SIT TO STAND (STS)
back to Functional Limitation Assessments
The STS quantifies the patient’s ability to rise from a seated to a standing position. Key components of this task include shifting the body’s COG forward from an initial position over the seat to a location centered over the base of support (feet), followed by extension of the body to an erect standing position while maintaining the centered COG position. The measured parameters are weight transfer time, rising index (force exerted to rise), sway velocity during the rising phase, and left/right symmetry of the rising force.
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STS Comprehensive Report
- The COG trace for each trial is displayed on the left side of the report.
- Weight Transfer is the time in seconds required to voluntarily shift COG forward beginning in the seated position and ending with full weight bearing on the feet.
- Rising Index is the amount of force exerted by the legs during the rising phase. The force is expressed as a percentage of the patient’s body weight.
- Cog Sway Velocity documents control of the COG over the base of support during the rising phase and for 5 seconds thereafter. Sway is expressed in degrees per second.
- Left/Right Weight Symmetry documents differences in the percentage of body weight borne by each leg during the active rising phase.
- The shaded area on each graphic represents performance outside of the normative data range. Green bars indicate performance within the normal range; red bars indicate performance outside the normal range. A numerical value is given at the top of each bar.
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Rising from a seated to a standing position is influenced by a number of musculoskeletal, movement control, and balance factors. Accurate control of COG position is critical to controlling the rise movement, as well as to maintaining postural stability. If the COG is not moved sufficiently forward or if the COG is moved too far forward, the patient will either fall back into the chair or fall forward. During the task, lateral stability depends on symmetrical distribution of force between the two legs. Finally, the rising maneuver also depends on adequate lower extremity and trunk strength, and range of motion.
The transfer process can be slowed by problems with range, strength and flexibility in the lower extremity or trunk. Movement or postural control impairments impact speed and COG position and control during the task. Functional consequences include the inability to rise from the seated position during performance of activities; rising from seats of variable heights; or a dependence on upper extremity assistance or the assistance of another person. Safety is a concern if instability occurs during or immediately following the rise, or while descending to sit.
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