Influence of contraction strength on single motor unit synchronous activity

Reliability of EMG determinism to detect changes in motor unit synchrony and coherence during submaximal contraction

“…Upon testing the coupling between discharges of wrist extensor motor unit pairs at different contraction levels in human subjects, we have recently shown that the occurrence of motor unit synchronous firings above-chance level was enhanced with moderate increases in contraction strength (Schmied and Descarreaux, 2010). Using this data obtained in the wrist extensor muscles originally tested by Del Santo et al (2006), our first objective was to determine if EMG DET was enhanced in association with the increase in motor unit synchrony established by cross-correlation analyses with stronger muscle contraction (Schmied and Descarreaux, 2010).…”

“…Using this data obtained in the wrist extensor muscles originally tested by Del Santo et al (2006), our first objective was to determine if EMG DET was enhanced in association with the increase in motor unit synchrony established by cross-correlation analyses with stronger muscle contraction (Schmied and Descarreaux, 2010).…”

Theoretical Model and Experimental Validation of the estimated proportions of common and independent input to motor neurons

“…For each number of MUST in the CST, we computed 100 realizations of coherence. A single estimate was then obtained by averaging coherence across all realizations and integrating in the frequency range [1][2][3][4][5] Hz, i.e. the bandwidth of the common synaptic input [2].…”

“…In particular, the common component of the drive has been shown to be the only component necessary for force control [2] and thus, its quantification may be useful for better understanding of complex physiological phenomena such as fatigue. The presence of common synaptic input to motor neurons may be either an efficient way to control motor performance [3] [4] or it may disrupt it [5] [6]. The common part of the synaptic input to motor neurons induces correlation between output spike trains which is thought to arise at a pre-synaptic level [7].…”

Synchronization of motor unit firings: an epiphenomenon of firing rate characteristics not common inputs

“…Dozens of reports have since adopted this notion, including the following, among others: 1) within the same muscle (Garland and Miles 1997;Kamen and Roy 2000;Keen et al 2012;Laine and Bailey 2011;Mellor and Hodges 2005;Nordstrom et al 1990;Schmied et al 1993); 2) across synergistic muscles (Barry et al 2009;Bremner et al 1991a, b;Carr et al 1994;Gibbs et al 1997;Keen and Fuglevand 2004;McIsaac and Fuglevand 2007;Powers et al 1989;Winges and Santello 2004); 3) during tremor (Halliday et al 1999;Logigian et al 1988;Semmler and Nordstrom 1995); 4) in various neuromuscular pathologies (Baker et al 1992;Farmer et al 1990Farmer et al , 1993Kirkwood et al 1984;Mottram et al 2010;Schmied et al 1999); 5) during various muscle contraction paradigms, such as precision grip tasks (Hockensmith et al 2005;Huesler et al 2000;Kilner et al 2002;Santello and Fuglevand 2004;Winges et al 2006); 6) in exercise training (Boonstra et al 2009;Dartnall et al 2008Dartnall et al , 2011Griffin et al 2009;Mochizuki et al 2005;Schmied and Descarreaux 2010); and 7) during muscle fatigue (Boonstra et al 2008;Grönlund et al 2009;…”