Postural control mechanisms during self-generated perturbation in standing

Investigators: Mrs Gill Emond, Dr Bev Phillips, Prof Mary Galea

Previous investigations of postural control mechanisms have focused on one specific area of the body, mainly the ankle or hip joints, rather than investigating the role that multiple joints and muscles play in the postural control system. In this project we are investigating the postural control mechanisms during self-generated perturbation in standing in healthy subject and chronic stroke patients, using electromyography (EMG) data from 12 muscles around the lower limb and trunk in conjunction with ground reaction force (GRF) data and kinematic analysis. Tasks include single leg stance, the Lateral Reach Test and the Functional Reach Test.

Preliminary analysis of the changes in Vertical Ground Reaction Force (Fz) in stroke subjects show that there is a significant difference between the stroke and non-stroke sides for the baseline Fz in both the Lateral Reach and Functional Reach tests and for the maximum Fz in the Lateral Reach Test (Fig 1). The smaller maximum Fz on the stroke side lateral reach corresponds with the significantly shorter average reach distance towards that side.

Figure 1 : Changes in the vertical ground reaction force during the Lateral Reach Test in stroke patients. The shaded area represents the changes during reaching to the non-affected side. The non-shaded area represents changes during reaching to the affected side. The bold line in each case represents the mean, and the dotted line, one standard deviation.

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