The knowns and unknowns of neural adaptations to resistance training

AbstractThe initial increases in force production with resistance training are thought to be primarily underpinned by neural adaptations. This notion is firmly supported by evidence displaying motor unit adaptations following resistance training; however, the precise locus of neural adaptation remains elusive. The purpose of this review is to clarify and critically discuss the literature concerning the site(s) of putative neural adaptations to short-term resistance training. The proliferation of studies employing non-invasive stimulation techniques to investigate evoked responses have yielded variable results, but generally support the notion that resistance training alters intracortical inhibition. Nevertheless, methodological inconsistencies and the limitations of techniques, e.g. limited relation to behavioural outcomes and the inability to measure volitional muscle activity, preclude firm conclusions. Much of the literature has focused on the corticospinal tract; however, preliminary research in non-human primates suggests reticulospinal tract is a potential substrate for neural adaptations to resistance training, though human data is lacking due to methodological constraints. Recent advances in technology have provided substantial evidence of adaptations within a large motor unit population following resistance training. However, their activity represents the transformation of afferent and efferent inputs, making it challenging to establish the source of adaptation. Whilst much has been learned about the nature of neural adaptations to resistance training, the puzzle remains to be solved. Additional analyses of motoneuron firing during different training regimes or coupling with other methodologies (e.g., electroencephalography) may facilitate the estimation of the site(s) of neural adaptations to resistance training in the future.

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Resistance Training: Cortical, Spinal, and Motor Unit Adaptations

Canadian Journal of Applied Physiology ◽

10.1139/h05-125 ◽

2005 ◽

Vol 30 (3) ◽

pp. 328-340 ◽

Cited By ~ 49

Author(s):

Lisa Griffin ◽

Enzo Cafarelli

Keyword(s):

Resistance Training ◽

Motor Unit ◽

Cortical Excitability ◽

Voluntary Contraction ◽

Force Output ◽

Single Motor Unit ◽

Neural Adaptations ◽

Maximal Force ◽

Early Stages ◽

Discharge Rates

During the first few weeks of isometric resistance training there is an increase in maximal muscle force output that cannot be accounted for by muscle hypertrophy. Early on, researchers postulated the existence of neural adaptations to training primarily through the use of surface electromyographic recordings. More recent evidence also suggests that increased excitation may occur at the cortical levels following short-term resistance training. Alterations in synergistic activation and reductions in antagonist activation are neural factors that have been identified as changing during the early stages of resistance training which could contribute to maximal force generation. Neural adaptations that occur during the ramp-up phase of isometric contraction include decreases in motor unit recruitment thresholds, increased motor unit discharge rates, and increases in double discharges. An increase in the maximal rate of force development also occurs during the early stages of resistance training, but whether the neural mechanisms associated with the increase in the rate of rise are also associated with the increase in maximal force has not been elucidated. More work is needed to examine the integration of changes in cortical and spinal excitability with single motor unit firing patterns during this simple form of exercise before we can extend our understanding to different types of training. Key words: strength training, neural adaptation, H-reflex, maximal voluntary contraction, cortical excitability

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Bee Markers: A Novel Method for Non-Invasive Short Term Marking of Bats

Acta Chiropterologica ◽

10.3161/15081109acc2019.21.2.020 ◽

2020 ◽

Vol 21 (2) ◽

pp. 465 ◽

Cited By ~ 1

Author(s):

Lucinda Kirkpatrick ◽

Grzegorz Apoznański ◽

Luc De Bruyn ◽

Ralf Gyselings ◽

Tomasz Kokurewicz

Keyword(s):

Short Term ◽

Non Invasive ◽

Novel Method

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Short-term effects of synchronized vs. non-synchronized NIPPV in preterm infants: study protocol for an unmasked randomized crossover trial

Trials ◽

10.1186/s13063-021-05351-0 ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Francesco Cresi ◽

Federica Chiale ◽

Elena Maggiora ◽

Silvia Maria Borgione ◽

Mattia Ferroglio ◽

...

Keyword(s):

Preterm Infants ◽

Work Of Breathing ◽

Respiratory Rhythm ◽

Assisted Ventilation ◽

Positive Pressure ◽

Invasive Ventilation ◽

Short Term ◽

Non Invasive ◽

Non Invasive Ventilation ◽

Short Term Effects

Abstract Background Non-invasive ventilation (NIV) has been recommended as the best respiratory support for preterm infants with respiratory distress syndrome (RDS). However, the best NIV technique to be used as first intention in RDS management has not yet been established. Nasal intermittent positive pressure ventilation (NIPPV) may be synchronized (SNIPPV) or non-synchronized to the infant’s breathing efforts. The aim of the study is to evaluate the short-term effects of SNIPPV vs. NIPPV on the cardiorespiratory events, trying to identify the best ventilation modality for preterm infants at their first approach to NIV ventilation support. Methods An unmasked randomized crossover study with three treatment phases was designed. All newborn infants < 32 weeks of gestational age with RDS needing NIV ventilation as first intention or after extubation will be consecutively enrolled in the study and randomized to the NIPPV or SNIPPV arm. After stabilization, enrolled patients will be alternatively ventilated with two different techniques for two time frames of 4 h each. NIPPV and SNIPPV will be administered with the same ventilator and the same interface, maintaining continuous assisted ventilation without patient discomfort. During the whole duration of the study, the patient’s cardiorespiratory data and data from the ventilator will be simultaneously recorded using a polygraph connected to a computer. The primary outcome is the frequency of episodes of oxygen desaturation. Secondary outcomes are the number of the cardiorespiratory events, FiO2 necessity, newborn pain score evaluation, synchronization index, and thoracoabdominal asynchrony. The calculated sample size was of 30 patients. Discussion It is known that NIPPV produces a percentage of ineffective acts due to asynchronies between the ventilator and the infant’s breaths. On the other hand, an ineffective synchronization could increase work of breathing. Our hypothesis is that an efficient synchronization could reduce the respiratory work and increase the volume per minute exchanged without interfering with the natural respiratory rhythm of the patient with RDS. The results of this study will allow us to evaluate the effectiveness of the synchronization, demonstrating whether SNIPPV is the most effective non-invasive ventilation mode in preterm infants with RDS at their first approach to NIV ventilation. Trial registration ClinicalTrials.gov NCT03289936. Registered on September 21, 2017.

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Short-term resistance training in older adults improves muscle quality: A randomized control trial

Experimental Gerontology ◽

10.1016/j.exger.2020.111195 ◽

2021 ◽

Vol 145 ◽

pp. 111195

Author(s):

Ashley A. Herda ◽

Omid Nabavizadeh

Keyword(s):

Older Adults ◽

Resistance Training ◽

Randomized Control Trial ◽

Muscle Quality ◽

Short Term ◽

Randomized Control

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The Effects of Spinal Manipulation on Motor Unit Behavior

Brain Sciences ◽

10.3390/brainsci11010105 ◽

2021 ◽

Vol 11 (1) ◽

pp. 105

Author(s):

Lucien Robinault ◽

Aleš Holobar ◽

Sylvain Crémoux ◽

Usman Rashid ◽

Imran Khan Niazi ◽

...

Keyword(s):

Motor Unit ◽

Conduction Velocity ◽

Spinal Manipulation ◽

Maximum Voluntary Contraction ◽

Force Production ◽

Movement Control ◽

Position Sense ◽

Joint Position Sense ◽

Voluntary Contraction ◽

Passive Movement

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity. High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design. Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”). A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, lower twitch torque motor units.

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