: 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. : Seventeen male endurance athletes (mean 25.8, 3.8 years) performed 4-min running bouts on an indoor track and the treadmill. : At all speeds (11, 13, and 15 km·h) 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 ((1,16) = 31.45,  .001,  = .663) compared to running on the track. Participants presented lower heart rate ((1,16) = 13.74,  .002, = .462) on the track at the speed of 11 and 13 km·h compared to the treadmill, but not at 15 km·h ( = .021). : 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.