Reflex Activation Of Muscles Research Articles

Physical therapy assessment and treatment protocol for nursing home residents.

This article describes a standard protocol for assessing physical function in elderly nursing home residents. Major physical dimensions that are measured with the protocol include range of motion, muscle force, muscle reflex activity, sensation, soft tissue status, balance/coordination, and posture. A practical, functionally prioritized treatment model based on the assessment is also presented. The standardized assessment and treatment plan may be useful to the physical therapist in (1) planning and prioritizing treatment, (2) identifying when goals have been met, (3) recognizing when there is a need for treatment plan modification, and (4) educating physical therapy students in applying problem-solving skills in their treatment sessions.

The nature of suprasegmental influences on the late reflex activity in human forearm muscles

The earliest component of the late EMG response (M2) to sudden strech of an isometrically contracting muscle is influenced by suprasegmental mechanism, but whether these are a tonic, phasic, or both, is uncertain. We have therefore investigated the nature of these mechanisms by varying the predictability of the direction of perturbation of forearm muscles held isometrically against a constant flexor or extensor force of 2.3 N. We found that the M2 response did not change appreciably regardless of whether the direction of pertubation was known in advance or which hand was used by the subject. These findings suggest that any tonic supraspinal influence on the M2 response is of little significance compared to the importance of phasic mechanisms and provide support for the existence of a cerebral are subserving this reflex component.

Skeletal Muscle in Health and Disease, A Textbook of Muscle Physiology

Part 1 Skeletal muscle structure: muscle fibres - size and number muscle organization the contractile proteins structural proteins sarcoplasmic reticulum T-tubular system the EM appearance of different fibre types other structures. Part 2 The mechanism of force generation: methods for measuring contractile properties length-tension relationship of skeletal muscle the nature of the interaction between thick and thin filaments force velocity characteristics biochemistry of force generation. Part 3 Innervation and electrical activity: connections between nerve and muscle the motor unit the neuromuscular junction excitation-contraction coupling calcium transients removal of calcium from the interior of a muscle fibre. Part 4 Histochemistry, contractile properties and motor control: histochemistry contractile properties the relationship between histochemistry and contractile properties the control of fibre type expression motor unit recruitment sensory receptors in skeletal muscle reflex activity coordination of muscular contractions. Part 5 Growth, development and ageing of muscle: embryonic origins and foetal development size of adult muscle endocrine influences on growth and development strength and muscle mass body proportions (somatotypes) the use of anabolic drugs in sport ageing and muscle function. Part 6 Training for power: power output and performance specificity of the training response changes in muscle strength and size during training the stimulus for increase in strength. Part 7 Adaptations for endurance exercise: central drive peripheral fatigue energy supply energy reserves and rates of utilization strategies for improving performance in endurance exercise cardiovascular or peripheral limitations to exercise temperature regulation and dehydration. Part 8 Fatigue: the definition of fatigue central factors the neuromuscular junction peripheral factors motor unit firing frequency fatigue during dynamic or prolonged exercise. Part 9 Muscle damage: physical trauma metabolic depletion damage due to eccentric contractions muscle regeneration. Part 10 Muscular pain: sensory nerves muscle pain during activity pain developing after exercise the effect of training on muscle pain muscle cramp myalgic pain. Part 11 Muscle diseases: atrophic myopathies inflammatory myopathies dystrophies congenital myopathies neuropathies myasthenia gravis neuromuscular changes in human immunodeficiency virus (HIV) infection post viral fatigue syndrome (myalgic encaphalomyelitis) disorders of energy metabolism myotonic syndromes the periodic paralyses malignant hyperpyrexia.

Long-latency stretch reflexes as co-ordinated functional responses in man.

1. Reflex activity in human arm muscles has been measured in response to torque perturbations around the elbow joint in the flexion-extension direction and/or the supination-pronation direction. Intramuscular fine-wire electrodes were used to record electromyographic (EMG) activity in the muscles. A pre-load was applied in the same direction as or in a different direction to the perturbation. The subjects were instructed to 'hold on', which means that they had to actively resist the perturbation without unduly co-activating their muscles. 2. The EMG activity showed segmented reflex responses with short-latency (25-50 ms) and long-latency (50-75 ms) components, followed by other bursts of activity which probably originated from the subject's voluntary or triggered reactions. 3. Motor units in m. triceps gave short-latency and long-latency responses to imposed elbow extension but only long-latency responses were seen to imposed pronation, which does not stretch m. triceps. Motor units in m. brachialis gave short-latency and long-latency excitatory (inhibitory) responses to imposed extension (flexion) torques. However, only long-latency inhibitory responses were observed to imposed pronation torques. Motor units in m. biceps gave short-latency and long-latency excitatory responses to imposed pronation torques. 4. These results show that the long-latency reflex cannot be the result of a simple feed-back mechanism that controls muscle length only. We argue that the long-latency reflex activity reflects the co-ordinated activation of muscles which is necessary for an adequate response. This hypothesis is supported by the fact that the distribution of long-latency reflex activity over muscles was found to be similar to the distribution of activation found during a voluntary exerted torque in the direction opposite to the applied perturbation.

Tactile hairs and the adjustment of body height in wandering spiders: Behavior, leg reflexes, and afferent projections in the leg ganglia

In spiders, stimulation of cuticular tactile hairs on the ventral aspects of proximal leg parts elicits reflex activity in certain leg muscles; contraction of these muscles raises the body. InCupiennius salei, using video film analysis, electromyography, and sensory recordings we studied the body-raising behavior and associated leg reflexes (i) in freely walking spiders, (ii) in animals tethered above a treadmill device, and (iii) in completely immobilized preparations. 1. Freely walking spiders abruptly (within 160 ms) raise their bodies by extending the legs when they touch a ventral flexible wire obstacle. The same animals collide with the obstacle when all tactile hairs on the sternum and on the ventral sides of all proximal leg segments have been removed (Fig. 1). 2. Body raising is also readily induced in tetheredCupiennius that are stimulated ventrally while standing on an air-suspended styrofoam sphere. Deflection of just one ventral hair can induce coordinated extension of all 8 legs (Fig. 2). Electromyograms reveal transient activity in several muscles that occurs almost simultaneously in all walking legs (Fig. 3). 3. Unlike the coordinated response of all legs in spiders tested on the treadmill, tactile reflex activity in spiders immobilized on their backs is confined to muscles of the particular leg being stimulated (‘local reflexes’). Again, deflection of a single tactile hair elicits activity in muscles such as the promotor/adductor of the leg coxa (muscle c2; Figs. 4, 7), which is involved in body raising. 4. The 3 bipolar, mechanosensory neurons innervating each tactile hair differ both in their rates of adaptation to maintained, step-like deflections of their hair shafts (Fig. 8) and in their frequency response to single and to repeated sinusoidal stimulus cycles. Tests with trains of sinusoidal hair deflections demonstrate that activity of one sensory-hair unit alone (unit ‘3’ in Fig. 8) is sufficient to drive the local tactile reflex in muscle c2. 5. Anterograde cobalt fillings of afferents from tactile hairs on the antero-ventral coxa (nerve ‘aCo’) into the fused subesophageal leg ganglia reveals a ventral group of fibers with ipsilateral, intrasegmental endings and a dorsal group with ipsilateral, plurisegmental arborizations in central neuropil (Fig. 9). A companion paper (Milde and Seyfarth 1988) identifies central neuronal correlates of the reflex activity described here.

Reflex effects evoked by stimulation of hypoglossal afferent fibers

In pentobarbitone-anesthetized cats, electrical stimulation of the central ends of the main trunks of transected hypoglossal nerves evoked vascular (pressor or depressor) reactions, mydriasis, slow and deep breathing, and reflex activation of laryngeal and facial muscles. Stimulation of the central end of the transected ramus descendens hypoglossi also provoked reflex contraction of cricothyroideus. These reflexes may be elicited also after intracranial section of hypoglossal nerve roots, but not after intracranial section of ipsilateral vagal roots. The above reflexes were abolished by acute section of the ipsilateral hypoglossonodosal branch, but they may be reproduced by electrical stimulation of the central end of this anastomotic branch between hypoglossal nerve and nodose ganglion. Stimulation of the central end of one transected hypoglossus evoked reflex efferent discharges in contralateral hypoglossus and contraction of contralateral tongue muscles. Stimulation of the central end of one transected hypoglossal end-branch inhibited efferent discharges in another end-branch. The crossed hypoglossohypoglossal reflex and the ipsilateral reflex inhibition were abolished by section of the hypoglossonodosal branch or vagal roots at the stimulated side. We conclude that reflexes evoked by stimulation of peripheral hypoglossal nerve in cats are mediated by afferent fibers directed to the nodose ganglion and entering the brain stem via vagal roots.

Response of genioglossus muscle activity to nasal airway occlusion in normal sleeping adults.

To determine the combined effect of increased subatmospheric upper airway pressure and withdrawal of phasic volume feedback from the lung on genioglossus muscle activity, the response of this muscle to intermittent nasal airway occlusion was studied in 12 normal adult males during sleep. Nasal occlusion at end expiration was achieved by inflating balloon-tipped catheters located within the portals of a nose mask. No seal was placed over the mouth. During nose breathing in non-rapid-eye-movement (NREM) sleep, nasal airway occlusion resulted in multiple respiratory efforts before arousal. Mouth breathing was not initiated until arousal. Phasic inspiratory genioglossus activity was present in eight subjects during NREM sleep. In these subjects, comparison of peak genioglossus inspiratory activity on the first three occluded efforts to the value just before occlusion showed an increase of 4.7, 16.1, and 28.0%, respectively. The relative increases in peak genioglossus activity were very similar to respective increases in peak diaphragm activity. Arousal was associated with a large burst in genioglossus activity. During airway occlusion in rapid-eye-movement (REM) sleep, mouth breathing could occur without a change in sleep state. In general, genioglossus responses to airway occlusion in REM sleep were similar in pattern to those in NREM sleep. A relatively small reflex activation of upper airway muscles associated with a sudden increase in subatmospheric pressure in the potentially collapsible segment of the upper airway may help compromise upper airway patency during sleep.

Intracranial stimulation of the trigeminal nerve in man. III. Sensory potentials.

Percutaneous electrical stimulation of the trigeminal root was performed in 18 subjects undergoing surgery for idiopathic trigeminal neuralgia or implantation of electrodes into Meckel's cave for recording of limbic epileptic activity. All subjects had normal trigeminal reflexes and evoked potentials. Sensory action potentials were recorded antidromically from the supraorbital (V1), infraorbital (V2) and mental (V3) nerves. In the awake subject, sensory potentials were usually followed by myogenic artifacts due to direct activation of masticatory muscles or reflex activation of facial muscles. In the anaesthetised and curarised subject, sensory potentials from the three nerves showed 1.4-2.2 ms onset latency, 1.9-2.7 ms peak latency and 17-29 microV amplitude. Sensory conduction velocity was computed at the onset latency (maximum CV) and at the peak latency (peak CV). On average, maximum and peak CV were 52 and 39 m/s for V1, 54 and 42 m/s for V2 and 54 and 44 m/s for V3. There was no apparent difference in CV between subjects with trigeminal neuralgia and those with epilepsy. A significant inverse correlation was found between CV and age, the overall maximum CV declining from 59 m/s (16 years) to 49 m/s (73 years). This range of CV is compatible both with histometric data and previous electrophysiological findings on trigeminal nerve conduction. Intraoperative intracranial stimulation is also proposed as a method of monitoring trigeminal function under general anaesthesia.

Kutaneo muskuläre Reflexe der menschlichen Hand - II. Neurophysiologische Aspekte der Reflex-Organisation und -Koordination

The organization and coordination of cutaneo-muscular reflexes of human finger and arm muscles to electrical stimulation of the digital nerves were investigated in 14 healthy volunteers. Thumb and finger muscles, although antagonists, showed homonymous reflex effects whereas the wrist and elbow muscles exhibited an reciprocally alternating reflex pattern in pairs of antagonists (Fig. 1). The mechanographical correlate of the homonymous reflex activity in distal muscles was a short release (Fig. 6). The receptive field for evoking such reflex effects covered both the palmar and dorsal surfaces of the fingers (Fig. 2). However, with stimulation of the thumb, the muscles of the fingers and of the wrist showed reflex reversal (Figs 3, 5). If the stimulus was moved from the second to the fifth fingers, a successive attenuation of the transcortical reflex component was seen (Fig. 4). It is concluded that the reflexes investigated are complex flexor reflexes comprising both a distal release and a proximal flexion synergy. According to opposition of the thumb in grasping, the receptive field terminates between thumb and index finger. These reflexes are supposed to have no assisting function during corticalized manipulatory movements--in contrast to the long-loop reflexes evoked by epicritic sensibility. The transcortical servo is blocked if the eliciting stimulus is contaminated by nociceptive signals; its receptive field is confined to those fingers used in the precision grip.

Subcortical and cortical responses following infraorbital nerve stimulation in man

Scalp responses following stimulation of the infraorbital nerve have been recorded in awake and anaesthetized subjects from non-cephalic (NCR) and vertex (VR) reference derivations. In awake subjects, after 3 very early potentials (W1, W2 and W3), 4 small components (P4, N5, P6 and N7) with widespread distribution have been constantly recorded from NCR derivations. Sometimes a further component, named N10, could be recorded in VR derivations on the scalp contralateral to the stimulus in the absence of earlier events. Large and inconstant waves were recorded following N7 in NCR and N10 in VR derivations. The muscular origin of these waves was demonstrated by simultaneous records taken from scalp and muscles. Records from NCR derivations in anaesthetized subjects showed that wave N7 was followed by a further event (N10) localized on the scalp contralateral to the stimulus and by a few slow waves. Wave N10 could also be recorded, in the absence of earlier events, from the VR derivation contralateral to the stimulus. All the responses recorded in these patients could be considered of neurogenic origin because curarization abolished any reflex activation of muscles. All the waves following W3 are of postsynaptic nature and, on the basis of their distribution and latency, we suggest that P4, N5, P6, N7 and N10 have their respective origins in the trigeminal nucleus, trigeminal lemniscus, thalamus, thalamic radiation and cortical projection of the stimulated area. It was also demonstrated that stimulation of lips and gums fails to evoke any neural event recordable from the scalp.

Voluntary supraspinal suppression of spinal reflex activity in paralyzed muscles of spinal cord injury patients

Having previously demonstrated that residual facilitatory brain influence on segmental structures occurs in paralyzed spinal cord injury patients, we sought evidence of suprasegmental suppression in such patients. By recording EMG activity from leg muscles, we studied changes in segmental excitability of the plantar reflex elicited by cutaneous stimulation of the plantar surface. Using surface EMG recordings, 50 paralyzed spinal cord injury patients were examined for their ability to volitionally suppress the plantar reflex on three repeated trials after three baseline trials. The patients, who had no voluntary EMG activity in the monitored muscles, were able to volitionally suppress the plantar reflex responses by 45% in the tibialis anterior, hamstring, and triceps surae muscles and to suppress the quadriceps response by 72%. In this patient group, 73 of 100 tibialis anterior muscle groups showed suppression of more than 20% compared with the control response. On reexamination, these findings were consistent during a period of 2 years in six patients. We conclude that suprasegmental suppression of segmental activity does occur in paralyzed spinal cord injury patients, and that in clinically complete patients, neurological evaluation should include assessment of the degree of preservation of suprasegmental neurocontrol on segmental activity below the lesion.

Does reflex inhibition of motor units follow the "size principle"?

The "size principle" is known to dictate the sequence of recruitment of motor neurons during voluntary or reflex activation of muscles. The present study sought to determine whether the size principle also determined the sequence of reflexly-elicited inhibition of motor neurones. It was found that all masseter motor units were about equally inhibited by a mildly-noxious stimulus to the lip, providing that they were tested at the same level of pre-stimulus excitability, i.e., firing frequency. At higher prestimulus firing frequencies, more intense stimuli were required to inhibit motor unit activity. Thus it is the firing frequency of individual motor neurons, rather than their size, which determines their susceptibility to inhibition.

Influences of periodontal and mandibular-joint receptors on reflex sensitivity of human jaw-closing muscles

Reflex sensitivity from stimulating the chin or the dental arch of the mandible and the influences of periodontal and mandibular joint receptors on jaw muscles were investigated by experiments with and without anaesthesia. The findings showed that periodontal receptors exert an inhibitory influence on motoneural excitability of jaw-closing muscles and facilitate α-motoneurones of the digastric muscle and that the silent period following a jaw jerk is partly caused by inhibition of α-motoneurones of jaw-closing muscles due to activity of periodontal receptors. The ratio of reflex activity in temporal and masseter muscles appeared to depend on the position of the applied stimulus. The mandibular joint receptors appear to play a major part in distributing active muscle-force over these muscles.

FOOT REFLEXES AND THE USE OF THE “INHIBITIVE CAST.”

The four diametrically opposed tonic reflex movements of the foot that can be elicited in normal children throughout the first year represent the peripheral segments of proximally cascaded reflex balance recovery systems. Clinical persistence of one or more of these obligatory movements in cerebral palsied children may habitually distort foot posture and recruit proximal reflex muscle activity and associated hypertonus. Inhibitive casting has proved to be a significant useful adjunct for management of both foot deformity and associated proximal hypertonicity.

Foot reflexes and the use of the "inhibitive cast".

The four diametrically opposed tonic reflex movements of the foot that can be elicited in normal children throughout the first year represent the peripheral segments of proximally cascaded reflex balance recovery systems. Clinical persistence of one or more of these obligatory movements in cerebral palsied children may habitually distort foot posture and recruit proximal reflex muscle activity and associated hypertonus. Inhibitive casting has proved to be a significant useful adjunct for management of both foot deformity and associated proximal hypertonicity.

Organization of stabilizing reflex responses in tibialis anterior muscles following ankle flexion perturbations of standing man

Reflex activity in human ankle muscles in response to 36 deg./s dorsi-flexion rotations of the feet was investigated in subjects standing upright and when leaning back so as to preactivate ankle flexor muscles. Short latency stretch reflex activity in soleus and inhibition in tibialis anterior muscles occured at 50 ms from ankle rotation onset. Two prominent bursts of tibialis activity followed at 83 and 131 ms, and preceded large stabilizing ankle torques. Head movements commenced 20 ms after foot rotations and acquired accelerations exceeding 100 deg./s 2 within 60 ms. It is suggested that the tibialis anterior activity is either a vestibulospinal reflex resulting rom the head movement, or a strethc reflex only present standing, since this activity was not observed when seated subjects received identical foot rotations.

Effects of dorsal cord stimulation on stretch reflexes

The effects of dorsal cord stimulation on phasic and tonic stretch reflex activity in extensor muscles were studied in decerebrate cats. The tonic stretch response was depressed in both fore- and hindlimb (stimulation at levels C1 and T8, respectively) and this often persisted for 5–20 min after the end of 1–10 min of dorsal cord stimulation. Depression of the phasic stretch response was only consistently seen in the forelimb during stimulation (C1) and this rarely outlasted the period of stimulation. These results support the idea that dorsal cord stimulation can reduce muscle tone but provide no explanation for the long-lasting effects of chronic, continuous stimulation in spastic man.

Nonketotic hyperglycemia: Clinical, biochemical, and therapeutic considerations

The salient features of nonketotic hyperglycinemia include apnea, feeding difficulties, lethargy, seizures, abnormal muscle tone and reflex activity, significant developmental delay, and, in most instances, early death. The pathogenesis of the biochemical defect leading to increased glycine concentration in blood, urine, and CSF is likely to concern derangements of the glycine cleavage enzyme and/or transport mechanisms of glycine. Our current state of knowledge of this disorder is incomplete. Therapeutic attempts, as described in Table 2, have been largely unsuccessful. Further basic research on the underlying biochemical perturbation, including additional documentation of the glycine cleavage enzyme deficiency patterns, of substrate inhibition of key metabolic pathways, and of glycine transport aberrations, as well as investigations of new pharmacologic approaches, will be a challenge for investigators in this field. It is hoped that new knowledge in these areas will eventually lead to reduction of morbidity and mortality in children with nonketotic hyperglycinemia.

Reflex activation of laryngeal muscles by sudden induced subglottal pressure changes

In measuring the effect of subglottal pressure changes on fundamental frequency (Fo) of phonation, the effects of changing laryngeal muscle activity must be eliminated. Several investigators have used a strategy in which pulsatile increases of subglottal pressure are induced by pushing on the chest or abdomen of a phonating subject. Fundamental frequency is then correlated with subglottal pressure changes during an interval before laryngeal response is assumed to occur. The present study was undertaken to repeat such an experiment while monitoring electromyographic (EMG) activity of some laryngeal muscles, to discover empirically the latency of the laryngeal response. The results showed a consistent response to each push, with a latency of about 30 ms. Despite this response, analyses of fundamental frequency versus subglottal pressure changes during the interval of constant EMG activity were in general agreement with previously published values. With respect to the nature of the electromyographic response itself, its timing was found to be within the range of latencies appropriate for peripheral feedback, and was also similar to that for an acoustically--or tactually--elicited startle reflex.

Coupled Stretch Reflexes in Ankle Muscles: An Evaluation of the Contributions of Active Muscle Mechanisms to Human Posture Stability

Publisher Summary This chapter examines the stabilizing role of stretch reflexes acting on the ankle flexors and extensors. For this purpose, the reaction forces and the EMG activity of the ankle musculature were recorded while a platform on which the subjects stood was quickly rotated about the ankles. The force responses correcting the postural disturbances were divided into three components: (1) Forces generated by short (40 msec) and medium (90 or 130 msec) latency muscle activity; (2) Visco-elastic forces of the activated muscles; (3) Inertial reaction forces. The analysis of the time course and amplitude of each of these components suggests that short-latency segmental reflexes have a minor role in correcting postural disturbances. Any improvements in the stiffness of the stretch reflex are predominantly provided by medium-latency responses. Because medium-latency responses in ankle flexors and extensors are organized as a time-locked coupled response, their net action stabilizes the standing posture. The force provided by medium latency reflex muscle activity approximately equaled that provided by the inherent visco-elasticity of activated muscles.