Biomechanic modeling of sit-to-stand to upright posture for mobility assessment of persons with chronic stroke.

OBJECTIVE

To test the suitability of using biomechanic measures associated with a minimum measured input model (MMIM) approach to assess mobility of people with chronic stroke during the execution of a sit-to-stand (STS) to upright posture motor task.

DESIGN

Single group, observational.

SETTING

Institutional settings in the United States and Italy.

PARTICIPANTS

Twenty-nine subjects with chronic unilateral lower-limb impairments and resultant mobility limitations secondary to stroke.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Manual measurement of lower-limb strength; performance-based tests including repeated chair standing, walking speed, and standing balance; and ground reactions measured with a force platform during STS and upright posture. The ground reactions were fed to a telescopic inverted pendulum model of the musculoskeletal system. Parameters representing the model outputs were compared with performance-based and strength measures to assess, respectively, motor ability and impairment-related changes in subjects' motor strategies.

RESULTS

The parameters derived from the model effectively differentiated between motor strategies associated with different performance-based scores, and allowed the identification of relevant difficulties encountered in STS execution. These difficulties could be associated with different strength scores. This was also true for subjects scoring the maximum in both performance-based and strength tests.

CONCLUSIONS

The MMIM is a relatively inexpensive and noninvasive approach that enhances mobility assessment of hemiparetic subjects with different motor ability levels. It provides information that correlates well with performance-based and strength scores and, in addition, it allows for subject-specific motor strategy identification.