Source
Journal of Biomechanics. 25(12):1383-91, 1992 Dec.
Abstract
Quantification of the biomechanical factors that underlie the
inability to rise from a chair can help explain why this
disability occurs and can aid in the design of chairs and of
therapeutic intervention programs. Experimental data collected
earlier from 17 young adult and two groups of elderly subjects, 23
healthy and 11 impaired, rising from a standard chair
under controlled conditions were analyzed using a planar
biomechanical model. The joint torque strength requirements
and the location of the floor reaction force at liftoff from the seat
in the different groups and under several conditions
were calculated. Analyses were also made of how body configurations
and the use of hand force affect these joint
torques and reaction locations. In all three groups, the required
torques at liftoff were modest compared to literature data
on voluntary strengths. Among the three groups rising with the use of
hands, at the time of liftoff from the seat, the
impaired old subjects, on an average, placed the reaction force the
most anterior, the healthy old subjects placed it
intermediately and the young subjects placed it the least anterior,
within the foot support area. Moreover, the results
suggest that, at liftoff, all subjects placed more importance on
locating the floor reaction force to achieve acceptable
postural stability than on diminishing the magnitudes of the needed
joint muscle strengths.