Overhead support systems differentially affect gait analysis of overground and treadmill walking

Background: Overhead support or catch systems are frequently used in gait studies involving clinical populations to ensure participant safety. These systems remain slack when the participant is upright and therefore are assumed to not interfere with gait biomechanics. However, these systems follow participant's transverse motion during walking via rail systems, which could produce additional inertial and frictional forces that affect gait biomechanics. Objective: Quantify the influence of overhead support systems on gait biomechanics during treadmill and overground walking. Methods: We recruited fifteen uninjured adults to perform treadmill and overground walking. In each of these walking conditions, we varied each participant's walking speed (80, 100, and 120 % of preferred speed) and attachment to an overhead support system. We measured the participants' joint angles, moments and ground reaction forces using a three-dimensional motion capture system and an instrumented treadmill built into an overground walkway. For overground and treadmill walking, we examined changes in each biomechanical variable across speed and harness conditions using one-dimensional statistical parametric mapping (spm1d). Results: During overground walking, the overhead support system altered ground reaction forces, joint kinematics, and moments, and these effects became more pronounced with increased speed. During treadmill walking, we found very few changes in gait biomechanics resulting from the harness. Conclusions: These results caution the use of experimental paradigms involving overground walking when an overhead support is required, although these results may be less pronounced in clinical populations with slower walking speeds. Overhead support systems can be used during treadmill walking without affecting biomechanical measurements.