Event standardization of sit-to-stand movements.

Background And Purpose: Unlike gait analysis, no commonly accepted method for studying sit-to-stand (STS) movements exists. Most previous studies describing STS events used various methods to identify movement events while restricting sitting positions and movements. The present study observed natural rising from a sitting position using a simple method for measuring this common task. The purposes of this study were to compare commonly performed STS movements and to propose a standard system for defining identifiable sequential events.

Subjects And Methods: Ground reaction forces of 100 adults who were healthy (50 male, 50 female) were recorded using a force platform as each participant performed 4 methods of rising from sitting on a standard chair. The 4 STS conditions were: with arms free, with hands on knees, using armrests, and with arms crossed.

Results: For each subject, 11 recorded events from the vertical, fore-aft, and lateral dimensions were identified for all arm-use conditions. The only significant and clinically relevant force difference among arm-use conditions was that the armrests condition produced less average force than the other 3 conditions during the seat-off and vertical peak force events. Among average event times, the armrests condition showed significantly longer time to the vertical peak force event than the other conditions.

Discussion And Conclusion: Because these events occurred invariably in sequential order for every individual for all arm-use conditions in a relatively large sample of observations during natural STS movements, this method may be useful for establishing a standard method to assess and compare patient functionality and allow comparisons among STS research studies.