VALIDATION OF THE COSMED K4B2 PORTABLE METABOLIC SYSTEM DURING RUNNING OUTDOORS

Ross, R, ALDuhishy, A, and González-Haro, C. Validation of the cosmed K4b2 portable metabolic system during running outdoors. J Strength Cond Res 34(1): 124–133, 2020—The aim of this study was to determine the agreement of the K4b² 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: K4b² indoor test (K1), K4b² outdoor test (K2), and DB indoor test. Gas-exchange parameters (V^_ O₂, V^_ CO₂, V^__E, V^__I, Respiratory Exchange Ratio, F_EO₂, and F_ECO₂) and heart rate were measured during K1, K2, and DB tests. For most of the variables (V^_ O₂, %V^_ O₂, %V^_ CO₂, V^__E, and V^__I), the agreement was better for K2 when compared with DB than for K1 when compared with DB. For V^_ CO₂, F_EO₂, and F_ECO₂, 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). K4b² 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 K4b² to measure gas-exchange parameters both during indoor and outdoor activities.