Objective: To evaluate the effect of seat height on sit-to-stand (STS) in children with cerebral palsy (CP) and in children without disabilities.
Design: A mixed design (subject type by seat height) with repeated measures for seat height.
Setting: Motion analysis laboratory.
Participants: Ten children with mild CP (mean age, 10.9+/-2.7 y) and 10 children without disabilities (mean age, 8.7+/-2.4 y).
Interventions: Kinematic and force measurements of STS were completed with 6 infrared cameras and 2 forceplates.
Main outcome measures: Phase duration of the STS movement, amplitude and timing of ground reaction forces, and maximum head velocity during the movement.
Results: Children with CP took significantly longer to rise to standing (1.71 s) than children without disabilities (1.24 s) (F(1,18)=16.97). The extension phase of STS was also significantly longer for children with CP (.85 s) than for children without disabilities (.45 s) (F(1,18)=18.73). Seat height did not affect time to stand for either children with CP or children without disabilities (F(1,18)=2.82, P>.05). The duration of the extension phase, maximum horizontal and vertical velocity of the head, and maximum vertical ground reaction force were all significantly greater when children stood from the low bench height than from the higher bench height, although we found no significant differences by subject type for maximum horizontal and vertical head velocity or for maximum vertical ground reaction force.
Conclusions: Although children with CP were able to modify their motor programs for STS to accommodate changes in seat height as readily as nondisabled children, the speed with which they extended against gravity was slower; therefore, the total STS movement took longer for them to complete than for children without disabilities. Because the time to complete STS from the low and high bench did not differ, it would appear that time to ascend from sitting may be invariant and therefore be a motor control parameter for the STS movement.