scholarly journals Intermediate Muscle Length and Tendon Vibration Optimize Corticospinal Excitability During Knee Extensors Local Vibration

2018 ◽  
Vol 9 ◽  
Author(s):  
Robin Souron ◽  
Marie Oriol ◽  
Guillaume Y. Millet ◽  
Thomas Lapole
Keyword(s):  
Muscle Length ◽  
Corticospinal Excitability ◽  
Knee Extensors ◽  
Tendon Vibration ◽  
Local Vibration

scholarly journals Muscle length effect on corticospinal excitability during maximal concentric, isometric and eccentric contractions of the knee extensors

2017 ◽  
Vol 102 (11) ◽  
pp. 1513-1523 ◽  
Author(s):  
Valentin Doguet ◽  
Kazunori Nosaka ◽  
Arnaud Guével ◽  
Gary Thickbroom ◽  
Kazuhiro Ishimura ◽  
...  
Keyword(s):  
Muscle Length ◽  
Corticospinal Excitability ◽  
Eccentric Contractions ◽  
Knee Extensors ◽  
Length Effect

scholarly journals Muscle length and joint angle influence spinal but not corticospinal excitability to the biceps brachii across forearm postures

2019 ◽  
Vol 122 (1) ◽  
pp. 413-423 ◽  
Author(s):  
Davis A. Forman ◽  
Daniel Abdel-Malek ◽  
Christopher M. F. Bunce ◽  
Michael W. R. Holmes
Keyword(s):  
Isometric Contraction ◽  
Elbow Joint ◽  
Joint Angle ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
Muscle Length ◽  
Elbow Flexion ◽  
Corticospinal Excitability ◽  
Biceps Brachii Muscle ◽  
Spinal Excitability

Forearm rotation (supination/pronation) alters corticospinal excitability to the biceps brachii, but it is unclear whether corticospinal excitability is influenced by joint angle, muscle length, or both. Thus the purpose of this study was to separately examine elbow joint angle and muscle length on corticospinal excitability. Corticospinal excitability to the biceps and triceps brachii was measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Spinal excitability was measured using cervicomedullary motor evoked potentials (CMEPs) elicited via transmastoid electrical stimulation. Elbow angles were manipulated with a fixed biceps brachii muscle length (and vice versa) across five unique postures: 1) forearm neutral, elbow flexion 90°; 2) forearm supinated, elbow flexion 90°; 3) forearm pronated, elbow flexion 90°; 4) forearm supinated, elbow flexion 78°; and 5) forearm pronated, elbow flexion 113°. A musculoskeletal model determined biceps brachii muscle length for postures 1–3, and elbow joint angles ( postures 4–5) were selected to maintain biceps length across forearm orientations. MEPs and CMEPs were elicited at rest and during an isometric contraction of 10% of maximal biceps muscle activity. At rest, MEP amplitudes to the biceps were largest during supination, which was independent of elbow joint angle. CMEP amplitudes were not different when the elbow was fixed at 90° but were largest in pronation when muscle length was controlled. During an isometric contraction, there were no significant differences across forearm postures for either MEP or CMEP amplitudes. These results highlight that elbow joint angle and biceps brachii muscle length can each independently influence spinal excitability. NEW & NOTEWORTHY Changes in upper limb posture can influence the responsiveness of the central nervous system to artificial stimulations. We established a novel approach integrating neurophysiology techniques with biomechanical modeling. Through this approach, the effects of elbow joint angle and biceps brachii muscle length on corticospinal and spinal excitability were assessed. We demonstrate that spinal excitability is uniquely influenced by joint angle and muscle length, and this highlights the importance of accounting for muscle length in neurophysiological studies.

Neural adaptations in quadriceps muscle after 4 weeks of local vibration training in young versus older subjects

2018 ◽  
Vol 43 (5) ◽  
pp. 427-436 ◽  
Author(s):  
Robin Souron ◽  
Thibault Besson ◽  
Thomas Lapole ◽  
Guillaume Y. Millet
Keyword(s):  
Vastus Lateralis ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
Voluntary Activation ◽  
Knee Extensors ◽  
Emg Activity ◽  
Local Vibration ◽  
Jump Performance ◽  
Vibration Training ◽  
Older Subjects

This study investigated the effects of a 4-week local vibration training (LVT) on the function of the knee extensors and corticospinal properties in healthy young and older subjects. Seventeen subjects (9 young and 8 older) performed 3 testing sessions: before (PRE1) and after (PRE2) a 4-week resting period to control the repeatability of the data as well as after the LVT (POST). Jump performance, maximal voluntary contraction (MVC) and electromyographic (EMG) activity on vastus lateralis and rectus femoris muscles were assessed. Single-pulse transcranial magnetic stimulation (TMS) allowed evaluation of cortical voluntary activation (VATMS), motor evoked potential (MEP) area, and silent period (SP) duration. All training adaptations were similar between young and older subjects (p > 0.05) and the following results reflect the pooled sample of subjects. MVC (+11.9% ± 8.0%, p < 0.001) and VATMS (+3.6% ± 5.2%, p = 0.004) were significantly increased at POST compared with PRE2. Maximal vastus lateralis EMG was significantly increased at POST (+21.9% ± 33.7%, p = 0.03). No changes were reported for MEPs on both muscles (p > 0.05). SPs recorded during maximal and submaximal contractions decreased in both muscles at POST (p < 0.05). Vertical jump performance was increased at POST (p < 0.05). LVT seems as effective in young as in older subjects to improve maximal functional capacities through neural modulations occurring at least partly at the supra-spinal level. Local vibration may be used as an efficient alternative training method to improve muscular performance in both healthy young and older subjects.

scholarly journals Effect of graded hypoxia on supraspinal contributions to fatigue with unilateral knee-extensor contractions

2010 ◽  
Vol 109 (6) ◽  
pp. 1842-1851 ◽  
Author(s):  
Stuart Goodall ◽  
Emma Z. Ross ◽  
Lee M. Romer
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Maximal Voluntary Contraction ◽  
Magnetic Stimulation ◽  
Voluntary Contraction ◽  
Corticospinal Excitability ◽  
Voluntary Activation ◽  
Severe Hypoxia ◽  
Knee Extensors ◽  
Moderate Hypoxia

Supraspinal fatigue, defined as an exercise-induced decline in force caused by suboptimal output from the motor cortex, accounts for over one-quarter of the force loss after fatiguing contractions of the knee extensors in normoxia. We tested the hypothesis that the relative contribution of supraspinal fatigue would be elevated with increasing severities of acute hypoxia. On separate days, 11 healthy men performed sets of intermittent, isometric, quadriceps contractions at 60% maximal voluntary contraction to task failure in normoxia (inspired O2 fraction/arterial O2 saturation = 0.21/98%), mild hypoxia (0.16/93%), moderate hypoxia (0.13/85%), and severe hypoxia (0.10/74%). Electrical stimulation of the femoral nerve was performed to assess neuromuscular transmission and contractile properties of muscle fibers. Transcranial magnetic stimulation was delivered to the motor cortex to quantify corticospinal excitability and voluntary activation. After 10 min of breathing the test gas, neuromuscular function and cortical voluntary activation prefatigue were unaffected in any condition. The fatigue protocol resulted in ∼30% declines in maximal voluntary contraction force in all conditions, despite differences in time-to-task failure (24.7 min in normoxia vs. 15.9 min in severe hypoxia, P < 0.05). Potentiated quadriceps twitch force declined in all conditions, but the decline in severe hypoxia was less than that in normoxia ( P < 0.05). Cortical voluntary activation also declined in all conditions, but the deficit in severe hypoxia exceeded that in normoxia ( P < 0.05). The additional central fatigue in severe hypoxia was not due to altered corticospinal excitability, as electromyographic responses to transcranial magnetic stimulation were unchanged. Results indicate that peripheral mechanisms of fatigue contribute relatively more to the reduction in force-generating capacity of the knee extensors following submaximal intermittent isometric contractions in normoxia and mild to moderate hypoxia, whereas supraspinal fatigue plays a greater role in severe hypoxia.

Corticospinal excitability changes following prolonged muscle tendon vibration

Neuroreport ◽  
2003 ◽  
Vol 14 (15) ◽  
pp. 2001-2004 ◽  
Author(s):  
Maarten Steyvers ◽  
Oron Levin ◽  
Marc Van Baelen ◽  
Stephan P. Swinnen
Keyword(s):  
Corticospinal Excitability ◽  
Tendon Vibration ◽  
Muscle Tendon Vibration

Muscle activation and blood flow do not explain the muscle length-dependent variation in quadriceps isometric endurance

2005 ◽  
Vol 98 (3) ◽  
pp. 810-816 ◽  
Author(s):  
R. D. Kooistra ◽  
C. J. de Ruiter ◽  
A. de Haan
Keyword(s):  
Blood Flow ◽  
Blood Supply ◽  
Vastus Lateralis ◽  
Muscle Length ◽  
Rectus Femoris ◽  
Surface Emg ◽  
Knee Extensors ◽  
Emg Activity ◽  
Central Activation ◽  
Full Occlusion

We investigated the role of central activation in muscle length-dependent endurance. Central activation ratio (CAR) and rectified surface electromyogram (EMG) were studied during fatigue of isometric contractions of the knee extensors at 30 and 90° knee angles (full extension = 0°). Subjects ( n = 8) were tested on a custom-built ergometer. Maximal voluntary isometric knee extension with supramaximal superimposed burst stimulation (three 100-μs pulses; 300 Hz) was performed to assess CAR and maximal torque capacity (MTC). Surface EMG signals were obtained from vastus lateralis and rectus femoris muscles. At each angle, intermittent (15 s on 6 s off) isometric exercise at 50% MTC with superimposed stimulation was performed to exhaustion. During the fatigue task, a sphygmomanometer cuff around the upper thigh ensured full occlusion (400 mmHg) of the blood supply to the knee extensors. At least 2 days separated fatigue tests. MTC was not different between knee angles (30°: 229.6 ± 39.3 N·m vs. 90°: 215.7 ± 13.2 N·m). Endurance times, however, were significantly longer ( P < 0.05) at 30 vs. 90° (87.8 ± 18.7 vs. 54.9 ± 12.1 s, respectively) despite the CAR not differing between angles at torque failure (30°: 0.95 ± 0.05 vs. 90°: 0.96 ± 0.03) and full occlusion of blood supply to the knee extensors. Furthermore, rectified surface EMG values of the vastus lateralis (normalized to prefatigue maximum) were also similar at torque failure (30°: 56.5 ± 12.5% vs. 90°: 58.3 ± 15.2%), whereas rectus femoris EMG activity was lower at 30° (44.3 ± 12.4%) vs. 90° (69.5 ± 25.3%). We conclude that differences in endurance at different knee angles do not find their origin in differences in central activation and blood flow but may be a consequence of muscle length-related differences in metabolic cost.

Modulation of soleus corticospinal excitability during Achilles tendon vibration

2015 ◽  
Vol 233 (9) ◽  
pp. 2655-2662 ◽  
Author(s):  
Thomas Lapole ◽  
John Temesi ◽  
Pierrick J. Arnal ◽  
Philippe Gimenez ◽  
Michel Petitjean ◽  
...  
Keyword(s):  
Achilles Tendon ◽  
Corticospinal Excitability ◽  
Tendon Vibration
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