Symmetry of weight distribution while rising from a chair in transtibial amputees

To characterize loading patterns of the intact and amputated limbs during the various events of sit-to-stand (STS) activity for two conditions: (i) rising from a commercially available, standard height chair without the use of upper limbs (WITHOUT condition), and (ii) rising with the aid of hands placed on armrests (WITH condition). Twelve transtibial amputees performed 3-5 STS trials for each of the WITH and WITHOUT conditions. Vertical ground reaction forces (GRF) from the chair and both feet were collected using a Tekscan Matscan system. The STS activity was divided into 5 events: (i) Start (ii) Accel (iii) Seat-off (iv) Decel (v) End. Symmetry of weight distribution was calculated using the GRF on amputated side and the GRF on intact side. Both the WITH and WITHOUT conditions yielded remarkably similar results. The weight distribution was asymmetrical at the Seat-off and Decel events, with a high degree of symmetry at the other three events. There was no significant difference between the WITH and WITHOUT conditions. Use of upper limbs had a negligible effect on the symmetry pattern, despite comparatively lower forces and moments at the knee joint. Better weight distribution symmetry can be achieved by addressing certain potential contributors of asymmetry, such as learned non-use.