Neurophysiological Adaptations in Response to Balance Training

Balance training is effective not only to improve postural control but also the rate of force development, the jumping behaviour, and the regeneration after injury. Furthermore, balance training reduces the incidence of ankle and knee injuries. The question is how the central nervous system (CNS) adapts in response to balance training in order to fulfil all these (different) actions. The present review article discusses neural adaptations within the CNS, which may be responsible for improving postural control, increasing explosive force and reducing the incidence of lower limb injuries after balance training. It emphasizes the plasticity of the sensorimotor system in general and spinal and cortical adaptations in particular. Current findings are displayed that were obtained with electrophysiological methods and imaging techniques. Studies investigating the spinal reflex circuitries during postural tasks by means of peripheral nerve stimulation suggest that balance training reduces the excitability of spinal reflexes. Experiments involving transcranial magnetic stimulation in order to infer changes in cortical excitability propose high cortical excitability at the beginning of balance training interventions, which decreases with improved task automatization. Changes in subcortical structures are less well understood but may partly undergo contrary development than adaptations of the primary motor cortex. Recent findings obtained by various imaging techniques support this idea and further highlight that grey and white brain matter adapt rapidly in response to balance training so that structural changes are already detectable after two training sessions. Based on the current knowledge it can be concluded that most likely supraspinal adaptations within the CNS are mainly responsible for improving functional parameters like balance skills, explosive strength or coordinative movement control.