Validity and reliability of the Cosmed K2 to measure oxygen uptake

The validity and reliability of the Cosmed K2 was tested in comparison with a Quinton on-line oxygen analysing system. A female subject was monitored on a treadmill using a progressive protocol and was measured on three occasions with each system. It was found at low workloads that the Cosmed K2 and the Quinton gave the same measure of oxygen uptake; at higher workloads the Cosmed K2 gave lower values, and at peak oxygen uptake the Cosmed K2 measured 22.2% less than the Quinton. The difference in the measurement of VE at peak oxygen uptake was 13%. The Cosmed K2's measurement of VO2 showed a greater variability between trials (variation coefficient 3.0-11.4%) than the Quinton (variation coefficient 1.1-3.9%).