Exercise I - RS Flashcards
How is caloric intake determined during exercise?
Oxygen consumption is a measure of energy expenditure. You need to know the caloric equivalent of consuming 1 liter of oxygen. And to know the caloric equivalent of O2 you need to know the fuel being metabolized. Which can be solved for with the respiratory quotient: RQ = VCO2/ VO2.
What is the energy yield from CHO, fat and protein?
CHO 4Kcal/g , RQ = 1.0. Kcal/LO2= 5.05
Fat 9.1Kcal/g , RQ = 0.7 Kcal/LO2= 4.70
Protein 4Kcal/g , RQ = 0.8 Kcal/LO2= 4.50
What is respiratory exchange ratio? Why is it used?
RQ can’t be measured in vivo, but is estimated with VCO2/ VO2. RER = RQ when the body’s total O2 stays constant AND when total CO2 content stays constant.
Assuming negligible contribution of protein to energy production and steady state condition, what can RER estimate?
The RER can provide an estimate of the relative amounts of carbohydrate versus fat that are being consumed. At rest this distribution is ~50%-50% for whole body energy expenditure and therefore RER would be 0.85.
What is the best single indicator of aerobic fitness or endurance?
VO2 increases linearly with exercise intensity to a point referred to as Max VO2. Max VO2 is considered to be the best single indicator of aerobic fitness or endurance performance.
How does heart rate respond to exercise?
HR increases fairly linearly with increasing VO2. Sympathetic input to the SA node increases (and parasympathetic input decreases) commensurate with the increasing physical stress of the exercise.
How does stroke volume respond to exercise?
Stroke volume increases initially at mild to moderate exercise intensities and then levels off or may even decline slightly at higher work rates. SV increases as venous return and contractility of the heart are stimulated
There is increasing extraction of O2 as exercise intensity increases, why does this happen?
1) better capillary perfusion, 2) a decreased myocyte PO2 and 3) a right shift in the oxygen-hemoglobin dissociation curve.
What limits VO2 max?
In most people it appears to be limited by left ventricular output or CO. “Blood doping” experiments have shown that more O2 would be used by muscle if the hear could get it there
Does the ability of skeletal muscle to consume oxygen ever limit VO2 max?
No, unless the pt. is highly deconditioned.
What happens to blood pressure with exercise?
Typically the systolic pressure goes up but diastolic does not change very much.
