Abstract:

Objective To study the human body's sit to stand transfer trajectory and kinematics based on knee joint support to provide a basis for designing the transfer aid with knee joint support.Methods From April to June, 2019, 20 healthy volunteers were recruited and divided into three groups according to height and gender. Under the premise of knee support, the sit to stand transfer experiments with 20 cm and 30 cm between feet were conducted respectively. All subjects were repeated twice for each experiment with an interval of one minute. High-definition camera was used to record the motion trajectories of each subject's shoulder (armpit) and knee joint during the experiment, and the kinematics rules of subjects with different heights and masses were analyzed.Results The body forward leaning displacement was less with 20 cm between feet than with 30 cm for subjects less than 172 cm tall; and was less with 30 cm than with 20 cm for subjects more than 173 cm tall. The forward flexion displacement of trunk was less with 20 cm between feet than with 30 cm for subjects with body mass index (BMI) < 23.9 kg/m ²; and was less with 30 cm than with 20 cm for subjects with BMI > 23.9 kg/m ². The average time during sit to stand transfer was (1.7±0.05) s.Conclusion In the process of sit to stand transfer, distance between feet may affect the way of joint extension, the body forward leaning distance and the forward flexion displacement of trunk. With the increase of height and mass, appropriate increase of distance between feet can reduce the difficulty of sit to stand transfer. With the increase of BMI, the time of sit to stand transfer also increases. The time spent on sit to stand transfer is more in female than in male.

Key words: sit to stand transfer, knee support, distance between feet, motion trajectories, law of motion