Treatment of hypertonicity in muscles of lip retraction.

An EMG biofeedback program was developed for a 56-year-old Parkinsonism patient who exhibited pathological lip hypertonia and retraction. The program was designed to achieve the following goals: (1) to demonstrate a reduction in postural lip hypertonicity and (2) to demonstrate a reduction in lip hypertonicity during a series of increasingly complex speech activities. To achieve the first goal, contrastive tasks of full contraction and relaxation were utilized. Each posture was sustained while voltage measurements were made at specific intervals. Procedures to modify lip retraction during speech included five tasks in which the patient was to monitor the audio feedback signal. The tasks involved: prolongation of a neutral vowel, consonant-vowel combinations, monosyllabic words, sentences, and a paragraph-reading task. Data collected over six biofeedback sessions are presented. Trend analyses showed consistent muscular reduction within each task. The following explanations for the decrease in the patient's hypertonicity were discussed: (1) reduction of anisometric contraction, (2) reduction of isometric contraction, (3) relearning of agonistic-antagonistic muscle balance.     

Transfer of Heart Rate Feedback Training to Reduce Heart Rate Response to Laboratory Tasks

To examine whether transfer of heart rate (HR) feedback training to tasks not used during training could be improved by using multiple tasks during training, a modified multiple baseline across tasks, single subject design study was conducted using six high HR-reactive young adults. Participants received HR feedback training during the presentation of a videogame, and transfer of training was assessed to a mental arithmetic challenge and handgrip task. Transfer of training was next assessed following training with the mental arithmetic challenge and handgrip task. HR responses to each training task with no HR feedback were assessed during a pre-treatment session, an immediate post-training period following training on each task, a short delay (1–2 days) post-training session, and a long delay (1–2 weeks) post-training session. HR response to a novel speech task was assessed at pre-treatment and during short delay and long delay post-training sessions. Results revealed that participants reduced HR during training and generally maintained this reduction in HR during the immediate post-training assessment when HR feedback was not present. Participants were not able to reduce HR responses to tasks during short delay and long delay post-training sessions, and they were unable to transfer HR reduction skills to the speech task. Transfer of HR feedback training to new tasks was limited in nature and efforts to train across multiple stressors did not appear to improve transfer of training.     

Treatment of phantom limb pain with combined EMG and thermal biofeedback: a case report

Phantom pain is a frequent consequence of the amputation of an extremity and causes considerable discomfort and disruption of daily activities. This study describes a patient with extreme phantom limb pain following amputation of the right upper limb. The treatment consisted of 6 sessions of EMG biofeedback followed by 6 sessions of temperature biofeedback. The patient did not use a prosthesis and had not received previous treatment for chronic pain. Results demonstrated complete elimination of phantom limb pain after treatment, which was maintained at a 3- and 12-month follow-up. Pain relief covaried with increase in skin temperature at stump and perceptual telescoping (retraction of phantom limb into stump).     

EMG biofeedback and discriminative muscle control

The awareness model of biofeedback suggests that training teaches new skills or enhances performance at old skills, while the cognitive or feed-forward models suggest that biofeedback brings attention to the response of interest but does not actually increase task skill. In a test of the predictions made by these models, subjects were tested on one or more cross-modal matching tasks, provided brief training, and retested on the task(s). Thirty subjects participated in integer-matching tasks in which they were instructed to produce various levels of frontalis activity corresponding to the levels of a ratio scale. Forty-five subjects participated in a tone-matching task in which they tried to match their frontalis tension to the pitch of a tone. The results indicated that the groups receiving biofeedback training improved at the more difficult integer task and at the tone task. Subjects performed better on the integer tasks than at the tone task. Our findings suggest that an awareness model accounts for changes occurring during biofeedback training. However, an awareness model may be applicable only for tasks of moderate difficulty; for relatively easy tasks, a feed-forward model may be more appropriate. The clinical utility of cross-modal matching tasks is also described.     

EMG biofeedback and discriminative muscle control

The awareness model of biofeedback suggests that training teaches new skills or enhances performance at old skills, while the cognitive or feed-forward models suggest that biofeedback brings attention to the response of interest but does not actually increase task skill. In a test of the predictions made by these models, subjects were tested on one or more cross-modal matching tasks, provided brief training, and retested on the task(s). Thirty subjects participated in integer-matching tasks in which they were instructed to produce various levels of frontalis activity corresponding to the levels of a ratio scale. Forty-five subjects participated in a tone-matching task in which they tried to match their frontalis tension to the pitch of a tone. The results indicated that the groups receiving biofeedback training improved at the more difficult integer task and at the tone task. Subjects performed better on the integer tasks than at the tone task. Our findings suggest that an awareness model accounts for changes occurring during biofeedback training. However, an awareness model may be applicable only for tasks of moderate difficulty; for relatively easy tasks, a feed-forward model may be more appropriate. The clinical utility of cross-modal matching tasks is also described.This paper is based on a thesis conducted by the second author under the direction of the first author. Portions of this paper were presented at the annual meeting of the Association for Applied Psychophysiology and Biofeedback, March 1989, San Diego.     

Neuromuscular fatigue differs with biofeedback type when performing a submaximal contraction.

The aim of the study was to examine alterations in contractile and neural processes in response to an isometric fatiguing contraction performed with EMG feedback (constant-EMG task) when exerting 40% of maximal voluntary contraction (MVC) torque with the knee extensor muscles. A task with a torque feedback (constant-torque task) set at a similar intensity served as a reference task. Thirteen men (26+/-5 yr) attended two experimental sessions that were randomized across days. Endurance time was greater for the constant-EMG task compared with the constant-torque task (230+/-156 s vs. 101+/-32s, P<0.01). Average EMG activity for the knee extensor muscles increased from 33.5+/-4.5% to 54.7+/-21.7% MVC EMG during the constant-torque task (P<0.001), whereas the torque exerted during the constant-EMG task decreased from 42.8+/-3.0% to 17.9+/-5.6% MVC torque (P<0.001). Comparable reductions in knee extensors MVC (-15.7+/-8.7% for the constant-torque task vs. -17.5+/-9.8% for the constant-EMG task, P>0.05) and voluntary activation level were observed at exhaustion. In contrast, excitation-contraction coupling process, assessed with an electrically evoked twitch and doublet, was altered significantly more at the end of the constant-EMG task despite the absence of M-wave changes for both tasks. Present results suggest that prolonged contractions using EMG biofeedback should be used cautiously in rehabilitation programs.     

Pharmacologic manipulation of postoperative labial wound contraction and midfacial growth in rabbits

Recent experimental work has suggested that increased lip pressure and scar contraction following lip repair with wide soft-tissue undermining may, in part, contribute to midfacial growth inhibition. The present study was designed to test this hypothesis through the application of pharmacologic agents reported to minimize scar contraction. Thirty-six 6-week-old rabbits were divided into six groups: unoperated controls, rabbits with surgically created defects left unrepaired (surgical controls), and four groups of rabbits with surgically created defects with lip repair and wide undermining on the maxillary surface. Animals with lip repair received either no injections or labial subcutaneous injections of distilled water (route-of-injection controls), normal saline, or papaverine hydrochloride for 2 weeks postoperatively. Rabbits with lip repair and saline or papaverine injections showed significantly (p less than 0.05) decreased lip pressure, relatively hypotonic orbicularis oris muscle EMG activity on the cleft lip side, and greater anteroposterior facial growth (assessed radiologically) from 2 to 24 weeks postoperatively compared with rabbits with lip repair and postoperatively compared with rabbits with lip repair and no injections or distilled water injections. Preliminary results suggest that wound contraction following lip repair and soft-tissue undermining may contribute to mid-facial growth inhibition, which may be reduced by pharmacologic manipulations in the rabbit model.     

Feel what you say: an auditory effect on somatosensory perception

In the present study, we demonstrate an audiotactile effect in which amplitude modulation of auditory feedback during voiced speech induces a throbbing sensation over the lip and laryngeal regions. Control tasks coupled with the examination of speech acoustic parameters allow us to rule out the possibility that the effect may have been due to cognitive factors or motor compensatory effects. We interpret the effect as reflecting the tight interplay between auditory and tactile modalities during vocal production.     

Evaluation of Novel EMG Biofeedback for Postural Correction During Computer Use

Postural correction is an effective rehabilitation technique used to treat chronic neck and shoulder pain, and is aimed toward reducing the load on the surrounding muscles by adopting a neutral posture. The objective of this investigation was to evaluate the effectiveness of real-time high-density surface EMG (HDsEMG) biofeedback for postural correction during typing. Twenty healthy participants performed a typing task with two forms of postural feedback: (1) verbal postural coaching and (2) verbal postural coaching plus HDsEMG biofeedback. The interface used activity from two HDsEMG arrays placed over the trapezius designed to shift trapezius muscle activity inferiorly. The center of gravity across both arrays was used to quantify the spatial distribution of trapezius activity. Planar angles taken from upper extremity reflective markers quantified cervicoscapular posture. During the biofeedback condition, trapezius muscle activity was located 12.74 ± 3.73 mm more inferior, the scapula was 2.58 ± 1.18° more adducted and 0.23 ± 0.24° more depressed in comparison to verbal postural coaching alone. The results demonstrate the short-term effectiveness of a real-time HDsEMG biofeedback intervention to achieve postural correction, and may be more effective at creating an inferior shift in trapezius muscle activity in comparison to verbal postural coaching alone.     

Effects of excitation-contraction uncoupling by stretch and hypertonicity on metabolism and tension in single frog muscle fibers

Metabolism and tension were examined in single fibers of the semitendinosus muscle of Rana pipiens at 15 degree C after excitation- contraction uncoupling by stretch and hypertonicity. Interrupted tetanic stimulation at 20 HZ for 150 s, of control fibers in isotonic Ringer at a rest sarcomere length (SL) of 2.3 micrometers, resulted in a steadily declining tension, stimulated glycolysis, and significantly reduced fiber phosphocreatine (PCr) and ATP concentrations. Stretching resting muscle fibers to an SL of 4.7 micrometers did not alter metabolite concentrations, but glucose-6-phosphate rose and PCr fell markedly when the stretched fibers were stimulated tetanically, although tension was absent. Immersion of untetanized fibers in 2.5 X isotonic Ringer produced a transient rise in resting tension, an increase in glucose-6-phosphate, and a significant reduction in PCr. During the transient rise in resting tension, PCr consumption per unit of tension-time integral was the same as that in fibers stimulated tetanically in isotonic Ringer. Tetanization of fibers in hypertonic solution did not further alter metabolite concentrations or produce tension. The results indicate that exposure to hypertonicity induces an increase in both tension and consumption of high-energy phosphate bonds (approximately P) in resting fibers, but stretch does not. during tetanic stimulation, stretch interferes with contraction but does not prevent activation, whereas hypertonicity inhibits activation as well as contraction.     

Stimulating the Lip Motor Cortex with Transcranial Magnetic Stimulation

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. Researchers have used single-pulse and repetitive TMS to stimulate the lip representation in the motor cortex. The excitability of the lip motor representation can be investigated by applying single TMS pulses over this cortical area and recording TMS-induced motor evoked potentials (MEPs) via electrodes attached to the lip muscles (electromyography; EMG). Larger MEPs reflect increased cortical excitability. Studies have shown that excitability increases during listening to speech as well as during viewing speech-related movements. TMS can be used also to disrupt the lip motor representation. A 15-min train of low-frequency sub-threshold repetitive stimulation has been shown to suppress motor excitability for a further 15-20 min. This TMS-induced disruption of the motor lip representation impairs subsequent performance in demanding speech perception tasks and modulates auditory-cortex responses to speech sounds. These findings are consistent with the suggestion that the motor cortex contributes to speech perception. This article describes how to localize the lip representation in the motor cortex and how to define the appropriate stimulation intensity for carrying out both single-pulse and repetitive TMS experiments.     

Learned helplessness and the facilitation of biofeedback performance

The present article reports the results of two studies, which, taken together, support the hypothesis that learned helplessness resulting in effort cessation, while detrimental to performance on cognitive tasks, is actually facilitative to performance in a biofeedback relaxation task. Data are presented indicating that false failure feedback leads to the typically reported decrement in performance on a cognitive arithmetic task, while such feedback leads to enhanced performance in biofeedback relaxation. Self-report data suggest that this occurs because when subjects encounter failure, they revise their expectancies of future success downward and consequently plan to exert less effort. Reduction of effort is proposed as the common mechanism underlying the contrast in results between the arithmetic and biofeedback tasks. Results are discussed in terms of their implications for the way in which theories of self-efficacy and learned helplessness are commonly interpreted.     

The Effect of a Single Session of Short Duration Biofeedback-Induced Deep Breathing on Measures of Heart Rate Variability During Laboratory-Induced Cognitive Stress: A Pilot Study

This study examines the acute effect of heart rate variability (HRV) biofeedback on HRV measures during and immediately after biofeedback and during the following laboratory-induced stress. Eighteen healthy males exposed to work-related stress were randomised into an HRV biofeedback group (BIO) or a comparative group (COM). Subjects completed a modified Stroop task before (Stroop 1) and after (Stroop 2) the intervention. Both groups had similar physiological responses to stress in Stroop 1. In Stroop 2, the COM group responded similarly to the way they did to Stroop 1: respiratory frequency (RF) and heart rate (HR) increased, RMSSD and high frequency (HF) power decreased or had a tendency to decrease, while low frequency (LF) power showed no change. The BIO group responded differently in Stroop 2: while RF increased and LF power decreased, HR, RMSSD and HF power showed no change. In the BIO group, RMSSD was higher in Stroop 2 compared to Stroop 1. In conclusion, HRV biofeedback induced a short term carry-over effect during both the following rest period and laboratory-induced stress suggesting maintained HF vagal modulation in the BIO group after the intervention, and maintained LF vagal modulation in the COM group.     

Time to task failure and muscle activation vary with load type for a submaximal fatiguing contraction with the lower leg.

The purpose was to compare the time to failure and muscle activation patterns for a sustained isometric submaximal contraction with the dorsiflexor muscles when the foot was restrained to a force transducer (force task) compared with supporting an equivalent inertial load and unrestrained (position task). Fifteen men and women (mean+/-SD; 21.1+/-1.4 yr) performed the force and position tasks at 20% maximal voluntary contraction force until task failure. Maximal voluntary contraction force performed before the force and position tasks was similar (333+/-71 vs. 334+/-65 N), but the time to task failure was briefer for the position task (10.0+/-6.2 vs. 21.3+/-17.8 min, P<0.05). The rate of increase in agonist root-mean-square electromyogram (EMG), EMG bursting activity, rating of perceived exertion, fluctuations in motor output, mean arterial pressure, and heart rate during the fatiguing contraction was greater for the position task. EMG activity of the vastus lateralis (lower leg stabilizer) and medial gastrocnemius (antagonist) increased more rapidly during the position task, but coactivation ratios (agonist vs. antagonist) were similar during the two tasks. Thus the difference in time to failure for the two tasks with the dorsiflexor muscles involved a greater level of neural activity and rate of motor unit recruitment during the position task, but did not involve a difference in coactivation. These findings have implications for rehabilitation and ergonomics in minimizing fatigue during prolonged activation of the dorsiflexor muscles.     

Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures.

Ten young men sustained an isometric contraction of the knee extensor muscles at 20% of the maximum voluntary contraction (MVC) torque on three separate occasions in a seated posture. Subjects performed an isometric knee extension contraction on a fourth occasion in a supine posture. The time to task failure for the seated posture was similar across sessions (291 +/- 84 s; P > 0.05), and the MVC torque was similarly reduced across sessions after the fatiguing contraction (42 +/- 12%). The rate of increase in electromyograph (EMG) activity (%MVC) and torque fluctuations during the fatiguing contractions were similar across sessions. However, the rate of increase in EMG differed among the knee extensor muscles: the rectus femoris began at a greater amplitude (31.5 +/- 11.0%) compared with the vastus lateralis and vastus medialis muscles (18.8 +/- 5.3%), but it ended at a similar value (45.4 +/- 3.1%). The time to task failure and increase in EMG activity were similar for the seated and supine tasks; however, the reduction in MVC torque was greater for the seated posture. These findings indicate that the time to task failure for the knee extensor muscles that have a common tendon insertion did not alter over repeat sessions as had been observed for the elbow flexor muscles (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003).     

Correspondence between laryngeal vocal fold movement and muscle activity during speech and nonspeech gestures.

To better understand the role of each of the laryngeal muscles in producing vocal fold movement, activation of these muscles was correlated with laryngeal movement during different tasks such as sniff, cough or throat clear, and speech syllable production. Four muscles [the posterior cricoarytenoid, lateral cricoarytenoid, cricothyroid (CT), and thyroarytenoid (TA)] were recorded with bipolar hooked wire electrodes placed bilaterally in four normal subjects. A nasoendoscope was used to record vocal fold movement while simultaneously recording muscle activity. Muscle activation level was correlated with ipsilateral vocal fold angle for vocal fold opening and closing. Pearson correlation coefficients and their statistical significance were computed for each trial. Significant effects of muscle (P < or = 0.0005) and task (P = 0.034) were found on the r (transformed to Fisher's Z') values. All of the posterior cricoarytenoid recordings related significantly with vocal opening, whereas CT activity was significantly correlated with opening only during sniff. The TA and lateral cricoarytenoid activities were significantly correlated with vocal fold closing during cough. During speech, the CT and TA activity correlated with both opening and closing. Laryngeal muscle patterning to produce vocal fold movement differed across tasks; reciprocal muscle activity only occurred on cough, whereas speech and sniff often involved simultaneous contraction of muscle antagonists. In conclusion, different combinations of muscle activation are used for biomechanical control of vocal fold opening and closing movements during respiratory, airway protection, and speech tasks.     

Orofacial and thumb-index finger ramp-and-hold isometric force dynamics in young neurotypical adults

The relation among several parameters of the ramp-and-hold isometric force contraction (peak force and dF/dt_max during the initial phase of force recruitment, and the proportion of hold-phase at target) was quantified for the right and left thumb-index finger pinch, and lower lip midline compression in 40 neurotypical right-handed young adults (20 female/20 males) using wireless force sensors and data acquisition technology developed in our laboratory. In this visuomotor control task, participants produced ramp-and-hold isometric forces as ‘rapidly and accurately’ as possible to end-point target levels at 0.25, 0.5, 1 and 2 Newtons presented to a computer monitor in a randomized block design. Significant relations were found between the parameters of the ramp-and-hold lip force task and target force level, including the peak rate of force change (dF/dt_max), peak force, and the criterion percentage of force within ±5% of target during the contraction hold phase. A significant performance advantage was found among these force variables for the thumb-index finger over the lower lip. The maximum voluntary compression force (MVCF) task revealed highly significant differences in force output between the thumb-index fingers and lower lip (∼4.47–4.70 times greater for the digits versus lower lip), a significant advantage of the right thumb-index finger over the non-dominant left thumb-index finger (12% and 25% right hand advantage for males and females, respectively), and a significant sex difference (∼1.65–1.73 times greater among males).     

Frontal EMG-biofeedback training of athetoid cerebral palsy patients

Six athetoid cerebral palsy patients participated in the following: speech and motor prebiofeedback training evaluation; frontal EMG biofeedback training, 6 wk; speech and motor postbiofeedback training evaluation, Frontal pretraining levels for the subjects averaged 28.9 µV p-p. Subjects' feedback consisted of an auditory signal(clicks) varying proportionately with frontal EMG activity. A visual meter display of the integrated EMG was also provided. Self-regulation of frontal EMG was evident for all subjects within session 1. Throughout all sessions, EMG levels of 2–4 µV were often attained. Trend analysis of EMG acquisition curves showed significant reduction in frontal tension across sessions for all but one subject. Frontal posttraining levels averaged 13.0 µV p-p. Parents or subjects, or both, reported subtle improvements in various speech and motor functions, a finding confirmed by objective postbiofeedback training evaluation. Only the 2 most severely impaired subjects, JA and DS, failed to improve significantly on the speech measures. All subjects improved significantly on those measures that tapped fine and gross motor skills. Collectively, these results indicate that EMG biofeedback training shows promise as an additional treatment modality in the habilitation of cerebral palsy patients.     

Sensorimotor Modulation Differs with Load Type during Constant Finger Force or Position

During submaximal isometric contraction, there are two different load types: production of a constant force against a rigid restraint (force task), and maintenance of position against a constant load (position task). Previous studies reported that the time to task failure during a fatigue task was twice as long in the force task compared with the position task. Sensory feedback processing may contribute to these differences. The purpose of the current study was to determine the influence of load types during static muscle contraction tasks on the gating effect, i.e., attenuation of somatosensory-evoked potentials (SEPs) and the cortical silent period (cSP). Ten healthy subjects contracted their right first dorsal interosseus muscle by abducting their index finger for 90 s, to produce a constant force against a rigid restraint that was 20% of the maximum voluntary contraction (force task), or to maintain a constant position with 10° abduction of the metacarpophalangeal joint against the same load (position task). Somatosensory evoked potentials (SEPs) were recorded from C3′ by stimulating either the right ulnar or median nerve at the wrist while maintaining contraction. The cortical silent period (cSP) was also elicited by transcranial magnetic stimulation. Reduction of the amplitude of the P45 component of SEPs was significantly larger during the position task than during the force task and under control rest conditions when the ulnar nerve, but not the median nerve, was stimulated. The position task had a significantly shorter cSP duration than the force task. These results suggest the need for more proprioceptive information during the position task than the force task. The shorter duration of the cSP during the position task may be attributable to larger amplitude of heteronymous short latency reflexes. Sensorimotor modulations may differ with load type during constant finger force or position tasks.     

The Use of a Respiratory Rate Biofeedback Device to Reduce Dental Anxiety: An Exploratory Investigation

Anxiety experienced by individuals visiting the dental office to receive treatment is common. Evidence has shown biofeedback to be a useful modality of treatment for numerous maladies associated with anxiety. The purpose of the current pilot study was to investigate the use of a novel biofeedback device (RESPeRATE™) to reduce patients’ pre-operative general anxiety levels and consequently reduce the pain associated with dental injections. Eighty-one subjects participated in this study, forty in the experimental group and forty-one in the control group. Subjects in the experimental group used the biofeedback technique, while those in the control group were not exposed to any biofeedback. All subjects filled out a pre-injection anxiety survey, then received an inferior alveolar injection of local anesthetic. Post-injection, both groups were given an anxiety survey and asked to respond to four questions regarding the injection experience using a Visual Analog Scale (VAS). With the use of the respiratory rate biofeedback device, there was a significant reduction of negative feelings regarding the overall injection experience, as measured by a VAS. Our findings demonstrate that this novel biofeedback technique may be helpful in the amelioration of dental anxiety, and may help produce a more pleasant overall experience for the patient.