There is evidence to support the hypothesis that the pelvis and trunk play an active role in gait, as opposed to the traditional view  which regards the core of the body as a “passenger unit” carried by the lower extremities, which are termed the “locomotor unit”. Responses triggered by balance perturbations involve neck, trunk and thigh muscles which contract simultaneously, even before the activation of muscles around the ankle joint in unimpaired subjects [2–5]. In prospective studies [6, 7], reduced strength and impaired proprioception around the core (pelvis and trunk) were found to be associated with increased risk of injuries, specifically around the knee. This suggests that good control of the movement of the core is a prerequisite for well controlled use of the legs.
Good control of the interaction between the trunk and pelvis is required to carry out activities of daily living. During level walking the nature of this interaction depends on walking speed [8–12]. At slow speeds the pelvis and trunk are coupled in the transverse plane and move in-phase, but as walking speed increases there is a transition from in-phase to anti-phase coupling [9, 10]. Retraction of the trunk, together with protraction of the pelvis on the swing leg side, increases step length and therefore improves the efficiency of gait.
One of the primary problems in cerebral palsy is reduced selective control of movement . Altered selective motor control of the pelvis and trunk hinders efficient gait and thereby activities of daily living. Improved ability to reduce in-phase coupling between the trunk and pelvis is expected to improve gait at normal walking speeds characterised by anti-phase coupling. Activities of daily living are also expected to benefit from the reduced in-phase coupling.
Due to their central location in the body’s linked chain of segments the trunk and pelvis are mechanically restricted to a greater degree than the extremities and the head. In spite of this constraint, movement of the trunk and pelvis can be altered through training [14, 15]. There are numerous reports of successfully using custom made computer games to both test and train movement control of the upper or lower extremities [16–19]. Applications of serious gaming focused on the pelvis and trunk, however, are scarce. Our Goblin Post Office (GPO) training game [20–25] is derived from the conceptual framework of Targeted Training  in that it allows sequential training of body segments from upper to lower, thereby increasing successively the complexity of the motor task. We report here some findings (from a larger training study) in which we observed changes in coupling between the pelvis and trunk when the game was controlled by movement of the pelvis.