Associations of Markerless Motion-Based Physical Function Test Performance with Running Gait Kinetics: Application for Therapeutic Monitoring.

Background: Easy-to-perform and effective assessments for runners are needed for high-volume screening of injury risk in clinical settings. Markerless motion capture systems offer comprehensive, fast, and less expensive tests for capturing kinematic and kinetic metrics that are related to running injury compared to traditional laboratory setups. Hypothesis/Purpose: The purposes of this study were to 1) characterize functional test performance in endurance runners using markerless motion capture, and 2) determine the strength of associations between markerless motion capture-based functional movement performance and instrumented treadmill-based kinetic features of running. Sex differences in functional performance tests and in gait characteristics were secondary exploratory analyses. Study Design: Cross-sectional study. Methods: Sixty-two recreational runners (40.3% female; 31.5±16.8 yr) ran on an instrumented treadmill, and performed a series of dynamic functional tests using a markerless motion system. Functional tests included lateral bound, multiple hop (5-Hop test), and single-legged jumps. Net ground reaction force (GRF) and vertical average loading rate (VALR) were calculated. Peak GRF at takeoff and landing, and performance scores (jump heights, distances, asymmetries) were obtained from functional tests. Correlations were determined for GRF, VALR, and performance scores from running and function. Results: Interlimb performance differences for these functional tests ranged from 2.6% (mulithop), 3.6% (lateral bound), and 14.3% (single-legged jump). Correlation coefficients between peak running GRFs and markerless motion-derived single-legged hop, lateral bound, and multihop tests were moderate-to-strong (r=0.641 to 0.882; all p<0.001). Performance scores (jump heights and bound distance) demonstrated fair-to-moderate relationships (r=0.502 to 0.882). Correlation coefficients between VALRs from running and GRFs obtained from functional tests were lower (r=0.147 to 0.742). Conclusions: Endurance runners demonstrated similar interlimb performance on multihop and lateral bound tests. Markerless motion testing-derived GRFs are correlated to GRFs obtained during running. Markerless motion capture may offer a cheaper, more time-efficient method to obtain meaningful translational kinetic values for runners. Level of Evidence: 3.