Term
| Why does lactic acidosis occur during exercise? |
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Definition
1) As O2 supply becomes inadequate, aeroboic respiration becomes anaerobic, producing lactic acidosis.
2) During exercise muscle cells also make more CO2 (increasing VCO2) that diffuses into tissue capillaries, and is transported to lungs
*If you don't increase Ve, then PaCO2 will increase** |
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Term
| What is the "anaerobic threshold" of exercise testing? |
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Definition
Point during exercise at which CO reaches a maximum, and CV system will longer be able to meet O2 demands, shifting toward anaerobic metabolism as a result.
**Determined by measuring the VO2 at which the rate of rise in CO2 production and Ve increases**
R will increase from 0.8 to >1. |
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Term
| Why might Ve exceed CO2 production? |
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Definition
To compensate for lactic acidosis.
It matches CO2 production after the anaerobic threshold is met, but later will have to compensate further. |
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Term
| In the absence of CV and pulmonary disease, what is the primary limitation on exercise? |
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Definition
| The amount of oxygen that can be delivered to skeletal muscles by the CV system prior to reaching the anaerobic threshold. |
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Term
| How can you distinguish between Cardiovascular and Respiratory limitations in exercise? |
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Definition
CV= VO2at <0.4 and VEmax <0.7, with HRmax >0.9
Resp= VO2at >0.4, Ve max 0.7 and HRmax< 0.9
1) VO2 max will be <90% of predicted value for both .
2) HRmax will be normal for CV limitation, but low for respiratory (respiratory reaches VO2max too quickly)
3) VO2at will be normal for respiratory limitation, but <0.4 for CV limitation
4) VEmax (MVV- breath out as strongly and quickly as possible for 12s and multiply by 5) is <0.7 for CV limitation (normal), but >0.7 for respiratory. |
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