The Enigma of the Motor Nerve Conduction Study.

Background: In motor nerve conduction studies (MNCS), proximal stimulation should give a longer duration and lower amplitude compound muscle action potential (CMAP) due to higher temporal dispersion. Yet the CMAP waveforms at the distal and proximal stimulation sites appear remarkably similar. The objective of this study was to confirm this anomaly and investigate its possible cause by studying the median and ulnar nerves.

Revisiting the compound muscle action potential (CMAP).

The compound muscle action potential (CMAP) is among the first recorded waveforms in clinical neurography and one of the most common in clinical use. It is derived from the summated muscle fiber action potentials recorded from a surface electrode overlying the studied muscle following stimulation of the relevant motor nerve fibres innervating the muscle. Surface recorded motor unit potentials (SMUPs) are the fundamental units comprising the CMAP.

Motor unit recruitment and firing rate at low force of contraction.

Introduction/aims: A prevailing concept of motor unit (MU) recruitment used for calculating recruitment ratio (RR) suggests a progressive linear increase in firing rate (FR). The objective of this study is to assess its validity.

Methods: Concentric needle electromyography (EMG) recordings were made in normal muscle and abnormal muscle of patients with neurogenic findings.

Estimation of contractile parameters of successive twitches in unfused tetanic contractions of single motor units - A proof-of-concept study using ultrafast ultrasound imaging in vivo.

During a voluntary contraction, motor units (MUs) fire a train of action potentials, causing summation of the twitch forces, resulting in fused or unfused tetanus. Twitches have been important in studying whole-muscle contractile properties and differentiation between MU types. However, there are still knowledge gaps concerning the voluntary force generation mechanisms.