Review
Physiology
Edith Elgueta-Cancino, Ethan Evans, Eduardo Martinez-Valdes, Deborah Falla
Summary: This review aims to synthesize the available evidence on the effect of resistance training (RT) on motor unit firing properties. The review revealed a lack of high-quality evidence for the effect of RT on motor unit firing properties, with heterogeneity across studies affecting the conclusions that can be drawn.
FRONTIERS IN PHYSIOLOGY
(2022)
Article
Mathematics, Interdisciplinary Applications
Matteo Beretta-Piccoli, Corrado Cescon, Ausilia Vistarini, Caterina Pisegna, Beatrice Vannini, Cristian Zampella, Luca Calanni, Emiliano Soldini, Marco Barbero, Giuseppe D'Antona
Summary: The study aimed to validate the relationship between fractal dimension (FD) of surface electromyographic (EMG) signal and firing rate and synchronization of motor units. Thirteen healthy subjects participated in an isometric knee extension task, and intramuscular and surface EMG signals were recorded concurrently. Results showed that FD was negatively correlated with motor unit synchronization and positively correlated with firing rate. However, the correlation between FD and firing rate was only significant during the initial 50 seconds of contraction. Therefore, FD of surface EMG signal is mostly related to firing rate and can be considered as an index of performance fatigability during sustained or prolonged contractions.
CHAOS SOLITONS & FRACTALS
(2023)
Article
Neurosciences
Shun Kunugi, Ales Holobar, Tsutomu Kodera, Heishiro Toyoda, Kohei Watanabe
Summary: Different neurophysiological strategies are used for force control and angle adjustment tasks. Motor unit firing rate is similarly regulated in the medial gastrocnemius muscle between the two tasks as force is increased. The increase in force does not seem to lead to early fatigue in position tasks.
JOURNAL OF NEUROPHYSIOLOGY
(2021)
Article
Clinical Neurology
Sanjeev D. Nandedkar, Paul E. Barkhaus, Erik Stalberg
Summary: This study assessed the validity of the prevailing concept of motor unit (MU) recruitment's progressive linear increase in firing rate (FR). The results indicated that MU FR does not exhibit a linear increase with recruitment, supporting the findings of other researchers. The firing rate of the fastest firing MU can be used as an indicator to detect MU loss in neurogenic processes.
Article
Physiology
Isabel A. Ely, Eleanor J. Jones, Thomas B. Inns, Siobhra Dooley, Sarah B. J. Miller, Daniel W. Stashuk, Philip J. Atherton, Bethan E. Phillips, Mathew Piasecki
Summary: This study found that targeted force accuracy training can improve the accuracy of knee extensor force tracking and reduce the variability of motor unit firing rates. This may be beneficial for older and clinical populations in performing daily activities.
EXPERIMENTAL PHYSIOLOGY
(2022)
Article
Clinical Neurology
Yu-ichi Noto, Kohei Watanabe, Ales Holobar, Takamasa Kitaoji, Yukiko Tsuji, Yuta Kojima, Fukiko Kitani-Morii, Toshiki Mizuno, Masanori Nakagawa
Summary: The study aimed to elucidate the characteristics of motor unit (MU) firing rate in CMT1A patients using high-density surface electromyography. Results showed that CMT1A patients had lower MU firing rates compared to healthy controls, and the firing rates decreased over time in CMT1A patients, suggesting that MU firing rate could serve as a potential short-term biomarker of axonal damage in CMT1A patients.
CLINICAL NEUROPHYSIOLOGY
(2021)
Article
Neurosciences
Eric A. Kirk, Kevin J. Gilmore, Charles L. Rice
Summary: This study compared motor unit firing rates during isometric and muscle-shortening contractions in young and very old adults. The findings showed that older adults had lower firing rates during isometric contractions but similar rates during shortening contractions compared to young adults. Neural drive during movement was task-dependent and minimally decreased in older adults.
JOURNAL OF NEUROPHYSIOLOGY
(2021)
Article
Nutrition & Dietetics
Dawid Lochynski, Maciej Pawlak, Inge Everaert, Tomasz Podgorski, Magdalena Gartych, Anna-Maria Borucka, Jan Celichowski, Wim Derave, Dominik Kaczmarek
Summary: The study found that long-term carnosine supplementation can maintain the force of FF muscle units at a higher level during rapid decline and result in less rapid force decline in both FF and FR muscle units. Carnosine supplementation did not change muscle antioxidant potential, mortality rate, or muscle mass with aging.
Article
Neurosciences
Alexander M. Zero, Eric A. Kirk, Kevin J. Gilmore, Charles L. Rice
Summary: This study investigated the changes in muscle firing rates during isokinetic contractions between two groups of adult males. The results showed that, despite differences in fatigue resistance, the reduction and recovery of firing rates were similar between the groups.
JOURNAL OF NEUROPHYSIOLOGY
(2023)
Article
Clinical Neurology
Yu-ichi Noto, Takamasa Kitaoji, Kohei Watanabe, Toshiki Mizuno
Summary: This study aimed to clarify the characteristics of motor unit (MU) firing rate and its association with clinical factors in amyotrophic lateral sclerosis (ALS) patients using high-density surface electromyography (HDSEMG) and MU decomposition analysis. Results showed that ALS patients had a higher MU firing rate during muscle contraction at a low force level, indicating a motor neuronal hyperexcitable state. The noninvasive assessment of MU firing rate by HDSEMG could provide a new evaluation method for ALS patients.
Article
Neurosciences
Lydia P. Kudina, Regina E. Andreeva
Summary: This study investigated the F-wave properties of single firing motor units in healthy humans and found that there was no association between the occurrence of F-waves and the firing behavior of motoneurons. Contrary to expectations, F-waves did not originate from the motoneuronal soma and could not provide evidence for motoneuron firing behavior.
JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY
(2022)
Article
Physiology
Alessandro Del Vecchio, Andrea Casolo, Jakob Lund Dideriksen, Per Aagaard, Francesco Felici, Deborah Falla, Dario Farina
Summary: Although maximal force increases with strength training, the rate of force development (RFD) may remain unaffected. This study investigates the neural and muscular mechanisms underlying rapid contractions after strength training and finds that the lack of change in RFD following training is primarily mediated by an unchanged maximal recruitment speed of motoneurons.
JOURNAL OF APPLIED PHYSIOLOGY
(2022)
Article
Physiology
Toshiyuki Aoyama, Yutaka Kohno
Summary: This study investigated the differences in recruitment and rate coding of motor units between postural and voluntary tasks. The results showed that postural tasks preferentially recruited motor units with lower recruitment threshold and higher firing rate, while voluntary tasks preferentially recruited motor units with higher recruitment threshold and amplitude.
FRONTIERS IN PHYSIOLOGY
(2022)
Article
Sport Sciences
Luca Ruggiero, Chris J. Mcneil
Summary: Little is known about the adaptations of motor units during acclimatization to high altitude.
MEDICINE & SCIENCE IN SPORTS & EXERCISE
(2023)
Article
Neurosciences
Alejandro Torrado Pacheco, Juliet Bottorff, Ya Gao, Gina G. Turrigiano
Summary: Homeostatic plasticity can bidirectionally regulate neuronal firing rates around a stable set point, and downward firing rate homeostasis (FRH) does not require NMDAR signaling and occurs during sleep.
