A Controlled Slip: Training Propulsion via Acceleration of the Trailing Limb

Walking function, which is critical to performing many activities of daily living, is commonly assessed by walking speed. Walking speed is dependent on propulsion, which is governed by ankle moment and the posture of the trailing limb during push-off. Here, we present a new gait training paradigm that utilizes a dual belt treadmill to train both components of propulsion by accelerating the belt of the trailing limb during push off. Accelerations require subjects to produce greater propulsive force to counteract inertial effects, and increase trailing limb angle through increased belt velocity. We hypothesized that exposure to our training p rogram would produce after effects in propulsion mechanics and, consequently, walking speed. We tested our protocol on healthy subjects at two acceleration magnitudes-Perceptible (PE), and Imperceptible, (IM)-and compared their results to a third control group (VC) that walked at a higher velocity during training. Results show that the PE group significantly increased walking speed following training (mean {+/-} s.e.m: 0.073 {+/-} 0.013 m/s, p < 0.001). The change in walking speed in the IM and VC groups was not significant at the group level (IM: 0.032 {+/-} 0.013 m/s; VC: -0.003 {+/-} 0.013 m/s). Responder analysis showed that changes in push-off posture and in neuro-motor control of ankle plantar-flexor muscles contributed to the larger increases in gait speed measured in the PE group compared to the IM and VC groups. Analysis of the effects during and after training suggest that changes in neuromotor coordination are consistent with use-dependent learning.