The effects of variable practice on locomotor adaptation to a novel asymmetric gait

Abstract

Very little is known about the effects of specific practice on motor learning of predictive balance control during novel bipedal gait. This information could provide an insight into how the direction and magnitude of predictive errors during acquisition of a novel gait task influence transfer of balance control, as well as yield a practice protocol for the restoration of balance for those with locomotor impairments. This study examined the effect of a variable practice paradigm on transfer of a novel asymmetric gait pattern in able-bodied individuals. Using a split-belt treadmill, one limb was driven at a constant velocity (constant limb) and the other underwent specific changes in velocity (variable limb) during practice according to one of three prescribed practice paradigms: serial, where the variable limb velocity increased linearly; random blocked, where variable limb underwent random belt velocity changes every 20 strides; and random practice, where the variable limb underwent random step-to-step changes in velocity. Random practice showed the highest balance control variability during acquisition compared to serial and random blocked practice which demonstrated the best transfer of balance control on one transfer test. Both random and random blocked practices showed significantly less balance control variability during a second transfer test compared to serial practice. These results indicate that random blocked practice may be best for generalizability of balance control while learning a novel gait, perhaps, indicating that individuals who underwent this practice paradigm were able to find the most optimal balance control solution during practice.

Contextual interference during adaptation to asymmetric split-belt treadmill walking results in transfer of unique gait mechanics

“…Therefore, the data from Transfer 1 demonstrate no effect of practice group. These findings are surprising given our previous findings from this cohort, where random blocked practice had less variability in balance control compared to the other groups ( Hinkel-Lipsker and Hahn, 2017 ). It is possible that since the 1.5:1 belt asymmetry was close to that of the maximum asymmetry experienced during acquisition, all subjects were able to easily generalize their acquired pattern to this new context.…”

“…These velocities differed according to specific practice paradigms. We observed that increased contextual interference in belt velocities on one limb led to better transfer of mediolateral balance control, but only to an extent; too much contextual interference resulted in less transfer as seen through worsened mediolateral balance control ( Hinkel-Lipsker and Hahn, 2017 ).…”

“…We have previously shown that random practice results in a significantly greater challenge to mediolateral balance control during acquisition ( Hinkel-Lipsker and Hahn, 2017 ). Therefore, the lack of increasing ankle dorsiflexion and significantly greater knee flexion angle and knee extensor moment during stance on the constant limb may be demonstrative of a potential strategy to limit forward propulsion onto the variable limb.…”

“…Since random practice was most difficult during acquisition, we hypothesized that (1) this group would have significantly different lower-limb mechanics compared to the other practice groups and baseline, symmetric walking. In our previous work, we found that random blocked practice had significantly better control of mediolateral balance during a transfer test (Transfer 1) that introduced an asymmetry close to what was experienced during the acquisition phase compared to the other practice groups ( Hinkel-Lipsker and Hahn, 2017 ). It is likely, then, that this group found a unique mechanical walking solution as a result of this practice paradigm.…”

A Novel Square-Stepping Exercise Program for Older Adults (StepIt): Rationale and Implications for Falls Prevention

“…Practicing a motor task that is varied along some task dimension is referred to as variable practice and it is considered to be a method that enhances the ability to transfer the learned task to a novel variation of the task or to a new environment (39). This happens because, similar to the mechanism just described for the RAS technique, the continuous attempt to adjust to altered conditions creates a trial-and-error mechanism that ultimately maximizes retention (40).…”