Physio 3 Flashcards
how to determine caloric expenditure during exercise
use oxygen consumption (VO2) as an index of energy expenditure. to translate to calories, you need to know caloric equivalent of consuming 1 liter of oxygen.
respiratory quotient
VCO2/VO2. if you know this, you can determine the types of fuels being used. RQ for carb is 1.0, for fats, it is 0.7, and for proteins it is 0.8.
respiratory exchange ratio
RER. RQ cant be measured in vivo but can be estimated. RER = RQ whenever the body’s total O2 content stays constant and when total CO2 content stays constant. Assuming negligble contribution of protein to energy production, RER can provide an estimate of the relative amounts of carbs versus fat being consumed
how do you measure VO2?
inspired and expired air is passed through a flow meter and oxygen and CO2 analyzers.
Vi * FiO2 - Ve * F3O2
Max VO2
VO2 increases linearly with exercise intensity to a point referred to as max VO2. considered to be the best single indicator of aerobic fitness or endurance performance
what limits VO2 max?
- pulmonary factors: ventilatory capacity, diffusion.
- cardiovascular factors: cardiac output, distribution of CO, capillarity of skeletal muscle
- Muscle factors: mitochondrial content
changes in respiratory parameters with increasing exercise intensity
total minute ventilation (Ve) increases linearly to the point of the ventilatory threshold then increases out of proportion to VO2 at high work intensity. hyperventilation decreases CO2, helping keep the pH normal
how does cardiac output and heart rate change with increasing work intensity?
both increases fairly linearly with increasing work intensity or VO2
how does stroke volume change with increasing work intensity
increases initially at mild to moderate exercise intensities and then levels off or may even decline slightly at higher work rates. increases as venous return and contractility of the heart are stimulated
what happens to the distribution of cardiac output during exercise
tissues needing more blood have arterioles dilate so they can receive 80-85% of the CO. inactive muscles receive less blood flow due to vasoconstriction in the arteriolar beds
what happens to the distribution of cardiac output during exercise
tissues needing more blood have arterioles dilate so they can receive 80-85% of the CO. inactive muscles receive less blood flow due to vasoconstriction in the arteriolar beds
what happens to oxygen extraction as exercise intensity increases
increases! due to better capillary perfusion, a decreased myocyte PO2, and a right shift in the oxygen-hemoglobin dissociation curve
does the cardiovascular system limit VO2 max?
limited by left ventricular output. if the heart could deliver more oxygen to muscle, muscle would use it. blood doping experiments support this. ability of skeletal muscle to consume oxyen never limits VO2 max
effect of exercise on blood pressure
depends on the muscle mass used in the exercise, whether the exercise is static or dynamic, body position, and temperature
