scholarly journals El impacto inicial con antepié incrementa la actividad muscular del gastrocnemios durante la carrera. Un estudio cuantitativo de actividad electromiográfica (The initial impact with forefoot increases the muscular activity of gastrocnemius during running)

Retos ◽  
2020 ◽  
pp. 271-275
Author(s):  
Oscar Valencia ◽  
Iver Cristi ◽  
Dario Ahumada ◽  
Keiny Meza ◽  
Rodrigo Salas ◽  
...  
Keyword(s):  
Lower Limb ◽  
Stance Phase ◽  
Maximum Voluntary Contraction ◽  
Neuromuscular Control ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Myoelectric Activity ◽  
Initial Contact ◽  
Limb Injuries

Un importante porcentaje de las lesiones de miembros inferiores ha sido vinculado a la técnica de carrera, en particular, al contacto inicial con retropié (RP) o antepié (AP). Sin embargo, existe limitada evidencia de la actividad electromiográfica (EMG) para ambas condiciones. El objetivo de este estudio fue comparar la amplitud EMG en miembros inferiores al utilizar técnicas de RP vs AP durante la carrera. Trece corredores fueron evaluado a una velocidad de trote autoseleccionada en dos condiciones: contacto inicial con RP y AP. Se registró la actividad mioeléctrica del recto femoral (RF), bíceps femoral (BF), tibial anterior (TA), gastrocnemio medial (GM) y lateral (GL). Se consideró la amplitud promedio de la EMG en 10 ciclos de carrera, normalizados a la contracción voluntaria máxima. Los resultados destacan una mayor activación significativa de los músculos GM y GL en el contacto AP durante la fase de apoyo, balanceo y en todo el ciclo de carrera. Adicionalmente, el TA presentó una mayor activación durante la fase de vuelo y el 100% del ciclo de carrera para la condición RP. No se encontraron otras diferencias significativas. En conclusión, el uso de la técnica AP incrementa la actividad muscular de GM y GL, posiblemente asociado a una mayor absorción del impacto durante la fase de apoyo. Por otro lado, el TA incrementa su actividad con RP, lo que podría implicar un mayor control previo al contacto inicial. La técnica de carrera se presenta como una condición modificable según situaciones de rendimiento o patología.Abstract. Running technique has an impact on lower limb injuries, particularly the initial contact pattern such as rearfoot (RF) or forefoot (FF). However, there is limited evidence of the electromyographic (EMG) activity for both conditions. The aim of this study was to compare the lower limb muscles EMG amplitude between RF and FF techniques during running. Thirteen runners were evaluated at a self-selected running speed under two conditions: initial contact with RF and FF. The myoelectric activity of the rectus femoris (RE), biceps femoris (BF), tibialis anterior (TA), medial gastrocnemius (GM) and lateral (GL) were analysed. The EMG amplitudes of 10 running cycles were averaged and normalized to the maximum voluntary contraction. The results included a significantly higher activation of GM and GL muscles for the FF condition during the stance phase, balance and the entire running cycle. In addition, TA showed higher activation during the swing phase and the 100% running cycle for the RP condition. No other significant differences were found. In conclusion, FF technique increases GM and GL myoelectric activity, possibly associated with a higher impact absorption during the stance phase. On the other hand, TA increases its activity for RF condition which may imply a greater neuromuscular control prior to initial contact. Finally, the running technique is presented as a modifiable condition which can be changed to enhance performance or in pathologic circumstances.

scholarly journals Forced Use of the Paretic Leg Induced by a Constraint Force Applied to the Nonparetic Leg in Individuals Poststroke During Walking

2017 ◽  
Vol 31 (12) ◽  
pp. 1042-1052 ◽  
Author(s):  
Chao-Jung Hsu ◽  
Janis Kim ◽  
Elliot J. Roth ◽  
William Z. Rymer ◽  
Ming Wu
Keyword(s):  
Maximum Voluntary Contraction ◽  
Gait Pattern ◽  
Swing Phase ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Resistance Force ◽  
Constraint Force ◽  
Gait Parameters ◽  
Integrated Emg

Background. Individuals with stroke usually show reduced muscle activities of the paretic leg and asymmetrical gait pattern during walking. Objective. To determine whether applying a resistance force to the nonparetic leg would enhance the muscle activities of the paretic leg and improve the symmetry of spatiotemporal gait parameters in individuals with poststroke hemiparesis. Methods. Fifteen individuals with chronic poststroke hemiparesis participated in this study. A controlled resistance force was applied to the nonparetic leg using a customized cable-driven robotic system while subjects walked on a treadmill. Subjects completed 2 test sections with the resistance force applied at different phases of gait (ie, early and late swing phases) and different magnitudes (10%, 20%, and 30% of maximum voluntary contraction [MVC] of nonparetic leg hip flexors). Electromyographic (EMG) activity of the muscles of the paretic leg and spatiotemporal gait parameters were collected. Results. Significant increases in integrated EMG of medial gastrocnemius, medial hamstrings, vastus medialis, and tibialis anterior of the paretic leg were observed when the resistance was applied during the early swing phase of the nonparetic leg, compared with baseline. Additionally, resistance with 30% of MVC induced the greatest level of muscle activity than that with 10% or 20% of MVC. The symmetry index of gait parameters also improved with resistance applied during the early swing phase. Conclusion. Applying a controlled resistance force to the nonparetic leg during early swing phase may induce forced use on the paretic leg and improve the spatiotemporal symmetry of gait in individuals with poststroke hemiparesis.

Reflex Inhibition of Normal Cramp Following Electrical Stimulation of the Muscle Tendon

2007 ◽  
Vol 98 (3) ◽  
pp. 1102-1107 ◽  
Author(s):  
Serajul I. Khan ◽  
John A. Burne
Keyword(s):  
Electrical Stimulation ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Muscle Cramp ◽  
Emg Activity ◽  
Reflex Inhibition ◽  
Experimental Conditions ◽  
Inhibitory Feedback ◽  
Two Phases ◽  
Stimulation Of

Muscle cramp was induced in one head of the gastrocnemius muscle (GA) in eight of thirteen subjects using maximum voluntary contraction when the muscle was in the shortened position. Cramp in GA was painful, involuntary, and localized. Induction of cramp was indicated by the presence of electromyographic (EMG) activity in one head of GA while the other head remained silent. In all cramping subjects, reflex inhibition of cramp electrical activity was observed following Achilles tendon electrical stimulation and they all reported subjective relief of cramp. Thus muscle cramp can be inhibited by stimulation of tendon afferents in the cramped muscle. When the inhibition of cramp-generated EMG and voluntary EMG was compared at similar mean EMG levels, the area and timing of the two phases of inhibition (I1, I2) did not differ significantly. This strongly suggests that the same reflex pathway was the source of the inhibition in both cases. Thus the cramp-generated EMG is also likely to be driven by spinal synaptic input to the motorneurons. We have found that the muscle conditions that appear necessary to facilitate cramp, a near to maximal contraction of the shortened muscle, are also the conditions that render the inhibition generated by tendon afferents ineffective. When the strength of tendon inhibition in cramping subjects was compared with that in subjects that failed to cramp, it was found to be significantly weaker under the same experimental conditions. It is likely that reduced inhibitory feedback from tendon afferents has an important role in generating cramp.

Effects of Experience on Gymnasts’ Kinematics and Performances

2021 ◽  
Vol 65 (1) ◽  
pp. 1280-1285
Author(s):  
Courtney Middelcoop ◽  
Colten Fales ◽  
Richard T. Stone ◽  
Joseph Kim ◽  
Kristina Schaffhausen ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Maximum Voluntary Contraction ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Voluntary Contraction ◽  
Initial Contact ◽  
Sweet Spot ◽  
Contact Phase ◽  
Consistent Performance ◽  
And Performance

In studying the effects of expertise on different performance aspects of the gymnastic vault event, various springboard types with similar compression forces were evaluated between expert and novice-level gymnasts. Surface EMGs (sEMG) were placed on four major muscles (biceps femoris, rectus femoris, gastrocnemius medialis, and tibialis anterior) to find each gymnasts’ maximum voluntary contraction. Similarly, board compression and knee flexion angles were also captured at various phases of the performed vaults. Given that gymnasts with more expertise were more consistent in their landing spot on the various vault boards, they had more consistent performance outputs as a result. Expert gymnasts did this by more accurately hitting the sweet spot, more consistently activating their hamstring and gastrocnemius, and decreasing variability during the initial contact phase. By doing this, board compression and performance were both optimized. Coaches can use this information to accelerate the development of novice gymnasts by targeting these aspects.

Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures

2003 ◽  
Vol 95 (4) ◽  
pp. 1515-1522 ◽  
Author(s):  
L Rochette ◽  
S. K. Hunter ◽  
N Place ◽  
R Lepers
Keyword(s):  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Task Failure ◽  
Rate Of Increase ◽  
Extensor Muscles ◽  
Seated Posture ◽  
Knee Extensor Muscles

Ten young men sustained an isometric contraction of the knee extensor muscles at 20% of the maximum voluntary contraction (MVC) torque on three separate occasions in a seated posture. Subjects performed an isometric knee extension contraction on a fourth occasion in a supine posture. The time to task failure for the seated posture was similar across sessions (291 ± 84 s; P > 0.05), and the MVC torque was similarly reduced across sessions after the fatiguing contraction (42 ± 12%). The rate of increase in electromyograph (EMG) activity (%MVC) and torque fluctuations during the fatiguing contractions were similar across sessions. However, the rate of increase in EMG differed among the knee extensor muscles: the rectus femoris began at a greater amplitude (31.5 ± 11.0%) compared with the vastus lateralis and vastus medialis muscles (18.8 ± 5.3%), but it ended at a similar value (45.4 ± 3.1%). The time to task failure and increase in EMG activity were similar for the seated and supine tasks; however, the reduction in MVC torque was greater for the seated posture. These findings indicate that the time to task failure for the knee extensor muscles that have a common tendon insertion did not alter over repeat sessions as had been observed for the elbow flexor muscles (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003).

scholarly journals Individuals with medial knee osteoarthritis show neuromuscular adaptation when perturbed during walking despite functional and structural impairments

2014 ◽  
Vol 116 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Deepak Kumar ◽  
Charles (Buz) Swanik ◽  
Darcy S. Reisman ◽  
Katherine S. Rudolph
Keyword(s):  
Knee Osteoarthritis ◽  
Muscle Activation ◽  
Weight Bearing ◽  
Joint Space Width ◽  
Neuromuscular Control ◽  
Emg Activity ◽  
Initial Contact ◽  
Knee Motion ◽  
Quadriceps Weakness ◽  
Knee Oa

Neuromuscular control relies on sensory feedback that influences responses to changing external demands, and the normal response is for movement and muscle activation patterns to adapt to repeated perturbations. People with knee osteoarthritis (OA) are known to have pain, quadriceps weakness, and neuromotor deficits that could affect adaption to external perturbations. The aim of this study was to analyze neuromotor adaptation during walking in people with knee OA ( n = 38) and controls ( n = 23). Disability, quadriceps strength, joint space width, malalignment, and proprioception were assessed. Kinematic and EMG data were collected during undisturbed walking and during perturbations that caused lateral translation of the foot at initial contact. Knee excursions and EMG magnitudes were analyzed. Subjects with OA walked with less knee motion and higher muscle activation and had greater pain, limitations in function, quadriceps weakness, and malalignment, but no difference was observed in proprioception. Both groups showed increased EMG and decreased knee motion in response to the first perturbation, followed by progressively decreased EMG activity and increased knee motion during midstance over the first five perturbations, but no group differences were observed. Over 30 trials, EMG levels returned to those of normal walking. The results illustrate that people with knee OA respond similarly to healthy individuals when exposed to challenging perturbations during functional weight-bearing activities despite structural, functional, and neuromotor impairments. Mechanisms underlying the adaptive response in people with knee OA need further study.

Effect of prosthetic ankle units on the gait of persons with bilateral trans-femoral amputations

2008 ◽  
Vol 32 (1) ◽  
pp. 111-126 ◽  
Author(s):  
Lexyne L. McNealy ◽  
Steven A. Gard
Keyword(s):  
Power Generation ◽  
Range Of Motion ◽  
Ankle Joint ◽  
Lower Limb ◽  
Stance Phase ◽  
Sagittal Plane ◽  
The Body ◽  
Control Group ◽  
Initial Contact ◽  
Ankle Motion

In able-bodied individuals, the ankle joint functions to provide shock absorption, aid in foot clearance during the swing phase, and provides a rocker mechanism during stance phase to facilitate forward progression of the body. Prosthetic ankles currently used by persons with lower limb amputations provide considerably less function than their anatomical counterparts. However, increased ankle motion in the sagittal plane may improve the gait of persons with lower limb amputations while providing a more versatile prosthesis. The primary aim of this study was to examine and quantify temporal-spatial, kinematic, and kinetic changes in the gait of four male subjects with bilateral trans-femoral amputations who walked with and without prosthetic ankle units. Two prosthesis configurations were examined: (i) Baseline with only two Seattle LightFoot2 prosthetic feet, and (ii) with the addition of Endolite Multiflex Ankle units. Data from the gait analyses were compared between prosthetic configurations and with a control group of able-bodied subjects. The amputee subjects' freely-selected walking speeds, 0.74 ± 0.19 m/s for the Baseline condition and 0.81 ± 0.15 m/s with the ankle units, were much less than that of the control subjects (1.35 ± 0.10 m/s). The amputee subjects demonstrated no difference in walking speed, step length, cadence, or ankle, knee, and hip joint moments and powers between the two prosthesis configurations. Sagittal plane ankle range of motion, however, increased by 3–8° with the addition of the prosthetic ankle units. Compared to the control group, following initial contact the amputee subjects passively increased the rate of energy storage or dissipation at the prosthetic ankle joint, actively increased the power generation at the hip, and increased the extension moment at the hip while wearing the prosthetic ankle configuration. The amputee subjects increased the power generation at their hips, possibly as compensation for the reduced rate of energy return at their prosthetic ankles. Results from subject questionnaires administered following the gait analyses revealed that the prosthetic ankle units provided more comfort during gait and did not increase the perceived effort to walk. The subjects also indicated that they preferred walking with the prosthetic ankle units compared to the Baseline configuration. The results of the study showed that the prosthetic ankle units improved sagittal plane ankle range of motion and increased the comfort and functionality of the amputee subjects’ prostheses by restoring a significant portion of the ankle rocker mechanism during stance phase. Therefore, prosthetic ankle mechanisms should be considered a worthwhile option when prostheses are prescribed for persons with trans-femoral amputations.

Sensorimotor adaptations to microgravity in humans

2001 ◽  
Vol 204 (18) ◽  
pp. 3217-3224
Author(s):  
V. R. Edgerton ◽  
G. E. McCall ◽  
J. A. Hodgson ◽  
J. Gotto ◽  
C. Goulet ◽  
...  
Keyword(s):  
Space Flight ◽  
Neural Control ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Motor Tasks ◽  
Extensor Muscles ◽  
The Individual ◽  
Consistent Response ◽  
Ankle Dorsiflexor

SUMMARY Motor function is altered by microgravity, but little detail is available as to what these changes are and how changes in the individual components of the sensorimotor system affect the control of movement. Further, there is little information on whether the changes in motor performance reflect immediate or chronic adaptations to changing gravitational environments. To determine the effects of microgravity on the neural control properties of selected motor pools, four male astronauts from the NASA STS-78 mission performed motor tasks requiring the maintenance of either ankle dorsiflexor or plantarflexor torque. Torques of 10 or 50% of a maximal voluntary contraction (MVC) were requested of the subjects during 10° peak-to-peak sinusoidal movements at 0.5Hz. When 10% MVC of the plantarflexors was requested, the actual torques generated in-flight were similar to pre-flight values. Post-flight torques were higher than pre- and in-flight torques. The actual torques when 50% MVC was requested were higher in- and post-flight than pre-flight. Soleus (Sol) electromyographic (EMG) amplitudes during plantarflexion were higher in-flight than pre- or post-flight for both the 10 and 50% MVC tasks. No differences in medial gastrocnemius (MG) EMG amplitudes were observed for either the 10 or 50% MVC tasks. The EMG amplitudes of the tibialis anterior (TA), an antagonist to plantarflexion, were higher in- and post-flight than pre-flight for the 50% MVC task. During the dorsiflexion tasks, the torques generated in both the 10 and 50% MVC tasks did not differ pre-, in- and post-flight. TA EMG amplitudes were significantly higher in- than pre-flight for both the 10 or 50% MVC tasks, and remained elevated post-flight for the 50% MVC test. Both the Sol and MG EMG amplitudes were significantly higher in-flight than either pre- or post-flight for both the 10 and 50% MVC tests. These data suggest that the most consistent response to space flight was an elevation in the level of contractions of agonists and antagonists when attempting to maintain constant torques at a given level of MVC. Also, the chronic levels of EMG activity in selected ankle flexor and extensor muscles during space flight and during routine activities on Earth were recorded. Compared with pre- and post-flight values, there was a marked increase in the total EMG activity of the TA and the Sol and no change in the MG EMG activity in-flight. These data indicate that space flight, as occurs on shuttle missions, is a model of elevated activation of both flexor and extensor muscles, probably reflecting the effects of programmed work schedules in flight rather than a direct effect of microgravity.

scholarly journals External torque as a factor to modify load in abdominal curl-up exercises

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Alicja Rutkowska-Kucharska ◽  
Agnieszka Szpala
Keyword(s):  
External Force ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Electromyographic Activity ◽  
Upper Limbs ◽  
External Torque ◽  
Lever Arm ◽  
Emg Signal ◽  
Ca 50

SummaryStudy aim: the aim of our study was to evaluate electromyography (EMG) activity in exercises where the load to the muscles is determined by the external torque. In a part of the exercises, we changed the value of the external force, while in the other we modified the length of the lever arm at which the force was applied.Material and methods: the study was carried out on a group of 12 subjects (21 ± 2 years, 61 ± 4.8 mass, 172 ± 5 cm height). Electromyographic activity of the rectus abdominis (RA) muscle was evaluated by recording the EMG signal. The length of the lever arm of the external force was changed by using four different positions of the upper limbs, whereas the magnitude of the external force was changed through adding the weights of 0.5, 1.0, and 1.5 kg. The data recorded were normalized with respect to EMG activity measured under maximum voluntary contraction (MVC) conditions.Results: it was found that the change of the lever arm at which the force was applied (any change in the position of the upper limbs) causes a change in EMG activity in each part of the RA muscle from ca. 50% to ca. 100% MVC (p < 0.001). Further, the change in the external load changes statistically significantly the EMG activity only in the left upper part of the RA muscle (p < 0.05).Conclusions: activity in the RA muscle that increased for longer lever arms of the external force, offers opportunities for changing the load used during the exercise in a manner that is safe for the vertebral column.

scholarly journals Effect of kinesio taping in myoelectric activity in patients with shoulder impingement

2020 ◽  
pp. 1-7
Author(s):  
William Dhein ◽  
Marcelo La Torre ◽  
And Jefferson Fagundes Loss
Keyword(s):  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
The Body ◽  
Wilcoxon Test ◽  
Shoulder Abduction ◽  
Myoelectric Activity ◽  
Kinesio Taping ◽  
Upper Trapezius ◽  
Occupational Activities ◽  
Impact Syndrome

Introduction: The complex shoulder joint is equipped with the greater joint mobility of the body, however, is commonly injured in repetitive, sport or occupational activities. Shoulder Impact Syndrome (SIS) is one of the most common injuries affecting the shoulder, thus causing limitations in its functionality. Several strategies have been used by physiotherapy for prevention and rehabilitation of SIS, one of them is the Kinesio Taping (KT). However, even with its abundant use there is still no clear evidence of its benefits. Objective: The aim of the study was to examine the effect of KT on myoelectric activity and the level of pain in patients with SIS. Method: Seven women with SIS participated, which performed the flexion and shoulder abduction up to 90° with and without KT. During the gestures, the pain level and surface electromyography data of the upper trapezoid, middle deltoid and anterior serratus were acquired. The treatment of the electromyography data was performed in the BIOMEC-SAS software and presented as percentage values of the maximum voluntary contraction. To compare the myoelectric activity and pain levels, it was performed, respectively, one way ANOVA and the Wilcoxon test (α <0.05). Results: Pain reductions were observed and myoelectric activity of upper trapezius (46.0±34.4% MVIC to 35.6 ± 19.5% MVIC) and middle deltoid (39.0±11.5% MVIC to 35.2±12.5% MVIC) in motion abduction use of KT. No changes were observed in the signs during flexion movement. Conclusion: Finally, the KT generated a reduction in the level of pain and myoelectric activity of the middle deltoid and upper trapezius in the movement of abduction in patients with SIS.

scholarly journals Influence of static stretching on viscoelastic properties of human tendon structures in vivo

2001 ◽  
Vol 90 (2) ◽  
pp. 520-527 ◽  
Author(s):  
Keitaro Kubo ◽  
Hiroaki Kanehisa ◽  
Yasuo Kawakami ◽  
Tetsuo Fukunaga
Keyword(s):  
Viscoelastic Properties ◽  
Plantar Flexion ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Static Stretching ◽  
Tendon Elongation ◽  
Before And After ◽  
Human Tendon

The purpose of this study was to investigate the influences of static stretching on the viscoelastic properties of human tendon structures in vivo. Seven male subjects performed static stretching in which the ankle was passively flexed to 35° of dorsiflexion and remained stationary for 10 min. Before and after the stretching, the elongation of the tendon and aponeurosis of medial gastrocnemius muscle (MG) was directly measured by ultrasonography while the subjects performed ramp isometric plantar flexion up to the maximum voluntary contraction (MVC), followed by a ramp relaxation. The relationship between the estimated muscle force (Fm) of MG and tendon elongation ( L) during the ascending phase was fitted to a linear regression, the slope of which was defined as stiffness of the tendon structures. The percentage of the area within the Fm- L loop to the area beneath the curve during the ascending phase was calculated as an index representing hysteresis. Stretching produced no significant change in MVC but significantly decreased stiffness and hysteresis from 22.9 ± 5.8 to 20.6 ± 4.6 N/mm and from 20.6 ± 8.8 to 13.5 ± 7.6%, respectively. The present results suggest that stretching decreased the viscosity of tendon structures but increased the elasticity.

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