Effects of protective step training on proactive and reactive motor adaptations in Parkinson's disease patients

Abstract

The aim of this study was to investigate to what extent PD affects the ability to walk, respond to balance perturbations in a single training session, and produce acute short-term effects to improve compensatory reactions and control of unperturbed walking stability. Understanding the mechanism of compensation and neuroplasticity to unexpected step perturbation training during walking and static stance can inform treatment of PD by helping to design effective training regimens that remediate fall risk. Current rehabilitation therapies are inadequate at reducing falls in people with Parkinson's disease (PD). While pharmacologic and surgical treatments have proved largely ineffective in treating postural instability and gait dysfunction in people with PD, studies have demonstrated that therapy specifically focusing on posture, gait, and balance may significantly improve these factors and reduce falls. The primary goal of this study was to assess the effectiveness of a novel and promising intervention therapy (protective step training - i.e., PST) to improve balance and reduce falls in people with PD. A secondary goal was to understand the effects of PST on proactive and reactive feedback responses during stance and gait tasks. Multiple-baseline, repeated measures analyses were performed on the multitude of proactive and reactive performance measures to assess the effects of PST on gait and postural stability parameters. In general, the results indicate that participants with PD were able to use experiences with perturbation training to integrate and adapt feedforward and feedback behaviors to reduce falls. The ability of the participants with PD to adapt to changes in task demands suggests that individuals with PD could benefit from the protective step training to facilitate balance control during rehabilitation.

Keywords: Parkinson’s disease; accidental falls; feedforward and feedback; gait and balance; motor adaptability; motor learning; physical therapy; protective step training.

Figure 1

Schematic of study design.

Figure 2

Illustration of comparison made between novel recovery from the first perturbation (i.e., GP₁ or PP₁) vs. trained recovery from the last two perturbations (i.e., GP_11,12 or PP_11,12).

Figure 3

GRAIL system with dualbelt instrumented treadmill.

Figure 4

Example of reactive recovery dynamics given a perturbation during stance or gait. The 1st dotted line identifies perturbation onset; the 2nd line identifies the reactive recovery step (rechc); the 3rd line marks the termination of the recovery period. (A) Gait perturbation example; (B) Postural perturbation example.

Figure 5

Feedforward Effects of PST during stance on the knee flexion angles with the means and standard deviations shown.

Figure 6

Feedforward Effects of PST during stance on the knee flexion angles of all participants.

Figure 7

Feedback Effects of PST during stance on reaction time of the stance foot with the mean reaction times and standard deviations shown.

Figure 8

Reaction time or Time_Latency (ms) associated with postural perturbation training during the first and the last perturbations. Participants were able to produce quicker responses to postural perturbations after the PST.

Figure 9

Feedforward Effects of gait perturbation training with the mean reaction times and standard deviations shown.

Figure 10

Individual effects of gait perturbation training on feedforward/proactive adaptation of trunk flexion.

Figure 11

Following repeated gait perturbation training a subject’s trunk flexion is greater throughout the gait cycle exhibiting feedforward/proactive adaptation.

Figure 12

Feedforward Effects of gait perturbation training with the mean hip flexion angles and standard deviations shown.

Figure 13

Individual effects of gait perturbation training on feedforward/proactive adaptation of hip flexion.

Figure 14

Feedforward Effects of gait perturbation training on heel contact velocity.

Figure 15

Individual effects of gait perturbation training on feedforward/proactive adaptation of heel contact velocity.