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Compton CT, Lockyer EJ, Benson RJ, Power KE. Interhemispheric inhibition is different during arm cycling than a position- and intensity-matched tonic contraction. Exp Brain Res 2022; 240:2425-2434. [DOI: 10.1007/s00221-022-06413-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 07/01/2022] [Indexed: 11/29/2022]
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2
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Power KE, Lockyer EJ, Botter A, Vieira T, Button DC. Endurance-exercise training adaptations in spinal motoneurones: potential functional relevance to locomotor output and assessment in humans. Eur J Appl Physiol 2022; 122:1367-1381. [PMID: 35226169 DOI: 10.1007/s00421-022-04918-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 02/11/2022] [Indexed: 12/14/2022]
Abstract
It is clear from non-human animal work that spinal motoneurones undergo endurance training (chronic) and locomotor (acute) related changes in their electrical properties and thus their ability to fire action potentials in response to synaptic input. The functional implications of these changes, however, are speculative. In humans, data suggests that similar chronic and acute changes in motoneurone excitability may occur, though the work is limited due to technical constraints. To examine the potential influence of chronic changes in human motoneurone excitability on the acute changes that occur during locomotor output, we must develop more sophisticated recording techniques or adapt our current methods. In this review, we briefly discuss chronic and acute changes in motoneurone excitability arising from non-human and human work. We then discuss the potential interaction effects of chronic and acute changes in motoneurone excitability and the potential impact on locomotor output. Finally, we discuss the use of high-density surface electromyogram recordings to examine human motor unit firing patterns and thus, indirectly, motoneurone excitability. The assessment of single motor units from high-density recording is mainly limited to tonic motor outputs and minimally dynamic motor output such as postural sway. Adapting this technology for use during locomotor outputs would allow us to gain a better understanding of the potential functional implications of endurance training-induced changes in human motoneurone excitability on motor output.
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Affiliation(s)
- Kevin E Power
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada. .,Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada.
| | - Evan J Lockyer
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada.,Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Alberto Botter
- Laboratory for Engineering of the Neuromuscular System (LISiN), Department of Electronics and Telecommunication, Politecnico di Torino, Turin, Italy.,PoliToBIOMed Lab, Politecnico di Torino, Turin, Italy
| | - Taian Vieira
- Laboratory for Engineering of the Neuromuscular System (LISiN), Department of Electronics and Telecommunication, Politecnico di Torino, Turin, Italy.,PoliToBIOMed Lab, Politecnico di Torino, Turin, Italy
| | - Duane C Button
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada.,Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
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3
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Lockyer EJ, Compton CT, Forman DA, Pearcey GE, Button DC, Power KE. Moving forward: methodological considerations for assessing corticospinal excitability during rhythmic motor output in humans. J Neurophysiol 2021; 126:181-194. [PMID: 34133230 DOI: 10.1152/jn.00027.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The use of transcranial magnetic stimulation to assess the excitability of the central nervous system to further understand the neural control of human movement is expansive. The majority of the work performed to-date has assessed corticospinal excitability either at rest or during relatively simple isometric contractions. The results from this work are not easily extrapolated to rhythmic, dynamic motor outputs, given that corticospinal excitability is task-, phase-, intensity-, direction-, and muscle-dependent (Power KE, Lockyer EJ, Forman DA, Button DC. Appl Physiol Nutr Metab 43: 1176-1185, 2018). Assessing corticospinal excitability during rhythmic motor output, however, involves technical challenges that are to be overcome, or at the minimum considered, when attempting to design experiments and interpret the physiological relevance of the results. The purpose of this narrative review is to highlight the research examining corticospinal excitability during a rhythmic motor output and, importantly, to provide recommendations regarding the many factors that must be considered when designing and interpreting findings from studies that involve limb movement. To do so, the majority of work described herein refers to work performed using arm cycling (arm pedaling or arm cranking) as a model of a rhythmic motor output used to examine the neural control of human locomotion.
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Affiliation(s)
- Evan J Lockyer
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.,Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Chris T Compton
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.,Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Davis A Forman
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Gregory E Pearcey
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Shirley Ryan Ability Lab, Chicago, Illinois
| | - Duane C Button
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.,Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Kevin E Power
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.,Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
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4
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Benson RJ, Lockyer EJ, Compton CT, Power KE. Interhemispheric inhibition to the biceps brachii during arm cycling. Appl Physiol Nutr Metab 2021; 46:186-189. [DOI: 10.1139/apnm-2020-0456] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This is the first demonstration of interhemispheric inhibition (IHI) during a locomotor output, arm cycling. IHI was quantified by assessing the depth of the ipsilateral silent period (iSP) evoked via transcranial magnetic stimulation of the motor cortex. There was a significant reduction in electromyography (EMG) amplitude of the iSP during cycling compared with the control EMG (16.8% ± 17.1%; p < 0.001). Depth and area for measuring the iSP during arm cycling are discussed. Novelty: This is the first study to demonstrate activation of the cortical circuit, interhemispheric inhibition, during a locomotor output.
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Affiliation(s)
- Ryan J. Benson
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
| | - Evan J. Lockyer
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
| | - Chris T. Compton
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
| | - Kevin E. Power
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
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5
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Lockyer EJ, Buckle NCM, Collins BW, Button DC. Neuromuscular fatigue of the elbow flexors during repeated maximal arm cycling sprints: the effects of forearm position. Appl Physiol Nutr Metab 2020; 46:606-616. [PMID: 33296273 DOI: 10.1139/apnm-2020-0519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Repeated sprint exercise (RSE) is often used to induce neuromuscular fatigue (NMF). It is currently not known whether NMF is influenced by different forearm positions during arm cycling RSE. The purpose of this study was to investigate the effects of a pronated versus supinated forearm position on elbow flexor NMF during arm cycling RSE. Participants (n = 12) completed ten 10-s maximal arm cycling sprints interspersed by 60 s of rest on 2 separate days using either a pronated or supinated forearm position. All sprints were performed on an arm cycle ergometer in a reverse direction. Prior to and following RSE, NMF measurements (i.e., maximal voluntary contraction (MVC), potentiated twitch (PT), electromyography median frequencies) were recorded. Sprint performance measures, ratings of perceived exertion (RPE) and pain were also recorded. Irrespective of forearm position, sprint performance decreased as sprint number increased. These decreases were accompanied by significant increases in RPE (p < 0.001, ηp2 = 0.869) and pain (p < 0.001, ηp2 = 0.745). Participants produced greater power output during pronated compared with supinated sprinting (p < 0.001, ηp2 = 0.728). At post-sprinting, the percentage decrease in elbow flexor MVC and PT force from pre-sprinting was significantly greater following supinated than pronated sprinting (p < 0.001), suggesting greater peripheral fatigue occurred in this position. The data suggest that supinated arm cycling RSE results in inferior performance and greater NMF compared with pronated arm cycling RSE. Novelty: NMF of the elbow flexors is influenced by forearm position during arm cycling RSE. Supinated arm cycling sprints resulted in worse repeated sprint performance and also greater NMF than pronated RSE.
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Affiliation(s)
- Evan J Lockyer
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.,Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Natasha C M Buckle
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Brandon W Collins
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - D C Button
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.,Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
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Lockyer EJ, Soran N, Power KE. Modulation of Corticospinal Excitability with Contralateral Arm Cycling. Neuroscience 2020; 449:88-98. [DOI: 10.1016/j.neuroscience.2020.10.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 09/30/2020] [Accepted: 10/01/2020] [Indexed: 01/07/2023]
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Chaytor CP, Forman D, Byrne J, Loucks-Atkinson A, Power KE. Changes in muscle activity during the flexion and extension phases of arm cycling as an effect of power output are muscle-specific. PeerJ 2020; 8:e9759. [PMID: 32983635 PMCID: PMC7500348 DOI: 10.7717/peerj.9759] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 07/28/2020] [Indexed: 01/08/2023] Open
Abstract
Arm cycling is commonly used in rehabilitation settings for individuals with motor impairments in an attempt to facilitate neural plasticity, potentially leading to enhanced motor function in the affected limb(s). Studies examining the neural control of arm cycling, however, typically cycle using a set cadence and power output. Given the importance of motor output intensity, typically represented by the amplitude of electromyographic (EMG) activity, on neural excitability, surprisingly little is known about how arm muscle activity is modulated using relative workloads. Thus, the objective of this study was to characterize arm muscle activity during arm cycling at different relative workloads. Participants (n = 11) first completed a 10-second maximal arm ergometry sprint to determine peak power output (PPO) followed by 11 randomized trials of 20-second arm cycling bouts ranging from 5–50% of PPO (5% increments) and a standard 25 W workload. All submaximal trials were completed at 60 rpm. Integrated EMG amplitude (iEMG) was assessed from the biceps brachii, brachioradialis, triceps brachii, flexor carpi radialis, extensor carpi radialis and anterior deltoid of the dominant arm. Arm cycling was separated into two phases, flexion and extension, relative to the elbow joint for all comparisons. As expected, iEMG amplitude increased during both phases of cycling for all muscles examined. With the exception of the triceps brachii and extensor carpi radialis, iEMG amplitudes differed between the flexion and extension phases. Finally, there was a linear relationship between iEMG amplitude and the %PPO for all muscles during both elbow flexion and extension.
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Affiliation(s)
- Carla P Chaytor
- Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Davis Forman
- Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Jeannette Byrne
- Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Angela Loucks-Atkinson
- Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
| | - Kevin E Power
- Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
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Pearcey GEP, Sun Y, Zehr EP. Plantarflexion force is amplified with sensory stimulation during ramping submaximal isometric contractions. J Neurophysiol 2020; 123:1427-1438. [PMID: 32159422 DOI: 10.1152/jn.00650.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Stimulating cutaneous nerves, causing tactile sensations, reduces the perceived heaviness of an object, suggesting that either descending commands are facilitated or the perception of effort is reduced when tactile sensation is enhanced. Sensory stimulation can also mitigate decrements in motor output and spinal cord excitability that occur with fatigue. The effects of sensory stimulation applied with coincident timing of voluntary force output, however, are yet to be examined. Therefore, the purpose of this study was to examine effects of sensory enhancement to nerves innervating opposed skin areas of the foot (top or bottom) on force production during voluntary plantarflexion or dorsiflexion contractions. Stimulation trains were applied for 2 s at either a uniform 150 Hz or a modulated frequency that increased linearly from 50 to 150 Hz and were delivered at the initiation of the contraction. Participants were instructed to perform a ramp contraction [~10% maximal voluntary contraction (MVC)/s] to ~20% MVC and then to hold ~20% MVC for 2 s while receiving real-time visual feedback. Cutaneous reflexes were evoked 75 ms after initiating the hold (75 ms after sensory enhancement ended). Force output was greater for all sensory-enhanced conditions compared with control during plantarflexion; however, force output was not amplified during dorsiflexion. Cutaneous reflexes evoked after sensory enhancement were unaltered. These results indicate that sensory enhancement can amplify plantarflexion but not dorsiflexion, likely as a result of differences in neuroanatomical projections to the flexor and extensor motor pools. Further work is required to elucidate the mechanisms of enhanced force during cutaneous stimulation.NEW & NOTEWORTHY The efficacy of behaviorally timed sensory stimulation to enhance sensations and amplify force output has not been examined. Here we show cutaneous nerve sensory stimulation can amplify plantarflexion force output. This amplification in force occurs irrespective of whether the cutaneous field that is stimulated resides on the surface that is producing the force or the opposing surface. This information may provide insights for the development of technologies to improve performance and/or rehabilitation training.
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Affiliation(s)
- Gregory E P Pearcey
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada
| | - Yao Sun
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada
| | - E Paul Zehr
- Rehabilitation Neuroscience Laboratory, University of Victoria, Victoria, British Columbia, Canada.,Human Discovery Science, International Collaboration on Repair Discoveries (ICORD), Vancouver, British Columbia, Canada.,Centre for Biomedical Research, University of Victoria, Victoria, British Columbia, Canada.,Division of Medical Sciences, University of Victoria, Victoria, British Columbia, Canada.,Zanshin Consulting, Inc., Victoria, British Columbia, Canada
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Nippard AP, Lockyer EJ, Button DC, Power KE. Corticospinal excitability to the biceps and triceps brachii during forward and backward arm cycling is direction- and phase-dependent. Appl Physiol Nutr Metab 2020; 45:72-80. [DOI: 10.1139/apnm-2019-0043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The purpose of this study was to evaluate corticospinal excitability to the biceps and triceps brachii during forward (FWD) and backward (BWD) arm cycling. Corticospinal and spinal excitability were assessed using transcranial magnetic stimulation and transmastoid electrical stimulation to elicit motor evoked potentials (MEPs) and cervicomedullary evoked potentials (CMEPs), respectively. MEPs and CMEPs were recorded from the biceps and triceps brachii during FWD and BWD arm cycling at 2 positions, 6 and 12 o’clock. The 6 o’clock position corresponded to mid-elbow flexion and extension during FWD and BWD cycling, respectively, while 12 o’clock corresponded to mid-elbow extension and flexion during FWD and BWD cycling, respectively. During the flexion phase, MEP and CMEP amplitudes of the biceps brachii were higher during FWD cycling. However, during the extension phase, MEP and CMEP amplitudes were higher during BWD cycling. For the triceps brachii, MEP amplitudes were higher during FWD cycling regardless of phase. However, CMEP amplitudes were phase-dependent. During the flexion phase, CMEPs of the triceps brachii were higher during FWD cycling compared with BWD, but during the extension phase CMEPs were higher during BWD cycling compared with FWD. The data suggest that corticospinal and spinal excitability to the biceps brachii is phase- and direction-dependent. In the triceps brachii, spinal, but not corticospinal, excitability is phase-dependent when comparing FWD and BWD cycling. Novelty This is the first study to assess corticospinal excitability during FWD and BWD locomotor output. Corticospinal excitability during arm cycling depends on the direction, phase, and muscle being assessed.
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Affiliation(s)
- Anna. P. Nippard
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
| | - Evan. J. Lockyer
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
| | - Duane. C. Button
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
| | - Kevin. E. Power
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
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10
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Three-week treadmill training changes the electrophysiological properties of spinal interneurons in the mice. Exp Brain Res 2019; 237:2925-2938. [PMID: 31494682 DOI: 10.1007/s00221-019-05647-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 09/03/2019] [Indexed: 12/20/2022]
Abstract
It was shown in previous studies that endurance training enhanced excitability of rat spinal motoneurons. However, the influence of the training on the spinal interneurons remains unclear. In this study, we investigated the training effects on spinal interneurons in dorsal and ventromedial area in mice (P42-P50). The electrophysiological properties of the interneurons were recorded from spinal cord slices (T13-L6) by whole-cell patch-clamp recording. The interneurons could be classified into three types based on their response to step currents: single spike (type 1), phasic firing (type 2), and tonic firing (type 3) in both control and trained mice. Interneurons collected from control mice possessed rheobase of 11.3 ± 6.0 pA and voltage threshold (Vth) of - 37.3 ± 4.7 mV. Treadmill training reduced the rheobase by 4.8 ± 1.5 pA and Vth by 3.1 ± 1.2 mV (P < 0.05). Furthermore, the training effects were dependent on the distribution and types of the interneurons. Treadmill training hyperpolarized Vth and decreased rheobase in ventromedial interneurons, while the significant change was observed only in the action potation height of the interneurons in dorsal horn. Treadmill training also hyperpolarized Vth and increased input resistance in type 3 interneurons, but none of these changes was shown in type 1 and 2 interneurons. Bath application of 5-HT (10-20 μM) increased the neuronal excitability in both control and trained mice. Serotonin had similar effect on membrane properties of the interneurons collected from both groups. This study suggested that treadmill training increased excitability of spinal interneurons of the mice and thus would make the spinal motor system easier to generate locomotion.
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11
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Lockyer EJ, Hosel K, Nippard AP, Button DC, Power KE. Corticospinal-Evoked Responses from the Biceps Brachii during Arm Cycling across Multiple Power Outputs. Brain Sci 2019; 9:brainsci9080205. [PMID: 31430879 PMCID: PMC6721304 DOI: 10.3390/brainsci9080205] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Revised: 08/13/2019] [Accepted: 08/15/2019] [Indexed: 11/30/2022] Open
Abstract
Background: We examined corticospinal and spinal excitability across multiple power outputs during arm cycling using a weak and strong stimulus intensity. Methods: We elicited motor evoked potentials (MEPs) and cervicomedullary motor evoked potentials (CMEPs) in the biceps brachii using magnetic stimulation over the motor cortex and electrical stimulation of corticospinal axons during arm cycling at six different power outputs (i.e., 25, 50, 100, 150, 200 and 250 W) and two stimulation intensities (i.e., weak vs. strong). Results: In general, biceps brachii MEP and CMEP amplitudes (normalized to maximal M-wave (Mmax)) followed a similar pattern of modulation with increases in cycling intensity at both stimulation strengths. Specifically, MEP and CMEP amplitudes increased up until ~150 W and ~100 W when the weak and strong stimulations were used, respectively. Further increases in cycling intensity revealed no changes on MEP or CMEP amplitudes for either stimulation strength. Conclusions: In general, MEPs and CMEPs changed in a similar manner, suggesting that increases and subsequent plateaus in overall excitability are likely mediated by spinal factors. Interestingly, however, MEP amplitudes were disproportionately larger than CMEP amplitudes as power output increased, despite being initially matched in amplitude, particularly with strong stimulation. This suggests that supraspinal excitability is enhanced to a larger degree than spinal excitability as the power output of arm cycling increases.
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Affiliation(s)
- Evan J Lockyer
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
| | - Katarina Hosel
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
- Department of Psychology, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
| | - Anna P Nippard
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
| | - Duane C Button
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada
| | - Kevin E Power
- Human Neurophysiology Lab, School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
- Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
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12
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Alcock LR, Spence AJ, Lockyer EJ, Button DC, Power KE. Short-interval intracortical inhibition to the biceps brachii is present during arm cycling but is not different than a position- and intensity-matched tonic contraction. Exp Brain Res 2019; 237:2145-2154. [DOI: 10.1007/s00221-019-05579-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 06/08/2019] [Indexed: 10/26/2022]
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13
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Button DC, Kalmar JM. Understanding exercise-dependent plasticity of motoneurons using intracellular and intramuscular approaches. Appl Physiol Nutr Metab 2019; 44:1125-1133. [PMID: 31075205 DOI: 10.1139/apnm-2018-0862] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Spinal motoneurons (MN) exhibit exercise-dependent adaptations to increased activity, such as exercise and locomotion, as well as decreased activity associated with disuse, spinal cord injury, and aging. The development of several experimental approaches, in both human and animal models, has contributed significantly to our understanding of this plasticity. The purpose of this review is to summarize how intracellular recordings in an animal model and motor unit recordings in a human model have, together, contributed to our current understanding of exercise-dependent MN plasticity. These approaches and techniques will allow neuroscientists to continue to advance our understanding of MN physiology and the plasticity of the "final common path" of the motor system, and to design experiments to answer the critical questions that are emerging in this field.
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Affiliation(s)
- Duane C Button
- School of Human Kinetics and Recreation and BioMedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1C 5S7, Canada
| | - Jayne M Kalmar
- Department of Kinesiology and Physical Education, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada
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14
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Corticospinal Excitability to the Biceps Brachii is Not Different When Arm Cycling at a Self-Selected or Fixed Cadence. Brain Sci 2019; 9:brainsci9020041. [PMID: 30769825 PMCID: PMC6406314 DOI: 10.3390/brainsci9020041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 02/11/2019] [Accepted: 02/12/2019] [Indexed: 11/17/2022] Open
Abstract
Background: The present study compared corticospinal excitability to the biceps brachii muscle during arm cycling at a self-selected and a fixed cadence (SSC and FC, respectively). We hypothesized that corticospinal excitability would not be different between the two conditions. Methods: The SSC was initially performed and the cycling cadence was recorded every 5 s for one minute. The average cadence of the SSC cycling trial was then used as a target for the FC of cycling that the participants were instructed to maintain. The motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation (TMS) of the motor cortex were recorded from the biceps brachii during each trial of SSC and FC arm cycling. Results: Corticospinal excitability, as assessed via normalized MEP amplitudes (MEPs were made relative to a maximal compound muscle action potential), was not different between groups. Conclusions: Focusing on maintaining a fixed cadence during arm cycling does not influence corticospinal excitability, as assessed via TMS-evoked MEPs.
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Gardiner PF, Ljubicic V. Special issue on nervous system and exercise. Appl Physiol Nutr Metab 2018; 43:v. [PMID: 30380929 DOI: 10.1139/apnm-2018-0393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Phillip F Gardiner
- a Spinal Cord Research Center, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Vladimir Ljubicic
- b Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
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