Sequential gait interventions reveal non-reciprocal transfer between instructional and sensorimotor adaptation mechanisms

Combining interventions is common in gait rehabilitation, but how prior adaptation influences subsequent responses and retained gait changes remains unclear. This study examines the sequential interaction between two interventions with distinct adaptation mechanisms: split-belt treadmill (SBT) which primarily engages sensorimotor recalibration, and asymmetric rhythmic auditory cueing (ARAC) which primarily engages instructional adaptation. Specifically, we assess the transfer of gait changes acquired during adaptation across interventions and their retention after perturbation removal in ten healthy young adults. We found that transfer from SBT to ARAC occurred only when the perturbation(s) were spatially and temporally aligned (i.e., congruent), while ARAC to SBT transfer also occurred under incongruent conditions—suggesting that ARAC may engage a more generalized, effector-independent adaptation process. Individuals who responded strongly to ARAC showed reduced retention, possibly due to cognitive fatigue. These results demonstrate that interlimb transfer may be non-reciprocal and sequence-dependent, and higher cognitive engagement may hinder retention despite facilitating adaptation. Tailoring the order and type of intervention based on individual dominant (or preferred) adaptation mechanism (sensorimotor or instructional) may enhance rehabilitation outcomes in populations with attenuated adaptive ability (e.g., post-stroke individuals). This work provides insights for sequencing principles in combined gait interventions and indicates trade-offs between cognitive engagement and motor memory retention. Our results generate testable hypotheses about when and why ordering and congruence might matter for transfer and retention.