Purpose: The purpose of this study was to investigate the differences in metabolic responses between the track and the treadmill (1% inclination) running. The latter is recommended for use in laboratory settings to mimic outdoor running. Method: Seventeen male endurance athletes (mean 25.8, s = 3.8 years) performed 4-min running bouts on an indoor track and the treadmill. Results: At all speeds (11, 13, and 15 km·h[superscript-1]) athletes showed better economy on the track running compared to the treadmill expressed as oxygen (7.9%, 5.2%, and 2.8%) and caloric (7.0%, 5.3%, and 2.6%) unit cost. Rating of perceived exertion was evaluated substantially higher at all speeds on the treadmill (F(1,16) = 31.45, p < 0.001, eta-squared[subscript p] = 0.663) compared to running on the track. Participants presented lower heart rate (F(1,16) = 13.74, p= 0.002, eta-squared[subscript p] = 0.462) on the track at the speed of 11 and 13 km·h[superscript -1] compared to the treadmill, but not at 15 km·h[superscript -1] (p = 0.021). Conclusions: We conclude that constant inclination (i.e. 1%) during the treadmill test might not be suitable to reproduce comparable effort to running on the track; rather, there is an optimal treadmill inclination for different intensities to reproduce similar effort compared to the track running.