-exercise oxygen consumption)


  • O2 demand is greater than consumed in early exercise, O2 consumed is greater than demand in early recovery
  • Replenish ATP/PCr, convert lactate to glycogen, replenish Hb and Mb, clear CO2
• EPOC factors


  • Rapid portion: resynthesis of PC, replenish muscle and blood O2 stores
  • Slow portion: elevated HR, breathing, temp, epi, norepi, convert lactate to glucose
• Lactate production


  Addition of two H forms NAD and Lactic acid by lactate dehydrogenase
• Lactate threshold


  Point when blood lactate drastically rises with incremental exercises, occurs at about half of VO2 max in untrained, 4 mmol/L
• Mechanisms of lactate threshold


  • Low muscle oxygen
  • Accelerated glycolysis
  • Recruitment of fast twitch fibers
  • Reduced rate of lactate removal
• Lactate removal


  1. 70% oxidized and used by heart and muscle, 20% to glucose, 10% to amino acids

  2. Removed faster with light exercise during recovery (walking to cool off)
• If lactate is not cleared immediately


  It is converted to lactate + H+ which causes acidosis
• Lactate utilization


  • Converted to glucose by the Cori cycle
  • Used as a fuel by Kreb cycle from acetyl CoA
  • Lactate shuttle between tissues
• Crossover concept


  • At 60% of VO2 max, carb metabolism takes over from fat as fuel due to recruitment of fast twitch fibers and increased epi
  • At 20% of VO2 max, fat is primary fuel but total fat oxidation is lower than at 50% of VO2 max where total energy expenditure is higher
• Carb sources during exercise


  • Muscle glycogen
  • Blood glucose
• Fat sources during exercise

  • Intramuscular triglycerides
  • Plasma FFA
• Ways plasma glucose is maintained

  • Mobilization of glucose from the liver
  • Mobilization of FFA from adipose tissue
  • Gluconeogenesis
  • Blocking entry into cell
• Hormones controlling blood glucose


  • Cortisol, growth hormone = slow
  • Epi and norepi, insulin, glucagon = fast-acting
• Fats burn in the flame of carbohydrates
• Glycogen is depleted during prolonged high intensity exercise
• Effects of glycogen depletion


  • Reduced rate of glycolysis and production of pyruvate
  • Reduced Kreb cycle
  • Reduced fat oxidation
• Growth hormone release


  Slow acting hormone, stimulates release of insulin like growth factors for muscle growth, long bone growth, spares plasma glucose, increased with increased intensity
• Cortisol


  Slow, maintain plasma glucose, FFA mobilization, gluconeogenesis, block uptake of glucose into cells, stimulated by stress and exercise, decrease during low intensity exercise and increase high intensity exercise
• Epi and norepi


  Fast, glycogen mobilization, FFA mobilization, glucose blocked from cell
• Insulin


  Fast uptake and storage of glucose and FFA, plasma concentration decreases during exercise, decreased insulin response after training
• Glucagon


  Fast, mobilize glucose and FFA, plasma concentration increases during exercise, decreased response after training
• Insulin concentrations decrease during exercise
• Depolarization


  Becoming more positive
• Steps of an action potential

  1. Resting MP (-70)

  2. Depolarizing stimulus

  3. Threshold (-55), Na and K channels open

  4. Rapid Na entry depolarizes the cell

  5. Na channel closes, K opens

  6. K channels remain open and efflux hyperpolarizes

  7. Channels close

  8. Cell back to resting MP
• Absolute refractory


  No stimulus can trigger another action potential
• Relative refractory


  A larger than normal stimulus can trigger an action potential
• Myelination

  Helps move the action potential down the axon
• Neurotransmitter termination


  Returned to axon terminal, enzymes inactivate, or diffuse out of the synaptic cleft