Specific modulation of spinal and cortical excitabilities during lengthening and shortening submaximal and maximal contractions in plantar flexor muscles

2014 ◽  
Vol 117 (12) ◽  
pp. 1440-1450 ◽  
Author(s):  
Julien Duclay ◽  
Benjamin Pasquet ◽  
Alain Martin ◽  
Jacques Duchateau
Keyword(s):  
Muscle Activation ◽  
Motor Evoked Potential ◽  
Silent Period ◽  
H Reflex ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Plantar Flexor ◽  
Lengthening Contractions ◽  
Flexor Muscles ◽  
Plantar Flexor Muscles

This study investigated the influence of the torque produced by plantar flexor muscles on cortical and spinal excitability during lengthening and shortening voluntary contractions. To that purpose, modulations of motor-evoked potential (MEP) and Hoffmann (H) reflex were compared in the soleus (SOL) and medial gastrocnemius (MG) during anisometric submaximal and maximal voluntary contraction (MVC) of the plantar flexor muscles. For the submaximal shortening and lengthening contractions, the target torque was set at 50% of their respective MVC force. The results indicate that the amplitudes of both MEP and H-reflex responses, normalized to the maximal M wave, were significantly ( P < 0.05) lower during lengthening compared with shortening submaximal contraction. For these two parameters, the reduction reached, respectively, 22.1 and 31.9% for the SOL and 34.5 and 29.3% for the MG. During MVC, normalized MEP and H reflex of the SOL were both reduced significantly by 19.9% ( P < 0.05) and 29.9% ( P < 0.001) during lengthening and shortening contraction, respectively, whereas no significant change ( P > 0.05) was observed for MG. In addition, the silent period in the ongoing electromyogram (EMG) activity following the MEP was significantly ( P < 0.01) briefer during lengthening than shortening contractions but did not differ ( P > 0.05) between contraction intensities and muscles. Together, these results indicate that cortical and spinal mechanisms involved in the modulation of muscle activation during shortening and lengthening contractions differ between synergistic muscles according to the torque produced. Data further document previous studies reporting that the specific modulation of muscle activation during lengthening contraction is not torque dependent.

Acute effect of muscle stretching on the steadiness of sustained submaximal contractions of the plantar flexor muscles

2011 ◽  
Vol 110 (2) ◽  
pp. 407-415 ◽  
Author(s):  
Emika Kato ◽  
Stéphanie Vieillevoye ◽  
Costantino Balestra ◽  
Nathalie Guissard ◽  
Jacques Duchateau
Keyword(s):  
Acute Effect ◽  
Medial Gastrocnemius ◽  
Matching Task ◽  
Emg Activity ◽  
Plantar Flexor ◽  
Fascicle Length ◽  
Muscle Stretching ◽  
Flexor Muscles ◽  
Two Parameters ◽  
Plantar Flexor Muscles

This paper examines the acute effect of a bout of static stretches on torque fluctuation during an isometric torque-matching task that required subjects to sustain isometric contractions as steady as possible with the plantar flexor muscles at four intensities (5, 10, 15, and 20% of maximum) for 20 s. The stretching bout comprised five 60-s passive stretches, separated by 10-s rest. During the torque-matching tasks and muscle stretching, the torque (active and passive) and surface electromyogram (EMG) of the medial gastrocnemius (MG), soleus (Sol), and tibialis anterior (TA) were continuously recorded. Concurrently, changes in muscle architecture (fascicle length and pennation angle) of the MG were monitored by ultrasonography. The results showed that during stretching, passive torque decreased and fascicle length increased gradually. Changes in these two parameters were significantly associated ( r2 = 0.46; P < 0.001). When data from the torque-matching tasks were collapsed across the four torque levels, stretches induced greater torque fluctuation ( P < 0.001) and enhanced EMG activity ( P < 0.05) in MG and TA muscles with no change in coactivation. Furthermore, stretching maneuvers produced a greater decrease (∼15%; P < 0.001) in fascicle length during the torque-matching tasks and change in torque fluctuation (CV) was positively associated with changes in fascicle length ( r2 = 0.56; P < 0.001), MG and TA EMG activities, and coactivation ( r2 = 0.35, 0.34, and 0.35, respectively; P < 0.001). In conclusion, these observations indicate that repeated stretches can decrease torque steadiness by increasing muscle compliance and EMG activity of muscles around the joint. The relative influence of such adaptations, however, may depend on the torque level during the torque-matching task.

Soleus- and Gastrocnemii-Evoked V-Wave Responses Increase After Neuromuscular Electrical Stimulation Training

2006 ◽  
Vol 95 (6) ◽  
pp. 3328-3335 ◽  
Author(s):  
Julien Gondin ◽  
Julien Duclay ◽  
Alain Martin
Keyword(s):  
Electrical Stimulation ◽  
Muscle Activation ◽  
Neuromuscular Electrical Stimulation ◽  
Voluntary Contraction ◽  
H Reflex ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Control Group ◽  
Plantar Flexor ◽  
V Wave

The aim of the study was to use combined longitudinal measurements of soleus (SOL) and gastrocnemii evoked V-wave and H-reflex responses to determine the site of adaptations within the central nervous system induced by 5 wk of neuromuscular electrical stimulation (NMES) training of the plantar flexor muscles. Nineteen healthy males subjects were divided into a neuromuscular electrostimulated group ( n = 12) and a control group ( n = 7). The training program consisted of 15 sessions of isometric NMES over a 5-wk period. All subjects were tested before and after the 5-wk period. SOL, lateral gastrocnemius (LG), and medial gastrocnemius (MG) maximal H-reflex and M-wave potentials were evoked at rest (i.e., Hmax and Mmax, respectively) and during maximal voluntary contraction (MVC) (i.e., Hsup and Msup, respectively). During MVC, a supramaximal stimulus was delivered that allowed us to record the V-wave peak-to-peak amplitudes from all three muscles. The SOL, LG, and MG electromyographic (EMG) activity as well as muscle activation (twitch interpolation technique) were also quantified during MVC. After training, plantar flexor MVC increased significantly by 22% ( P < 0.001). Torque gains were accompanied by an increase in muscle activation (+11%, P < 0.05), SOL, LG, and MG normalized EMG activity (+51, +54, and +60%, respectively, P < 0.05) and V/Msup ratios (+81, +76, and +97%, respectively, P < 0.05). Hmax/Mmax and Hsup/Msup ratios for all three muscles were unchanged after training. In conclusion, the increase in voluntary torque after 5 wk of NMES training could be ascribed to an increased volitional drive from the supraspinal centers and/or adaptations occurring at the spinal level.

scholarly journals Specific modulation of corticomuscular coherence during submaximal voluntary isometric, shortening and lengthening contractions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Dorian Glories ◽  
Mathias Soulhol ◽  
David Amarantini ◽  
Julien Duclay
Keyword(s):  
H Reflex ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Beta Band ◽  
Lengthening Contractions ◽  
Time Frequency ◽  
Corticomuscular Coherence ◽  
Emg Signal ◽  
Voluntary Contractions ◽  
Spinal Excitability

AbstractDuring voluntary contractions, corticomuscular coherence (CMC) is thought to reflect a mutual interaction between cortical and muscle oscillatory activities, respectively measured by electroencephalography (EEG) and electromyography (EMG). However, it remains unclear whether CMC modulation would depend on the contribution of neural mechanisms acting at the spinal level. To this purpose, modulations of CMC were compared during submaximal isometric, shortening and lengthening contractions of the soleus (SOL) and the medial gastrocnemius (MG) with a concurrent analysis of changes in spinal excitability that may be reduced during lengthening contractions. Submaximal contractions intensity was set at 50% of the maximal SOL EMG activity. CMC was computed in the time–frequency domain between the Cz EEG electrode signal and the unrectified SOL or MG EMG signal. Spinal excitability was quantified through normalized Hoffmann (H) reflex amplitude. The results indicate that beta-band CMC and normalized H-reflex were significantly lower in SOL during lengthening compared with isometric contractions, but were similar in MG for all three muscle contraction types. Collectively, these results highlight an effect of contraction type on beta-band CMC, although it may differ between agonist synergist muscles. These novel findings also provide new evidence that beta-band CMC modulation may involve spinal regulatory mechanisms.

scholarly journals Effect of footwear on intramuscular EMG activity of plantar flexor muscles in walking

2020 ◽  
Vol 55 ◽  
pp. 102474
Author(s):  
Annamária Péter ◽  
Anton Arndt ◽  
András Hegyi ◽  
Taija Finni ◽  
Eva Andersson ◽  
...  
Keyword(s):  
Emg Activity ◽  
Plantar Flexor ◽  
Flexor Muscles ◽  
Plantar Flexor Muscles

scholarly journals Activation of human plantar flexor muscles increases after electromyostimulation training

2002 ◽  
Vol 92 (4) ◽  
pp. 1383-1392 ◽  
Author(s):  
Nicola A. Maffiuletti ◽  
Manuela Pensini ◽  
Alain Martin
Keyword(s):  
Voluntary Activation ◽  
Emg Activity ◽  
Control Group ◽  
Neural Activation ◽  
Plantar Flexor ◽  
Postactivation Potentiation ◽  
Short Term ◽  
Flexor Muscles ◽  
Electrically Evoked Contractions ◽  
Plantar Flexor Muscles

Neuromuscular adaptations of the plantar flexor muscles were assessed before and subsequent to short-term electromyostimulation (EMS) training. Eight subjects underwent 16 sessions of isometric EMS training over 4 wk. Surface electromyographic (EMG) activity and torque obtained under maximal voluntary and electrically evoked contractions were analyzed to distinguish neural adaptations from contractile changes. After training, plantar flexor voluntary torque significantly increased under isometric conditions at the training angle (+8.1%, P< 0.05) and at the two eccentric velocities considered (+10.8 and +13.1%, P < 0.05). Torque gains were accompanied by higher normalized soleus EMG activity and, in the case of eccentric contractions, also by higher gastrocnemii EMG ( P < 0.05). There was an 11.9% significant increase in both plantar flexor maximal voluntary activation ( P < 0.01) and postactivation potentiation ( P < 0.05), whereas contractile properties did not change after training. In the absence of a change in the control group, it was concluded that an increase in neural activation likely mediates the voluntary torque gains observed after short-term EMS training.

Older Adults Use a Unique Strategy to Lift Inertial Loads With the Elbow Flexor Muscles

2000 ◽  
Vol 83 (4) ◽  
pp. 2030-2039 ◽  
Author(s):  
Andrew E. Graves ◽  
Kurt W. Kornatz ◽  
Roger M. Enoka
Keyword(s):  
Young Adults ◽  
Elbow Joint ◽  
Muscle Activation ◽  
Angular Displacement ◽  
Elbow Flexor ◽  
Lengthening Contractions ◽  
Old Adults ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles ◽  
Target Force

The purpose of this study was to determine the effect of age on the ability to exert steady forces and to perform steady flexion movements with the muscles that cross the elbow joint. An isometric task required subjects to exert a steady force to match a target force that was displayed on a monitor. An anisometric task required subjects to raise and lower inertial loads so that the angular displacement around the elbow joint matched a template displayed on a monitor. Steadiness was measured as the coefficient of variation of force and as the normalized standard deviation of wrist acceleration. For the isometric task, steadiness as a function of target force decreased similarly for old adults and young adults. For the anisometric task, steadiness increased as a function of the inertial load and there were significant differences caused by age. Old adults were less steady than young adults during both shortening and lengthening contractions with the lightest loads. Furthermore, old adults were least steady when performing lengthening contractions. These behaviors appear to be associated with the patterns of muscle activation. These results suggest that different neural strategies are used to control isometric and anisometric contractions performed with the elbow flexor muscles and that these strategies do not change in parallel with advancing age.

scholarly journals Relative index of ankle muscle activations on agonistic phase between subjects with and without flat foot

2015 ◽  
Vol 2 (1) ◽  
pp. 129 ◽  
Author(s):  
Paul S. Sung
Keyword(s):  
Muscle Activation ◽  
Time Window ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Flat Foot ◽  
Relative Index ◽  
Ankle Motion ◽  
Co Activation ◽  
Relative Activation ◽  
Ankle Muscle

Background: Although co-activation of ankle muscles has been reported, relative ankle muscle activation in subjects with flat foot has not been carefully investigated. The aim of this study was to compare the relative activation index (RAI) on the tibialis anterior (TA) and medial gastrocnemius (GTN) muscles during active ankle range of motion (ROM) between subjects with and without flat foot. Methods: There were 17 subjects with flat foot and 17 age- and gender-matched control subjects who participated in this study. The RAI based on electromyography (EMG) was measured during the agonist phase at a controlled velocity of ankle motion (10°/second). The subject was seated upright with the tested foot held firmly onto a footplate that was attached to a torque sensor. The ankle being measured was strapped to the leg support of the Intel stretch device at 60° of knee flexion. The RAI was analyzed by the summation of EMG activity from the agonistic time window divided by the total EMG activity during full active ankle ROM. Results: The RAI was significantly different on the TA muscle (t = 3.08, P = 0.004), but no difference was found on the GTN muscle (t = -1.24, P = 0.23) in subjects with flat foot. There was an interaction between group and RAI (F =7.89, P = 0.007); however, the RAI demonstrated no interaction with age (F = 2.59, P = 0.14), height (F = 3.73, P = 0.06), or weight (F = 2.96, P = 0.09). Conclusions: The RAI indicated a lack of TA muscle activation in the flat foot group. Such dissociated activation in the flat foot group might be relevant to the inefficiency of synergistic motions. The relative activation of the agonistic phase needs to be further investigated to compare co-activation of synergistic muscle activation with various functional tasks. 

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