Flashcards in Exercise Physiology Deck (63)
Index of oxygen consumption, VO2
mL/min/kg At rest:L 3.5ml/min/kg = 1.5 MET
The types of fuel being utilized can be determined by Respiratory Quotient (RQ)
RQ= VCO/VO2 (volume of carbon dioxide to the rate of oxygen consumption)
RQ for carb is
RQ for fat is variable but averages to
RQ for protein is
0.8 (it is not used as a fuel because we save these for proteins)
If we were to measure an RQ of 0.7, that would tell us what?
the person is deriving 100% of energy from fat metabolism not from carbohydrates
If we were to measure an RQ of 1.0, what would that tell us?
it would tell us that the person is deriving their energy from carb
RQ cannot be measure in vivo - it is measure of what's going on at the cellular level but the best to do is to measure it
at the mouth- called respiratory exhcnge ratio. We can adjust CO2 by adjusting our breathing rate. If you hyperventilate you increase co2 given off so RER WOULD NOT EQUAL RQ Here. Same for if you hypoventilate
So RER (respiratory exchange ratio) = RQ when
the body's total CO2 content stays constant
1 MET = 1 Kcal/kg/hour
e.g. a 70 kg person performing a 3 MET activity for 1 hour would consume approximately 210 Kcal/hr (3x 70)
Machine that measures O2 consumption: rate of O2 inspired times the fractional O2 minus rate of O2 expired times the fractional O2 gives you the volume of O2 consumed
ViO2 x FiO2 -- ViO2 x FeO2
When you start with a person at rest their O2 consumption is miniscule. As you start to increase the intensity of exercise this raises O2 consumption initially then it comes to a steady state
O2 demand = supply. As you continue to increase the intensity, O2 comsumption increases and levels off. But this doesn't stay like this forever. At some point you intensity will be increased so much and you will see no further increase in O2 consumption. They have reached their max VO2. Their maximal ability to consume oxygen
Linear relationship between O2 consumption and exercise intensity. As you increase this for a long time you will reach max VO2
but some people can go to supramax. But this is not supported by aerobic metabolism at this point. VO2 max is the best measure of aerobic fitness
What limits maximal O2 consumption?
lungs, heart, vasculature and muscle itself can limit it
Linear phase of ventilatory response is when you are doing mild to moderate exercise. You would expect that arterial stuff is stimulating ventilation but you do not see any change in arterial PO2 though mild to moderate. Neither do Arterial PCO2 and pH. Therefore there are other things (joint receptors, muscle receptors, catecholamines)
But then there is a breakpoint where ventilation increases out of proportion to exercise intensity. Here anerobic mechanisms take over as a result lactic acid is made, and pH is decreases (acidosis)==>> hyperventilation (helps to resolve the acidosis.
In heavy exercise, alveolar O2 will increase because of the hyperventilation. Arterial CO2 decreases (cuz you are breathing it out.
Venous O2 will be decreased and CO will be increased. Does the lung limit O2 consumption? NOOOOOOOO
Hb sat is the same as when you are at rest.
Does the heart limit O2 consumption?
CO response to increasing exercise intensity is linear.
CO = HR x SV
HR response is linear increasing - because of increased sympathetic drive to the SA node
SV increases linearly with mild to moderate exercise then it levels off.
SV = EDV - ESV (as exercsise intensity increases, ESV decreases). So the problem is with EDV that causes the leveling...EDV = filling volume time x heart rate. Filling time is reduced...so there are two competing factors: increasing ESV and decreasing EDV so you get a leveling off).
So in mild to moderate exercise heart rate and SV are both contributing to the increase in CO
In intense exercise
we rely more on HR to contribute to the increased cardiac output as compared to SV
CO distribution in muscle during exercise
Blood flow to skeletal muscel increases 5 fold more than CO becausse we start diverting more O2 to muscles when blood vessels are vasodilating.
There is also vasoconstriction in the gut, spleen and inactive muscles.
Muscles are better at extracting O2 from blood vessels (so venous content progressively decreases). Arterial stays constant
Does the CO limit maximal O2 consumption?
If that were true, then if we could deliver more O2 to working skeletal muscle, max oxygen consumption would increase. We can increase O2 delivery to skeletal muscle by blood doping.---adding back RBC to increase Hb and increasing oxygen carrying capacity. if you increase HCT by 10% then the O2 consumption would increase by 10%
Does the ability of the skeletal muscle to consume O2 ever limit VO2 max?
not usual in normal people but pts. with COPD, dialysis or pts. on bed rest
Answer: it is the maximal ability of the LV to pump blood to the skeletal muscle that
will limit your maximal O2 consumption
BP Response depends on
1. muscle mass being used.
Using large muscles you would expect no increase in Diastolic BP. You would expect Systolic BP to increase. MAP should increase but not greatly...modestly.
BP and small muscle groups
you get a greater increase in systolic pressure and greater increase in MAP. It is the amount muscle, the more muscle, the lower the BP
BP and large muscle
vasodilation and vasoconstriction in inactive muscle so groups SO TPR will decrease. Using large muscle groups you will get more vasodilation and you BP will not be high
BP Response depends on
2. static v. dynamic contraction
Blood flow substantially increases when performing static contractions up to 30% but as you increase the intensity beyond 30%, the blood flow starts to decline. By 70% MCV- vessels to that muscle occlude so BP increases when performing static (isometric) contractions. Advice: use them rhythmically
Anerobic ATP production are fast to turn on in response to need but are not long term
are limited in the capacity to sustain repeated contractions. Myokinase catalyzes ATP to keep the levels up. Creatine phosphate rephosphorylates ADP to make ATP. Glycolysis
Aerobic methods include
oxidation of carbs and fatty acids
Anerobically provided ATP is important
a. during the transition period from one level of activity to a higher level of activity
b. whenever exercise demands the anerobic threshold of the individual - you don't use anerobic until you hit the lactate threshold and you increase lactic acid production at high intensity exercises. Ventilatory threshold correlates with the lactic threshold