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Compound Motor Action Potential

Electrophysiological Marker for Muscle Training

Molin, Carl Johan; Punga, Anna R.

Journal of Clinical Neurophysiology: August 2016 - Volume 33 - Issue 4 - p 340–345
doi: 10.1097/WNP.0000000000000252
Original Research

Purpose: The compound motor action potential (CMAP) represents the summated action potentials of all stimulated motor endplates and potentially reflects muscle hypertrophy and increased muscle contractions. Since electrophysiological biomarkers for high-resistance strength training are lacking, the authors evaluated whether the CMAP of distal and proximal muscles differs between healthy men and women who perform and do not perform high-resistance muscle training.

Methods: Motor neurography was performed with stimulation of the median nerve (recording of abductor pollicis brevis muscle), peroneal nerve (recording of extensor digitorum brevis muscle), femoral nerve (recording of rectus femoris muscle) and musculocutaneous nerve (recording of biceps brachii muscle), and isometric muscle strength, measured with a hand-held dynamometer, were performed on 83 healthy subjects (52 women).

Results: Trained women had 25% higher CMAP amplitude in the rectus femoris muscle than untrained women (P < 0.001), whereas CMAP amplitude in the trained male cohort was 25% higher in the biceps (P = 0.005) compared with untrained men. In the trained group, CMAP amplitude in the biceps correlated with isometric muscle strength (R = 0.30; P = 0.046).

Conclusions: The authors' propose the CMAP as an objective neurophysiological parameter for proximal muscle status and training effects in future interventional studies of patients with neuromuscular disorders.

Department of Neuroscience, Clinical Neurophysiology, Uppsala University, Uppsala, Sweden.

Address correspondence and reprint requests to Anna R. Punga, MD, PhD, Department of Neuroscience, Clinical Neurophysiology, Uppsala University, Akademiska sjukhuset, entrance 85, 75185 Uppsala, Sweden; e-mail:

© 2016 by the American Clinical Neurophysiology Society