 The performance of trunk rehabilitation exercises while sitting on movable surfaces with feet on the ground can increase trunk and leg muscle activations and constraining the feet to move with the seat isolates control of the trunk. Additionally, there are no detailed studies on the effects of these different leg supports on the trunk and leg muscle activations under unstable and forcefully perturbed seating conditions. To address this issue, we have recently devised a trunk rehabilitation robot that can generate unstable and forcefully perturbed sitting surfaces and can be used with ground mounted or seat connected footrests. In this study, we have evaluated the differences in balance performance, trunk movement and muscle activation, trunk and legs, of 14 healthy adults caused by the use of these different footrest configurations under the different seating scenarios. The center of pressure and trunk movement results show that the seat connected footrest may be a more suitable choice for use in a balanced recovery focused rehabilitation protocol, while the ground mounted footrest may be a more suitable choice for a trunk movement focused rehabilitation protocol. Additionally, the results provide limited. This article was authored by Amra Aizad, Hoseul Lee, Sanghan Pyo and others. We are article.tv, links in the description below.