Effects of variation in physical effort on frontalis EMG activity

The physiological mechanisms underlying forehead muscle biofeedback for stress reduction are not well understood. A common hypothesis considers the frontales to be key muscles uniquely indexing the degree of tension present in the general musculature. We tested this hypothesis under conditions ranging from relaxation to maximum physical effort. The hypothesis was not supported. Changes in forehead muscle activity were limited primarily to reflecting changes in head and neck muscle tension.This research was supported by Grant No. GM26504 from the National Institute of General Medical Sciences. Portions of this paper were presented at the annual meeting of the Society for Psychophysiological Research.     

The Effect of Facial and Trapezius Muscle Tension on Respiratory Impedance in Asthma

This study tested two theories about the relationship between voluntary changes in muscle tension and pulmonary function in asthma. Kotses has theorized that decreased facial muscle tension decreases respiratory impedance via a hypothesized vagaltrigeminal reflex, but that muscle tension in other muscle groups has no such effect. Others have suggested that decreased thoracic muscle tension improves pulmonary function. Subjects were 19 volunteer asthmatic adults. They performed 3-minute cycles of deliberate muscle contraction, alternating two each for the shoulder and forehead muscles, followed by dominant forearm contraction. Surface EMG was measured from the frontalis and right trapezius areas. Airway impedance was measured by forced oscillation pneumography. Cardiac interbeat interval and respiratory sinus arrhythmia were measured to assess vagal tone. Frequency dependence of respiratory impedance increased during shoulder tension, giving some support to the theory relating thoracic tension to impairment in pulmonary function. Correlational analyses suggested a negative relationship between changes in cardiac interbeat interval and both frontalis muscle tension and decreased compliance of tissues in the airways. These findings are the opposite of those predicted by the vagal-trigeminal reflex theory.     

Effects of ischemia on VO2, tension, and vascular resistance in contracting canine skeletal muscle

This study examined the changes in O2 consumption (VO2), vascular resistance, and tension development during skeletal muscle contractions at reduced flow. We tested the hypothesis that when VO2 is limited by O2 supply, the skeletal muscle vasculature is not maximally dilated because of the fall in contractile force that accompanies the decrease in O2 supply. During 30 min of ischemic contractions, tension fell by 45 +/- 4% and VO2 fell 54 +/- 1% from preischemic levels. The O2 cost per unit tension did not change compared with nonischemic muscles. After the initial flow reduction, flow fell an additional 16 +/- 3% over 30 min. Adenosine infusion after 30 min of ischemic contractions increased flow by 42 +/- 3% but increased VO2 by only 9.8 +/- 2.3% and had no effect on tension development. When perfusion pressure was returned to normal after 30 min of ischemic contractions, twitch tension did not begin to recover within 20 min but tetanic tension showed a small improvement. VO2, although increased, remained well below the preischemic level. These results suggest that because of the reduced tension during ischemic contractions, the O2 supply-to-consumption ratio is nearly normal, which could explain the presence of the vasodilator reserve. The defect in tension development is long lived, producing a "stunned" muscle in which excess O2 supply does not restore function or VO2 to normal.     

Racial and gender effects on the relaxation response: Implications for the development of hypertension

This study was designed to explore the effect of race and gender on the forehead muscle tension and finger temperature response to biofeedback-assisted relaxation training in individuals with normal blood pressure. Forty-five subjects—18 Black and 27 White, 25 males and 20 females—participated in eight sessions of autogenic relaxation training and thermal biofeedback. Multivariate analysis of variance of the variables measured at baseline (systolic BP, diastolic BP, sodium excretion, anxiety) was significant for gender. Univariate analysis showed males different from females in DBP, Na⁺ excretion, and trait anxiety. Pretest values of muscle tension were similar by gender, but pretest temperatures were lower in males than females. Repeated measures ANOVA for muscle tension showed a significant effect of period. For temperature, a significant effect of period, gender, and gender × period was observed. Males increased temperature more than females. There was no effect of history of hypertension on the relaxation response. Multiple regression performed on change in muscle tension and change in temperature showed that pretest muscle tension predicted change in muscle tension. Four variables contributed to the variance in change in temperature: pretest temperature, sodium excretion, and state and trait anxiety.     

The Pattern of Activation in the Sartorius Muscle of the Frog

The development of isometric twitch tension has been compared with the redevelopment of isometric tension in the fully active frog sartorius muscle following release. At 0°C the rate of rise of isometric twitch tension is the same as that for the muscle in the fully active state at the same tension but not until about 40 msec. after the stimulus and then only for a few milliseconds. The rates of rise of tension in the twitch and in the redevelopment of tension in the fully active muscle appear to be nearly the same at low tensions. Substitution of nitrate for chloride in the Ringer's solution bathing the muscle retards the development of tension during the early part of the contraction phase of the twitch and the effect reaches a maximum within 3 minutes after changing the solutions. These observations have been discussed in connection with some possible patterns of activation and the hypothesis has been advanced that the rate of activation of a sarcomere is determined mainly by the rate at which the transverse component of the link between excitation and contraction is propagated inwards from the periphery to the center of the fiber. This hypothesis has been discussed in relation to others concerning the nature of excitation-contraction coupling.     

Sustained effects of biofeedback-assisted relaxation therapy in essential hypertension.

The usefulness of biofeedback-assisted relaxation as an adjunct or substitute for pharmacotherapy in essential hypertension can be enhanced if the effects are shown to persist after formal treatment has ended. Patients with essential hypertension successfully treated with biofeedback-assisted relaxation were recalled for follow-up yearly after the termination of treatment. Twenty-six of 40 patients met the BP criterion for success. At one-, two-, and three-year follow-up, 31%, 38%, and 27% of the successful completers continued to meet the criterion for success. The pretreatment-posttreatment decreases in BP were accompanied by decreases in forehead muscle tension and urinary cortisol. Forehead muscle tension, urinary cortisol, and anxiety levels were significantly lower than pretreatment one year after the end of treatment. Self-report data were used to assess continued relaxation practice. No relationship was found between practice and any other dependent measure. It appears that some patients trained in biofeedback-assisted relaxation can maintain lowered blood pressure, muscle tension, anxiety, and cortisol levels over the long term; however, the role of relaxation practice in maintaining these lowered levels remains unclear.     

Sustained effects of biofeedback-assisted relaxation therapy in essential hypertension

The usefulness of biofeedback-assisted relaxation as an adjunct or substitute for pharmacotherapy in essential hypertension can be enhanced if the effects are shown to persist after formal treatment has ended. Patients with essential hypertension successfully treated with biofeedback-assisted relaxation were recalled for follow-up yearly after the termination of treatment. Twenty-six of 40 patients met the BP criterion for success. At one-, two-, and three-year follow-up, 31%, 38%, and 27% of the successful completers continued to meet the criterion for success. The pretreatment-posttreatment decreases in BP were accompanied by decreases in forehead muscle tension and urinary cortisol. Forehead muscle tension, urinary cortisol, and anxiety levels were significantly lower than pretreatment one year after the end of treatment. Self-report data were used to assess continued relaxation practice. No relationship was found between practice and any other dependent measure. It appears that some patients trained in biofeedback-assisted relaxation can maintain lowered blood pressure, muscle tension, anxiety, and cortisol levels over the long term; however, the role of relaxation practice in maintaining these lowered levels remains unclear.     

Noninactivating tension in rat skeletal muscle. Effects of thyroid hormone

Inactivation of excitation-contraction coupling was examined in extensor digitorum longus (EDL) and soleus muscle fibers from rats injected daily with tri-iodothyronine (T3, 150 micrograms/kg) for 10-14 d. Steady-state activation and inactivation curves for contraction were obtained from measurements of peak potassium contracture tension at different surface membrane potentials. The experiments tested the hypothesis that noninactivating tension is a "window" tension caused by the overlap of the activation and inactivation curves. Changes in the amplitude and voltage dependence of noninactivating tension should be predicted by the changes in the activation and inactivation curves, if noninactivating tension arises from their overlap. After T3 treatment, the area of overlap increased in EDL fibers and decreased in soleus fibers and the overlap region was shifted to more negative potentials in both muscles. Noninactivating tension also appeared at more negative membrane potentials after T3 treatment in both EDL and soleus fibers. The effects of T3 treatment were confirmed with a two microelectrode voltage-clamp technique: at the resting membrane potential (-80 mV) contraction in response to a brief test pulse required less than normal depolarization in EDL, but more than normal depolarization in soleus fibers. After T3 treatment, the increase in contraction threshold at depolarized holding potentials (attributed to inactivation) occurred at more depolarized holding potentials in EDL, or less depolarized holding potentials in soleus. The changes in contraction threshold could be accounted for by the effects of T3 on the activation and inactivation curves. In conclusion, (a) T3 appeared to affect the expression of both activation and inactivation characteristics, but the activation effects could not be cleanly distinguished from T3 effects on the sarcoplasmic reticulum and contractile proteins, and (b) the experiments provided evidence for the hypothesis that the noninactivating tension is a steady-state "window" tension.     

Rate-limiting steps in the tension development of freeze-glycerinated vascular smooth muscle

A method for "skinning" arterial smooth muscle is presented which yields isometric tension development typically 60-80% of maximum physiological tension in the presence of micromolar Ca++ and millimolar Mg-ATP, while retaining essentially the native protein content. Using the methods of "CA jump," the time-course of Ca++-activated tension development in the skinned artery can be made identical to, but not faster than, the rate of tension development in the intact artery. In the skinned artery, activating free [Ca++] does not substantially alter the rate at which tension development approaches the final steady tension attained at that free [Ca++] (less than 25% decline in speed for a 10-fold decrease in [Ca++]). These observations are taken to mean that the rate-limiting step in isometric tension development in arterial smooth muscle does not depend directly on Ca++.     

Predictors of success in hypertensives treated with biofeedback-assisted relaxation

This paper describes differences in response in seventeen patients with essential hypertension who participated in a treatment program consisting of electromyograph biofeedback assisted relaxation training. Responders were found to have higher treatment values of urinary and plasma cortisol, Trait Anxiety and forehead muscle tension compared to treatment failures. Responders also sustained greater decreases in plasma, and urinary cortisol after treatment. These data are discussed in light of the ability to predict which hypertensive patients may be most benefitted by a relaxation based treatment.     

A mathematical model for estimating muscle tension in vivo during esophageal bolus transport

We present a model of esophageal wall muscle mechanics during bolus transport with which the active and "passive" components of circular muscle tension are separately extracted from concurrent manometric and videofluoroscopic data. Local differential equations of motion are integrated across the esophageal wall to yield global equations of equilibrium which relate total tension within the esophageal wall to intraluminal pressure and wall geometry. To quantify the "passive" (i.e. inactive) length-tension relationships, the model equations are applied to a region of the esophagus in which active muscle contraction is physiologically inhibited. Combining the global equations with space-time-resolved intraluminal pressure measured manometrically and videofluoroscopic geometry data, the passive model is used to separate active and "passive" components of esophageal muscle tension during bolus transport. The model is of general applicability to probe basic muscle mechanics including the space-time stimulation of circular muscle, the relationship between longitudinal muscle tension and longitudinal muscle shortening, and the contribution of the collagen matrix surrounding muscle fibers to passive tension during normal human esophageal bolus transport and in pathology. Example calculations of normal esophageal function are given where active tone is found to extend only over a short intrabolus segment near the bolus tail and segmental regions of active muscle squeeze are demonstrated.     

A 10-year experience in nasal reconstruction with the three-stage forehead flap

Because of its ideal color and texture, forehead skin is acknowledged as the best donor site with which to resurface the nose. However, all forehead flaps, regardless of their vascular pedicles, are thicker than normal nasal skin. Stiff and flat, they do not easily mold from a two-dimensional to a three-dimensional shape. Traditionally, the forehead is transferred in two stages. At the first stage, frontalis muscle and subcutaneous tissue are excised distally and the partially thinned flap is inset into the recipient site. At a second stage, 3 weeks later, the pedicle is divided. However, such soft-tissue "thinning" is limited, incomplete, and piecemeal. Flap necrosis and contour irregularities are especially common in smokers and in major nasal reconstructions. To overcome these problems, the technique of forehead flap transfer was modified. An extra operation was added between transfer and division.At the first stage, a full-thickness forehead flap is elevated with all its layers and is transposed without thinning except for the columellar inset. Primary cartilage grafts are placed if vascularized intranasal lining is present or restored. Importantly, at the first stage, skin grafts or a folded forehead flap can be used effectively for lining. A full-thickness skin graft will reliably survive when placed on a highly vascular bed. A full-thickness forehead flap can be folded to replace missing cover skin, with a distal extension, in continuity, to supply lining. At the second stage, 3 weeks later during an intermediate operation, the full-thickness forehead flap, now healed to its recipient bed, is physiologically delayed. Forehead skin with 3 to 4 mm of subcutaneous fat (nasal skin thickness) is elevated in the unscarred subcutaneous plane over the entire nasal inset, except for the columella. Skin grafts or folded flaps integrate into adjacent normal lining and can be completely separated from the overlying cover from which they were initially vascularized. If used, a folded forehead flap is incised free along the rim, completely separating the proximal cover flap from the distal lining extension. The underlying subcutaneous tissue, frontalis muscle, and any previously positioned cartilage grafts are now widely exposed, and excess soft tissue can be excised to carve an ideal subunit, rigid subsurface architecture. Previous primary cartilage grafts can be repositioned, sculpted, or augmented, if required. Delayed primary cartilage grafts can be placed to support lining created from a skin graft or a folded flap. The forehead cover skin (thin, supple, and conforming) is then replaced on the underlying rigid, recontoured, three-dimensional recipient bed. The pedicle is not transected. At a third stage, 3 weeks later (6 weeks after the initial transfer), the pedicle is divided.Over 10 years in 90 nasal reconstructions for partial and full-thickness defects, the three-stage forehead flap technique with an intermediate operation was used with primary and delayed primary grafts, and with intranasal lining flaps (n = 15), skin grafts (n = 11), folded forehead flaps (n = 3), turnover flaps (n = 5), prefabricated flaps (n = 4), and free flaps for lining (n = 2). Necrosis of the forehead flap did not occur. Late revisions were not required or were minor in partial defects. In full-thickness defects, a major revision and more than two minor revisions were performed in less than 5 percent of patients. Overall, the aesthetic results approached normal.The planned three-stage forehead flap technique of nasal repair with an intermediate operation (1) transfers subtle, conforming forehead skin of ideal thinness for cover, with little risk of necrosis; (2) uses primary and delayed primary grafts and permits modification of initial cartilage grafts to correct failures of design, malposition, or scar contraction before flap division; (3) creates an ideal, rigid subsurface framework of hard and soft tissue that is reflected through overlying skin and blends well into adjacent recipient tissues; (4) expands the application of lining techniques to include the use of skin grafts for lining at the first stage, or as a "salvage procedure" during the second stage, and also permits the aesthetic use of folded forehead flaps for lining; (5) ensures maximal blood supply and vascular safety to all nasal layers; (6) provides the surgeon with options to salvage reconstructive catastrophes; (7) improves the aesthetic result while decreasing the number and difficulty of revision operations and overall time for repair; and (8) emphasizes the interdependence of anatomy (cover, lining, and support) and provides insight into the nature of wound injury and repair in nasal reconstruction.     

Effects of a non-divalent cation binding mutant of myosin regulatory light chain on tension generation in skinned skeletal muscle fibers.

Each myosin molecule contains two heavy chains and a total of four low-molecular weight light chain subunits, two "essential" and two "regulatory" light chains (RLCs). Although the roles of myosin light chains in vertebrate striated muscle are poorly understood at present, recent studies on the RLC have suggested that it has a modulatory role with respect to Ca2+ sensitivity of tension and the rate of tension development, effects that may be mediated by Ca2+ binding to the RLC. To examine possible roles of the RLC Ca2+/Mg2+ binding site in tension development by skeletal muscle, we replaced endogenous RLC in rabbit skinned psoas fibers with an avian mutant RLC (D47A) having much reduced affinity for divalent cations. After replacement of up to 80% of the endogenous RLC with D47A RLC, maximum tension (at pCa 4.5) was significantly reduced compared with preexchange tension, and the amount of decrease was directly related to the extent of D47A exchange. Fiber stiffness changed in proportion to tension, indicating that the decrease in tension was due to a decrease in the number of tension-generating cross-bridges. Decreases in both tension and stiffness were substantially, although incompletely, reversed after reexchange of native RLC for D47A. RLC exchange was also performed using a wild-type RLC. Although a small decrease in tension was observed after wild-type RLC exchange, the decrease was not proportional to the extent of RLC exchange and was not reversed by reexchange of the native RLC. D47A exchange also decreased the Ca2+ sensitivity of tension and reduced the apparent cooperativity of tension development. The results suggest that divalent cation binding to myosin RLC plays an important role in tension generation in skeletal muscle fibers.     

Endoscopic correction of eyebrow asymmetry in associated forehead soft-tissue injuries

Supported by anatomical principles, a subgaleal endoscopically assisted selective myotomy of the forehead and glabellar muscles was used to achieve eyebrow symmetry in patients with unilateral facial nerve palsy and associated forehead soft-tissue injuries. Selective myotomy equalizes the agonist-antagonist muscle relationship on both sides of the forehead, thereby allowing the untouched muscle to exert its activity without opponent restriction. Selective myotomy allows for the management of the muscles' group action as well as individual manipulation of each muscle in accordance with its participation in the eyebrow deformity.     

Phosphorylation of rabbit skeletal muscle myosin in situ

Myosin light chain (P light chain) is phosphorylated by Ca2+ X calmodulin-dependent myosin light chain kinase. Based on studies with rat skeletal muscles, it has been shown that P light chain phosphorylation correlated to the extent of potentiation of isometric twitch tension. It is not clear whether this correlation exists in rabbit skeletal muscle, which has been the primary source of contractile proteins for biochemical studies. Therefore, phosphorylation of myosin P light chain in rabbit slow-twitch soleus and fast-twitch plantaris muscles in situ was examined. Electrical stimulation (5 Hz, 20 seconds) of plantaris muscle produced an increase in the phosphate content of P light chain from 0.17 to 0.45 mol phosphate/mol P light chain. This increase in phosphate content was accompanied by a 58% increase in maximal isometric twitch tension. Tetanic stimulation (100 Hz, 15 seconds) of rabbit soleus muscle resulted in only a small increase in P light chain phosphate content from 0.02 to 0.10 mol phosphate/mol P light chain, and posttetanic twitch tension did not increase significantly. The correlation between potentiated isometric twitch tension and P light chain phosphorylation in rabbit fast-twitch muscle is similar to that observed in rat skeletal muscle. These results were consistent with the hypothesis that phosphorylation of rabbit skeletal muscle myosin, which results in an increase in actin-activated ATPase activity, may be related to isometric twitch potentiation.     

The Effect of Quinidine on Calcium Accumulation by Isolated Sarcoplasmic Reticulum of Skeletal and Cardiac Muscle

Quinidine potentiates twitch tension and (at higher concentrations) causes contracture of skeletal muscle whereas the same drug reduces tension development of cardiac muscle. To gain insight into the possible differences in the excitation-contraction coupling mechanism of the two types of muscle the effect of quinidine on calcium accumulation by isolated sarcoplasmic reticulum from skeletal and cardiac muscle was investigated. In a medium containing ATP, Mg⁺⁺, oxalate, and ⁴⁵Ca, pharmacologically active concentrations of the drug inhibited calcium accumulation by both skeletal and cardiac sarcoplasmic reticulum. The inhibition of the rates of calcium, uptake by the skeletal muscle preparation ranged from 11% with 10^-4 M quinidine to 90% with 10^-3 M quinidine. With the cardiac muscle preparation the inhibition ranged from 16% with 3 x 10^-6 M quinidine to 100% with 10^-3 M quinidine. With both preparations the inhibition of calcium transport was accompanied by an inhibition of the Ca⁺⁺-activated ATPase activity of the sarcoplasmic reticulum. The effect of quinidine on the skeletal sarcoplasmic reticulum supports the hypothesis that this compound produces twitch potentiation and contracture by interfering with intracellular calcium, sequestration. Its effect on cardiac sarcoplasmic reticulum. has been interpreted in terms of the hypothesis that cardiac contractility is a function of the amount of calcium released from the sarcoplasmic reticulum which is in turn dependent upon the absolute calcium content of the reticulum. Hence, following inhibition of calcium transport there would be less calcium available for coupling.     

Tetanic fatigue and proximate post-tetanic recuperation in sartorius and flexor carpi radialis muscles of the male frog. Effects of iodoacetic acid (author's transl)]

The time-course of the isometric tension output, at 20 degrees C, during a long tetanus and after a short period of rest, was investigated in two isolated frog muscles : the sartorius and flexor carpi radialis muscles. To prevent aerobie and glycolytic recovery processes, some muscles were poisoned with 0,4 mM iodoacetic acid (IAA) and nitrogen, for 20 or 40 min. 1. For the unpoisoned sartorius muscle, tetanic tension declined quickly, but after a 0,8 sec period of rest, the muscle was able to develop high tension. Poisoning with IAA-N2 increased fatigue without suppressing the property of a proximate post-tetanic recuperation. 2. In the flexor carpi radialis muscle resistance to fatigue was very large before poisoning and diminished after poisoning. Proximate recuperation was very weak. 3. The results show that the recovery processes are not a primary factor of the development of the short-term fatigue ; they enhance the hypothesis that a failure of the electromechanical coupling can explain the rate of the tension fall in tetanized sartorius muscles.     

Deficient Discrimination of EMG Levels and Overestimation of Perceived Tension in Chronic Pain Patients

Twenty chronic low back pain patients (CBP), twenty tension headache (THA) patients, and twenty healthy controls (HC) participated in a tension production task where subjects had to attain four levels (4, 8, 12, 16 V) of muscle tension at the m. frontalis and the m. erector spinae. Ratings of perceived tension, pain, and aversiveness as well as EMG, heart rate, and skin conductance levels were recorded. Signal detection and correlational methods revealed that the patients were deficient in muscle tension discrimination at high tension levels in both muscles. They generally overestimated low and underestimated high levels of muscle tension, especially in the CBP group. At low muscle tension levels, both healthy controls and patients showed deficient discrimination ability. Perceived muscle tension, aversiveness, and pain ratings during the tasks were higher in the patient groups. These data confirm and clarify previous reports of deficient tension perception and show concurrent overestimation of bodily symptoms in chronic musculoskeletal pain patients.     

Support for a linear length-tension relation of the torso extensor muscles: An investigation of the length and velocity EMG-force relationships

This study investigated the hypothesis that the length-tension relation of the torso erectors would be linear, mirroring the observed linear increase in extension strength capability toward full flexion. The effect of torso extension velocity on the tension capability of these muscles was also investigated for common motion speeds. A myoelectric-based approach was used wherein a dynamic biomechanical model incorporating active and passive tissue characteristics provided muscle kinematic estimates during controlled sagittal plane extension motions. A double linear optimization formulation from the literature provided muscle tension estimates. The data of five male subjects supported the hypothesis of a linear length-tension relation toward full flexion for both the erector spinae and latissimus muscles. Velocity trends agreed with that predicted by Hill's exponential relation, although linear trends were found to fit the data almost as well. The results have implications for muscle tension estimation in biomechanical torso modeling, and suggest a possible low back pain injury mechanism through tissue strain while lifting in fully flexed postures.     

Effects of alternative control procedures for electromyographic biofeedback relaxation training

Twenty-four college students participated in a single session of electromyographic (EMG) biofeedback in a comparison of three experimental control procedures commonly employed in biofeedback relaxation training research. One group received contingent EMG biofeedback from the forehead area, and each subject in this group served as his or her own control. Subjects in a second group received noncontingent EMG feedback from a tape recorder but were instructed to use the feedback signal to relax their forehead muscles (single blind). Subjects in a third group received the same auditory feedback as those in the second group but were not told the purpose or source of the feedback stimulus (yoked control). The contingent feedback group showed significantly less EMG activity when compared to the other two groups. However, this group did not exhibit significant EMG level decrements from the beginning to end of the session. This seemingly contradictory finding may have been due to statistically capitalizing on the artifactually high EMG level of the experimental and control groups, although the single-blind and yoked-control groups showed nonsignificant increases across the session. The single-blind group's data had a variance several times larger than the other two groups' variance. Findings are discussed with respect to a probing hypothesis as opposed to the previously offered frustration hypothesis. Of the three control procedures, the data suggest the yoked control as the procedure of choice for EMG biofeedback relaxation research.The authors would like to thank David Kazar and Claudia Coleman for their technical assistance with this article.