Forward acceleration is an important factor to control in biomechanics studies investigating walking/running, as human kinetics and kinematics vary with changes in acceleration. During overground running studies, acceleration is typically estimated using the net anterior-posterior ground reaction force impulse, as measured with force plates. However, as studies move outside the lab, there is limited validation of alternative methods of quantifying acceleration when force plates are unavailable. The purpose of this study was to assess the validity of alternative methods for estimating acceleration in overground running. We evaluated the use of timing lights and motion capture, as indicators of acceleration, to measure change in velocity. We hypothesized that the change in velocity calculated from timing lights and motion capture markers near the center of mass would have a strong positive correlation with the relative anterior-posterior ground reaction force impulse measured with force plates. Ten participants ran in an indoor lab while measurements were collected using timing lights, motion capture and a force plate. The correlation between the relative anterior-posterior impulse and velocity changes measured by timing lights was weak (r = -0.01, r = 0.27 and r = 0.15, respectively). In contrast, the correlation between the relative anterior-posterior impulse and velocity change determined by motion capture was strong (r = 0.81). In studies where force plates are not available, measuring changes in velocity with motion capture is a promising method for calculating and controlling acceleration. However, measuring changes in velocity with timing lights does not show as much promise due to weak correlation values and should therefore be avoided.