Chronic resistance training enhances the spinal excitability of the biceps brachii in the non-dominant arm at moderate contraction intensities

•Supraspinal excitability of the biceps brachii in the non-dominant arm was not different between chronic resistance trained and non-resistance trained individuals.•Chronic resistance trained individuals had greater spinal excitability of the biceps brachii in the non-dominant arm.•Increased strength in the non-dominant limb in chronic resistance-individuals is, in part, spinally mediated. The purpose of the study was to assess corticospinal excitability of the biceps brachii in the non-dominant arm of chronic resistance-trained (RT) and non-RT individuals. Seven chronic-RT and six non-RT male participants performed 4 sets of 5s pseudo-randomized contractions of the non-dominant elbow flexors at 25, 50, 75, 90, and 100% of maximum voluntary contraction (MVC). During each contraction, transcranial magnetic stimulation, transmastoid electrical stimulation, and Erb’s point electrical stimulation were administered to assess the amplitudes of motor evoked potentials (MEPs), cervicomedullary evoked potentials (CMEPs), and maximal muscle compound potentials (Mmax), respectively, in the biceps brachii. MEP and CMEP amplitudes were normalized to Mmax. Training did not affect (p>0.14) MEP amplitudes across any contraction intensity. CMEP amplitudes were significantly (p