Adaptation of multi-joint balance coordination to whole body force fields

摘要: Background and aim: The ankles the hips play an important role in standing balance. Multi-joint coordination adapts with task, magnitude type of disturbance [1]. Arm studies show that postural responses are highly dependent on externally applied force fields [2]. Our aim is to study how multi-joint depend such fields, using closed loop system identification techniques (CLSIT) where two disturbances [3]. This offers knowledge about plasticity neuromuscular controller; e.g. adaptive capacity maintain We hypothesize application a stabilizing field will lead downscaling responses. Methods: Ten healthy subjects maintained balance while whole-body were three conditions 1) no 2) stiffness at hip 3) shoulder. In addition, unpredictable continuous pushing pulling forces (0.05-5Hz) shoulder level (Figure 1). Leg trunk segment angles recorded ankle torques obtained from ground reaction by inverse dynamics. With CLSIT, Frequency Response Function (FRF) controller was estimated. The FRF describes for each frequency signal relative timing (gain phase) corrective joint evoked motions leg segment. Results: Figure 2 shows provides relatively more torque low frequencies dominant higher frequencies. Hip compensates both movement, whereas only movement legs. phases all FRFs decreased frequency, indicating delayed response. Addition mainly frequencies, dominates. Stiffness or reduce slightly reduced additional stiffness. Conclusion: By adding (i.e. stiffness) balance, adapt lowering their control action torque. gain reduced, as stabilized maintenance becomes easier. Downscaling indeed occurs. future studies, our methods allow pathological changes well its capacity. References: [1] Kim et al, J Biomech, 2012 [2] Franklin Exp Brain Res, 2003 [3] Boonstra JNER, 2013