Abstract
The aim of this study was to determine the agreement of the K4b(2) metabolic system in comparison with the Douglas bags (DB) method for determining gas-exchange variables during both indoor treadmill and outdoor running. Nineteen endurance-trained males undertook 3 maximal incremental running tests, separated by at least 2 days: K4b(2) indoor test (K1), K4b(2) outdoor test (K2), and DB indoor test. Gas-exchange parameters ((V) over dotO(2), (V) over dotco(2), (V) over dot(E), (V) over dot(I), Respiratory Exchange Ratio, FEO2, and FECO2) and heart rate were measured during K1, K2, and DB tests. For most of the variables ((V) over dotO(2), %(V) over dotO(2), %(V) over dotco(2), (V) over dot(E), and (V) over dot(I)), the agreement was better for K2 when compared with DB than for K1 when compared with DB. For (V) over dotco(2), FEO2, and FECO2, the agreement was better between K1 when compared with DB than for K2 when compared with DB. Respiratory Exchange Ratio showed a similar agreement between both conditions (K1 vs. DB and K2 vs. DB). K4b(2) seems valid for measuring gas-exchange variables during submaximal and maximal running velocities in an outdoor environment. Although K2 mean systematic error (bias) was low, the aleatory error was moderate. These considerations should be taken into account when using K4b(2) to measure gas-exchange parameters both during indoor and outdoor activities.