BIOMECHANICS AND MUSCULAR-ACTIVITY DURING SIT-TO-STAND TRANSFER

In the present study 10 healthy subjects were measured, performing sit -to-stand transfers in a natural way. Starting position and speed of m ovement were standardized. Sagittal kinematics, the ground reaction fo rce, and muscle activity of nine leg muscles were recorded. During sit -to-stand transfer the mass centre of the body was moved forward and u pward. Based on the velocity of the mass centre of the body three phas es were distinguished. In horizontal direction forward rotation of the upper body contributed to the velocity of the mass centre of the body , whereas extension of the legs contributed considerably in vertical d irection. After seat-off most muscles were concentrically active, wher eas the shortening velocity of the rectus femoris was very low. Thus h ip and knee joints were extended and a relatively high knee moment was delivered to control the ground reaction force in a slightly backward direction. Co-contraction of hamstrings and rectus femoris in sit-to- stand transfer was judged to be efficient. Relevance To identify disab ility problems in the performance of sit-to-stand transfer a complete set of normative data on kinematics, kinetics, and muscle activation d uring sit-to-stand transfer is needed. Moreover, to analyse these prob lems or to evaluate the effects of therapeutic interventions, some und erstanding of the complex biomechanics underlying the performance of n ormal sit-to-stand transfer is required.