Treadmill vs. overground trotting - a comparison of two kinetic measurement systems

Force plates are considered the gold standard for kinetic gait analysis, benefiting from measuring three-dimensional ground reaction forces. Nevertheless, the major disadvantage is that many trials are required during overground locomotion to capture adequate single-limb contacts. Additionally, the dogs slightly change velocities during overground walking, influencing kinetic and kinematic gait parameters. An alternative is using an instrumented treadmill that benefits from capturing many steady-state gait cycles at a constant speed quickly. The goal of this study was (1) to compare overground with treadmill locomotion and (2) to compare the instrumented treadmill with force plates for dogs kinetics measurements. Twelve client-owned dogs were measured during treadmill trotting while the treadmill was placed on force plates. Additionally, the dogs were measured during trotting along an alley over eight force plates. Bland-Altman plots, Pearson's (r), and concordance correlation coefficients (r_c) were computed to explore the relative and general agreement between the measurement methods and overground and treadmill trotting. Overground and treadmill trotting gave an excellent agreement in peak vertical forces and impulses (r > 0.9, r_c > 0.9). The instrumented treadmill showed similar force-time curves in shape and size and provided an excellent congruity for all parameters compared to force plates (r > 0.8, r_c > 0.8). As a reliable tool in measuring key gait parameters, the instrumented treadmill may benefit from fast and reproducible data comparable to overground trotting.