What Does EMC Tell Us about Muscle Function?

Motor Control ◽  
1999 ◽  
Vol 3 (1) ◽  
pp. 9-11 ◽  
Author(s):  
Stan C.A.M. Gielen
Keyword(s):  
Muscle Function ◽  
Muscle Force ◽  
Motor Units ◽  
Contractile Properties ◽  
Emg Activity ◽  
Motor Tasks ◽  
Muscle Properties

EMG recordings are frequently used to obtain a better understanding in the coordination of movements. However, EMG activity is made up by the weighted summation of activity of many motor units with different contractile properties. Recent studies have revealed that different motor units contribute to muscle force in different motor tasks. The flexible recruitment of motor units with various contractile properties allows a flexible tuning of muscle properties, but also complicates the interpretation of EMG activity.

Motor-unit properties following cross-reinnervation of cat lateral gastrocnemius and soleus muscles with medial gastrocnemius nerve. I. Influence of motoneurons on muscle

1987 ◽  
Vol 57 (4) ◽  
pp. 1210-1226 ◽  
Author(s):  
R. C. Foehring ◽  
G. W. Sypert ◽  
J. B. Munson
Keyword(s):  
Motor Unit ◽  
Muscle Fibers ◽  
Motor Units ◽  
Contractile Properties ◽  
Medial Gastrocnemius ◽  
Similar Degree ◽  
Muscle Properties ◽  
Lateral Gastrocnemius ◽  
Type Distribution ◽  
Unit Type

This study addresses two questions: is reinnervation of mammalian skeletal muscle selective with respect to motor-unit type? And to what degree may muscle-unit contractile properties be determined by the motoneuron? Properties of individual motor units were examined following cross-reinnervation (X-reinnervation) of lateral gastrocnemius (LG) and soleus muscles by the medial gastrocnemius (MG) nerve in the cat. We examined animals at two postoperative times: 9-10 wk (medX) and 9-11 mo (longX). For comparison, properties of normal LG and soleus motor units were studied. Motor units were classified on the basis of their contractile response as fast contracting fatigable, fast intermediate, fast contracting fatigue resistant, or slow (types FF, FI, FR, or S, respectively) (13,29). Muscle fibers were classified on the basis of histochemical properties as fast glycolytic, fast oxidative glycolytic, or slow oxidative (types FG, FOG, or SO, respectively) (61). Reinnervation of LG and soleus was not selective with respect to motor-unit type. Both muscles were innervated by a full complement of MG motoneuron types, apparently in normal MG proportions. MG motoneurons determined LG muscle fibers' properties to a similar degree as reinnervated MG muscle fibers. In contrast, soleus muscle fibers "resisted" the influence of MG motoneurons. Thus, although longX-reinnervated LG muscle (longX LG) had a motor-unit type distribution similar to normal or self-reinnervated MG, longX soleus contained predominantly type S motor units. Overall mean values for muscle-unit contractile properties reflected this motor-unit type distribution. Muscle units in longX LG and longX soleus had contractile properties typical of the same motor-unit type in normal LG or soleus, respectively. Motor-unit types were recognizable at 10 wk X-reinnervation, although muscle-unit tensions were lower than after 10 mo. The proportions of fast and slow motor units in medX LG were similar to longX LG, although a greater proportion of fast units were resistant to fatigue at 10 wk. There were fewer fast units in medX soleus than longX soleus, which suggested that motor-unit type conversion or innervation of muscle fibers by fast motoneurons is not complete at 10 wk. We conclude that reinnervation of the LG and soleus muscles by MG motoneurons was not selective with respect to motor-unit type. MG motoneurons determined LG muscle properties to a similar degree as self-reinnervated MG muscle fibers. Soleus muscle fibers resisted the influence of MG motoneurons, representing a limit to neural determination of muscle properties.

scholarly journals Clinical Effects of Theophylline on Inspiratory Muscle Drive in Tetraplegia

1999 ◽  
Vol 13 (3) ◽  
pp. 191-197 ◽  
Author(s):  
Gary T. Ferguson ◽  
Narendra Khanchandani ◽  
Chris D. Lattin ◽  
Harry G. Goshgarian
Keyword(s):  
Spinal Cord ◽  
Muscle Function ◽  
Muscle Force ◽  
Cervical Spinal Cord ◽  
Inspiratory Muscle ◽  
Emg Activity ◽  
Neural Activation ◽  
Clinical Effects ◽  
Respiratory Drive ◽  
Before And After

Theophylline has been shown to restore diaphragmatic function in animals following cervical spinal cord hemisection, which induces hemidiaphragm paralysis. Although theophylline had been used clinically in the treatment of various pulmonary diseases, its effects on respiratory muscle function in cervical spinal cord injured tetraplegics has not been studied. In the present case study, we evaluated a patient injured in 1979 with a chronic asymmetric C5-7 tetraplegia (left C5-6, right C6-7) before and after receiving theophylline chronically by mouth for three weeks and again before and after receiving acute intravenous (IV) aminophylline after the effects of the chronic drug administration wore off. Neural activation to inspiratory muscles was assessed by right and left parasternal intercostal and diaphragm EMGs during quiet breathing and max imal inspiratory efforts. Global respiratory drive was assessed by P100, and inspiratory muscle force was assessed by maximal inspiratory pressures and vital capacity. Both long-term orally administered and acute IV theophylline increased neural activation to the diaphragm, especially on the more affected left side. Theophylline treatment was also associated with an increase in global central respiratory drive and inspiratory muscle force, without changing expiratory airflows. Left diaphragm EMG activity was markedly increased following the administration of theophylline. Of interest, upper parasternal intercostal EMG activity was also recruited on the left in spite of being below the level of cervical injury. We speculate that the administration of theophylline in selected patients with an asymmetric cervical spinal cord injury may activate la tent bulbospinal respiratory pathways and improve inspiratory muscle function, re ducing the likelihood of associated respiratory failure.

scholarly journals Physiological tremor reveals how thixotropy adapts skeletal muscle for posture and movement

2016 ◽  
Vol 3 (5) ◽  
pp. 160065 ◽  
Author(s):  
Carlijn A. Vernooij ◽  
Raymond F. Reynolds ◽  
Martin Lakie
Keyword(s):  
Skeletal Muscles ◽  
Muscle Force ◽  
Motor Units ◽  
Movement Speed ◽  
Physiological Tremor ◽  
Muscle Properties ◽  
Naturally Occurring ◽  
Neural Input ◽  
The Subject ◽  
Smooth Transitions

People and animals can move freely, but they must also be able to stay still. How do skeletal muscles economically produce both movement and posture? Humans are well known to have motor units with relatively homogeneous mechanical properties. Thixotropic muscle properties can provide a solution by providing a temporary stiffening of all skeletal muscles in postural conditions. This stiffening is alleviated almost instantly when muscles start to move. In this paper, we probe this behaviour. We monitor both the neural input to a muscle, measured here as extensor muscle electromyography (EMG), and its output, measured as tremor (finger acceleration). Both signals were analysed continuously as the subject made smooth transitions between posture and movement. The results showed that there were marked changes in tremor which systematically increased in size and decreased in frequency as the subject moved faster. By contrast, the EMG changed little and reflected muscle force requirement rather than movement speed. The altered tremor reflects naturally occurring thixotropic changes in muscle behaviour. Our results suggest that physiological tremor provides useful and hitherto unrecognized insights into skeletal muscle's role in posture and movement.

scholarly journals A model of the rat medial gastrocnemius muscle based on inputs to motoneurons and on an algorithm for prediction of the motor unit force

2018 ◽  
Vol 120 (4) ◽  
pp. 1973-1987 ◽  
Author(s):  
R. Raikova ◽  
J. Celichowski ◽  
S. Angelova ◽  
P. Krutki
Keyword(s):  
Motor Unit ◽  
Input Data ◽  
Gastrocnemius Muscle ◽  
Muscle Force ◽  
Motor Units ◽  
Contractile Properties ◽  
Medial Gastrocnemius ◽  
Physiological Data ◽  
Excitation Signal ◽  
Medial Gastrocnemius Muscle

The muscle force is the sum of forces of multiple motor units (MUs), which have different contractile properties. During movements, MUs develop unfused tetani, which result from summation of twitch-shape responses to individual stimuli, which are variable in amplitude and duration. The aim of the study was to develop a realistic muscle model that would integrate previously developed models of MU contractions and an algorithm for the prediction of tetanic forces. The proposed model of rat medial gastrocnemius muscle is based on physiological data: excitability and firing frequencies of motoneurons, contractile properties, and the number and proportion of MUs in the muscle. The MU twitches were modeled by a six-parameter analytical function. The excitability of motoneurons was modeled according to a distribution of their rheobase currents measured experimentally. Processes of muscle force regulation were modeled according to a common drive hypothesis. The excitation signal to motoneurons was modeled by two form types: triangular and trapezoid. The discharge frequencies of MUs, calculated individually for each MU, corresponded to those recorded for rhythmic firing of motoneurons. The force of the muscle was calculated as the sum of all recruited MUs. Participation of the three types of MUs in the developed muscle force was presented at different levels of the excitation signal to motoneurons. The model appears highly realistic and open for input data from various skeletal muscles with different compositions of MU types. The results were compared with three other models with different distribution of the input parameters.NEW & NOTEWORTHY The proposed mathematical model of rat medial gastrocnemius muscle is highly realistic because it is based strictly on experimentally determined motor unit contractile parameters and motoneuron properties. It contains the actual number and proportion of motor units and takes into consideration their different contributions to the whole muscle force, depending on the level of the excitation signal. The model is open for input data from other muscles, and additional physiological parameters can also be included.

scholarly journals Effects of Diacutaneous Fibrolysis on Passive Neuromuscular Response and Mechanosensitivity in Athletes with Hamstring Shortening: A Randomized Controlled Trial

2021 ◽  
Vol 18 (12) ◽  
pp. 6554
Author(s):  
Aida Cadellans-Arróniz ◽  
Carlos López-de-Celis ◽  
Albert Pérez-Bellmunt ◽  
Jacobo Rodríguez-Sanz ◽  
Luis Llurda-Almuzara ◽  
...  
Keyword(s):  
Gluteus Maximus ◽  
Biceps Femoris ◽  
Post Treatment ◽  
Contractile Properties ◽  
Lower Limbs ◽  
Injury Incidence ◽  
Single Session ◽  
Muscle Properties ◽  
Neuromuscular Response ◽  
Control Limb

Introduction. Diacutaneous Fibrolysis is defined as specific instrumental intervention to normalize function in the musculoskeletal system. It is considered a treatment method for the mechanical alterations of the locomotor system, and it is widely used in sports for therapeutic and preventive purposes. Despite the clinical benefits observed in different musculoskeletal conditions, the action mechanism of diacutaneous fibrolysis remains uncertain. There are no studies evaluating the neuromuscular response on the posterior muscular chain of the lower extremity in athletes, where overload, stiffness, and injury incidence are high. Objective. To evaluate the immediate, and 30 min post treatment effects of a single diacutaneous fibrolysis session on passive neuromuscular response and mechanosensitibity on hamstring and gluteus in athletes with shortening. Design. A randomized within participant clinical trial. Methods. Sixty-six athletes with hamstring shortening were included (PKE < 160). The lower limbs were randomized between the experimental limb and control limb, regardless of dominance. A single session of diacutaneous fibrolysis was applied to the posterior gluteus maximus, biceps femoris, and semitendinosus of the experimental lower limb whereas the control limb was not treated. Viscoelastic muscle properties (myotonometry), contractile muscle properties (tensomiography), and mechanosensitivity (algometry) were tested before treatment (T0), after treatment (T1), and 30 min post treatment (T2). Results. Regarding viscoelastic properties, in the intra-group analysis we found statistically significant differences in the experimental limb at T1, decreasing muscle stiffness in gluteus maximus (p < 0.042), in biceps femoris (p < 0.001) and in semitendinosus (p < 0.032). We also observed statistically significant differences in Tone decrease (p < 0.011) and relaxation increase (p < 0.001) in biceps femoris. At T2, the decrease in stiffness in all tested muscles was maintained (p < 0.05). There were statistically significant inter-groups differences in stiffness on gluteus (p < 0.048) and biceps femoris (p < 0.019) and in tone on biceps femoris (p < 0.009) compared to the control limb. For contractile properties, we only found statistically significant differences on maximal radial displacement (Dm) in gluteus, both control and experimental at T2 (p < 0.05) and in biceps femoris control (p < 0.030). No changes were found in the mechanosensitivity. Conclusions. A single session of diacutaneous fibrolysis produces changes in some parameters related to viscoelasticity properties of the biceps femoris and gluteus. There were no changes on contractile properties on semitendinosus. Only small changes on the contractile properties on the gluteus maximus and biceps femoris were found. No effect was found on the mechanosensitivity of the posterior chain muscles in athletes with hamstring shortening.

Speech-Motor Equivalence in Aging Subjects

1987 ◽  
Vol 64 (2) ◽  
pp. 635-638 ◽  
Author(s):  
Michael P. Rastatter ◽  
Richard A. Mc Guire ◽  
Laurel Bushong ◽  
Michele Loposky
Keyword(s):  
Muscle Function ◽  
The Elderly ◽  
The Other ◽  
Elderly Subjects ◽  
Emg Activity ◽  
Facial Muscle ◽  
Motor Equivalence ◽  
Children And Young Adults ◽  
Masseter Muscles ◽  
Speech Motor

The peak amplitude of EMG activity was measured from the orbicularis oris superior (OOS), orbicularis oris inferior (OOI), and masseter muscles for three normal, geriatric women (range 70 to 75 yr.) and compared with prior data for a group of normal, 4- and 8-yr.-old children and young adults (range 21 to 29 yr.) The elderly groups' variability across the three muscles paralleled that of the 4-yr.-olds, suggesting that speech-motor equivalence returns to an earlier level of operation in aging speakers. Also, the elderly subjects evidenced reduced levels of average peak EMG activity as compared to those of the other groups. This finding was interpreted as reflecting a loss of general muscle function, a possible concomitant of facial muscle atrophy that accompanies advanced age.

Reflex responses in active muscles elicited by stimulation of low-threshold afferents from the human foot

1992 ◽  
Vol 67 (5) ◽  
pp. 1375-1384 ◽  
Author(s):  
A. M. Aniss ◽  
S. C. Gandevia ◽  
D. Burke
Keyword(s):  
Motor Units ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Onset Latency ◽  
Single Motor ◽  
Reflex Responses ◽  
Posterior Tibial ◽  
Single Motor Units ◽  
Low Threshold ◽  
Stimulation Of

1. Reflex responses were elicited in muscles that act at the ankle by electrical stimulation of low-threshold afferents from the foot in human subjects who were reclining supine. During steady voluntary contractions, stimulus trains (5 pulses at 300 Hz) were delivered at two intensities to the sural nerve (1.2-4.0 times sensory threshold) or to the posterior tibial nerve (1.1-3.0 times motor threshold for the intrinsic muscles of the foot). Electromyographic (EMG) recordings were made from tibialis anterior (TA), peroneus longus (PL), soleus (SOL), medial gastrocnemius (MG), and lateral gastrocnemius (LG) muscles by the use of intramuscular wire electrodes. 2. As assessed by averages of rectified EMG, stimulation of the sural or posterior tibial nerves at nonpainful levels evoked a complex oscillation with onset latencies as early as 40 ms and lasting up to 200 ms in each muscle. The most common initial responses in TA were a decrease in EMG activity at an onset latency of 54 ms for sural stimuli, and an increase at an onset latency of 49 ms for posterior tibial stimuli. The response of PL to stimulation of the two nerves began with a strong facilitation of 44 ms (sural) and 49 ms (posterior tibial). With SOL, stimulation of both nerves produced early inhibition beginning at 45 and 50 ms, respectively. With both LG and MG, sural stimuli produced an early facilitation at 52-53 ms. However, posterior tibial stimuli produced different initial responses in these two muscles: facilitation in LG at 50 ms and inhibition in MG at 51 ms. 3. Perstimulus time histograms of the discharge of 61 single motor units revealed generally similar reflex responses as in multiunit EMG. However, different reflex components were not equally apparent in the responses of different single motor units: an individual motor unit could respond slightly differently with a change in stimulus intensity or background contraction level. The multiunit EMG record represents a global average that does not necessarily depict the precise pattern of all motor units contributing to the average. 4. When subjects stood erect without support and with eyes closed, reflex patterns were seen only in active muscles, and the patterns were similar to those in the reclining posture. 5. It is concluded that afferents from mechanoreceptors in the sole of the foot have multisynaptic reflex connections with the motoneuron pools innervating the muscles that act at the ankle. When the muscles are active in standing or walking, cutaneous feedback may play a role in modulating motoneuron output and thereby contribute to stabilization of stance and gait.

EMG Changes in Human Thenar Motor Units With Force Potentiation and Fatigue

2006 ◽  
Vol 95 (3) ◽  
pp. 1518-1526 ◽  
Author(s):  
C. K. Thomas ◽  
R. S. Johansson ◽  
B. Bigland-Ritchie
Keyword(s):  
Motor Unit ◽  
Motor Units ◽  
Emg Activity ◽  
Single Motor Unit ◽  
Tetanic Force ◽  
Twitch Force ◽  
Emg Amplitude ◽  
Before And After ◽  
Induced Changes ◽  
Motor Unit Emg

Few studies have analyzed activity-induced changes in EMG activity in individual human motor units. We studied the changes in human thenar motor unit EMG that accompany the potentiation of twitch force and fatigue of tetanic force. Single motor unit EMG and force were recorded in healthy subjects in response to selective stimulation of their motor axons within the median nerve just above the elbow. Twitches were recorded before and after a series of pulse trains delivered at frequencies that varied between 5 and 100 Hz. This stimulation induced significant increases in EMG amplitude, duration, and area. However, in relative terms, all of these EMG changes were substantially smaller than the potentiation of twitch force. Another 2 min of stimulation (13 pulses at 40 Hz each second) induced additional potentiation of EMG amplitude, duration, and area, but the tetanic force from every unit declined. Thus activity-induced changes in human thenar motor unit EMG do not indicate the alterations in force or vice versa. These data suggest that different processes underlie the changes in EMG and force that occur during human thenar motor unit activity.

scholarly journals Geniohyoid muscle function in awake canines

2003 ◽  
Vol 95 (2) ◽  
pp. 810-817 ◽  
Author(s):  
M. Yokoba ◽  
H. G. Hawes ◽  
P. A. Easton
Keyword(s):  
Muscle Function ◽  
Breathing Pattern ◽  
Muscle Length ◽  
Upper Airway ◽  
Mechanical Action ◽  
Emg Activity ◽  
Airway Occlusion ◽  
Lateral Decubitus ◽  
The Right ◽  
Emg Electrodes

The geniohyoid (Genio) upper airway muscle shows phasic, inspiratory electrical activity in awake humans but no activity and lengthening in anesthetized cats. There is no information about the mechanical action of the Genio, including length and shortening, in any awake, nonanesthetized mammal during respiration (or swallowing). Therefore, we studied four canines, mean weight 28.8 kg, 1.5 days after Genio implantation with sonomicrometry transducers and bipolar electromyogram (EMG) electrodes. Awake recordings of breathing pattern, muscle length and shortening, and EMG activity were made with the animal in the right lateral decubitus position during quiet resting, CO2-stimulated breathing, inspiratory-resisted breathing (80 cmH2O · l-1 · s), and airway occlusion. Genio length and activity were also measured during swallowing, when it shortened, showing a 9.31% change from resting length, and its EMG activity increased 6.44 V. During resting breathing, there was no phasic Genio EMG activity at all, and Genio showed virtually no movement during inspiration. During CO2-stimulated breathing, Genio showed minimal lengthening of only 0.07% change from resting length, whereas phasic EMG activity was still absent. During inspiratory-resisted breathing and airway occlusion, Genio showed phasic EMG activity but still lengthened. We conclude that the Genio in awake, nonanesthetized canines shows active contraction and EMG activity only during swallowing. During quiet or stimulated breathing, Genio is electrically inactive with passive lengthening. Even against resistance, Genio is electrically active but still lengthens during inspiration.

Sign in / Sign up

Export Citation Format

Share Document