RESUMEN
OBJECTIVE: To analyze the role of the rectus femoris muscle in nondisabled gait at various walking velocities using fine-wire dynamic electromyography. DESIGN: Descriptive study. Fine-wire electromyography data were collected from the rectus femoris during level walking at four walking speeds. Rectus femoris activity patterns in the loading response phase and the pre- and initial-swing phase of the gait cycle were compared using paired t tests. SETTING: A gait laboratory. SUBJECTS: Ten nondisabled adult volunteers. MAIN OUTCOME MEASURES: Amplitude of rectus femoris activity in the loading response phase and the pre- and initial-swing phase during walking at four speeds. RESULTS: There was a bimodal pattern of rectus femoris activity in all subjects, at all speeds, in both phases, with high variability in the onsets, durations, and amplitudes of activity, and paired t tests revealed no significant differences (p > .05) between phases at any walking speed. CONCLUSION: Activity in the rectus femoris in the pre- and initial-swing phase in nondisabled individuals at all speeds suggests that similar activity detected in individuals with stiff-legged gait may not be inappropriate.
Asunto(s)
Marcha/fisiología , Músculo Esquelético/fisiología , Adulto , Electrodos , Electromiografía/instrumentación , Electromiografía/métodos , Electromiografía/estadística & datos numéricos , Humanos , Contracción Muscular/fisiología , Valores de ReferenciaRESUMEN
To determine if there is a correlation between the degree of delayed increase in signal intensity (SI) of muscle after exercise on magnetic resonance (MR) images and the amount of ultrastructural (ULS) injury and delayed-onset muscle soreness (DOMS), MR imaging-guided muscle biopsy was performed to obtain tissue from the legs of nine sedentary subjects 48 hours after downhill running on a treadmill. The degree of soreness was subjectively graded. T1-weighted, spin-density, T2-weighted, and short inversion time inversion-recovery images were obtained before and after biopsy, at 48 and 96 hours after exercise, respectively. The delayed SI increase of muscle on images obtained before biopsy was subjectively graded and measured. The degree of ULS injury was determined with electron micrographs. Serum creatine kinase levels were obtained before and up to 144 hours after exercise at 24-hour intervals. The measured SI, SI grades, and DOMS grades were correlated with the degree of ULS injury. Linear regression analysis revealed poor correlation between the DOMS grades and the degree of ULS injury and good correlation between the SI grade and the degree of ULS injury.
Asunto(s)
Ejercicio Físico , Imagen por Resonancia Magnética , Músculos/ultraestructura , Enfermedades Musculares/patología , Adulto , Creatina Quinasa/sangre , Femenino , Humanos , Masculino , Enfermedades Musculares/sangre , Enfermedades Musculares/etiologíaRESUMEN
We have measured capillary distribution in costal and crural canine diaphragm using two methods: histochemical processing and perfusion fixation. Each of 18 dogs was deeply anesthetized, the abdomen opened, and the left inferior phrenic artery cannulated. The animal was heparinized and overdosed with pentobarbital. The right hemidiaphragm was frozen, either postexcision (Protocol 1) or intact with no preload (Protocol 2), for histochemical processing. The left hemidiaphragm was fixed by perfusion in situ using 2% glutaraldehyde, either with preload (Protocol 1) or without (Protocol 2). Costal and crural regions of each hemidiaphragm were sampled for analysis. Frozen samples were sectioned and processed for acid-stable (pH 4.0) ATPase activity; perfusion-fixed samples were postfixed, stained, embedded in Epon, and sectioned. Measurements were made using a digital imaging system. We found that muscle fibers had smaller cross-sectional areas in costal than in crural diaphragm; capillary-to-fiber ratio (C:F) did not differ by region and regional differences in capillary density could be attributed to differences in fiber size. Results depended critically on methodology. In perfusion-fixed muscle, fiber area was less, C:F was greater, and capillary density was greater than in histochemically-processed tissue. We conclude that capillary distribution is similar in costal vs. crural diaphragm and that perfusion fixation identifies capillaries more effectively than histochemistry.
Asunto(s)
Diafragma/irrigación sanguínea , Perros/anatomía & histología , Animales , Capilares/anatomía & histología , Fijadores , Histocitoquímica , Técnicas Histológicas , Modelos Anatómicos , PerfusiónRESUMEN
Although exercise-induced muscle fiber hyperplasia has been demonstrated through direct fiber counts following nitric-acid digestion of muscle, morphological studies to determine the mechanism of hyperplasia have not been performed previously. In this study, light and electron microscopy were used to evaluate evidence of muscle fiber splitting or de novo formation of new muscle fibers. Since both fiber hypertrophy and hyperplasia may result in alterations in the muscle nuclear populations, myonuclear number and satellite cell frequency were assessed quantitatively to determine their role in regulating muscle fiber size. Ten adult cats performed weight-lifting exercise, and the right (exercised) and left (control) forelimbs were fixed by vascular perfusion. Spaced serial sections were used to evaluate muscle fiber morphology along the length of fibers, and muscle fiber areas were measured. Myonuclei and satellite cells were counted using electron microscopy. Morphological evidence supporting muscle fiber hyperplasia was observed in exercised muscles. These observations included the presence of small fibers which may signify de novo fiber formation. Myonuclear counts indicate that myonuclear density is not a primary regulator of fiber size. Satellite cell frequency was unchanged following exercise. Autoradiographic studies revealed satellite cell activation by uptake of tritiated thymidine in exercised muscles. Satellite cell activation appears to result from increased activity in exercised muscles. These findings confirm previous studies demonstrating muscle fiber hyperplasia following weight-lifting exercise, and suggest that de novo fiber formation is the major mechanism contributing to muscle fiber hyperplasia in this model.
Asunto(s)
Músculos/patología , Esfuerzo Físico , Animales , Gatos , Núcleo Celular/patología , Femenino , Hiperplasia , Masculino , Microscopía Electrónica , Condicionamiento Físico Animal , Levantamiento de PesoRESUMEN
Progressive resistance exercise was used to induce hypertrophy in the right palmaris longus muscle (PLM) of 16 cats. The left PLM served as the non-exercised intra-animal control. After an average 150 +/- 26.6 wk of training, left and right PLMs were removed and weighed. Muscle fibers were typed using standard histochemical techniques. Mean fiber cross-sectional area, connective tissue content, and muscle fiber length were determined. The right exercised PLM demonstrated a 24.2 +/- 6.9% increase in muscle mass. Mean muscle fiber cross-sectional area increased 11.0 +/- 7.3% in the exercised muscles. No change in connective tissue content, fiber length, or fiber type composition was observed. The results show that increases in muscle fiber cross-sectional area do not account for all the observed increases in muscle mass, and that other mechanisms, such as muscle fiber hyperplasia, may play a role in contributing to muscle mass increases.
Asunto(s)
Músculos/anatomía & histología , Condicionamiento Físico Animal , Animales , Gatos , Hiperplasia , Hipertrofia , Músculos/patología , Levantamiento de PesoRESUMEN
For periods ranging from 26 to 87 weeks, the morphological characteristics of the flexor carpi radialis (FCR) muscle were examined in four cats trained to perform weight-lifting exercise. Four untrained, sex and weight-matched cats served as controls. The right FCR from each cat was surgically isolated, attached to a tension transducer, and set at its optimal length. The forelimb was perfused with 2% glutaraldehyde in 0.1 M cacodylate buffer. Small bundles of fibers were teased from their origin and insertion tendons and embedded in Epon. Spaced serial sections were used to examine the morphological features of the fibers for trained and control animals. Ultrastructural examination revealed muscle fiber degenerative changes, such as pyknotic nuclei, disruption of the sarcolemma, vacuolation, and disorganization of myofilaments. Such changes were observed at a higher frequency in trained muscle than in control muscle. Spaced serial sections of fiber bundles showed that the degree of degeneration varied along the length of the fiber. Fiber area measurements showed that trained muscle had both larger and smaller fibers than control samples. The very small fibers observed in the trained muscle were considered to be regenerating or "new" fibers since they had not undergone degenerative changes. "Satellite-like" cells were observed in trained muscle. Such cells resembled satellite cells but also contained developing myofilaments. Since evidence of degeneration-regeneration was observed in control samples, but at a lower frequency, it was postulated that weight-lifting exercise accelerates muscle fiber turnover in the cat FCR.
Asunto(s)
Músculos/patología , Regeneración , Deportes , Levantamiento de Peso , Animales , Gatos , Femenino , Masculino , Microscopía Electrónica , Músculos/fisiología , Músculos/ultraestructura , Necrosis , Factores de TiempoRESUMEN
Investigations of the structure and function of the flexor carpi radialis muscle (FCR) in the cat have led to the hypothesis that the compartmentalized (nonuniform) distribution of fiber types within the muscle relate to the complex motor skills of the cat. To test this hypothesis a study was undertaken to compare the FCR in four mammalian species of similar body size but with different forelimb motor tasks. The species chosen were: dog, opossum, armadillo, and cat. Comparisons were made among species with regard to general muscle morphology, fiber types and sizes, fiber proportions, and fiber distributions. The FCR of all species was morphologically similar and contained three muscle fiber types (SO, FOG, and FG). The mean area of muscle fibers was largest in opossum, while the FCR fibers of dogs were smallest. The percentage of SO fibers in the dog FCR was greater than in the other species studied. The opossum FCR also contained a high percentage of SO fibers. The armadillo FCR consisted of a high percentage of FG fibers. In the cat FCR the percentages of all three fiber types were similar. For each species, individual fiber proportions were in agreement with the results for fiber percentages. Compartmentalized distribution of fiber types existed in each species with the dog having the most compartmentalized fiber type distribution and the cat the least compartmentalized distribution. Therefore it seems that the compartmentalized organization of the FCR is not related to any specialized motor task, but may be a generalized pattern associated with motor patterns shared among all species studied.