Posture and locomotion coupling: a target for rehabilitation interventions in persons with Parkinson's disease

Abstract

Disorders of posture, balance, and gait are debilitating motor manifestations of advancing Parkinson's disease requiring rehabilitation intervention. These problems often reflect difficulties with coupling or sequencing posture and locomotion during complex whole body movements linked with falls. Considerable progress has been made with demonstrating the effectiveness of exercise interventions for individuals with Parkinson's disease. However, gaps remain in the evidence base for specific interventions and the optimal content of exercise interventions. Using a conceptual theoretical framework and experimental findings, this perspective and review advances the viewpoint that rehabilitation interventions focused on separate or isolated components of posture, balance, or gait may limit the effectiveness of current clinical practices. It is argued that treatment effectiveness may be improved by directly targeting posture and locomotion coupling problems as causal factors contributing to balance and gait dysfunction. This approach may help advance current clinical practice and improve outcomes in rehabilitation for persons with Parkinson's disease.". . .postural activity should be regarded as a function in its own right and not merely as a component of movement. . ."James Purdon Martin.

Figure 1

Forward internal model for posture and locomotion coupling during the initiation of gait. To initiate stepping locomotion, posture and locomotion networks are activated in parallel to generate motor commands where the posture network acts on the stepping controller. This motor output modifies the body center of mass-base of support (COM-BOS) relationship. With external posture assistance (e.g., mechanical or sensory simulation of single stance limb loading) that enhances weight transfer to the single stance limb, an efferent copy of the motor commands and sensory information about the actual state of the body can be used by the CNS to modify the two commands in advance based on an internal representation of the body and external environment (forward model). Online sensory information can also modulate posture and locomotion via external feedback.

Figure 2

The group mean values plus 1 SD for (a) APA duration, (b) first-step onset time relative to APA onset, and (c) first-step duration in control subjects (CS: white bars) and subjects with Parkinson's disease off medication (off: gray bars). The four experimental conditions are initial baseline trials without postural assistance (Baseline), trials with lateral postural assistance (Postural assistance), follow-up trials without postural assistance (No assistance), and trials with a mechanical tug that provided no direct postural assistance (Tug). Data from [18]. ^†Significant differences between groups. ***Significant difference between the postural assistance condition (ASSIST) and the others.

Figure 3

The group mean values (±1 SD) for patients with Parkinson's disease (PD) on medication (gray bars) and healthy control subjects (white bars) during rapid self-paced step initiation under the different experimental conditions are presented for (a) APA duration, (b) APA amplitude, (c) step onset relative to the APA onset, and (d) first-step speed. Data from [53]. ^†Significant differences between groups. ***Significant difference between the postural assistance condition (DROP) and the other two.

Figure 4

The group mean values plus 1 SEM for initial swing limb APA (a) rate of loading force and (b) peak loading force amplitude measured at baseline prior to posture assist locomotion (PAL) training (pre), immediately after training (post), and six weeks after the completion of training (ret) PD subjects in drop assist and vibration assist training groups. Unpublished data.

Figure 5

The group mean values plus 1 SEM for first-step (a) speed, (b) length, and (c) height measured at baseline prior to posture-assisted locomotion (PAL) training (pre), immediately after training (post), and six weeks after the completion of training (ret) PD subjects in drop assist and vibration assist training groups. Unpublished data.