An Analysis of Sit-to-Stand Transfer in Normal Children

ABSTRACT

OBJECTIVE: Rising from a sitting position is a very common, yet essential activity in daily life. The activity to perform the sit-to-stand (STS) transfer is a prerequisite for upright mobility. This study aims to provide fundamental data concerning the execution of the STS, and in particularly the followings 1) how do the angles of the lower limbs change throughout the process of rising from a chair; 2) how much motion torque and power in each joint are required per kilogram of body weight to complete the STS transfer? METHOD: Twenty-one children who have developed normally and could understand the command requested are involved as subjects. Their age ranged from 3 to 5 years old. Motion analysis of STS transfer were assessed with the Vicon 370 M.A (Oxford Metrics Limited, United Kingdom). The changes in joint angle, maximal moment and power in lower limb were calculated throughout the STS transfer. RESULTS: A series of transition points was observed in the angles of the hip, knee and ankle joints throughout the sit-to-stand movements, which was classified into five stages. The first stage is trunk and hip flexion phase; second stage, buttock take-off; third stage, ankle dorsiflexion and knee extension; forth stage, just-standing; fifth stage, stabilizing phase. The extension moment of each joint is 0.65 Nm/kg on right, 0.71 Nm/kg on left in hip, 0.41 Nm/kg on right, 0.38 Nm/kg on left in knee and 0.21 Nm/kg on right, 0.22 Nm/kg on left in ankle joint. The extension power is 0.60 watt/kg on right, 0.68 watt/kg on left in hip, 0.59 watt/kg on right, 0.50 watt/kg on left in knee and 0.15 watt/kg on right, 0.15 watt/kg on left in ankle joint. CONCLUSION: A consistent pattern was observed throughout the sit-to-stand transfer and six transition points were observed in the angles of the hip, knee and ankle joints throughout the STS transfer. By these 6 points, the movement of the STS transfer was classified into 5 stages. Major changes in angle, moment, and power of each joint were observed in sagittal plane. There were no side to side difference during the STS transfer.