Impact forces during running: Loaded questions, sensible outcomes

Load carriage was used as an experimental tool to evaluate the ability of an anatomically-based, two-mass model of the human body to predict vertical impact and peak forces during running from only four inputs: body weight (W_b), contact time (t_c), aerial time, (t_a), and lower-limb acceleration (a₁). Simultaneous motion and force data were acquired from seven subjects during steady-speed trials (3.0-6.0 m·s^-1) on a custom, force-instrumented treadmill under three loading conditions: unloaded (1.0 W_b), 15% added weight (1.15 W_b) and 30% added weight (1.30 W_b). Model-predicted impact and peak forces corresponded with measured values, on average, to within 14.9±1.3% and 13.8±0.6%, respectively (R² best-fits=0.82 and 0.88, n=71). Ankle jerk and velocity data derived from optical position-time data suggest wearable sensor acquisition of the model-needed inputs is fully feasible. We conclude that the two-mass model offers a promising approach to quantifying running ground reaction forces using wearable technologies.