During dynamic or sustained isometric contractions, bursts of muscle activity appear in the electromyography (EMG) signal. Theoretically, these bursts of activity likely occur because motor units are constrained to fire temporally close to one another and thus the impulses are "clustered" with short delays to elicit bursts of muscle activity. The purpose of this study was to investigate whether...

In this chapter we refer to the decomposition of the myoelectric (ME) signal as the procedure by which the ME signal is separated into its constituents motor units action potential trains (MUAPTs). This concept is illustrated in Figure 1. The development of a system to accomplish such a decomposition will be beneficial to both researchers interested in understanding motor unit properties and be...

Targeted muscle reinnervation (TMR) is a surgical procedure used to redirect nerves originally controlling muscles of the amputated limb into remaining muscles above the amputation, to treat phantom limb pain and facilitate prosthetic control. While this procedure effectively establishes robust prosthetic control, there is little knowledge on the behavior and characteristics of the reinnervated...

The electrical signals produced by the muscles and nerves are analyzed to assess the state of neuromuscular function in subjects with suspected neuromuscular disorders. The repetitive activation of several individual motor units (MUs) results in a superposed pulse train and constitutes the electromyogram (EMG) signal. The analysis of the EMG is based on its basic constituent i.e. motor-unit act...

Objective: A satellite potential is a late component of the motor unit action potential (MUAP) that occurs both in pathologic and normal muscle. We investigated the physiological mechanisms responsible for satellite potentials in normal muscle by relating the latencies of MUAP features to the timing of the underlying electrical events. Methods: We analyzed 21 MUAPs with satellite potentials tha...

Objective: To evaluate the performance of a recently proposed motor unit action potential (MUAP) averaging method based on a sliding window, and compare it with relevant published methods in normal and pathological muscles. Methods: Three versions of the method (with different window lengths) were compared to three relevant published methods in terms of signal analysis-based merit figures and M...

The purpose of this study was to examine the effects of aging on the contractile and electrophysiological properties of human thenar motor units (MUs). Percutaneous electrical stimulation of single motor axons within the median nerve was used to isolate and examine the twitch tensions, contractile speeds, and surface-detected MU action potential (S-MUAP) sizes of 48 thenar MUs in 17 younger sub...

PURPOSE: Despite suggestions that low-intensity (LI) blood flow restricted exercise (BFRE) may be as effective as high intensity (HI) resistance exercise for the purpose of enhancing the recruitment of type II motor units (MU); individual MU acute response to LI BFRE has never been observed and/or reported. Recently, the decomposition of the surface electromyographic (EMG) signals introduced ne...

Quantification in clinical, diagnostic electromyography (EMG) currently includes motor unit action potential (MUAP) analysis and interference pattern analysis. Early efforts to examine the frequency/power spectra of the interference pattern showed modest value but the technique was not developed further. This paper re-examines spectral analysis, extending it into the time-varying domain, which ...

The spatial and temporal summation of all the single muscle fibers’ electrical activity corresponding to that AHC depolarization is referred to as a motor unit action potential (MUAP/MUP; Fig. 2). In other words, the MUAP is essentially the electrical correlate to the anatomic motor unit. The above noted MUAP’s respective “spatial” and “temporal” qualifiers are related to the fact that: 1) all ...