Use of electromyography to study leg muscle activity in patients with arthritis and in normal subjects during rising from a chair.

A previous study indicated the need for patients with arthritis to have an armchair from which it is easy to rise. To determine criteria for such a chair a greater understanding of the rising activity and the objective assessment of chair design is required. The major muscle groups of the leg were monitored by electromyography (EMG) in normal subjects and for patients with arthritis during rising from a chair. The effects on EMG patterns of changes of seat height, foot position, and the use of armrests were studied. This paper outlines the practical difficulties that must be borne in mind when designing an EMG study on arthritic and elderly subjects. The results did not illustrate any differences in the pattern of muscle activity between arthritic and normal subjects, nor did they show any differences caused by changing the variables of chair design.