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

• Published in: Neuroscience letters Vol. 585; pp. 12 - 16
• Main Authors: Philpott, Devin T.G., Pearcey, Gregory E.P., Forman, Davis, Power, Kevin E., Button, Duane C.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 12.01.2015
• Subjects: Adult; Arm - innervation; Arm - physiology; Biceps brachii; Chronic resistance training; Corticospinal excitability; Elbow - physiology; Elbow flexion; Electric Stimulation; Evoked Potentials; Functional Laterality; Humans; Male; Motoneuron; Motor Neurons - physiology; Muscle Contraction; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Resistance Training; Spinal Cord - physiology; Transcranial Magnetic Stimulation; Chronic resistance training; Elbow flexion; Corticospinal excitability; Motoneuron; Biceps brachii
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/j.neulet.2014.11.009

•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<0.05) higher in the chronic-RT group at 50% and 75% of MVC by 38% and 27%, respectively, and there was a trend for higher amplitudes at 25%, 90%, and 100% MVC by 25% (p=0.055), 36% (p=0.077), and 35% (p=0.078), respectively, compared to the non-RT group. Corticospinal excitability of the non-dominant biceps brachii was increased in chronic-RT individuals mainly due to changes in spinal excitability.