Corticospinal and spinal adaptations following lower limb motor skill training: a meta-analysis with best evidence synthesis

Motor skill training alters the human nervous system; however, lower limb motor tasks have been less researched compared to upper limb tasks. This meta-analysis with best evidence synthesis aimed to determine the cortical and subcortical responses that occur following lower limb motor skill training, and whether these responses are accompanied by improvements in motor performance. Following a literature search that adhered to the PRISMA guidelines, data were extracted and analysed from six studies (n = 172) for the meta-analysis, and 11 studies (n = 257) were assessed for the best evidence synthesis. Pooled data indicated that lower limb motor skill training increased motor performance, with a standardised mean difference (SMD) of 1.09 being observed. However, lower limb motor skill training had no effect on corticospinal excitability (CSE), Hoffmann's reflex (H-reflex) or muscle compound action potential (M_MAX) amplitude. The best evidence synthesis found strong evidence for improved motor performance and reduced short-interval cortical inhibition (SICI) following lower limb motor skill training, with conflicting evidence towards the modulation of CSE. Taken together, this review highlights the need for further investigation on how motor skill training performed with the lower limb musculature can modulate corticospinal responses. This will also help us to better understand whether these neuronal measures are underpinning mechanisms that support an improvement in motor performance.