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.

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

Human motor control of landing from a drop in simulated microgravity

2016 ◽  
Vol 121 (3) ◽  
pp. 760-770 ◽  
Author(s):  
C. N. Gambelli ◽  
D. Theisen ◽  
P. A. Willems ◽  
B. Schepens
Keyword(s):  
Motor Control ◽  
Lower Limb ◽  
Sensory Information ◽  
Muscular Activity ◽  
The Body ◽  
Experimental Conditions ◽  
Human Motor Control ◽  
Lower Limb Muscles ◽  
Human Motor ◽  
Drop Landings

Landing on the ground on one's feet implies that the energy gained during the fall be dissipated. The aim of this study is to assess human motor control of landing in different conditions of fall initiation, simulated gravity, and sensory neural input. Six participants performed drop landings using a trapdoor system and landings from self-initiated counter-movement jumps in microgravity conditions simulated in a weightlessness environment by different pull-down forces of 1-, 0.6-, 0.4-, and 0.2 g. External forces applied to the body, orientation of the lower limb segments, and muscular activity of 6 lower limb muscles were recorded synchronously. Our results show that 1) subjects are able to land and stabilize in all experimental conditions; 2) prelanding muscular activity is always present, emphasizing the capacity of the central nervous system to approximate the instant of touchdown; 3) the kinetics and muscular activity are adjusted to the amount of energy gained during the fall; 4) the control of landing seems less finely controlled in drop landings as suggested by higher impact forces and loading rates, plus lower mechanical work done during landing for a given amount of energy to be dissipated. In conclusion, humans seem able to adapt the control of landing according to the amount of energy to be dissipated in an environment where sensory information is altered, even under conditions of non-self-initiated falls.

Motor control of landing from a countermovement jump in simulated microgravity

2016 ◽  
Vol 120 (10) ◽  
pp. 1230-1240 ◽  
Author(s):  
C. N. Gambelli ◽  
D. Theisen ◽  
P. A. Willems ◽  
B. Schepens
Keyword(s):  
Motor Control ◽  
Lower Limb ◽  
Muscular Activity ◽  
Damping Coefficient ◽  
Gravity Level ◽  
Countermovement Jump ◽  
Lower Limb Muscles ◽  
Limb Muscles ◽  
Stiffness And Damping Coefficient ◽  
Stiffness And Damping

Landing from a jump implies proper positioning of the lower limb segments and the generation of an adequate muscular force to cope with the imminent collision with the ground. This study assesses how a hypogravitational environment affects the control of landing after a countermovement jump (CMJ). Eight participants performed submaximal CMJs on Earth (1- g condition) and in a weightlessness environment with simulated gravity conditions generated by a pull-down force (1-, 0.6-, 0.4-, and 0.2- g0 conditions). External forces applied to the body, movements of the lower limb segments, and muscular activity of six lower limb muscles were recorded. 1) All subjects were able to jump and stabilize their landing in all experimental conditions, except one subject in 0.2- g0 condition. 2) The mechanical behavior of lower limb muscles switches during landing from a stiff spring to a compliant spring associated with a damper. This is true whatever the environment, on Earth as well as in environments where sensory inputs are altered. 3) The motor control of landing in simulated 1 g0 reveals an increased “safety margin” strategy, illustrated by increased stiffness and damping coefficient compared with landing on Earth. 4) The motor command is adjusted to the task constraints: muscular activity of lower limb extensors and flexors, stiffness and damping coefficient decrease according to the decreased gravity level. Our results show that even if in daily living gravity can be perceived as a constant factor, subjects can cope with altered sensory signals, taking advantage of the remaining information (visual and/or decreased proprioceptive inputs).

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 Electromyographic Assessment of the Lower Leg Muscles during Concentric and Eccentric Phases of Standing Heel Raise

Healthcare ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 465
Author(s):  
Ukadike C. Ugbolue ◽  
Emma L. Yates ◽  
Kerensa Ferguson ◽  
Scott C. Wearing ◽  
Yaodong Gu ◽  
...  
Keyword(s):  
Lower Limb ◽  
Muscle Activation ◽  
Lower Limbs ◽  
Emg Activity ◽  
Neutral Position ◽  
Muscle Action ◽  
Gastrocnemius Medialis ◽  
Muscle Activation Patterns ◽  
Lower Limb Muscles ◽  
Limb Muscles

Only a small number of muscle activation patterns from lower limbs have been reported and simultaneous muscle activation from several lower limb muscles have not yet been investigated. The purpose of this study was to examine any gender differences in surface electromyography (EMG) activity from six recorded lower limb muscles of the dominant limb at baseline (i.e., with the foot placed flat on the floor and in the neutral position), and during concentric and eccentric phases when performing a heel raise task. In total, 10 females and 10 males performed a standing heel raise task comprising of three continuous phases: baseline, unloading (concentric muscle action), and loading (eccentric muscle action) phases. Muscle activation from six muscles (gastrocnemius medialis, gastrocnemius lateralis, soleus, tibialis anterior, peroneus longus, and peroneus brevis) were measured using the Myon 320 EMG System. Root mean squared values of each muscle were calculated for each phase. Descriptive and inferential statistics were incorporated into the study. Statistically significant p values were set at 0.05. The results showed no significant differences between baseline, concentric, and eccentric phases with respect to each of the muscles investigated. Except for the gastrocnemius medialis at baseline and concentric phases, no significant differences were observed between genders or contractions. The data suggests that gender does not significantly influence the eccentric phase during the standing heel raise task.

EMG Activity of Lower Limb Muscles During Leg Press Adopting Different Methods of Knee Stabilization

2015 ◽  
Vol 47 ◽  
pp. 356
Author(s):  
CLAUDIO M. BENTES ◽  
Wallace Machado ◽  
Gabriel A. Paz ◽  
Marianna F. Maia ◽  
Vicente P. Lima ◽  
...  
Keyword(s):  
Lower Limb ◽  
Emg Activity ◽  
Leg Press ◽  
Lower Limb Muscles ◽  
Limb Muscles

Multimodality intraoperative monitoring during complex lumbosacral procedures: indications, techniques, and long-term follow-up review of 61 consecutive cases

2004 ◽  
Vol 1 (3) ◽  
pp. 243-253 ◽  
Author(s):  
Andrei V. Krassioukov ◽  
Roger Sarjeant ◽  
Homan Arkia ◽  
Michael G. Fehlings
Keyword(s):  
Lower Extremity ◽  
Lower Limb ◽  
Emg Activity ◽  
Content Type ◽  
Lower Limb Muscles ◽  
Limb Muscles ◽  
Long Term Follow Up ◽  
Fine Print

Object. The purpose of this study was to examine the neurological outcomes after complex lumbosacral surgery in patients undergoing multimodality neurophysiological monitoring. Methods. Sixty-one patients were consecutively enrolled in this study. These patients underwent complex intra- and extradural lumbosacral procedures with concomitant intraoperative electromyography (EMG) monitoring of the lower-limb muscles, external anal and urethral sphincters (EAS and EUS), and lower-limb somatosensory evoked potentials (SSEPs). Long-term (minimum 2-year) clinical follow-up data were obtained in all cases. Most patients were treated for spinal/spinal cord tumors (61%) or adult tethered cord syndrome (25%). Recordable lower-extremity SSEPs were reported in 54 patients (89%). New postoperative neurological deficits occurred in only three patients (4.9%), and remained persistent in only one patient (1.6%) at long-term follow-up examination. In only one of these cases was a significant decrease in SSEP amplitude detected. Spontaneous EMG activity was observed in the lower-extremity muscles and/or EAS and EUS in 51 cases (84%). Intraoperatively, EMG demonstrated activity only in the EUS in 5% of patients and only in the EAS in 28%. In seven patients (11%) spontaneous intraoperative EMG activity was observed in both the EAS and the EUS; however, in only three of these cases was EMG activity recorded in both sphincters simultaneously. In addition to spontaneously recorded EMG activity, electrically evoked EMG activity was also used as an intraoperative adjunct. A bipolar stimulating electrode was used to identify functional neural tissue before undertaking microsurgical dissection in 58 individuals (95%). In the majority of these patients, evoked EMG activity occurred either in one (33%) or in two muscles (9%) simultaneously. The presence of electrically evoked EMG activity in structures encountered during microdissection altered the plan of treatment in 24 cases (42%). Conclusions. The authors conclude that the combined SSEP and EMG monitoring of lower-limb muscles, EAS, and EUS is a practical and reliable method for obtaining optimal electrophysiological feedback during complex neurosurgical procedures involving the conus medullaris and cauda equina. Analysis of the results indicates that these intraoperative adjunctive modalities positively influence decision making with regard to microsurgery and reduce the risk of perioperative neurological complications. Validation of the clinical value of these approaches, however, will require further assessment in a larger prospective cohort of patients.

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