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Heinz Lowis also stated, that there is a big difference between walking and running, which is clearly reflected in physiological parameters (e.g. hear rate, breathing rate, O2-uptake and therefore also MET).
Source: http://www.uta.edu
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In the citation below you find another short description of the limitations of the Bruce protocol and a table with MET values. As you can see they fit quite well to what custo diagnostic is reporting.
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Source: Brown, S.P., Miller, W.C. & Eason, J.M. (2006): Exercise physiology. Basis of human movement in health and disease. (see page 486)
http://books.google.de/books?id=1b0iwv8-jGcC&printsec=frontcover&hl=de#v=onepage&q&f=false
2002_AHA-Guideline for exercise testing
AHA, page 18.
The translation of exercise duration or workload into METs (oxygen uptake expressed in multiples of basal oxygen uptake, 3.5 O2 mL/kg per minute) has the advantage of providing a common measure of performance regardless of the type of exercise test or protocol used. Although such translations are based on
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