Currently, over seven million people die of cancer each year; some of whom suffer from pain caused by bone metastasis. In their final stages of life, the pain is such that they cannot even roll over, one of the activities of daily life. With this in mind, in this research, we aim to develop equipment for patients with cancer bone metastasis to support roll-overs in terminal care. Specifically, the EMG signal, which is the input signal of the equipment, is discussed in this paper. The activities of four muscles affecting trunk movement were monitored during the process of rolling over. Following an EMG experiment with four subjects, the internal abdominal oblique (IO) muscle was seen to be active in the early stages of roll-over motion, although IO muscle was relatively prevalent in previous works. If we support roll-over at this point, the patient feels no pain, because the timing is detected before the strongest burden movement, which involves buoying the trunk and rotating the pelvis. Hence, the EMG signal of the IO muscle is suitable for the input of the signal to support roll-overs.