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

Kline, Joshua C.; Luca, Carlo J. De

doi:10.1152/jn.00452.2015

Cited by 29 publications

(21 citation statements)

References 86 publications

(86 reference statements)

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“…Supporting this notion, previous studies (Milner‐Brown et al., ; Semmler & Nordstrom, ; Semmler, ; Folland & Williams, ) have reported increased MU synchronization in strength athletes compared to endurance athletes or untrained individuals, which has been accompanied by similar observations for RFD (Kyrolainen & Komi, ; Paasuke et al., ; Andersen et al., ). However, in spite of its apparent wide acceptance, there is a lack of empirical evidence supporting the notion that increased common synaptic inputs to spinal motor neurons result in enhanced MU synchronization under voluntary conditions (Kline & De Luca, ). In fact, a recent study (Kline & De Luca, ) concluded that as the force generated by the muscle increases, the firing rate slope decreases and the synchronization consequently decreases.…”

Section: Physiological Factors That Can Affect Rate Of Force Developmentmentioning

confidence: 99%

Physiological and methodological aspects of rate of force development assessment in human skeletal muscle

Rodríguez-Rosell

Pareja‐Blanco

Aagaard

et al. 2017

Clin Physio Funct Imaging

156

148

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Rate of force development (RFD) refers to the ability of the neuromuscular system to increase contractile force from a low or resting level when muscle activation is performed as quickly as possible, and it is considered an important muscle strength parameter, especially for athletes in sports requiring high-speed actions. The assessment of RFD has been used for strength diagnosis, to monitor the effects of training interventions in both healthy populations and patients, discriminate high-level athletes from those of lower levels, evaluate the impairment in mechanical muscle function after acute bouts of eccentric muscle actions and estimate the degree of fatigue and recovery after acute exhausting exercise. Notably, the evaluation of RFD in human skeletal muscle is a complex task as influenced by numerous distinct methodological factors including mode of contraction, type of instruction, method used to quantify RFD, devices used for force/torque recording and ambient temperature. Another important aspect is our limited understanding of the mechanisms underpinning rapid muscle force production. Therefore, this review is primarily focused on (i) describing the main mechanical characteristics of RFD; (ii) analysing various physiological factors that influence RFD; and (iii) presenting and discussing central biomechanical and methodological factors affecting the measurement of RFD. The intention of this review is to provide more methodological and analytical coherency on the RFD concept, which may aid to clarify the thinking of coaches and sports scientists in this area.

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Section: Physiological Factors That Can Affect Rate Of Force Developmentmentioning

confidence: 99%

Physiological and methodological aspects of rate of force development assessment in human skeletal muscle

Rodríguez-Rosell

Pareja‐Blanco

Aagaard

et al. 2017

Clin Physio Funct Imaging

156

148

View full text Add to dashboard Cite

show abstract

“…Recently the existence of common input has been debated: while some argue that synergistic muscles share most of their synaptic input (Laine et al, 2015 ), others have argued that common input provides no explanation for MN synchronization (Kline and De Luca, 2016 ). Apart from common input being used to explain different types of MN synchronization, this dispute mainly arises from the absence of a clear definition of common input (cf.…”

mentioning

confidence: 99%

Using Computational Neuroscience to Define Common Input to Spinal Motor Neurons

Boonstra

Farmer

Breakspear

2016

Front. Hum. Neurosci.

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“…The first one is short-term synchronization (STS) that occurs within short time period (around 5 ms) as reflected with a narrow peak in the cross-correlogram (Kirkwood et al, 1982 ). The STS may either arise from the common axonal inputs to pairs of motoneurones (Sears and Stagg, 1976 ; Nordstrom et al, 1992 ) or be just an epiphenomenon of firing rate characteristics (Kline and de Luca, 2016 ). The other form of synchronization is long-term (or broad-peak) one (LTS) that occurs within broader time band (>20 ms) (Kirkwood et al, 1982 ; Freund, 1983 ).…”

Section: Discussionmentioning

confidence: 99%

Parameters of Surface Electromyogram Suggest That Dry Immersion Relieves Motor Symptoms in Patients With Parkinsonism

et al. 2018

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Dry immersion (DI) is acknowledged as a reliable space flight analog condition. At DI, subject is immersed in water being wrapped in a waterproof film to imitate microgravity (μG). Microgravity is known to decrease muscle tone due to deprivation of the sensory stimuli that activate the reflexes that keep up the muscle tone. In contrary, parkinsonian patients are characterized by elevated muscle tone, or rigidity, along with rest tremor and akinesia. We hypothesized that DI can diminish the elevated muscle tone and/or the tremor in parkinsonian patients. Fourteen patients with Parkinson's disease (PD, 10 males, 4 females, 47–73 years) and 5 patients with vascular parkinsonism (VP, 1 male, 4 females, 65–72 years) participated in the study. To evaluate the effect of DI on muscles' functioning, we compared parameters of surface electromyogram (sEMG) measured before and after a single 45-min long immersion session. The sEMG recordings were made from the biceps brachii muscle, bilaterally. Each recording was repeated with the following loading conditions: with arms hanging freely down, and with 0, 1, and 2 kg loading on each hand with elbows flexed to 90°. The sEMG parameters comprised of amplitude, median frequency, time of decay of mutual information, sample entropy, correlation dimension, recurrence rate, and determinism of sEMG. These parameters have earlier been proved to be sensitive to PD severity. We used the Wilcoxon test to decide which parameters were statistically significantly different before and after the dry immersion. Accepting the p < 0.05 significance level, amplitude, time of decay of mutual information, recurrence rate, and determinism tended to decrease, while median frequency and sample entropy of sEMG tended to increase after the DI. The most statistically significant change was for the determinism of sEMG from the left biceps with 1 kg loading, which decreased for 84% of the patients. The results suggest that DI can promptly relieve motor symptoms of parkinsonism. We conclude that DI has strong potential as a rehabilitation method for parkinsonian patients.

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

Abstract: Kline JC, De Luca CJ. Synchronization of motor unit firings: an epiphenomenon of firing rate characteristics not common inputs.

Cited by 29 publications

References 86 publications

Physiological and methodological aspects of rate of force development assessment in human skeletal muscle

Physiological and methodological aspects of rate of force development assessment in human skeletal muscle

Using Computational Neuroscience to Define Common Input to Spinal Motor Neurons

Parameters of Surface Electromyogram Suggest That Dry Immersion Relieves Motor Symptoms in Patients With Parkinsonism

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