Assessing corticospinal excitability to the biceps brachii during maximal repeated arm cycling sprints

Abstract This study examined the feasibility of assessing corticospinal and spinal excitability of the biceps brachii during maximal repeated arm cycling sprints. Twelve recreationally active participants (10 male, 2 female) completed five maximal arm cycling sprints (17–22s) against a torque factor of 5% body weight, separated by 90s of rest. Corticospinal, spinal and peripheral excitability were assessed via transcranial magnetic stimulation (TMS) transmastoid electrical stimulation (TMES), Erb’s point stimulation, respectively. Stimuli were delivered during arm cycling at the 3 o’clock crank position (start of elbow flexion) at an intensity of 130% of active motor threshold (AMT) (determined during submaximal cycling). Mean power and total work both declined by 36.8% from sprints 1–5 ( p < 0.001). Motor evoked potential (MEP), cervicomedullary evoked potential (CMEP), and compound muscle action potential (M max ) amplitudes did not change during the sprint protocol ( p > 0.05). However, following the sprint protocol, the TMES intensity required to evoke CMEPs was reduced by 4.57% compared to pre-sprint values ( p = 0.01), and M max amplitude increased ( p = 0.01) from pre- to post-sprinting by 12.1%. Despite substantial declines in performance, corticospinal and spinal excitability assessed via evoked response amplitudes remained unchanged during maximal sprinting, likely reflecting saturation of the motoneuron pool during high voluntary drive. In contrast, the post-sprint reduction in CMEP threshold and increase in M max indicate enhanced spinal excitability following repeated arm cycling sprints. These findings demonstrate both the feasibility and limitations of assessing corticospinal excitability during sprint exercise and highlight the importance of stimulation intensity selection when probing neural adaptations during high-intensity, dynamic tasks.