Exercise metabolism Flashcards
What Energy system produces almost 100% of ATP at rest?
Aerobic metabolism
What is the resting O2 consumption?
0.25 L/min (baseline for activity units)
Rest to exercise transition
ATP production rapidly increases (change in metabolic rate = 25-fold)
Oxygen uptake rapidly increases (reaches steady-state; 1-4 mins, primary energy = aerobic )
Initial increases through aerobic pathways (ATP-PC systems + Glycolysis)
Oxygen deficit is created
What is meant by an oxygen deficit?
Discrepancy between initial ATP production and oxygen consumption
Why do endurance trained individuals have a lower O2 deficit than untrained?
Better bioenergetic capacity:
- Greater regional blood flow to active muscles
- Increased cellular adaptation and efficiency
- Increased mitochondrial volume in muscle fibres result in less lactate production at beginning of exercise
What factors influence EPOC (excess post-exercise oxygen consumption)?
Magnitude
Duration
Intensity of exercise
EPOC is broken down into two components?
Fast (rapid) phase and Slow phase
Describe the Fast Phase of EPOC
Re-synthesis of stored PC in muscle (complete recovery in 60-120 seconds)
Replenishment of muscle (myoglobin) and blood (haemoglobin) O2 stores
Describe the slow phase of EPOC
Elevated heart rate and breathing increase O2 demand
Elevated body temp = increase metabolic rate
Elevated blood levels of epinephrine and norepinephrine = increase metabolic rate
Conversion of lactic acid to glucose (gluconeogenesis)
How much energy yield from carbohydrates and where is it stored and its breakdown process?
4 kcal/g
Liver and muscle glycogen
Glycogenolysis
How much energy yield from fats and where it is stored and how it is broken down?
9 kcal/g
Muscle and adipose tissue (triglycerides)
Lipolysis
How much energy yield from proteins and how it contributes energy (not a primary source of energy)?
4 kcal/g
Contributes by:
- Gluconeogenesis in the liver
- Can be converted to metabolic intermediates (compounds that participate in bioenergetics)
Measuring of aortic gas exchange provides a non-invasive technique to estimate fuel utilisation during exercise (T or F)
F - measurement of pulmonary gas exchange provides a technique to estimate fuel utilisation
What does RER stand for?
Respiratory exchange ratio
How do you calculate a R value?
R = VCO2/VO2
Caveats to an estimation of fuel utilisation test using RER?
Measurements must be taken during steady-state exercise (below lactate threshold) to be reflective of metabolic exchange of gases in tissue.
Assumes that “0” protein is used
Resistance to breathing can increase stress levels and therefore cause hyperventilation (inaccurate reading)
Palmitic acid (fat) C16H32O2 has an RER value of …………
0.70
Glucose (Carbs) C6H12O6 has an RER value of ……………
1
What is the caloric equivalent for oxygen when the RER value is 0.7 (fats)?
4.69 kcal per L per O2
What is the caloric equivalent for oxygen when the RER is 1 (glucose)?
5.05 kcal * L-1 O2
Exercise intensity as a factor governing fuel selection during exercise. Explain……
Cross over concept; shift from fat to CHO metabolism as exercise intensity increases.
Due to:
- Recruitment of fast muscle fibres (abundance of glycolytic enzymes, fewer lipolytic enzymes)
- Increasing blood levels of epinephrine stimulates glycolysis and lactate production (inhibits fat metabolism by reducing the availability of fat as a substrate)
Exercise duration as a factor governing fuel selection during exercise. Explain …….
The longer the duration, the more fat metabolism comes the predominant energy source.
Due to an increase rate of lipolysis;
- breakdown of triglycerides (by lipases) = glycerol and Free fatty acids.
- Stimulated by rising levels of several hormones (epinephrine, norepinephrine and glucagon)
What is the impact of glycogen stores being depleted during high intensity prolonged exercise?
Reduction is glycolysis an production of pyruvate, therefore, reduction in kreb-cycle activity.
Reduction in Kreb-cycle intermediates causes a decrease in fat oxidation rates.
This results in fatigue, can be mitigate by a sports drink or gel (CHO supply)
What is the best intensity to burn fat?
From a relative perspective; Low intensity exercise provides a higher percentage of energy from fat compared to high intensity.
From an absolute perspective; Moderate intensity exercise causes greater energy expenditure, therefore when we look at total fat oxidation it is greater than low intensity.
