Interlimb transfer of motor skill learning during walking: No evidence for asymmetric transfer

Abstract

Several studies have shown that learning a motor skill in one limb can transfer to the opposite limb–a phenomenon called as interlimb transfer. The transfer of motor skills between limbs, however, has shown to be asymmetric, where one side benefits to a greater extent than the other. While this phenomenon has been well-documented in the upper-extremity, evidence for interlimb transfer in the lower-extremity is limited and mixed. This study investigated the extent of interlimb transfer during walking, and tested whether this transfer was asymmetric using a foot trajectory-tracking paradigm that has been specifically used for gait rehabilitation. The paradigm involved learning a new gait pattern which required greater hip and knee flexion during the swing phase of the gait while walking on a treadmill. Twenty young adults were randomized into two equal groups, where one group (right-to-left: RL) practiced the task initially with the dominant right leg and the other group (left-to-right: LR) practiced the task initially with their non-dominant left leg. After training, both groups practiced the task with their opposite leg to test the transfer effects. The changes in tracking error on each leg were computed to quantify learning and transfer effects. The results indicated that practice with one leg improved the motor performance of the other leg; however, the amount of transfer was similar across groups, indicating that there was no asymmetry in transfer. This finding is contradictory to most upper-extremity studies (where asymmetric transfer has been reported) and points out that both differences in neural processes and types of tasks may mediate interlimb transfer.

Cerebral Contribution to the Execution, But Not Recalibration, of Motor Commands in a Novel Walking Environment

“…However, leg-specific adaptation in hybrid walking may result from the peculiar nature of this task and may, therefore, not apply to other locomotor adaptation paradigms. In fact, more recent studies have demonstrated interlimb transfer of adapted motor patterns during conventional split-belt walking (Krishnan et al, 2017(Krishnan et al, , 2018, which argues against leg-specific recalibration. Thus, we believe that recalibration of corrective responses is not affected after cerebral lesions, which is also supported by a lack of association between individual stroke survivors' motor impairments (i.e., Fugl-Meyer scores) and the amount of adaptive-based modulation of corrective responses.…”

Learning new gait patterns is enhanced by specificity of training rather than progression of task difficulty

“…Participants included 43 healthy adults (Age: 22.7±5.4 years; Height: 1.72±0.10 meters; Weight: 67.3±13.1 kilograms) with no history of major orthopedic or neurological conditions, injuries in their lower extremities, uncontrolled illnesses, and/or medication changes in the past 3 months. All participants were classified right-foot dominant based on the leg with which they preferred to kick a ball (Krishnan, 2015;Krishnan et al, 2017;Ranganathan et al, 2016). Participants provided informed, written consent prior to participation, and all protocols received approval from the University of Michigan Institutional Review Board.…”

“…The experiment began by first having the participant walk normally on the treadmill to obtain ensemble averages of their right hip and knee angles across the entire trial. The ensemble averaged normal walking hip and knee trajectories were then scaled (3% to 30%) to create target templates, which were projected in the end-point space (i.e., as a foottrajectory template, which represents the spatial path of the participant's lateral malleolus relative to the hip [local coordinate system] on the sagittal plane) (Krishnan et al, 2017;Krishnan et al, 2018;Ranganathan et al, 2016) using the following forward kinematic equation.…”

Cerebral contribution to the execution, but not recalibration, of motor commands in a novel walking environment

“…However, leg-specific adaptation in hybrid walking may result from the peculiar nature of this task and may, therefore, not apply to other locomotor adaptation paradigms. In fact, more recent studies have demonstrated interlimb transfer of adapted motor patterns during split-belt walking forwards with both legs (Krishnan et al, 2017(Krishnan et al, , 2018, which argues against leg-specific recalibration. Moreover, we have observed that subjects adopt a steady state pattern in the split condition that is influenced by ipsilateral and contralateral speeddemands (Iturralde and Torres-Oviedo, 2019), further arguing against leg-specific recalibration.…”