scholarly journals Using transcranial magnetic stimulation to map the cortical representation of lower-limb muscles

2019 ◽  
Author(s):  
Jennifer L Davies
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Lower Limb ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
The Body ◽  
Double Cone ◽  
Cortical Representation ◽  
Lower Limb Muscles ◽  
Main Effect ◽  
Limb Muscles

AbstractThe aim of this study was to evaluate the extent to which transcranial magnetic stimulation (TMS) can identify discrete cortical representation of lower-limb muscles in healthy individuals. Data were obtained from 16 young healthy adults (12 women, four men; mean [SD] age 23.0 [2.6] years). Motor evoked potentials were recorded from the resting vastus medialis, rectus femoris, vastus lateralis, medial and lateral hamstring, and medial and lateral gastrocnemius muscles on the right side of the body using bipolar surface electrodes. TMS was delivered through a 110-mm double-cone coil at 63 sites over the left hemisphere. Location and size of the cortical representation and the number of discrete peaks were quantified for each muscle. Within the quadriceps muscle group there was a main effect of muscle on anterior-posterior centre of gravity (p = 0.010), but the magnitude of the difference was very small. Within the quadriceps there was a main effect of muscle on medial-lateral hotspot (p = 0.027) and map volume (p = 0.047), but no post-hoc tests were significant. The topography of each lower-limb muscle was complex, displaying multiple peaks that were present across the stimulation grid, and variable across individuals. The results of this study indicate that TMS delivered with a 110-mm double-cone coil could not reliably identify discrete cortical representations of resting lower-limb muscles when responses were measured using bipolar surface electromyography. The characteristics of the cortical representation of lower-limb muscles reported here provide a basis against which to evaluate cortical reorganisation in clinical populations.

scholarly journals Inter-muscle differences in modulation of motor evoked potentials and posterior root-muscle reflexes evoked from lower-limb muscles during agonist and antagonist muscle contractions

2020 ◽  
Author(s):  
Akira Saito ◽  
Kento Nakagawa ◽  
Yohei Masugi ◽  
Kimitaka Nakazawa
Keyword(s):  
Lower Limb ◽  
Motor Evoked Potentials ◽  
Voluntary Contraction ◽  
Spinal Reflex ◽  
Posterior Root ◽  
Antagonist Muscle ◽  
Lower Limb Muscles ◽  
Limb Muscles ◽  
Agonist And Antagonist ◽  
Muscle Reflexes

AbstractVoluntary contraction facilitates corticospinal and spinal reflex circuit excitabilities of the contracted muscle and inhibits spinal reflex circuit excitability of the antagonist. It has been suggested that modulation of spinal reflex circuit excitability in agonist and antagonist muscles during voluntary contraction differs among lower-limb muscles. However, whether the effects of voluntary contraction on the excitabilities of corticospinal and spinal reflex circuits depend on the tested muscles remains unknown. The purpose of this study was to examine inter-muscle differences in modulation of the corticospinal and spinal reflex circuit excitabilities of multiple lower-limb muscles during voluntary contraction. Eleven young males performed isometric plantar-flexion, dorsi-flexion, knee extension, and flexion at low torque levels. Motor evoked potentials (MEPs) and posterior root-muscle reflexes from seven lower-leg and thigh muscles were evoked by transcranial magnetic stimulation and transcutaneous spinal cord stimulation, respectively, at rest and during weak voluntary contractions. MEP and posterior root-muscle reflex amplitudes of agonists were significantly increased as agonist torque level increased, except for the reflex of the tibialis anterior. MEP amplitudes of antagonists were significantly increased in relation to the agonist torque level, but those of the rectus femoris were slightly depressed during knee flexion. Regarding the posterior root-muscle reflex of the antagonists, the amplitudes of triceps surae and the hamstrings were significantly decreased, but those of the quadriceps femoris were significantly increased as the agonist torque level increased. These results demonstrate that modulation of corticospinal and spinal reflex circuit excitabilities during agonist and antagonist muscle contractions differed among lower-limb muscles.

Lower Extremity Muscle Morphology and Plantar Loading During Squatting with Different Heel Heights

2020 ◽  
Vol 10 (5) ◽  
pp. 1210-1215
Author(s):  
Tanyan Xie ◽  
Yan Zhang ◽  
Jan Awrejcewicz ◽  
Yaodong Gu
Keyword(s):  
Lower Limb ◽  
Plantar Pressure ◽  
Muscle Thickness ◽  
Pennation Angle ◽  
The Body ◽  
Muscle Morphology ◽  
Lower Limb Muscles ◽  
Heel Height ◽  
Lower Extremity Muscle ◽  
Limb Muscles

Objective: Although it is widely reported that high-heeled changes gait pattern in terms of motions and forces throughout the body, the biomechanics while high-heeled squatting has not been examined. This study aimed to explore the acute effects of different heel heights on muscle morphology and plantar loading during high-heeled squatting. Methods: Fourteen healthy females performed squats on high-heeled shoes with different heights: flat (0.8 cm), moderate (4.0 cm), and high (7.0 cm). Muscle thickness and pennation angle of selected lower limb muscles were measured by ultrasound imaging. Plantar pressure distribution and COP trajectory during an entire squatting motion were recorded. Results: As the heel height increased, the average and peak pressure consistently increased in the heel and hallux regions, while reversely changed in MF and LF regions. In addition, the selected lower limb muscles except for the lateral gastrocnemius and vastus medialis showed significant differences in muscle thickness and pennation angle between heel heights. Conclusion: The findings of this study indicate that increased heel height would enhance the immediate effects on muscle morphology as well as plantar pressure redistribution potentially causing lower limb muscle fatigue and injuries.

Potential of lower-limb muscles to accelerate the body during cerebral palsy gait

2012 ◽  
Vol 36 (2) ◽  
pp. 194-200 ◽  
Author(s):  
Tomas A. Correa ◽  
Anthony G. Schache ◽  
H. Kerr Graham ◽  
Richard Baker ◽  
Pam Thomason ◽  
...  
Keyword(s):  
Cerebral Palsy ◽  
Lower Limb ◽  
The Body ◽  
Lower Limb Muscles ◽  
Limb Muscles

Intracortical inhibition of lower limb motor-evoked potentials after paired transcranial magnetic stimulation

1997 ◽  
Vol 117 (3) ◽  
pp. 437-443 ◽  
Author(s):  
D. S. Stokic´ ◽  
W. Barry McKay ◽  
Lillian Scott ◽  
Arthur M. Sherwood ◽  
Milan R. Dimitrijevic´
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Lower Limb ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Intracortical Inhibition

scholarly journals Neuromechanics of Dynamic Balance Tasks in the Presence of Perturbations

2021 ◽  
Vol 14 ◽  
Author(s):  
Victor Munoz-Martel ◽  
Alessandro Santuz ◽  
Sebastian Bohm ◽  
Adamantios Arampatzis
Keyword(s):  
Motor Control ◽  
Mechanical Loading ◽  
Lower Limb ◽  
The Body ◽  
Muscle Synergy ◽  
Emg Activity ◽  
Modular Organization ◽  
Joint Moments ◽  
Lower Limb Muscles ◽  
Limb Muscles

Understanding the neuromechanical responses to perturbations in humans may help to explain the reported improvements in stability performance and muscle strength after perturbation-based training. In this study, we investigated the effects of perturbations, induced by unstable surfaces, on the mechanical loading and the modular organization of motor control in the lower limb muscles during lunging forward and backward. Fifteen healthy adults performed 50 forward and 50 backward lunges on stable and unstable ground. Ground reaction forces, joint kinematics, and the electromyogram (EMG) of 13 lower limb muscles were recorded. We calculated the resultant joint moments and extracted muscle synergies from the stepping limb. We found sparse alterations in the resultant joint moments and EMG activity, indicating a little if any effect of perturbations on muscle mechanical loading. The time-dependent structure of the muscle synergy responsible for the stabilization of the body was modified in the perturbed lunges by a shift in the center of activity (later in the forward and earlier in the backward lunge) and a widening (in the backward lunge). Moreover, in the perturbed backward lunge, the synergy related to the body weight acceptance was not present. The found modulation of the modular organization of motor control in the unstable condition and related minor alteration in joint kinetics indicates increased control robustness that allowed the participants to maintain functionality in postural challenging settings. Triggering specific modulations in motor control to regulate robustness in the presence of perturbations may be associated with the reported benefits of perturbation-based training.

Responses of Ankle Extensor and Flexor Motoneurons to Transcranial Magnetic Stimulation

2002 ◽  
Vol 88 (1) ◽  
pp. 124-132 ◽  
Author(s):  
P. Bawa ◽  
G. R. Chalmers ◽  
H. Stewart ◽  
A. A. Eisen
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Statistical Tests ◽  
Motor Units ◽  
Surface Emg ◽  
Contralateral Side ◽  
The Body ◽  
Single Motor Unit

Transcranial magnetic stimulation (TMS) of the motor cortex excites limb muscles of the contralateral side of the body. Reports of poorly defined, or a complete lack of systematic excitatory responses of soleus motoneurons compared with those of tibialis anterior (TA) motoneurons has led to the proposal that while all ankle flexor motoneurons receive strong corticomotoneuronal connections, very few soleus motoneurons do. In addition, the connections to these few motoneurons are weak. The nature of corticomotoneuronal connections onto these two motoneuron pools was re-evaluated in the following experiments. The leg area of the left motor cortex was stimulated with a large double-cone coil using Magstim 200, while surface electromyographic (EMG) and single motor unit (SMU) responses were recorded from soleus and TA muscles of healthy adult subjects. Under resting conditions, the onset (25–30 ms) and duration of concomitantly recorded short latency motor evoked potentials (MEPs) in surface EMG from both muscles were similar. The input-output relationships of the simultaneously recorded soleus and TA EMG responses showed much greater increases in TA MEPs compared with soleus MEPs with identical increases in stimulus intensity. Under resting and nonisometric conditions, a later peak with onset latency of approximately 100 ms was observed in soleus. During isometric conditions or with vibration of the TA tendon, the second soleus peak was abolished indicating reflex origin of this peak. Recordings from 42 soleus and 39 TA motor units showed clear response peaks in the peristimulus time histograms (PSTHs) of every unit. Two statistical tests were done to determine the onset and duration of response peaks in the PSTHs. With χ2 test, the duration was 6.9 ± 4.2 ms (mean ± SD) for soleus and 5.1 ± 2.1 ms for TA. Using the criterion of discerning a peak by bin counts being three SDs above background, the duration was 10.0 ± 4.4 ms for soleus and 7.8 ± 2.6 ms for TA. Results of these experiments do not suggest a lack of systematic corticomotoneuronal connections on soleus motoneurons when compared with those on TA, though some differences in the strengths of corticomotoneuronal connections onto the two pools do exist.

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