Anticipatory Postural Adjustments During Gait Initiation in Stroke Patients

Abstract

Prior to gait initiation (GI), anticipatory postural adjustments (GI-APA) are activated in order to reorganize posture, favorably for gait. In healthy subjects, the center of pressure (CoP) is displaced backward during GI-APA, bilaterally by reducing soleus activities and activating the tibialis anterior (TA) muscles, and laterally in the direction of the leading leg, by activating hip abductors. In post-stroke hemiparetic patients, TA, soleus and hip abductor activities are impaired on the paretic side. Reduction in non-affected triceps surae activity can also be observed. These may result in a decreased ability to execute GI-APA and to generate propulsion forces during step execution. A systematic review was conducted to provide an overview of the reorganization which occurs in GI-APA following stroke as well as of the most effective strategies for tailoring gait-rehabilitation to these patients. Sixteen articles were included, providing gait data from a total of 220 patients. Stroke patients show a decrease in the TA activity associated with difficulties in silencing soleus muscle activity of the paretic leg, a decreased CoP shift, lower propulsive anterior forces and a longer preparatory phase. Regarding possible gait-rehabilitation strategies, the selected studies show that initiating gait with the paretic leg provides poor balance. The use of the non-paretic as the leading leg can be a useful exercise to stimulate the paretic postural muscles.

Keywords: anticipatory postural adjustments; balance; gait initiation; rehabilitation; stroke.

Figure 1

(A) Example of biomechanical traces obtained for one representative normal subject initiating gait at a spontaneous velocity (one trial). Anteroposterior direction x”G: anteroposterior center of mass velocity; z”G: vertical center of mass velocity; peak vGRF: the maximal moment of vertical Ground Reaction Force; xP, Center of pressure (COP) displacement; xPmax: maximal backward shift of CoP. Mediolateral direction yP, mediolateral COP displacement; yPmax, maximal mediolateral shift of COP. Vertical lines, t0 onset variation of biomechanical traces; FO, Swing foot off; FC, Swing foot contact. FL, Foot lift. Horizontal dashed line: dGI-APA, duration of Gait Initiation-Anticipatory Postural Adjustments; d-EXE, duration of execution phase. SOL-SW, Soleus electromyographical activity of swing leg; SOL-ST, Soleus electromyographical activity of stance leg; TA-ST, Tibialis Anterior electromyographical activity of stance leg; TA-SW, Tibialis Anterior electromyographical activity of swing leg. (B) Stick representation of the different phases and temporal events of gait initiation in a normal subject. QS, quiet standing; GI-APA, gait initiation-anticipatory postural adjustments; EXE, execution phase.

Figure 2

Study selection procedures and results reported in a flow-chart, as suggested by Moher et al. (15) and according to CONSORT statement.