Motor unit synchronous firing as revealed by determinism of surface myoelectric signal

Recurrence quantification analysis of surface electromyographic signal: Sensitivity to potentiation and neuromuscular fatigue

“…The increase in %Det is classically attributed to EMG self-organization into more periodic waves, a process which may be caused by an increase in the probability that motor units will discharge in unity (Webber et al, 1995). This mechanism can be consistent with greater motor unit synchronization, which is in agreement with previous studies (Farina et al, 2002;Del Santo et al, 2006). Liu et al (2004) reported similar results during dynamic exercise and indicated that the increase in %Det was correlated with muscle fatigue, even though the underlying physiological mechanisms are still not completely understood, particularly the implication of the different fatigue components.…”

“…Indeed, motor unit synchronization, which is presented in the literature as a potential mechanism underlying the %Det increase, can involve either purely central pathways (central command) or an interaction between central and peripheral components. As an example, the recurrent inhibition of Renshaw cells, known to influence motor unit synchronization (Mattei et al, 2003;Del Santo et al, 2006;Uchiyama and Windhorst, 2007), can be affected by descending central command per se and/or by sensorial muscle afferences during contractions that induce fatigue (Windhorst, 1996;Gandevia, 2001).…”

Motor unit synchronization during fatigue: Described with a novel sEMG method based on large motor unit samples

“…This makes the estimated level of MU synchronization not necessarily representative for the entire muscle (Semmler, 2002) and might blur the association with force tremor. On the other hand, the methods to obtain MU synchronization from the sEMG signal (Del Santo et al, 2006;Farina et al, 2002;Kleine et al, 2001) are dependent on muscle fiber conduction velocity (MFCV) and therefore constricted to un-fatigued contractions since MFCV is affected by fatigue (Arendt-Nielsen et al, 1989). Recently, we developed a new method to quantify changes in level of MU synchronization using sEMG (Grö nlund et al, in press).…”

Neural Adjustment in the Activation of the Lower Leg Muscles through Daily Physical Exercises in Community-Based Elderly Persons

“…Recent reports appreciate novel method based on surface EMG using indexes extracted from recurrence quantification analysis such as the percentage of determinism for the quantification of motor unit synchronization (Felici et al 2001;Fattorini et al 2005;Del Santo et al 2006). Further study based on such an analysis may precisely demonstrate our suggestion that motor unit synchronization contributes to the change of motor unit firing induced by the physical intervention as ours.…”