This research was carried out to analyze the actions of caregivers when aiding a patient to sit up in bed. The new system showed that three dimensional analysis could be performed even on points on the subjects' bodies that were hidden from view. We also developed a method to estimate the load on the lumbar region of caregivers based on the kinetic analysis of the human body. Using this system we were able to evaluate the performance of both lay and professional caregivers. We found a clear difference between the performances of the two types of caregivers, and noted that the professional adopted a posture that was safe and did not stress the lumbar vertebrae, whereas the layperson tended to adopt an unsafe posture.