Motor unit discharge rate following twitch potentiation in human triceps brachii muscle

• Published in: Neuroscience letters Vol. 316; no. 3; pp. 153 - 156
• Main Authors: Klein, C.S, Ivanova, T.D, Rice, C.L, Garland, S.J
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 28.12.2001; Elsevier
• Subjects: Action Potentials - physiology; Adult; Arm - innervation; Arm - physiology; Biological and medical sciences; Contractile properties; Electromyography; Fundamental and applied biological sciences. Psychology; Humans; Male; Motoneuron; Motor Neurons - physiology; Muscle Contraction - physiology; Muscle Fibers, Skeletal - physiology; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Neural Conduction - physiology; Neuromuscular Junction - physiology; Rate coding; Reaction Time - physiology; Recruitment; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; Contractile properties; Motoneuron; Rate coding; Recruitment; Human; Electrophysiology; Motor neuron; Muscle contraction; Triceps muscle; Motor unit
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/S0304-3940(01)02389-8

It has been proposed that during brief voluntary contractions, twitch potentiation may sustain force output despite a decline in motor unit discharge rate. This study examined the evoked twitch force and motor unit discharge rates during submaximal voluntary contractions of the triceps brachii muscle before and after a 5 s conditioning contraction (CC) at 75% of maximal voluntary force. After the CC, twitch force potentiated (∼1.3–2-fold), and the discharge rate in 33 of 35 motor units declined significantly by 1–6 Hz. The increase in twitch force was significantly correlated with the decline in discharge rate ( r=−0.74). These findings suggest that the extent of the decrease in motor unit discharge rate following a CC is associated with the magnitude of twitch potentiation.