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PubMed1991

Muscle damage induced by eccentric contractions of 25% strain.

Contractile and morphological properties were measured in the rabbit tibialis anterior muscle 1 h after isometric contraction (IC), passive stretch (PS), or eccentric contraction (EC). Maximal tetanic tension (Po) was reduced after 30 min of PS (P less than 0.001), IC (P less than 0.001), or EC (P less than 0.0001). However, the magnitude of the force deficit was a function of the treatment method. After 30 min of cyclic PS, Po decreased by 13%, whereas after IC or EC, Po decreased by 31 and 69%, respectively. The time course of tension decline in the various groups suggested that the EC-induced injury occurred during the first few minutes of treatment. Although the morphology of samples from the PS and IC groups appeared normal, eccentrically exercised muscles exhibited portions of abnormally large fibers (diam greater than or equal to 110 microns) when viewed in cross section. Examination of 231 such fibers from 6 muscles revealed that all enlarged fibers were exclusively of the fast-twitch glycolytic fiber type. Although no ultrastructural abnormalities were observed in any of the muscles from the IC or PS groups, a significant portion of the fibers in the EC group displayed various degrees of disorganization of the sarcomeric band pattern. Taken together, these studies highlight the importance of fiber oxidative capacity in EC-induced injury, which may be related to the damage mechanism.

Animals↗

PubMed1992

Vagal afferent and reflex responses to changes in surface osmolarity in lower airways of dogs.

In anesthetized dogs we examined the sensitivity of afferent vagal endings in the lungs to changes in airway fluid osmolarity. Injection of 0.25-0.5 ml/kg water or hyperosmotic sodium chloride solutions (1,200-2,400 mmol/l) into a lobar bronchus caused bradycardia, arterial hypotension, apnea followed by rapid shallow breathing, and contraction of tracheal smooth muscle. All effects were abolished by vagotomy. We examined the sensory mechanisms initiating these effects by recording afferent vagal impulses arising from the lung lobe into which the liquids were injected. Water stimulated pulmonary and bronchial C-fibers and rapidly adapting receptors; isosmotic saline and glucose solutions were ineffective. Hyperosmotic saline (1,200-9,600 mmol/l, 0.25-1 ml/kg) stimulated these afferents in a concentration-dependent manner. Stimulation began 1-10 s after the injection and sometimes continued for several minutes. Responses of slowly adapting stretch receptors varied. Our results suggest that non-isosmotic fluid in the lower airways initiates defense reflexes by stimulating pulmonary and bronchial C-fibers and rapidly adapting receptors. Conceivably, stimulation of these afferents as a result of evaporative water loss from airway surface liquid could contribute to exercise-induced asthma.

Animals↗

PubMed1981

Muscle receptors with fine afferent fibers which may evoke circulatory reflexes.

The majority of afferent nerve fibers in mammalian skeletal muscle are thin myelinated (A delta or group III) and unmyelinated (C or group IV) afferents. Some 50% of these units appear to be responsible for the reception of noxious chemical, mechanical, and thermal stimuli, i.e., they are nociceptors. The other receptive units with fine afferent fibers presumably are activated by moderate innocuous stimuli such as light stretch, contractions, and light local touching. They possibly play a role in the circulatory and respiratory adjustments during exercise, i.e. they may be ergoreceptors. The data presently available suggest that the nociceptive as well as the ergoreceptive units are very heterogeneous groups with diverse receptive properties. The sensitivity of an individual unit may be restricted to the mechanical domain or to a single chemical substance, whereas other receptors respond to a great variety of chemical, mechanical, and probably thermal stimuli. Each receptor, however, seems to have a preferred susceptibility or "dominant sensitivity" to one or the other stimulus. This sensitivity may be modified by various factors, such as the local concentration of prostaglandins or serotonin. The concept of different types of fine afferent units is supported by preliminary ultrastructural findings showing a great structural diversity both in regard to the localization and the structural design of the receptive endings of these afferents.

Animals↗

PubMed1998

[Exercise and sports: an undervalued health resource].

The importance of physical activity for health is internationally recognised. The physiological and the epidemiological evidence for health effects of both moderate and vigorous intensity exercise is demonstrated and a "Physical Activity Pyramid" is recommended: Half an hour of moderate intensity activities a day at the base level are already promising substantial health effects. On the second step, additional benefits can be derived from cardiorespiratory fitness training, strength training and stretching exercises. The top of the pyramid can be reached by further sports activities.

Adult↗

PubMed2000

Management of spasticity in stroke.

Spasticity treatment must be considered in relation to other impairments with functional goals defined prior to intervention. The effects of muscle co-contraction and involuntary limb movement associated with exaggerated cutaneous reflexes or effort as well as stretch reflex hyperexcitability need to be considered. Exacerbating factors such as pain must be identified. Physical therapy and conventional orthoses are the mainstays of spasticity management during acute rehabilitation. Botulinum toxin shows promise but needs further evaluation in the context of acute rehabilitation. Phenol chemodenervation can produce good results in spasticity refractory to standard treatments. Muscle strengthening exercises may be appropriate in chronic hemiparesis without adversely affecting tone. Electrical stimulation may be a useful adjunct to other spasticity treatments. Difficulty demonstrating functional benefit from antispasticity treatment may imply that interventions directed at single motor impairments whether weakness or spasticity are not likely to result in functional benefit, but it is their combination that is important.

Humans↗

PubMed1997

Mononeuropathy of a distal branch of the femoral nerve in a body building champion.

A unique case of a body building champion with localised atrophy of the distal portion of the vastus lateralis muscle is reported; neurophysiological evaluation suggests a selective lesion of a distal branch of the vastus lateralis nerve (a motor branch of the femoral nerve). A necroscopic study in four cases was performed to better clarify the site and mechanism of nerve lesion. The data suggest that stretching and compression of the nerve has probably occurred during strenous exercise.

Adult↗

PubMed1997

Stretch-induced enhancement of mechanical power output in human multijoint exercise with countermovement.

The relation between the eccentric force developed during a countermovement and the mechanical power output was studied in squatting exercises under nominally isotonic load (50% of 1-repetition maximum). The subjects (n = 5) performed squatting exercises with a countermovement at varied deceleration rates before lifting the load. The ground reaction force and video images were recorded to obtain the power output of the body. Net muscle moments acting at hip, knee, and ankle joints were calculated from video recordings by using inverse dynamics. When an intense deceleration was taken at the end of downward movement, large eccentric force was developed, and the mechanical power subsequently produced during the lifting movement was consistently larger than that produced without the countermovement. Both maximal and mean power outputs during concentric actions increased initially with the eccentric force, whereas they began to decline when the eccentric force exceeded approximately 1.4 times the sum of load and body weight. Video-image analysis showed that this characteristic relation was predominantly determined by the torque around the knee joint. Electromyographic analyses showed no consistent increase in time-averaged integrated electromyograph from vastus lateralis with the power output, suggesting that the enhancement of power output is primarily caused by the prestretch-induced improvement of an intrinsic force-generating capability of the agonist muscle.

Adult↗

PubMed2005

Management of work-related low back pain: a population-based survey of physical therapists.

BACKGROUND AND PURPOSE: Physical therapy often is used in the management of work-related low back pain (LBP). Little information, however, is known about the types of interventions used by physical therapists in the management of this condition. The objective of this study was to describe the interventions used by physical therapists in the treatment of workers with acute or subacute LBP, with or without radiating pain below the knee. SUBJECTS: Clinical management questionnaires for workers without and with radiating pain were returned by 190 and 139 physical therapists, respectively. METHODS: For each treatment session, therapists recorded treatment objectives, interventions, and education provided to 2 workers with LBP, 1 with radiating pain and 1 without radiating pain. RESULTS: The majority of physical therapists used stretching and strengthening exercises, spinal mobilization, soft tissue mobilization and massage, manual traction, posture correction, interferential current, ultrasound, heat, and functional activities education. With radiating pain, the majority of the therapists also used cold and the McKenzie approach. Treatment objectives pursued by the majority of the therapists were decrease of pain, increase of range of motion, increase of muscle strength (force-generating capacity of muscle), decrease of muscle tension, and worker education. DISCUSSION AND CONCLUSION: Physical therapists use an array of interventions with workers with LBP. The effectiveness of most interventions reported has not been well studied.

Absenteeism↗

PubMed1989

Iliopsoas myofascial dysfunction: a treatable cause of "failed" low back syndrome.

Most patients with low back pain experience loss of spinal and hip extension range of motion. The limitation appears to involve significant iliopsoas myofascial dysfunction manifested in tenderness, as shown by deep abdominal palpation of the psoas muscle, hip flexor contracture, pain elicited by the stretch maneuver of the spine and hip, and relative weakness of the psoas muscle when tested manually. These signs assisted in identifying the source of low back pain in six patients who had failed to respond to prior treatment. Therapy consisted of iliopsoas trigger point treatment using a dry needling technique, followed by self-administered postisometric relaxation exercise of the iliopsoas. In all cases, marked improvement of hip and spine extension, dramatic reduction of pain, and return to normal activity resulted. Given the low risk-to-benefit ratio, trigger point treatment is indicated in "failed back syndrome" and chronic low back pain after conservative therapy or surgery have been tried without success.

Abdominal Muscles↗

PubMed1995

Leg cramps: differential diagnosis and management.

Leg cramps are a common problem, especially in the elderly. The differential diagnosis is extensive and includes the following conditions: true cramps, such as those related to heat, hemodialysis and electrolyte disturbances, as well as idiopathic cramps (the most common type); contractures occurring in conditions such as metabolic myopathies and thyroid disease; tetany, which is usually related to electrolyte disturbances, and dystonias, such as occupational cramps and those related to antipsychotic medications. Other leg problems that are not cramps, such as restless legs syndrome and periodic leg movements, also must be distinguished. The etiology of idiopathic leg cramps is not clear. Treatments for leg cramps include stretching exercises, quinine sulfate and vitamin E, but no treatment is conclusively effective. Nonetheless, in many patients relief of symptoms is achieved with one or more of these treatments.

Diagnosis, Differential↗

PubMedDate not supplied

Effects of stretching the gastrocnemius muscle.

Many authors currently disagree on the amount of time necessary to provide an adequate stretch flexibility. Since gastrocnemius equinus has been recognized as a cause of athletic injury, the authors performed a study to test what may be an adequate amount of stretching a gastrocnemius to improve flexibility. This study could not be conducted blind, and it was hoped that the contralateral leg could offer some control. The results of this study are presented here and should be kept in mind when evaluating and treating patients with ankle equinus, especially when considering surgical intervention.

Adult↗

PubMed1999

Mechanisms of muscle injury after eccentric contraction.

Eccentric contractions of skeletal muscles produce injury and, ultimately, muscle strengthening. Current data suggests that the earliest events associated with injury are mechanical in nature and may be based primarily on the sarcomere strain experienced by the muscle. In this review, recent experimental data, primarily from rabbit dorsiflexor muscles, are used to provide general information regarding the factors that cause injury and means for preventing injury. Mechanical experiments reveal that excessive sarcomere strain is the primary cause of injury. We hypothesize that excessive strain permits extracellular or intracellular membrane disruption that may permit hydrolysis of structural proteins leading to the myofibrillar disruption that is commonly observed. Inflammation that occurs after injury actually further degrades the tissue, but prevention of the inflammation leads to a long-term loss in muscle function. Simple treatments such as increasing muscle oxidative capacity ("getting into shape") or cyclic stress-relaxation of tissue ("stretching out") have no measurable effect on the magnitude of muscle injury that occurs. Ultimately, an improved understanding of the damage mechanism may improve our ability to provide rehabilitative and strengthening prescriptions that have a rational scientific basis.

Animals↗

PubMed1988

Neural adaptation to resistance training.

Strength performance depends not only on the quantity and quality of the involved muscles, but also upon the ability of the nervous system to appropriately activate the muscles. Strength training may cause adaptive changes within the nervous system that allow a trainee to more fully activate prime movers in specific movements and to better coordinate the activation of all relevant muscles, thereby effecting a greater net force in the intended direction of movement. The evidence indicating neural adaptation is reviewed. Electromyographic studies have provided the most direct evidence. They have shown that increases in peak force and rate of force development are associated with increased activation of prime mover muscles. Possible reflex adaptations related to high stretch loads in jumping and rapid reciprocal movements have also been revealed. Other studies, including those that demonstrate the "cross-training" effect and specificity of training, provide further evidence of neural adaptation. The possible mechanisms of neural adaptation are discussed in relation to motor unit recruitment and firing patterns. The relative roles of neural and muscular adaptation in short- and long-term strength training are evaluated.

Adaptation, Physiological↗

PubMed2000

Elasticity of tendon structures of the lower limbs in sprinters.

The present study aims to investigate the elasticity of tendon structures of the lower limbs in sprinters and its relation with sprint performance. Subjects were 10 male sprinters and 14 controls whose anthropometric variables and isometric maximum strength were similar. The elongation (L) of the tendon and aponeurosis of vastus lateralis (VL) and medial gastrocnemius muscles (MG) during isometric knee extension and planter flexion, respectively, were determined using a real-time ultrasonic apparatus in vivo, while the subjects developed a gradually increasing torque from zero (relax) to maximal effort (MVC) within 5 s. While sprinters compared with controls showed significantly greater L above 500 N (about 50% of MVC) and higher dL/dF for VL at less than 20% of MVC during knee extension, there were no significant differences between the two groups in L and dL/dF for MG at every 10% of MVC during plantar flexion. Moreover, the average value of dL/dF above 50% of MVC, proposed as the compliance of tendon structures, did not significantly differ between sprinters and controls in either VL or MG. In a regression analysis within sprinters, the compliance of VL was negatively correlated to 100-m sprint time, r=-0.757 (P < 0.05), but that of MG was not, r=0.228 (P > 0.05). Thus the present results indicate that the elasticity of tendon structures of VL and MG at high force production levels, which might be assumed to associate with the storage and subsequent release of energy during exercises involving the stretch-shortening cycle, are similar in both sprinters and controls. For sprinters, however, the tendon structures of VL are more compliant than that for controls at low force production levels, and its elasticity at high force production levels may influence sprint performance.

Adult↗

PubMed2005

Affective images: relieving chronic pain and enhancing quality of life for older persons.

With increasing life expectancy, the incidence of chronic illness and chronic pain also increase. Chronic pain robs older people of their quality of life, and limits functional mobility and ambulation, which leads to muscle atrophy. Older people are often reluctant to request pain relief, attempting to endure pain as a "normal" part of ageing. Innovative non-pharmacological interventions in pain management are appealing. In this study, affective images and pictures were used in 15 elderly patients (12 female and three male) in chronic pain who needed to perform stretching and standing exercises in their physiotherapy sessions. Pain scores were measured by the Visual Analogue Scale (VAS), and health-related quality of life was measured by the Medical Outcomes Study Short Form 36 (SF-36). VAS and SF-36 were administered in weeks 1 and in 6. Pain scores were measured during physiotherapy session in the following weeks. There was a significant decreased in VAS from week 1 to week 6 (t = 3.607; df = 14; p < 0.05). Also, a significant decrease in VAS occurred when the patients were watching affective pictures while performing the physiotherapy exercise in weeks 2 and 3, but not in weeks 4 and 5. SF-36 increased in week 6, which indicated an increase in health-related quality of life, though not statistically significant. Affective images and pictures appear to be an effective non-pharmacological intervention in pain management for the older person.

Affect↗

PubMed1988

Comparison of cyclic and sustained passive stretching using a mechanical device to increase resting length of hamstring muscles.

The purpose of this study was to compare the effects of cyclic versus sustained passive stretching with a mechanical device on resting hamstring muscles' length. Group 1 subjects (5 men, 17 women) underwent cyclic stretching of their right hamstring musculature, and Group 2 subjects (5 men, 16 women) underwent sustained stretching of their right hamstring musculature. The stretching procedures were performed for 15 minutes on 5 consecutive days. A follow-up examination of the subjects' relative knee flexion range of motion was made one week posttreatment. The Group 1 subjects had a mean ROM increase of 15.4 +/- 5.0 degrees after the five stretching treatments and maintained a mean ROM increase of 10.4 +/- 5.5 degrees on the follow-up examination (p less than .001). In Group 2, the five stretching treatments resulted in a mean ROM increase of 13.4 +/- 4.4 degrees, and a mean increase of 7.9 +/- 4.0 degrees was maintained on the follow-up examination (p less than .001). Linear regression analysis revealed that initial ROM, sex, and treatment method significantly contributed to increases in ROM from Day 1 of treatment to the follow-up examination (F = 6.04; df = 4,36; p less than .0008). The cyclic stretching method resulted in a greater gain in ROM when the other variables were considered. Predicted values of ROM increases were also examined and discussed.

Adult↗

PubMed1988

Neuronal activity of the cat supraoptic nucleus is influenced by muscle small-diameter afferent (groups III and IV) receptors.

In anesthetized cats, responses of single neurosecretory neurons of the supraoptic nucleus to activation of muscle receptors were investigated. Electrical stimulation (1-3 pulses at 200 Hz) of group III and IV pure muscle afferents (gastrocnemius nerve) evoked excitation of greater than 50% of supraoptic nucleus neurons (n = 50), whereas stimulation of group Ia or Ib fibers was ineffective. Baroreceptor stimulation inhibited 95% of these supraoptic nucleus neurons that responded to activation of muscle afferents. Excitation of receptors in the gastrocnemius muscle by intra-arterial injection of chemicals (NaCl, KCl, and bradykinin) increased firing rates of most (84%, 74%, and 80%, respectively) neurosecretary neurons. The magnitude of the excitatory response was dose dependent--bradykinin being the most effective. The response disappeared after muscle denervation. When the gastrocnemius muscle alone was contracted phasically by ventral root stimulation, discharges of the supraoptic nucleus neurons increased, whereas quick stretch of the muscle had no effect. We conclude that activation of muscle receptors by chemical or mechanical stimulus can directly excite neurosecretory neurons in the supraoptic nucleus and that afferent impulses are carried by polymodal fibers of small diameter but not by the largest afferents (group I) from the muscle. The results may relate to increased concentrations of plasma vasopressin during exercise.

Animals↗

PubMed1991

The electro-mechanical delay of the erector spinae muscle: influence of rate of force development, fatigue and electrode location.

Electro-mechanical delay (EMD) values of the erector spinae muscle were obtained using a technique based on the cross-correlation between the force and the electromyogram (EMG). Seven subjects performed a series of 20 submaximal dynamic isometric contractions in a seated position at two frequencies (0.5 Hz and 1 Hz) to study the influence of the rate of force development on EMD. Mean EMD values of 125.7 (SD 28.1) ms (1 Hz) and 136.8 (SD 28.6) ms (0.5 Hz) were shown to differ significantly (P = 0.02). This finding supports the hypothesis that EMD is inversely related to the rate of force development and implies that the time to stretch the series elastic component is an important factor determining EMD. After performing a series of fatiguing contractions EMD did not differ significantly from the control value. Multiple regression analysis showed that maximal voluntary contraction force (MVC) and endurance time of the fatiguing exercise correlated significantly with EMD. The site from which the EMG signal was recorded had no significant influence on EMD. However, the coefficient of correlation between force and the EMG-signal differed significantly between electrode positions. The magnitude of the EMD values found emphasized the need to account for this delay when interpreting temporal patterns of activation of the muscles in, for example, lifting tasks.

Adult↗