Gender comparisons of the mechanomyographic responses to maximal concentric and eccentric isokinetic muscle actions

PURPOSE: The purpose of this study was to determine whether there is a gender difference in the velocity-related patterns of mechanomyographic (MMG) responses to maximal isokinetic concentric (CON) and eccentric (ECC) muscle actions. METHODS: Adult males (N = 15) and females (N = 16) performed maximal CON and ECC muscle actions of the leg extensors on a calibrated Cybex 6000 dynamometer at velocities of 30, 90, and 150 degrees.s-1. MMG was detected by a piezoelectric crystal contact sensor placed over the vastus lateralis muscle. RESULTS: The results indicated that there were decreases in CON peak torque (PT) across velocities, while ECC PT remained constant with increasing velocity for both genders. MMG amplitude increased significantly (P < 0.05) with velocity in both the males and females for CON and ECC muscle actions. There was a gender difference in the velocity-related patterns of MMG responses to maximal isokinetic CON muscle actions; however, there was no gender difference in the pattern of ECC MMG responses. CONCLUSIONS: The gender difference in CON MMG responses may be attributed to the greater percent decline in CON PT across velocity for the females than the males. In addition, the males displayed greater CON and ECC MMG amplitudes at all muscle action velocities than the females, possibly because of gender differences in muscle mass and/or thickness of the adipose tissue layer.     

An unusual insertion of accessory biceps brachii muscle

Nutritional intake appears to be an important factor contributing to aging. In the present study we describe changes in physical health related to nutritional intake among elderly persons in a 10-y longitudinal study. Among 304 healthy elderly participants (median age 72 y on entry into the study in 1980), 97 (34.2%) are still in good health 10 y later in 1990, 74 (26.5%) have become frail or sick, 54 (19.1%) have died, and 57 (20.1%) have dropped out of the study. Women with lower or higher energy intakes (in 1980 and 1981) than the current Recommended Daily Allowance (RDA; between 25 and 30 kcal/kg) were more likely to become frail or sick or to die in 1990 than those with energy intake in the midrange (below RDA, odds ratio (OR) = 3.3, confidence interval (CI) = 1.2-8.6; above RDA, OR = 3.4, CI: 1.1-10.7). Moreover, women with protein intakes greater than the midrange of 0.8-1.2 g/kg of body weight (1.20-1.76 g/kg in 1980 and 1981) tended to have fewer health problems over the next 10 y than those with protein intakes < 0.8 g/kg, suggesting that the mean protein requirement in elderly adults is greater than that established by the 1985 joint World Health Organization/ FAO/UNU Expert Committee. Moreover, a decrease in energy intake was greater in elderly persons who died or dropped out of the study because of illness.     

Doublet potentiation during eccentric and concentric contractions of cat soleus muscle

The addition of an extra stimulus pulse, or doublet, at the beginning of a low-frequency train has been shown to substantially increase isometric force. This study examined the effects of muscle movement on this doublet potentiation. The soleus muscles of anesthetized cats were stimulated at 10 Hz for 1 s, with and without an added doublet (0.01-s interval). Isovelocity releases reduced but did not eliminate peak and early doublet potentiation (average 0.0-0.5 s after the doublet). Large releases, >0.4 s after the doublet, completely abolished sustained doublet potentiation (average 0.5-1.0 s after the doublet). In contrast, early isovelocity stretches boosted peak doublet potentiation. Yet, large stretches later in the stimulus almost completely eliminated sustained doublet potentiation. This suggests that a different mechanism is responsible for early and sustained doublet potentiations. Because peak and average initial doublet potentiation were not strongly affected by movement, doublets still offer a viable control strategy to increase force during movement while minimizing the number of stimulus pulses.     

Accuracy and variability of leg velocities during concentric and eccentric actions of the quadriceps femoris muscles

This study examined the ability to control leg velocities during concentric and eccentric actions of the right quadriceps muscles. Ten healthy women (M age = 25.9 +/- 3.5 yr.) were tested using the Isotonic Program of the KIN-COM II 500H dynamometer. They attempted to match velocity tracings of 10 degrees, 20 degrees, and 40 degrees/sec. through 70 degrees of knee range of motion at a load equal to 10% of their maximal mean concentric force. The actual mean velocities, mean percent deviation from the target velocities, and the coefficient of variation for both actions were calculated for 15 degrees-75 degrees (full range of motion), 15 degrees-45 degrees (shorter range of motion), and 46 degrees-75 degrees (longer range of motion). Separate one-way analyses of variance with two trial factors (action x velocity) showed faster concentric velocities through the full and longer ranges of motion, and faster eccentric velocities through the shorter range of motion. Mean percent deviations indicated that the eccentric velocities were generally more accurate within all ranges of motion. Larger concentric coefficients of variation were found within the full and longer ranges of motion, and the coefficients of variation for both actions decreased as the velocities increased. An exaggerated 'velocity overshoot' at the onset of both actions probably contributed to differences in the velocities and coefficients of variation. The results indicated differences between the concentric and eccentric actions, explained in part by the testing methodology used and by the known mechanical and physiological characteristics of the two muscle actions.     

Influence of stimulus cross talk on results of the twitch-interpolation technique at the biceps brachii muscle

Biceps brachii muscles of five healthy volunteers were tested with a high-resolution twitch-interpolation technique. Parameters of the electrical surface stimulation were varied. It was found that a supramaximal stimulus strength activates both biceps and triceps brachii motor units simultaneously severely affecting twitch-interpolation results. Crosstalk contamination of twitches, however, can be avoided, if submaximal stimuli are used yielding twitch-interpolation results for the biceps-brachii that are similar to those of the quadriceps muscle.     

Reliability of eccentric isokinetic knee flexion and extension measurements

This study assessed the test-retest reliability of knee isokinetic eccentric muscle performance in subjects with and without a history of tibio-femoral pathology. Nineteen adults were tested at 60 degrees/sec and 180 degrees/sec on three occasions using a standardized protocol that incorporates a same-session learning phase. Results revealed moderate to excellent reliability for average peak torque test-retest ICC (2,1) = .58 to .96, total work ICC = .63 to .93, and power ICC = .67 to .93. Joint angle at peak torque was unreliable (ICC = .01 to .69) for both muscle groups at both angular velocities. Knee flexion reliability was higher than extension reliability at both 60 degrees/sec and 180 degrees/sec. Subjects with tibio-femoral pathologies had ICC values lower than the healthy subjects. Reliable eccentric isokinetic measurements can be obtained for average peak torque, total work, and power. Clinicians should not assume the same degree of reliability in testing patients as in testing healthy subjects.     

The effect of leg flexion angle on the mechanomyographic responses to isometric muscle actions

INTRODUCTION: An ROC analysis was carried out in order to determine the reliability of digital luminescence radiography review at a PC and this was compared with a radiological work station and with X-ray film on a viewing box. MATERIAL AND METHOD: 54 chest images obtained by digital luminescence radiography were selected, 31 of these contained small pulmonary nodules. In order to evaluate critical detail, five images of a phantom showing round foci were used. Five radiologists examined these, using a Siemens Magic View work station, a PC with proprietary software (ViewMed) and X-ray films on a viewing box. Image processing of the work station used the standard clinical application. ViewMed performs linear scaling of grey levels to 8 Bit. The results were examined statistically by means of a t-test. RESULTS: As far as the chest images were concerned there was no significant difference in the diagnostic value of these methods. There was, however, a highly significant loss of diagnostic information with respect to the round focus phantom when using the PC compared with the other methods. CONCLUSION: In the configuration in which it was used, the PC should not be relied on as a primary means of examination since critical details cannot always be seen. In routine use these play a subordinate role and there was no significant diagnostic loss where the chest images were concerned. We expect that by improvements in the frequency and contrast processing the PC accuracy will be considerably increased.     

Tuberculous abscess of the brachialis and biceps brachii muscles without osseous involvement. A case report

In July 1997 Professor Harry Rilbe passed away at the age of 84. Harry Rilbe was an outstanding personality skilled in chemistry, optics and mathematics, and he will be remembered for his important contributions to the development of separation methods, notably moving boundary electrophoresis and isoelectric focusing. The latter method is used for analytical and preparative purposes in thousands of laboratories worldwide. Isoelectric focusing is indispensable for characterization of proteins from humans, animals, plants and microorganisms. Isoelectric focusing is thus useful for the understanding of the function of genes and, accordingly, for progress in the life sciences. A biographical retrospect, "A scientific life with chemistry, optics and mathematics", was published by Harry Rilbe in Electrophoresis 1984, 5, 1-17.     

Biceps brachii muscle attached to the extensor carpi radialis brevis muscle: an unreported anatomical variation in humans

We observed a case of folliculitis decalvans involving the beard and the scalp with a tufted hair folliculitis aspect in the occipital region. The presence of two clinical presentations in the same patient has not been reported in the literature. This would suggest that the two entities could be morphological aspects of the same pathological process which might cause either atrophy with loss or the annexes or tufted hair folliculitis depending upon the depts and destructive capacity of the inflammatory process.     

Cross-sectional study of the isokinetic muscle trunk strength among school children

Our surveys have shown lifetime prevalence of L.BP. over 30% among schoolchildren. The purpose of this study was to evaluate the relationship between back and isokinetic trunk strength, anthropometric parameters, and sports activities. One hundred and seventeen healthy children aged 10-16 years were included. All these volunteers had semi-structured interview, anthropometric and dynamic strength measurements. Lifetime prevalence of back pain was 44.5% and point prevalence was 13%. In this cross-sectional study, anthropometric and strength profiles were significantly related to age and gender. Non specific low back pain was not correlated to trunk muscle strength and/or sports activities.     

Cutaneous reflexes during human gait: electromyographic and kinematic responses to electrical stimulation

The functions of ipsilateral cutaneous reflexes were studied with short trains of stimuli presented pseudorandomly to the superficial peroneal (SP) and tibial nerves during human gait. Electromyograms (EMGs) of tibialis anterior (TA), soleus, lateral and medial gastrocnemius, vastus lateralis (VL), and biceps femoris (BF) muscle were recorded, together with ankle and knee joint angles. Net reflex EMG responses were quantified in each of the 16 parts of the step cycle according to a recently developed technique. After SP nerve stimulation, TA muscle showed a significant suppression during swing phase that was highly correlated to ankle plantarflexion. BF and VL muscles were both excited throughout swing and significantly correlated to knee flexion during early swing. Tibial nerve stimulation caused dorsiflexion during late stance, but plantarflexion during late swing. We argue that SP nerve reflexes are indicative of a stumbling corrective response to nonnoxious electrical stimulation in humans. The correlated kinematic responses after tibial nerve stimulation may allow smooth movement of the swing leg so as to prevent tripping during swing and to assist placing and weight acceptance at the beginning of stance.     

Manipulation of knee extensor force using percutaneous electrical myostimulation during eccentric actions: effects on indices of muscle damage in humans

In Hirschsprung's disease (HD), certain intestinal nervous plexuses are absent. Sprouting nerve endings contain different amounts of synaptophysin (SY), a protein and main constituent of acetylcholinesterase (AChE) storage compartments. Due to the lack of specific markers for synapses, a qualitative analysis of nerve endings of intestinal segments affected by HD has not yet been undertaken. For this study, resected colorectal specimens from patients with HD (n = 8, mean age 2.1 years) were investigated in parallel for AChE, SY, and content of small synaptic vesicles by biochemical, immunohistochemical, and electronmicroscopic means. In the microdissected muscular layer, reduced SY (1.4 microgram/mg total protein, normal 24 +/- 0.3) was observed. Immunohistochemistry showed in affected tissues reduced numbers of SY-positive nerve fibers and nerve endings, which in turn were thickened and distorted, in both the muscle proper and the muscularis mucosae. Combining both morphologic and biochemical findings, in HD the number of cholinergic vesicles in the remaining nerve endings seems to be increased as measured by SY, a marker molecule specific for synaptic vesicles. Our data also suggest that nerve endings in HD may contain high concentrations of cholinergic vesicles, paralleling the known high amounts of acetylcholine and AChE found in intestinal segments of patients with HD.     

Anatomical study of the cutaneous perforator arteries and vascularisation of the biceps femoris muscle

We present an anatomical study that describes the distribution of the cutaneous perforators (CP) of both heads of the biceps femoris muscle.

Material and methods

In this study, we dissected 18 legs from nine cadavers. The study was centered on the biceps femoris muscle and musculocutaneous perforator arteries from both muscular heads. Only perforator arteries with comitant vein diameters of over 0.5 mm were selected. The vascular origin and length were also studied. In all cases, measurements were taken from the bicondyle line.

Results

The measurements taken from the muscle bellies of the biceps gave the following results; for the long head 33.91 cm as medium length (SD=2.70) and for the short head 23.85 cm as medium length (SD=2.96).The total number of perforator arteries obtained from the two muscle bellies was 139, with the greatest percentage located in the lower half of the thigh. The majority follow an intramuscular route (80.48%) and less frequently they are septals (19.52%).The lengths of perforator arteries from its origin in the axial vessel of the muscle to the subcutaneous fat were, for the short head 5.01±1.33 (3.0–10.0), whereas the same measurement, in the long head was 4.54±1.36 (2.5–9.0).The principal vascular origin of the perforator arteries was the popliteal artery in both muscle bellies, whilst the second arterial vessel in importance was the first and second profunda perforator artery.

Conclusion

From the results obtained in our work, we can deduce that it is always possible to locate perforator arteries in both muscle bellies; most frequently they have intramuscular distribution and are located in the proximity of the vascular septum. Their most common origins are the popliteal artery and first and second profunda perforator artery. Finally, it is possible to design pedicle and free flaps, with less morbidity and more versatility than musculocutaneous flaps.     

The utility of isokinetic dynamometry in the assessment of human muscle function

Isokinetic dynamometry has become a favoured method for the assessment of dynamic muscle function in both clinical research and sports environments. Several indices, such as peak torque, are used in the literature to characterise individual, group or larger population performance via these sophisticated data acquisition systems. Research suggests that there are several competing demands on the design of the measurement protocol which may affect the measurement of isokinetic strength and subsequent suitability of data for meaningful evaluation and interpretation. There is a need to increase measurement rigour, reliability and sensitivity to a level which is commensurate with the intended application, via more elaborate multiple-trial protocols. However, this may be confounded by logistical and financial constraints or reduced individual compliance. The net effect of the interaction of such demands may be considered to be the utility of the isokinetic dynamometry protocol. Of the factors which impinge on utility, those which relate to reliability afford the most control by the test administrator. Research data suggest that in many measurement applications, the reliability and sensitivity associated with all frequently-used indices of isokinetic leg strength which are estimated via single-trial protocols, are not sufficient to differentiate either performance change within the same individual or between individuals within a homogeneous group. While such limitation may be addressed by the use of protocols based on 3 to 4 inter-day trials for the index of peak torque, other indices which demonstrate reduced reliability, for example the composite index of the ratio of knee flexion to extension peak torque, may require many more replicates to achieve the same level of sensitivity. Here, the measurement utility of the index may not be sufficient to justify its proper deployment.     

Generalization of frontalis electromyographic feedback to adjacent muscle groups: a critical review

The widespread utilization of frontalis electromyographic feedback as a general relaxation strategy far preceded empirical evidence demonstrating its efficacy for this purpose. This article reviews parametric studies testing the association between frontalis reduction and concomitant EMG decreases in nontargeted muscle groups. The current research supports the contention that biofeedback reinforces discriminative responding to a specific muscle group and not generalized relaxation to adjacent muscle groups. Methodological problems are noted, and implications for future research are addressed.     

Variety of muscle responses to tactile stimuli

Influences exerted by tactile stimuli on the muscle activity were investigated with two methods: (1) analysis of kinematics and electromyographic (EMG) activity of eight forelimb muscles during contact placing (CP) reactions elicited by tactile stimuli applied to the dorsal, medial or lateral sides of the paw in cats, and (2) the Hoffmann (H)-reflex technique to quantify the effects of the tactile stimuli on the excitability of the alpha motoneurones of the soleus muscle in awake rats. The first group of the data showed that the tactile stimuli applied to dorsal, medial or lateral aspects of the paw led to different strategies of the forelimb movements during CP reactions. These differences arose from various patterns of activation of the elbow flexor and extensor muscles at the beginning of CP reactions and a various involvement of the medio-lateral components of movements, depending on the site of the tactile stimulus application. With the H-reflex technique it was found that the tactile stimulus diminished the excitability of alpha motoneurones of the soleus muscle when applied to the skin overlying the lateral side of the ankle joint. This effect was in line with the observation that the tactile stimulus applied to the lateral side of the paw activated the elbow flexor muscles but not their antagonists to initiate CP reaction.     

The reliability of monopolar and bipolar fine-wire electromyographic measurement of muscle fatigue

This longitudinal study was designed to examine reciprocal relationships between feeding practices and infant growth over the first 6 mo of life. The following three hypotheses were tested: 1) early feeding practices predict later infant growth; 2) early infant growth predicts later feeding practices; and 3) these relationships occur after controlling for related background variables. The sample included 226 healthy, well-nourished infants born at the Queen Elizabeth Hospital, Bridgetown, Barbados. Assessments were made at birth, 7 wk, and 3 and 6 mo of age. Factor analysis of a feeding practices questionnaire for those mothers who attended all three postnatal visits yielded five uncorrelated factors. Three of these factors, preference for breast-feeding, feeding intensity and feeding difficulty, declined with infant age. Two of these factors, father helps and relatives help, increased with infant age. Several background variables, including maternal age, anthropometry and reproductive history, and reliance on outside sources of information were correlated with infant growth. Multivariate analyses confirmed all three hypotheses. The group of feeding practices (particularly the preference for breast-feeding) at 7 wk predicted increases in infant lengths at subsequent ages. Conversely, infant weights at 3 and 6 mo predicted subsequent feeding practices, especially feeding intensity. These reciprocal relationships remained even after statistically controlling for the influence of the background variables. Implications for public policy include the need for comprehensive programs advocating breast-feeding and supporting the general health of mothers and infants.     

Inflammatory responses to ischemia and reperfusion in skeletal muscle

Skeletal muscle ischemia and reperfusion is now recognized as one form of acute inflammation in which activated leukocytes play a key role. Although restoration of flow is essential in alleviating ischemic injury, reperfusion initiates a complex series of reactions which lead to neutrophil accumulation, microvascular barrier disruption, and edema formation. A large body of evidence exists which suggests that leukocyte adhesion to and emigration across postcapillary venules plays a crucial role in the genesis of reperfusion injury in skeletal muscle. Reactive oxygen species generated by xanthine oxidase and other enzymes promote the formation of proinflammatory stimuli, modify the expression of adhesion molecules on the surface of leukocytes and endothelial cells, and reduce the bioavailability of the potent antiadhesive agent nitric oxide. As a consequence of these events, leukocytes begin to form loose adhesive interactions with postcapillary venular endothelium (leukocyte rolling). If the proinflammatory stimulus is sufficient, leukocytes may become firmly adherent (stationary adhesion) to the venular endothelium. Those leukocytes which become firmly adherent may then diapedese into the perivascular space. The emigrated leukocytes induce parenchymal cell injury via a directed release of oxidants and hydrolytic enzymes. In addition, the emigrating leukocytes also exacerbate ischemic injury by disrupting the microvascular barrier during their egress across the vasculature. As a consequence of this increase in microvascular permeability, transcapillary fluid filtration is enhanced and edema results. The resultant increase in interstitial tissue pressure physically compresses the capillaries, thereby preventing microvascular perfusion and thus promoting the development of the no-reflow phenomenon. The purpose of this review is to summarize the available information regarding these mechanisms of skeletal muscle ischemia/reperfusion injury.