The effect of foot placement on sit to stand in healthy young subjects and patients with hemiplegia

Objective: To determine the effect of altering the foot placement of the dominant limb in young healthy subjects and the uninvolved limb of subjects with hemiplegia on their ability to perform sit to stand (STS). Design: Controlled biomechanical experiment, Setting: Research laboratory of a university health science center. Participants: Nonrandom convenience sample of 10 healthy and 10 subjects with hemiplegia. Respective mean ages were 26 and 59 years. All patients with hemiplegia could ambulate and STS independently. The mean time since the stroke was 3.6 years. Interventions: Subjects came from a sitting to a standing position under 3 different conditions: (1) normal condition, where both limbs were placed in 100degrees of knee flexion; (2) limb extended condition, where the dominant or uninvolved limb was extended to 75degrees of knee flexion; and (3) limb elevated condition, where the dominant or uninvolved limb was placed on a dense foam support equal to 25% of the subject's knee height. Main Outcome Measures: Vertical and anteroposterior ground reaction forces (GRFs) and bilateral tibialis anterior and quadriceps electromyogram (EMG) activity. Results: In the young subjects, the normally placed nondominant limb compensated for the extended or elevated position of the dominant limb. Peak GRFs and EMG amplitudes were all significantly greater for the nondominant limb. In patients with hemiplegia, the EMG of the involved limb increased 39171 in the limb-elevated and -extended conditions compared with the normal condition. Respective values for the uninvolved limb decreased. GRFs were significantly greater for the uninvolved limb except for the vertical force in the limb-extended position. Conclusions: Muscle activity and GRFs can be influenced by altering the initial foot placement of the dominant or uninvolved limb during STS. These initial data have positive implications for the rehabilitation of patients with hemiplegia who could be taught to overcome a reduced ability to use their impaired limb after stroke.