Determination of reliable force platform parameters and number of trial to evaluate sit-to-stand movement.

Abstract

Sit-to-stand (STS) movement is useful for evaluating lower limb muscle function, especially from force platforms. Nevertheless, due to a lack of standardization of the STS movement (e.g., position, subject's instructions, etc.), it is difficult to compare results obtained in previous studies. The aim of the present study was to determine the most relevant condition, parameters, and number of trial to perform STS movements. In this study, STS mechanical (maximal and mean force, impulse) and temporal parameters were measured in the vertical, medio-lateral and antero-posterior axes using a force platform. Five STS conditions (i.e., with or without armrests, variation of the height of the chair and the movement speed) were analyzed to evaluate repeatability of different standardized procedures. Most of the mechanical and temporal parameters were influenced by the STS condition (p<0.05). Regarding vertical axis, results showed a strong to perfect repeatability for all parameters (0.72<ICC<0.9) for only one condition: STS performed as rapidly as possible with a 90° knee angle when seated, without using armrests. Regardless conditions of performance, our results also showed that the most repeatable parameters were mean and peak force in medio-lateral axis, and the impulse measured in the three directions. Three trials should be performed to reach high repeatability. Our results suggest that the fast condition, with a 90° knee joint angle, with arms crossed over the chest, is the most reliable condition to evaluate performance during STS movement.