Chapter 4 PowerPoint Flashcards
Energy requirements at rest
100% of ATP produced by aerobic metabolism.
Blood lactate levels are low (<1.0 mmol/L).
Resting O2 consumption: 0.25 L/min (absolute) and 3.5 ml/kg/min (relative).
Why is there a lower oxygen deficit when the individual is trained?
Better developed aerobic bioenergetic capacity.
Cardiovascular and muscular adaptations.
Recovery from exercise
O2 uptake increases then rest during recovery from exercise.
Excess post-exercise oxygen consumption (EPOC).
Factors contributing to EPOC
Resynthesis of phosphocreatine in muscle.
Lactate conversion to glucose.
Restoration of muscle and blood oxygen stores.
Elevated body temperature.
Post-exercise elevation of HR and breathing.
Elevated hormones.
Rapid portion of EPOC
Resynthesis of stored phosphocreatine.
Replenishing muscle and blood O2 stores.
Slow potion of EOPC
Elevated heart rate and breaking = increase energy needed.
Elevated body temperature = increased metabolic rate.
Elevated epinephrine and norepinephrine = increased metabolic rate.
Conversation of lactic acid to glucose (glucogenesis).
Metabolic responses to short-term, high intensity exercise
First 1-5 seconds = ATP via ATP-PC system.
>5 seconds = shift to ATP via glycolysis.
Events >45 seconds = ATP via ATP-PC, glycolysis, and aerobic (60 seconds = 70% anaerobic/30% aerobic; 2 minutes = 50% anaerobic/50% aerobic).
Metabolic responses to prolonged exercise:
Prolonged exercise is more than 10 minutes.
Steady state oxygen uptake can generally be maintained during submaximal exercise (below lactate threshold.
Changes in oxygen uptake during incremental exercise:
The VO2 steadily increases and the work rate (increases), but the VO2 plateaus once the work rate reaches 250 watts.
Changes in blood lactate concentration during incremental exercise:
The amount of lactate increases very slowly until VO2 max reaches 60%, where the lactate threshold is reached. The lactate then increases dramatically.
Mechanisms to explain the lactate threshold
Low muscle oxygen
Accelerated glycolysis
Recruitment of fast-twitch fibers
Reduced rate of lactate removal
Practical uses of the lactate threshold:
Prediction of performance, combined with exercise economy.
Planning training programs: marker of training intensity, choosing a training heart rate based on lactate threshold.
Lactic acid removal following exercise:
70% of it is oxidized by cells and used as a substrate by the heart and skeletal muscle.
20% of it is converted to glucose.
10% of it is converted to amino acids.
Does lactate cause muscle soreness?
Physiological evidence does not support this claim. Lactate removal is rapid (60 minutes) following exercise. If lactate caused muscle soreness, power athletes (sprinters) would experience delayed onset muscle soreness (DOMS) after every workout.
What causes DOMS?
Microscopic injury to muscle fibers leads to inflammation.
Occurs 24-48 hours following an exercise session.
As VO2 max increases, the energy from fats _________, and the energy from carbohydrates ____________.
Decreases
Increases
Is low-intensity exercise best for burning fat?
At low exercise intensities (about 20% VO2 max), a high percent of energy expenditure is derived from fat, while the total energy expenditure is low. This means that the total fat oxidation is also low.
At higher exercise intensities (about 60% VO2 max), a lower percent of energy expenditure is derived from fat, while the total energy expended is higher. This means that the total fat oxidation is also higher.
Glycogen depleted in prolonged high-intensity exercise…
Decrease rate of glycolysis and production of pyruvate.
Decrease Kreb’s cycle intermediates.
Decrease fat oxidation.
Sources of protein during exercise:
Proteins broken down into amino acids. Muscle can directly metabolize BCAAs and alanine. The liver can convert alanine to glucose.
Only 2% to total energy production during exercise. May increase to 50-10% late in prolonged-duration exercise.
