Exercise Metabolism Flashcards
VO2Max
Cori Cycle
location: liver & skeletal muscle
process: turning lactate into glucose
lactate threshold
the work rate at which blood lactic acid rises systematically during incremental exercise
LC ranges compared to VO2 Max
- appears at 50-60% VO2 max in untrained subjects
- occurs at higher work rates (65-80% VO2 max) in endurance trained subjects
OBLA
onset of blood lactate accumulation: exercise intensity at which blood lactate levels reach 4 mmol/L
explanations for lactate threshold
- low muscle oxygen (hypoxia)
- recruitment of fast-twitch muscle fibers
- reduced rate of lactate removal from the blood
- accelerated glycolysis
practical uses of lactate threshold
- prediction of endurance performance
- planning training programs
ATP requirements at rest
- almost 100% of ATP produced by aerobic metabolism
- blood lactate levels are low ( <1.0 mmol/L)
- resting O2 consumption
*0.25 L/min
*3.5 ml/kg/min
oxygen deficit
lag in oxygen uptake at the beginning of exercise
training effects on oxygen deficit
they have a lower oxygen deficit
> better developed aerobic bioenergetic capacity due to:
- cardiovascular adaptations
- muscular adaptations
> increased mitochondrial volume in muscle fibers
- results in less lactate production at beginning of exercise
oxygen debt
the elevated O2 consumption post exercise was repayment for O2 deficit at onset of exercise
EPOC
excess post-exercise oxygen consumption
- replaced the term “oxygen debt”
- terminology reflects that only 20% elevated O2 consumption used to “repay” O2 deficit
Rapid portion of EPOC
- elevated O2 consumption used for:
> re-synthesis of stored PC in muscle
> replenishing muscle (myoglobin) and blood (hemoglobin) O2 stores
Slow portion of EPOC
- increased O2 needed for elevated heart rate and breathing
- increased body temp = increased metabolic rate
- increased blood levels of epinephrine and norepinephrine = increased metabolic rate
- conversion of lactic acid to glucose (gluconeogenesis)
Metabolic response to exercise:
1 -5 seconds
ATP produced via ATP-PC system
MRE:
intense exercise > 5 seconds
shift to ATP production via glycolysis
MRE:
events lasting > 45 seconds
- ATP production through ATP- PC, glycolysis, and aerobic systems
> 70 % anaerobic/ 30% aerobic at 60 seconds
> 50 % anaerobic/ 50% aerobic at 2 minutes
MRE:
prolonged exercise (>10 minutes) in cool environment
- ATP production primarily from aerobic metabolism
- Steady-state oxygen uptake can generally be maintained during submaximal exercise ( below LT)
MRE:
prolonged exercise in hot & humid environment or at high intensity
results in upward drift in oxygen uptake over time due to increase in body temperature and increasing blood levels of epinephrine and norepinephrine
physiological influences on VO2 max
- maximum ability of cardiorespiratory system to deliver oxygen to the muscle
- ability of muscles to use oxygen and produce ATP aerobically
verification of VO2 max
- gold standard is a plateau in O2 consumption with increase in work rate ( most do not achieve plateau)
- second criteria:
> reaching age-predicted max heart rate (+/- 10 beats/min)
> achieving blood lactate concentration of 8mM or higher
> attaining a respiratory exchange ratio of 1.15 or higher - doesn’t always prove
removal of lactate
leaves blood rapidly ( within 60 minutes) following exercise
* does not cause muscle soreness
sources of fuel supply during exercise
carbohydrate:
> muscle glycogen
> blood glucose (diet and liver)
Free fatty acids:
> muscle fat stores
> white adipocytes-numerous locations in body
factors governing fuel selection
high intensity
carbs are primary fuel (> 70% VO2 max)
