Van Hooren et al. 2020, Treadmill versus overground running biomechanics

Systematic review and meta-analysis of crossover studies. Motorised treadmill and overground running are biomechanically broadly comparable in stride time, length, frequency and peak vertical ground reaction force, with minor differences in sagittal-plane footstrike kinematics and lower peak propulsive force on the treadmill. Submaximal oxygen cost is similar, though heart rate and perceived exertion can differ. Strong (for the broad comparability).