It is now well understood that exercise provides numerous benefits to the human brain. Importantly, acute exercise has been shown to modify neuroplasticity (the ability of the brain to adapt). However, it has remained unknown how regular exercise interacts with various plasticity-inducing techniques (i.e., skill training and non-invasive brain stimulation). Furthermore, it was unknown whether the benefits of exercise are confined to the areas of the brain responsible for controlling movement (specific to working muscles). Therefore, the overarching aim of this thesis was to investigate how regular exercise modulates both use-dependent and experimentally induced plasticity.
I first had to optimise the parameters of transcranial magnetic stimulation (TMS) (e.g., stimulation intensity and frequency) to be used for the region of the human cortex dedicated to lower limb muscles. This study successfully identified the optimal methods for activating interneuron circuits that are important for neuroplasticity. These findings were necessary for the subsequent investigation of how regular physical activity (endurance cycling) influences neuroplasticity induced by skill training involving the upper (non-exercised) and lower (exercised) limb muscles. Endurance-trained participants showed enhanced motor cortex plasticity following skill training. Importantly, this effect was not exclusive to muscle groups directly involved in the exercise.
Finally, this thesis aimed to determine if regular endurance training enhanced TMS-induced plasticity following a single exercise session. Endurance-trained participants demonstrated improved neuroplasticity following acute exercise compared with sedentary participants. Together, these studies provide novel evidence showing that regular endurance training promotes both use-dependent and experimentally induced motor cortex plasticity.