A simulation system for a combined musculoskeletal and augmentation device system, the combined musculoskeletal and augmentation device system including segments and joints connecting the segments, the simulation system for enabling design of signals of an augmentation device controller comprising: - a dynamics model of the combined musculoskeletal and augmentation device system, the model arranged and configured to receive computed torques at the joints as inputs and to deliver simulated kinematic data of the segments as outputs; - an augmentation device controller for control of the augmentation device arranged and configured to receive the simulated kinematic data as inputs and to deliver assist torques as outputs; - an inverse dynamics model of the musculoskeletal and augmentation device system arranged and configured to receive the simulated kinematic data, desired kinematic data of the segments and the assist torques as inputs and to deliver raw computed torques; characterized in that said simulation system comprises: - a muscle force and muscle capacity module arranged and configured to receive the raw computed torques as inputs, to compute muscle forces from the raw computed torques, to compute a muscle force from a muscular torque being the difference between a said raw computed torque and a said assist torque at a joint, to compare the computed muscle forces with physiological muscle capacity, to compare the muscle forces with and without the assist torque in order to assess whether the assist torque control has helped or hindered the motion, and, if the assist torque control hinders motion, to adjust the muscle forces and to compute feasible adjusted joint torques, and to deliver the adjusted joint torques as outputs being the computed torques receivable by the dynamics model as inputs. - a dynamics model of the combined musculoskeletal and augmentation device system, the model arranged and configured to receive computed torques at the joints as inputs and to deliver simulated kinematic data of the segments as outputs; - an augmentation device controller for control of the augmentation device arranged and configured to receive the simulated kinematic data as inputs and to deliver assist torques as outputs; - an inverse dynamics model of the musculoskeletal and augmentation device system arranged and configured to receive the simulated kinematic data, desired kinematic data of the segments and the assist torques as inputs and to deliver raw computed torques; characterized in that said simulation system comprises: - a muscle force and muscle capacity module arranged and configured to receive the raw computed torques as inputs, to compute muscle forces from the raw computed torques, to compute a muscle force from a muscular torque being the difference between a said raw computed torque and a said assist torque at a joint, to compare the computed muscle forces with physiological muscle capacity, to compare the muscle forces with and without the assist torque in order to assess whether the assist torque control has helped or hindered the motion, and, if the assist torque control hinders motion, to adjust the muscle forces and to compute feasible adjusted joint torques, and to deliver the adjusted joint torques as outputs being the computed torques receivable by the dynamics model as inputs.