Abstract
While walking on split-belt treadmills (two belts running at different speeds), the slower limb shows longer anterior steps than the limb dragged by the faster belt. After returning to basal conditions, the step length asymmetry is transiently reversed (after-effect). The lower limb joint dynamics, however, were not thoroughly investigated. In this study, 12 healthy adults walked on a force-sensorised split-belt treadmill for 15 min. Belts rotated at 0.4 m s−1 on both sides, or 0.4 and 1.2 m s−1 under the non-dominant and dominant legs, respectively. Spatiotemporal step parameters, ankle power and work, and the actual mean velocity of the body’s centre of mass (CoM) were computed. On the faster side, ankle power and work increased, while step length and stance time decreased. The mean velocity of the CoM slightly decreased. As an after-effect, modest converse asymmetries developed, fading within 2–5 min. These results may help to decide which belt should be assigned to the paretic and the unaffected lower limb when split-belt walking is applied for rehabilitation research in hemiparesis.
Highlights
Walking on a split-belt treadmill was proposed both as an experimental model for studying the neural control of walking [1] and as a form of “re-symmetrising” therapeutic exercise for patients with unilateral motor impairments [2,3,4,5,6]
The step length (SL) and stance time are shortened on the faster belt, giving rise to the appearance of a pathologic-like “escape limp”, wherein the plantar flexor muscles, which are the main drivers of body propulsion [7,8,9,10,11], are forced to provide more power and work to sustain the “escape” [7]
“split” motor pattern [15,16,17] and can reduce the asymmetries in SL [15,18], characterising various clinical conditions [19,20,21], providing the rationale for applications of split-belt walking to rehabilitation
Summary
Walking on a split-belt treadmill (two belts running at different velocities) was proposed both as an experimental model for studying the neural control of walking [1] and as a form of “re-symmetrising” therapeutic exercise for patients with unilateral motor impairments [2,3,4,5,6]. On return to baseline after 5–20 min (“tied” belts, post-adaptation), an “after-effect” was described [12,13,14,15], i.e., a transient reversal of the kinematic asymmetries. The after-effect, which is a common phenomenon in various human behaviours, is considered here as evidence of learning and transient retention of the “split” motor pattern [15,16,17] and can reduce the asymmetries in SL [15,18], characterising various clinical conditions [19,20,21], providing the rationale for applications of split-belt walking to rehabilitation
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