Bidirectional locomotion induces asymmetric limb adaptations

Humans can acquire and maintain motor skills throughout their lives through motor learning. Motor learning and skill acquisition are essential for rehabilitation after neurological disease or injury. Adaptation, the initial stage of motor learning, involves short-term changes in motor performance in response to a new demand in the person's environment. Repeated adaptation can improve skill performance and result in long-term skill retention. Locomotor adaptation has been extensively studied with split-belt treadmill paradigms. In this study we explored whether bidirectional walking (BDW) on a split-belt treadmill can induce short-term gait adaptations. Twelve healthy volunteers participated in our single session, starting with 2 min of forward walking (FW), followed by four 5-min blocks of BDW with a 1-min passive rest in between blocks, and ending with another 2-min block of FW. We recorded body kinematics and ground reaction forces throughout the experiment. Participants modified both temporal (interlimb phasing, double stance duration) and spatial (step length) aspects of gait to meet the mechanical demands of backward dual walking (BDW). Adaptation occurred rapidly, with bilateral reductions in step length, adjustments in stance and swing phase timing, alterations in interlimb phasing, and decreased double stance duration in the limb walking backward. Notably, only the backward-walking limb (right) exhibited persistent aftereffects upon return to FW. These results demonstrate that BDW elicits adaptations in both spatial and temporal gait parameters, with transient aftereffects consistent with short-term motor learning. To our knowledge, this is the first report characterizing such spatiotemporal adaptations during BDW.NEW & NOTEWORTHY In this study, we demonstrate that bidirectional walking, i.e. walking with symmetrical limb speeds but in opposite directions, induces spatiotemporal adjustments and adaptations that persist for several minutes upon returning to forward walking. This study serves to validate bidirectional walking as a complementary paradigm to other split-belt training paradigms with unique biomechanical characteristics to investigate locomotor adaptation and learning.