The effect of resistance training on corticospinal excitability

While it is generally accepted that initial strength gains during a resistance-training program are due to changes in corticospinal excitability (CE), it is presently unclear whether the predominant site of those adaptations is of supraspinal or spinal origin, though it is likely that both are involved. Transcranail magnetic stimulation (TMS) is often employed to assess CE. The difficulty of using TMS alone for determining changes in CE is that the amplitude of a TMS-induced motor evoked potential (MEP) could be affected anywhere along the corticospinal pathway (i.e. from corticoneurones in the brain to the motoneurones in the spinal cord). A relatively new and underutilized technique, transmastoid electrical stimulation (TES), which stimulates the corticospinal tracts independent of the corticoneurones, can be used in combination with TMS to identify whether or not changes in CE are of supraspinal or spinal origin (Carroll et al., 2009, Martin et al., 2009, McNeil et al., 2011). As a resistance training program progresses, further increases in strength are thought to be mainly influenced by morphological adaptations of the muscle (Folland and Williams, 2007). However, very few studies have examined how long-term (chronic) resistance training affects the manner in which the central nervous system (CNS) generates force output. This presentation will focus on recent research from the Exercise and Movement Neuroscience Lab at the School of Human Kinetics and Recreation, which focused on how supraspinal and spinal excitability changes during various force outputs due to chronic resistance training.