-
The American Journal of Physiology Jun 1994Activation of a metabolically generated reflex in exercising skeletal muscle (muscle metaboreflex) in humans is known to trigger increases in sympathetic nerve activity...
Activation of a metabolically generated reflex in exercising skeletal muscle (muscle metaboreflex) in humans is known to trigger increases in sympathetic nerve activity (SNA) to resting skeletal muscles. In seven healthy human subjects, to determine whether this reflex mechanism also increases SNA to the exercising muscles, we recorded muscle SNA with microelectrodes in the right peroneal nerve and in fascicles of the left peroneal nerve selectively innervating the exercising muscles of the left foot. Subjects performed static toe extension at 20% maximal voluntary contraction alone or in combination with foot ischemia. Only static toe extension at 20% MVC during ischemia activated the muscle metaboreflex. This paradigm caused increases in SNA to exercising muscle that paralleled those to the resting muscles: during the first minute of exercise SNA was unchanged, but during the second minute SNA increased from 29 +/- 2 to 38 +/- 2 bursts/min (P < 0.05) to the exercising muscles and from 30 +/- 3 to 40 +/- 2 bursts/min (P < 0.05) to the resting muscles. These bilateral increases in SNA were maintained when metaboreflex activation was sustained by postexercise foot ischemia. In conclusion, these data provide neurophysiological evidence that the muscle metaboreflex evokes parallel sympathetic activation in exercising and resting human skeletal muscle.
Topics: Adult; Humans; Ischemia; Leg; Male; Muscle Contraction; Muscles; Physical Exertion; Reflex; Rest; Sympathetic Nervous System; Toes
PubMed: 8024012
DOI: 10.1152/ajpheart.1994.266.6.H2508 -
The Journal of Physiology Jul 19711. Senile muscle atrophy is characterized by a marked reduction in the frequency of spontaneous transmitter release with no electrophysiological evidence of...
1. Senile muscle atrophy is characterized by a marked reduction in the frequency of spontaneous transmitter release with no electrophysiological evidence of denervation.2. In spite of the reduced number of muscle fibres, there is no ultrastructural evidence for denervation at the end-plates. There is agglutination of synaptic vesicles, neurotubules and filaments, thickening of the basement membrane, widening of the primary synaptic cleft, and irregular branching of the junctional infoldings, but no axonal degeneration.3. The contractile process in senile muscles is slowed down as is indicated by a prolongation of contraction time, latency period, maximum rate of twitch tension and relaxation time.4. The muscle fibres show proliferation of the T system and increased SR but no fragmentation as is observed in denervation atrophy.5. Senile muscle atrophy thus presents some specific features affecting both pre- and post-synaptic structures, related to a very slow process of deterioration of the neuromuscular contact.
Topics: Action Potentials; Agglutination; Aging; Animals; Atrophy; Axons; Basement Membrane; Electrophysiology; Male; Membrane Potentials; Microscopy, Electron; Muscle Contraction; Muscle Denervation; Muscles; Myofibrils; Neuromuscular Junction; Rats; Relaxation; Synaptic Transmission; Synaptic Vesicles
PubMed: 4326996
DOI: 10.1113/jphysiol.1971.sp009528 -
Biochemical and Biophysical Research... Jul 1990The principal finding in this study is that vascular smooth muscle generates a labile relaxing factor that possesses pharmacological and chemical properties that are...
The principal finding in this study is that vascular smooth muscle generates a labile relaxing factor that possesses pharmacological and chemical properties that are similar to those of authentic nitric oxide. MDRF was generated by perfusion of endothelium-denuded bovine pulmonary artery as assessed by bioassay. In addition, endothelium-denuded arterial rings that were incubated at 37 degrees C for 24 hr to lower endogenous L-arginine levels relaxed in response to L-arginine but not D-arginine. Freshly mounted, endothelium-denuded arterial rings were not relaxed by L-arginine but did relax in response to the dipeptide L-arginyl-L-alanine. Relaxant responses were accompanied by increases in smooth muscle levels of cyclic GMP and nitrite, and were inhibited by oxyhemoglobin, methylene blue, and NG-nitro-L-arginine. NG-Nitro-L-arginine also caused endothelium-independent contractile responses. Thus, a relaxing factor with the properties of nitric oxide can be generated from vascular smooth muscle.
Topics: Animals; Biological Assay; Cattle; Cyclic GMP; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Nitrites
PubMed: 2164813
DOI: 10.1016/0006-291x(90)91243-l -
Proceedings of the Royal Society of... Aug 1951
Topics: Electromyography; Humans; Muscle Tonus; Muscles; Reflex; Reflex, Oculocardiac; Relaxation
PubMed: 14864560
DOI: No ID Found -
Cancer Nursing Apr 1993The purpose of this exploratory study was to examine the effects of therapeutic massage (consisting of effleurage, petrissage, and myofascial trigger point therapy) on... (Review)
Review
The purpose of this exploratory study was to examine the effects of therapeutic massage (consisting of effleurage, petrissage, and myofascial trigger point therapy) on pain perception, anxiety, and relaxation levels in hospitalized patients experiencing significant cancer pain. Thirty minutes of therapeutic massage was administered on two consecutive evenings to nine hospitalized males diagnosed with cancer and experiencing cancer pain. The subjects' self-reports of pain and relaxation (measured by Visual Analogue Scales) as well as anxiety (measured by the Spielberger State Anxiety Inventory) were recorded before and immediately after the intervention. The objective physiologic measures of heart rate, respiratory rate, and blood pressure were obtained before, immediately after, and, finally, 10 min after the massage intervention. Massage therapy significantly reduced the subjects' level of pain perception (average = 60%) and anxiety (average = 24%) while enhancing their feelings of relaxation by an average of 58%. In addition to these subjective measures, all physiological measures (heart rate, respiratory rate, and blood pressure) tended to decrease from baseline, providing further indication of relaxation. In conclusion, although the exact mechanism is not known, therapeutic massage is a beneficial nursing intervention that promotes relaxation and alleviates the perception of pain and anxiety in hospitalized cancer patients.
Topics: Adult; Aged; Analgesics; Anxiety; Blood Pressure; Heart Rate; Humans; Male; Massage; Middle Aged; Muscles; Neoplasms; Pain; Pain Measurement; Relaxation; Respiration
PubMed: 8477405
DOI: No ID Found -
The American Journal of Physiology Aug 1994Glyconeogenesis in muscle was assessed during a 3-h recovery period after prolonged submaximal exercise represented by a 4-h swim. Rats fasted for 12 h and previously...
Glyconeogenesis in muscle was assessed during a 3-h recovery period after prolonged submaximal exercise represented by a 4-h swim. Rats fasted for 12 h and previously catheterized underwent this protocol with the concomitant infusion of [6-3H]glucose and one of the following: 1) [14C]bicarbonate, 2) [U-14C]lactate, and 3) [1-14C]glucose. Rested rats served as controls. The incorporation of 14C label ([14C]bicarbonate and [U-14C]lactate) or its transfer to the sixth position of glucosyl units of glycogen, over and above that taken up from circulating glucose (and determined from [6-3H]glucose uptake), was used as an index of muscle glyconeogenesis. 14C from 14CO2 is not expected to be incorporated into glycogen in muscle, and any incorporation that is not from circulating glucose is used to define experimental error. [14C]lactate incorporation measures equilibration with circulating lactate, and label randomization in glucosyl units beyond that seen in plasma glucose is taken as evidence of glyconeogenesis from locally accumulated glycolytic products. The results of these studies demonstrate 1) no glyconeogenesis in the soleus; 2) in the red and white gastrocnemii, glyconeogenesis takes place only from glycolytic products within the muscle. Approximately 35-40% of the [6-14C]glucose in glycogen can only be accounted for by muscle glyconeogenesis. The substrate does not equilibrate with circulating lactate to a detectable extent. 3) Glyconeogenesis appears to persist throughout the recovery period and uses substrate at the level of pyruvate. This is consistent with a continuing elevation of glycolysis during this period.
Topics: Animals; Gluconeogenesis; Glycogen; Glycolysis; Male; Muscles; Physical Endurance; Rats; Rats, Sprague-Dawley; Rest; Swimming
PubMed: 8074200
DOI: 10.1152/ajpendo.1994.267.2.E210 -
Journal of Applied Physiology... Apr 1987Intracellular pH of in vitro diaphragm preparations was determined following low- (5 Hz, 1.5 min) and high- (75 Hz, 1 min) frequency stimulation, using glass...
Intracellular pH of in vitro diaphragm preparations was determined following low- (5 Hz, 1.5 min) and high- (75 Hz, 1 min) frequency stimulation, using glass microelectrodes of the liquid membrane type (pHm). Results were compared with values obtained by the standard homogenate technique (pHh). High- and low-frequency stimulation reduced peak tetanic tension to 21 +/- 1 (SE) and 71 +/- 2% of initial values, respectively. Peak tetanic tension returned to resting values after 10- to 15-min recovery from high- or low-frequency stimulation. Resting pHm was 7.063 +/- 0.011 (n = 72), and after fatiguing stimulation declined to values as low as 6.33. During recovery pHm significantly increased and by 10 min had returned to prefatigue values. No difference was observed in the recovery of pHm between the low- and high-frequency stimulation groups (analysis of variance test, ANOVA), and in both groups pHm recovery was highly correlated to the recovery of peak tetanic tension (r = 0.94, P less than 0.001). Resting pHh was 7.219 +/- 0.023 (n = 13), which was significantly higher than the pHm value. In contrast to pHm, intracellular pHh was significantly higher during recovery from 75- vs. 5-Hz stimulation (P less than 0.05). For both groups pHh increased significantly with time and by 10 min returned to prestimulation values. The ANOVA test demonstrated that pHh values were significantly higher than pHm values during recovery from fatigue. The results from this study support our hypothesis that fatigue from both high- and low-frequency stimulation is at least partially due to the deleterious effects of intracellular acidosis on excitation-contraction coupling.
Topics: Animals; Female; Hydrogen; Hydrogen-Ion Concentration; Intracellular Membranes; Isometric Contraction; Methods; Microelectrodes; Muscles; Rats; Rats, Inbred Strains; Rest
PubMed: 3597214
DOI: 10.1152/jappl.1987.62.4.1392 -
The Journal of General Physiology Sep 1963When deprived of calcium the slow striated muscle fibers of the frog develop reversible contractures in either hypertonic or isotonic solutions. While calcium...
When deprived of calcium the slow striated muscle fibers of the frog develop reversible contractures in either hypertonic or isotonic solutions. While calcium deprivation continues because of a flowing calcium-free solution the muscles relax slowly and completely. Restoration of calcium during contracture relaxes the muscle promptly to initial tension. When relaxed during calcium lack the return of calcium does not change tension and the muscle stays relaxed. When contractures are induced by solutions containing small amounts of calcium relaxation does not occur or requires several hours. The rate of tension development depends upon the rate at which calcium moves outward since the contractures develop slower in low concentrations of calcium and are absent or greatly slowed in a stagnant calcium-free solution. Withdrawal of calcium prevents the contractile responses to ACh, KCl, or electrical stimulation through the nerve. Muscles return to their original excitability after calcium is restored. Origin of the contractures is unrelated to nerve activity since they are maximal during transmission failure from calcium lack, occur in denervated muscles, and are not blocked by high concentrations of d-tubocurarine, procaine, or atropine. The experiments also indicate that the contractures do not originate from repetitive activity of muscle membranes. The findings are most simply explained by relating the outward movement of calcium as a link for initiating contraction in slow type striated muscle.
Topics: Animals; Anura; Calcium; Contracture; Electric Stimulation; Muscle Contraction; Muscle Fibers, Skeletal; Muscle, Skeletal; Muscles; Physiology; Potassium; Research
PubMed: 14065284
DOI: 10.1085/jgp.47.1.133 -
The Journal of General Physiology Nov 19541. Ethylenediamine tetraacetic acid (EDTA) in low concentrations imitates all the known effects of the relaxation factor ("Marsh factor"). In extracted muscle fibers...
1. Ethylenediamine tetraacetic acid (EDTA) in low concentrations imitates all the known effects of the relaxation factor ("Marsh factor"). In extracted muscle fibers which have contracted in a solution containing adenosinetriphosphate (ATP), the addition of EBTA causes relaxation, the subsequent addition of CaCl(2), contraction. 2. In fibers which have been briefly immersed in 5 MM EDTA, ATP causes rapid relaxation if Mg is also present. These fibers have essentially the same properties as briefly extracted fibers. Brief immersion into a solution containing CaCl(2) restores at once the original condition. It is concluded that EDTA produces its action by firmly combining with bound Ca, thereby inactivating it. 3. In relaxed muscle fibers not only Ca, but also lowering the concentration of Mg below a critical level, causes contraction. In such fibers Mg in the lowest effective concentrations increases contraction, but the effect reverses above a certain concentration. 4. At 0 degrees Mg in the presence of ATP has a relaxing effect without the relaxation factor. 5. The results indicate that Mg has two distinct effects in the presence of ATP. It causes contraction at low concentrations, but above a critical concentration its relaxing action prevails. The last of these effects is blocked by bound Ca. If the latter is inactivated by EDTA, Mg in sufficiently high concentrations causes relaxation. The action of the relaxation factor can similarly be explained by assuming that it acts as a complexing agent which inactivates bound Ca. 6. Previous evidence that the relaxed state depends on the formation of an enzymatically inactive ATP-protein complex was confirmed. It was found that PP in low concentrations strongly increases the relaxing effect of ATP in briefly extracted fibers.
Topics: Adenosine Triphosphate; Muscles
PubMed: 13211992
DOI: 10.1085/jgp.38.2.149 -
Journal of Ultrasound in Medicine :... May 2018The traditional activation ratio divides contracted muscle thickness by resting muscle thickness while an abdominal draw-in maneuver is performed during hook lying....
OBJECTIVES
The traditional activation ratio divides contracted muscle thickness by resting muscle thickness while an abdominal draw-in maneuver is performed during hook lying. Ultrasound imaging during function, such as standing or gait, or peak knee flexion in a single-leg squat allows for further visualization of muscle activity. The goal of this study was to examine activation ratio calculations for transverse abdominis function in supine versus loaded conditions to determine the most informative normalization strategy for muscle activity based on thickness values.
METHODS
Transverse abdominis thickness was measured via ultrasound in 35 healthy participants under 4 different conditions. Comparisons were made between the traditional activation ratio tabletop, standing activation ratio (standing abdominal draw-in maneuver thickness/quiet standing thickness), and functional activation ratio (single-leg squat thickness/quiet standing thickness). Additionally, a cued activation ratio (single-leg squat with cued abdominal draw-in maneuver thickness/single-leg squat thickness) during the single-leg squat was obtained. Activation ratios of greater than 1.0 indicated that participants could activate the muscle during activity, and values were compared by analysis of variance.
RESULTS
The participants included 23 women and 12 men with a mean age ± SD of 21.3 ± 2.7 years, mass of 66.1 ± 14.4 kg, and height of 168.5 ± 10.1 cm. Activation ratios exceeded 1.0 in 94.3% for the traditional activation ratio, 85.7% for the standing activation ratio, 82.9% for the cued activation ratio, and 82.9% for the functional activation ratio. With groups defined as tabletop activated or not, the standing, cued, and functional activation ratios were all significantly different (all P < .05).
CONCLUSIONS
Normalizing muscle thickness to the corresponding functional position quiet value provides a useful functional activation ratio and may help clinicians better understand the transverse abdominis role during complex functional tasks. Assessment techniques using various formulas for activation ratios reveal that the muscle functions differently during weight bearing compared to traditional measures.
Topics: Abdominal Muscles; Adult; Female; Humans; Male; Movement; Muscle Contraction; Posture; Reference Values; Rest; Ultrasonography; Weight-Bearing; Young Adult
PubMed: 29076538
DOI: 10.1002/jum.14466