Muscles In Normal Subjects Research Articles

Effects of diagnostic occlusion on ocular alignment in normal subjects

Diagnostic occlusion is used in strabismus to examine the changes in the angle of squint after a period of disrupted fusion. The aim of the present study was to investigate the effect of diagnostic occlusion on ocular alignment in normal subjects without strabismus and other ocular motility related symptoms. Diagnostic occlusion of the non-dominant eye was applied to ten subjects for three days. In all cases a small horizontal deviation was seen in the primary position and in three cases also a small vertical deviation was noted. Diagnostic occlusion for seven days was applied in nine persons. Changes in alignment of approximately the same size as after three days of occlusion were seen. In both groups incomitances of ocular alignment were noted that indicate small muscle imbalances particularly in the oblique muscles of normal subjects that are easily compensated by normal motor fusion.

Myofascial trigger points show spontaneous needle EMG activity.

Monopolar needle electromyogram (EMG) was recorded simultaneously from trapezius myofascial trigger points (TrPs) and adjacent nontender fibers (non-TrPs) of the same muscle in normal subjects and in two patient groups, tension headache and fibromyalgia. Sustained spontaneous EMG activity was found in the 1-2 mm nidus of all TrPs, and was absent in non-TrPs. Mean EMG amplitude in the patient groups was significantly greater than in normals. The authors hypothesize that TrPs are caused by sympathetically activated intrafusal contractions.

Influence of Trunk Muscle Activity on Surface Electromyographic Recordings from Intercostal Muscles in Normal Subjects

The influence on surface electromyographic (EMG) recordings of intercostal muscle (IC) activity by contraction from serratus anterior (SA), the diaphragm (DIA) and external abdominus obliquus (EAO) was studied in five normal adults. The results demonstrate that during isometric contraction of any one muscle, there is always some activity recorded over the ICs. This is thought to be due in part to co-activation of muscles and also to cross-talk as the muscles examined are in close proximity and interdigitated with each other. This study highlights the problem of using surface electrodes for making EMG recordings of IC muscle activity as they may be influenced by activity from other trunk muscles. Due to the functional similarity and proximity of the ICs and the diaphragm, it is not possible to distinguish these two muscles with surface EMG. Therefore, it is more appropriate to refer to the EMG activity recorded from the lower intercostal spaces as respiratory muscle activity rather than IC muscle activity....

Amino acid metabolism in human subcutaneous adipose tissue in vivo

1. Arteriovenous differences for alanine, glutamate and glutamine were measured across subcutaneous adipose tissue and forearm muscle in normal subjects. 2. After an overnight fast, adipose tissue showed net production of alanine and glutamine and uptake of glutamate in each of 11 subjects. 3. In seven subjects, adipose tissue blood flow was measured and the measurements were continued for 6 h after eating a mixed meal. The pattern of amino acid metabolism across the adipose tissue was remarkably little disturbed after the meal, except for a short period of apparent uptake of alanine as the concentration of that amino acid rose. 4. The pattern of amino acid metabolism across adipose tissue was qualitatively similar to that across the forearm, although it differed quantitatively in that glutamate uptake was more prominent (compared with glutamine release) in the adipose tissue. 5. The rates of alanine and glutamine release observed suggest that adipose tissue may play a substantial role in the whole-body production of these amino acids.

Stretch reflex inhibition using electrical stimulation in normal subjects and subjects with spasticity

The effect of electricallys timulating the tibialis anterior muscle on the stretch reflex of the soleus muscle in normal subjects and subjects with spasticity is investigated. Stimulation of the tibialis anterior just prior to the onset of a mechanical disturbance, which causes a stretch in the soleus, inhibits the stretch reflex of the soleus in normal subjects and may inhibit clonus in subjects with spasticity.

On the Force of Flexors and Extensors of Trunk Muscles in Normal Subjects

On the Force of Flexors and Extensors of Trunk Muscles in Normal Subjects

Recording and physical characteristics of disposable concentric needle EMG electrodes

There is currently considerable interest in using disposable concentric needle (CN) electrodes for clinical electromyography (EMG). To determine how these electrodes compare with reusable CN electrodes, we have compared signals recorded by these two electrode types from the same muscle in normal subjects. We also made similar recordings with two groups of reusable electrodes. There was no difference in the features of motor unit action potentials (MUAPs) recorded by the two groups of reusable electrodes. Disposable electrodes performed satisfactorily in conventional EMG examination. However, compared to reusable electrodes, the disposable electrodes recorded MUAPs with smaller amplitude and area but with the same area:amplitude ratio and MUAP duration. The physical and electrical properties of the CNE groups were also investigated. Disposable electrodes had lower electrical resistance and greater capacitance than reusable electrodes when measurements were made in saline. Photomicrographs showed that the disposable electrodes had smaller recording surfaces and that the central wire was frequently eccentric in the cannula. The differences in electrical recording characteristics could be due to differences in the size of the recording surface, eccentric placement of the central wire in the cannula or differences in the metal used for the central wire. We conclude that electrical and physical testing may not predict the recording characteristics of needle electrodes. Electrophysiologic testing is necessary to determine how EMG signals recorded by new types of electrodes compare with those recorded by currently used electrodes.

Mirror movements studied in a patient with Klippel‐Feil syndrome.

1. Electromyographic (EMG) recordings have been made from upper limb muscles in a patient with well-defined congenital mirror movements occurring in association with Klippel-Feil syndrome and the results compared to those obtained in normal control subjects. 2. In the patient, liminal percutaneous electrical or magnetic brain stimulation applied over either hemisphere elicited bilateral and symmetrical short-latency muscle responses in relaxed intrinsic hand muscles. In the normal subjects unilateral brain stimulation only elicited contralateral muscle responses. 3. F response and H reflex studies for the patient's ulnar-supplied intrinsic hand muscles were normal. No crossed responses were recorded in the homologous muscles of the contralateral hand. 4. Scalp-recorded somatosensory-evoked responses following ulnar or median nerve stimulation were of normal latency and distribution in the patient. 5. In the patient, cross-correlation analysis of on-going single and multiunit needle EMGs recorded between muscles of left and right hands revealed a central peak in the cross-correlogram. No cross-correlogram peaks were found between left- and right-hand muscles in normal subjects. The magnitude and time course of the central peaks in the cross-correlograms constructed between the firing of motor units on opposite sides of the body in the patient were similar to those found in cross-correlograms constructed between the firing of motor units from muscles on the same side of the body in the patient and in normal subjects. 6. The magnitude of cross-correlogram peaks detected within a muscle and those detected between left and right homologous muscles showed a gradient in which the largest peaks were found in the intrinsic hand and forearm extensor muscles. The smallest peaks were observed in the forearm flexor muscles. No peaks were detected between left and right biceps brachii muscles. In intrinsic hand muscles, the size of the cross-correlogram peak detected between the EMGs of homologous muscle pairs was greater than that found for non-homologous muscle pairs. 7. Cutaneous reflex responses were recorded from first dorsal interosseous muscle following unilateral electrical stimulation of the digital nerves of the index finger. In the patient, this produced an early excitatory (E1) response on the stimulated side. Later excitatory (E2 and E3) responses, of approximately equal size and latency, were distributed bilaterally. In the normal subjects, reflex responses were confined to the stimulated side.(ABSTRACT TRUNCATED AT 400 WORDS)

Length-Tension Relations of the Masticatory Elevator Muscles in Normal Subjects and Pain Dysfunction Patients

Myofascial pain and dysfunction is the primary diagnosis in a large proportion of facial pain complaints. Myofascial disease can present in the form of trigger points, fibromyositis, myositis, muscle spasm, and muscle weakness. The purpose of this study is to research for quantifiable physiological differences between groups of normal subjects and myofascial pain dysfunction (MPD) patients. The first specific aim was to determine the opening of the jaw at which maximal isometric tension can be produced by the jaw closing muscles, with the hypothesis that this opening of maximal tension would be less for a group of MPD patients than for a group of normal subjects being tested. The second aim was to test the hypothesis that the maximal isometric bite forces for the two groups would differ. Patients with mandibular dysfunction are reported to have a lower maximal bite than normal subjects. Bite force was measured with the T-Scan system. An 80 micron horseshoe-shaped sensor connected to a dedicated IBM XT computer recorded the data. A self-contained printer produced the hard copy for later analysis. Vertical dimension or jaw opening was increased in 0.5-mm increments using double flat plane appliances standardized by the Relator. A MANOVA was used for statistical analysis of the data. MPD patients had significantly higher bite forces at 8.0, 8.5, 9, and 9.5 mm. Normal subjects had higher force values at 5.0 mm. There was no significant difference in mean maximal bite force between groups.

Median averaging of electromyographic motor unit action potentials: comparison with other techniques

A technique of extracting individual motor unit action potentials (MUAPs) from EMG signals by median averaging, a modification of an existing method, is presented. To compare different techniques of MUAP extraction, 89 MUAPs were recorded with a concentric needle electrode in the brachial biceps muscle of normal subjects and patients with nerve and muscle diseases. MUAPs were also extracted by another method, called split-sweep median averaging, in which alternate MUAP discharges are averaged independently in two computer buffers until the two averaged signals appear equal on visual inspection by the operator. The amplitude, area, area: amplitude ratio, duration and number of phases and turns of each extracted MUAP were determined by each technique. Overall, there was a strong correlation between all features of the MUAPs extracted by median and splitsweep averaging, although the latter method required, on average, twice as many MUAP discharges to produce acceptable signals. We thus conclude that median averaging is a fast and accurate method that requires relatively few MU discharges to extract MUAP signals from spurious background signals.

Cellular infiltrates in human skeletal muscle: Exercise induced damage as a model for inflammatory muscle disease?

The type and distribution of mononuclear cell infiltrates in muscle biopsies taken from 9 subjects at differing times after exercise in which the muscle is stretched (eccentric exercise) has been characterized. The appearances are compared to those seen in muscle from patients with inflammatory muscle disease. After exercise infiltrating cells were seen in perivascular, perimysial and endomysial regions, the extent being greater in the later biopsies (9–14 days). The predominant cell type was the macrophage (46–100% of all infiltrating cells), the remainder were T lymphocytes with a predominance of the CD4 positive helper/inducer subset. Approximately one third of the T cells expressed DA2 (class 2) antigen indicating that they were activated. Very few B lymphocytes and no Leu7 positive cells were seen. There was evidence of class 1 expression on some of the damaged muscle fibres. The appearance of the experimentally damaged muscle in normal subjects was very similar to untreated polymyositis suggesting that a proportion of the infiltrating cells seen in this disease may be present as part of a natural response to damage rather than being its cause.

Impact of physical training on the ultrastructure of midthigh muscle in normal subjects and in patients treated with glucocorticoids.

Exercise-training might be a logical method to reverse muscle atrophy and weakness in patients treated with glucocorticoids. The purpose of the present investigation was to establish whether a treatment with low dose prednisone (10 +/- 2.9 mg/d) modulates the effect of a moderate strength type isokinetic training during 7 wk (21 sessions of 20 min) on "muscle efficiency" (power output/muscle mass) and on concomitant changes in ultrastructure of the thigh muscle measured by quantitative electron-microscopic morphometry. Training caused a similar increase in "muscle efficiency" in patients on prednisone (n = 9) as in normal volunteers (n = 9). In normal subjects the increase in muscle efficiency was associated with an increase in sarcoplasm, whereas in patients on prednisone the functional improvement was associated with an increase in sarcoplasm, capillaries, and mitochondria content. Thus, a therapy with low dose prednisone does not abrogate training-induced improvement of muscle efficiency but modulates the ultrastructural response of the muscle to the training.

Cardiovascular responses and the sense of effort during attempts to contract paralysed muscles: Role of the spinal cord

To determine whether spinal transection affects the cardiovascular response and the sense of effort which accompany attempts to contract paralysed muscles in normal subjects, paraplegic patients tried to contract paralysed leg muscles. During attempted contractions, paraplegic subjects reported a sense of effort but did not change heart rate or blood pressure. However, these subjects had a normal cardiovascular response to handgrip contractions. These data suggest that pathways descending to and arising from the spinal cord below the lesion are required to generate a cardiovascular response but are not necessary for the sense of effort.

Activity Analysis: Electromyographic and Electrogoniometric Verification

The purpose of this study was to document, using electromyography and electrogoniometry, the normal function and interaction of extrinsic finger muscles of normal subjects during five exercises to establish a baseline of “normality.” The exercises, typical components of occupational therapy activities, were resisted grasp, resisted finger extension, rapid and slow unresisted finger extension, and grasp-release of a lightweight cylinder. A high percentage of electrical output of all three extrinsic finger muscles was generated during resisted or rapid exercises A very low percentage of output was generated during unresisted slow exercises Carryover effects of the exercises (i.e., changes seen in movement after versus before) were limited to increased range of motion and increased level of electrical activity of the three muscles during rhythmical opening of the hand after resisted grasp and rapid extension The most common pattern of usage was reciprocal between agonist and antagonist, although no muscle was ever silent. True cocontraction occurred in only the most resistive exercise—grasp. No correlation was found between average wrist position and percent of muscle output. Intersubject variability suggests that the specific results of this study cannot be generalized However, the concept that resistance and speed increase motor unit recruitment of antagonist as well as agonist may be generalized.

Isometric contractions of normal and spastic human skeletal muscle.

Isometric contractile properties of human elbow flexor muscles were examined in 27 normal subjects (7 females and 20 males). Contractions of elbow flexors were elicited by application of electrical pulses to the biceps motor points. The tension development was recorded at the wrist with the elbow angle fixed at 90 degrees--100 degrees. The data for the time to peak and time to half relaxation of the twitch, the twitch tension-to-tetanus tension ratio, and the posttetanic twitch potentiation are reported. The contractile properties of spastic elbow flexor muscles from 7 subjects who had been hemiparetic for periods ranging from 4 months to 60 months were found to be similar to those of muscles in normal subjects and unaffected muscles in hemiparetic subjects.

Activities of hexokinase, phosphofructokinase, fructose bisphosphatase and 2-oxoglutarate dehydrogenase in muscle of normal subjects and very ill surgical patients.

1. The activities of hexokinase, phosphofructokinase, fructose bisphosphatase and 2-oxoglutarate dehydrogenase have been measured in the vastus lateralis and rectus abdominus muscle of normal human subjects and in very ill surgical patients. 2. The activities of these enzymes in the muscle of control subjects were similar to the pattern seen in the skeletal muscle of other mammals and lower vertebrates. 3. Fructose bisphosphatase and phosphofructokinase activities were significantly lower in the muscle of ill patients although the depression of the activity of fructose bisphosphatase was much greater than that of phosphofructokinase in both muscle types of ill patients. 4. The maximum rate of cycling in the fructose 6-phosphate--fructose, 1,6-diphosphate cycle may be altered in the ill. 5. This decreased cycling may have a direct influence on the sensitivity of glycolysis to regulators such as the adenine nucleotides and may reduce the ability to maintain body temperature. 6. Increased glycogen synthesis in these muscles may indicate that the role of fructose bisphosphatase is unlikely to be solely in glycogen resynthesis.

Electromyographic activity of shoulder muscles during unilateral upper extremity proprioceptive neuromuscular facilitation patterns.

Twenty-nine normal adults were tested to measure the electrical activity of the anterior, middle, and posterior portions of the deltoid muscle and sternal portion of the pectoralis major muscle during the performance of four upper extremity diagonal patterns with the elbow straight, flexing, and extending. The patterns were performed through range of motion, with an isometric contraction performed in the shortened range. With the elbow straight, the middle portion of the deltoid muscle was primarily active with shoulder flexion, abduction, and external rotation; the anterior portion of the deltoid muscle with shoulder flexion, adduction, and external rotation; the posterior portion of the deltoid muscle with shoulder extension, abduction, and internal rotation; and the sternal portion of the pectoralis major muscle with shoulder extension, adduction, and internal rotation. The middle and anterior portions of the deltoid muscle exhibited significantly greater activity in their optimal patterns with the elbow strainght, followed by patterns with the elbow flexing and significantly less activity with the elbow extending. The posterior portion of the deltoid muscle in its optimal pattern produced greatest activity with the elbow straight or extending. Findings confirm the patterns considered optimal for monitored portions of these two muscles in normal subjects. Suggestions are made for study of patients who exhibit imbalances of muscle strength.

Influence of electrode geometry on bipolar recordings of the surface electromyogram

A 2-dimensional conducting-paper analogue and a 3-dimensional field-theory model are used to investigate the influence of electrode spacing and size on the waveshape and frequency spectrum of the signal detected by bipolar surface electrodes, when an action potential propagates in a muscle fibre below the skin surfce. The spatial selectivity of bipolar electrodes, and its possible enhancement by linear filtering techniques, are then discussed. Finally, predicted e.m.g power spectra are compared with some practical measurements on biceps brachii muscle in normal subjects.

Guanylate cyclase activity in normal and diseased human muscle.

Guanylate cyclase activity has been studied in muscle of normal subjects and of patients suffering from muscular and neuromuscular diseases. In normal tissue a guanylate cyclase activity was found in both soluble and particulate fractions of homogenate. We found also that the kinetic analysis of the enzyme of soluble differed from that of particulate fraction. A decrease of guanylate cyclase activity in crude homogenate was observed in muscular dystrophies, in neuromuscular atrophies, and in inflammatory forms of muscle disease.

Effect of ethanol on lactic acid production by exercised normal muscle.

Several studies have suggested that muscle lactic acid production is defective in alcoholic myopathy. However, normal controls have not been evaluated. To study the effects of ethanol on the production of lactic acid in normal exercised muscle, oral ethanol (1 g per kg body weight, 20% v/v) was given to eight nonalcoholic subjects. Forearm ischemic exercise with a total work load of 7.2 kg-m/min was performed just before and 90 min after ingestion of ethanol. At the time of exercise, the serum ethanol level was 95.7 +/- 15.1 mg% (mean +/- SD). Resting serum lactic acid was significantly higher after ingestion of ethanol (15.7 +/- 4.5 mg%) than before (8.5 +/- 4.7 mg%). Lactic acid generation with ischemic exercise was significantly lower after ethanol ingestion. The mean peak serum lactic acid level (expressed as percentage elevation above resting) was 330.5 +/- 118.2% before and 127.9 +/- 75.1% after (p less than .05). These results indicate that a single oral dose of ethanol decreases lactic acid production by exercised muscle in normal subjects.