[Reversibility of the plastic stretching of smooth muscles].
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A discussion of bruxism, mandibular deviation and hypermobility problems producing temporomandibular joint (TMJ) and masticatory muscle pathology is presented. The pathophysiology of painful masticatory muscle hyperactivity, TMJ dysfunction and chondromalacia are presented. The role that pain mediators play in the degradation of TMJ fibrocartilage, acute synovitis and joint and muscle pain is analyzed. Isokinetic and stretching exercises are described to assist in correcting or preventing pathology and dysfunction of these structures.
Muscle strain injuries are some of the most frequent injuries in sports and command a great deal of attention in an effort to understand their etiology. These injuries may be the culmination of a series of subcellular events accumulated through repetitive lengthening (eccentric) contractions during exercise, and they may be influenced by a variety of variables including fiber strain magnitude, peak joint torque, and starting muscle length. To assess the influence of these variables on muscle injury magnitude in vivo, we measured fiber dynamics and joint torque production during repeated stretch-shortening cycles in the rabbit tibialis anterior muscle, at short and long muscle lengths, while varying the timing of activation before muscle stretch. We found that a muscle subjected to repeated stretch-shortening cycles of constant muscle-tendon unit excursion exhibits significantly different joint torque and fiber strains when the timing of activation or starting muscle length is changed. In particular, measures of fiber strain and muscle injury were significantly increased by altering activation timing and increasing the starting length of the muscle. However, we observed differential effects on peak joint torque during the cyclic stretch-shortening exercise, as increasing the starting length of the muscle did not increase torque production. We conclude that altering activation timing and muscle length before stretch may influence muscle injury by significantly increasing fiber strain magnitude and that fiber dynamics is a more important variable than muscle-tendon unit dynamics and torque production in influencing the magnitude of muscle injury.
1. Increases in strength and size of the quadriceps muscle have been compared during 12 weeks of either isometric or dynamic strength training. 2. Isometric training of one leg resulted in a significant increase in force (35 +/- 19%, mean +/- S.D., n = 6) with no change in the contralateral untrained control leg. 3. Quadriceps cross-sectional area was measured from mid-thigh X-ray computerized tomography (c.t.) scans before and after training. The increase in area (5 +/- 4.6%, mean +/- S.D., n = 6) was smaller than, and not correlated with, the increase in strength. 4. The possibility that the stimulus for gain in strength is the high force developed in the muscle was examined by comparing two training regimes, one where the muscle shortened (concentric) and the other where the muscle was stretched (eccentric) during the training exercise. Forces generated during eccentric training were 45% higher than during concentric training. 5. Similar changes in strength and muscle cross-sectional area were found after the two forms of exercise. Eccentric exercise increased isometric force by 11 +/- 3.6% (mean +/- S.D., n = 6), and concentric training by 15 +/- 8.0% (mean +/- S.D., n = 6). In both cases there was an approximate 5% increase in cross-sectional area. 6. It is concluded that as a result of strength training the main change in the first 12 weeks is an increase in the force generated per unit cross-sectional area of muscle. The stimulus for this is unknown but comparison of the effects of eccentric and concentric training suggest it is unlikely to be solely mechanical stress or metabolic fluxes in the muscle.
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Pain and weakness are prominent symptoms which occur after a delay in muscles which have been stretched during contraction (eccentric contraction). These symptoms are particularly severe when the exercise is unaccustomed and when the stretch occurs in muscles on the descending limb of the force-length relation, i.e. at long muscle lengths. It is known that sarcomeres are potentially unstable on the descending limb and it has been proposed by Morgan that uncontrolled elongation of some sarcomeres occurs during eccentric contractions on the descending limb. In this article, the evidence that this mechanism leads to the reduced force is considered. If overextended sarcomeres persist after the eccentric exercise it will cause a shift in the peak of the force-length curve. There is also evidence that in some types of muscle, excitation-contraction coupling is impaired and contributes to the muscle weakness. Cytoskeletal proteins stabilize the sarcomeric structure and may be injured either by the overextended sarcomeres or by activation of proteases. The potential of these mechanisms to contribute to the effects of muscle training and to the symptoms of muscle disease, such as muscular dystrophy, is considered.
BACKGROUND: Stress reaction in bone, which may proceed to a fracture, is a significant problem in military recruits and in athletes, particularly long distance runners. OBJECTIVES: To evaluate the evidence from randomised controlled trials of interventions for prevention or management of lower-limb stress fractures and stress reactions of bone in active young adults. SEARCH STRATEGY: We searched the Cochrane Musculoskeletal Injuries Group Specialised Register (April 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2004), MEDLINE (1966 to September week 1, 2004), EMBASE, CINAHL, Index to UK Theses, reference lists of relevant articles and contacted trialists. SELECTION CRITERIA: Any randomised or quasi-randomised trials evaluating interventions for preventing or treating lower limb stress reactions of bone or stress fractures in active young adults. DATA COLLECTION AND ANALYSIS: We independently selected trials for inclusion, assessed trial quality and extracted data. Only limited data pooling was undertaken. MAIN RESULTS: We included 16 trials. All 13 prevention trials involved military recruits undergoing training. Participants of two of the three treatment trials were military personnel. Ten prevention trials tested the effects of various foot inserts and other footwear modifications. While pooling of data was not possible, the four trials evaluating the use of "shock-absorbing" boot inserts versus control found fewer stress injuries of the bone in their intervention groups. However, the only trial showing a significant benefit lacked important information about trial design. A key issue in several trials was the acceptability, in terms of practicality and comfort, of the boot inserts. Two cluster-randomised prevention trials found no significant effect of leg muscle stretching during warm up before exercise. Pooled data from three small but very different trials testing the use of pneumatic braces in the rehabilitation of tibial stress fractures showed a significant reduction in the time to recommencing full activity (weighted mean difference -33.39 days, 95% confidence interval -44.18 to -22.59 days). These results were highly heterogeneous (I squared = 90%), which is likely to reflect the underlying differences of the trials, including differences in the control group interventions and definitions of outcomes. AUTHORS' CONCLUSIONS: The use of shock absorbing inserts in footwear probably reduces the incidence of stress fractures in military personnel. There is insufficient evidence to determine the best design of such inserts but comfort and tolerability should be considered. Rehabilitation after tibial stress fracture may be aided by the use of pneumatic bracing but more evidence is required to confirm this.
An investigation was made on the relationship between music practice and musculo-skeletal disorders among piano students, with the main aim of developing health education programmes that would improve the performance and health of the students. The investigation covered three areas: (a) Analysis of study organization and main musculo-skeletal complaints achieved by a questionnaire distributed to all piano students at the Milan Conservatory. (b) Vocational electromyographic analysis of the effort exerted by the various muscle groups of the trunk, of the shoulder and shoulder blade girdle, and of the arm during performance of a standard set of piano exercises, an unseen passage and a passage of maximum difficulty. This analysis was made on a sample of six subjects. (c) A series of preventive measures was developed on the basis of a critical assessment of the results (38% of the students practised for excessively long periods without breaks; 62% had from 1 to 5 complaints, the most affected sites being the spine and the trapezius muscles). These consisted largely of a health education programme aimed at helping the students to suitably organize practice and rest periods and in instructing them in appropriate exercises for relaxation and stretching of overused muscle groups and strengthening the supporting muscle groups. Changes in lifestyle were also suggested.
Muscle cramp is a common, painful, physiological disturbance of skeletal muscle. Many athletes are regularly frustrated by exercise-induced muscle cramp yet the pathogenesis remains speculative with little scientific research on the subject. This has resulted in a perpetuation of myths as to the cause and treatment of it. There is a need for scientifically based protocols for the management of athletes who suffer exercise-related muscle cramp. This article reviews the literature and neurophysiology of muscle cramp occurring during exercise. Disturbances at various levels of the central and peripheral nervous system and skeletal muscle are likely to be involved in the mechanism of cramp and may explain the diverse range of conditions in which cramp occurs. The activity of the motor neuron is subject to a multitude of influences including peripheral receptor sensory input, spinal reflexes, inhibitory interneurons in the spinal cord, synaptic and neurotransmitter modulation and descending CNS input. The muscle spindle and golgi tendon organ proprioceptors are fundamental to the control of muscle length and tone and the maintenance of posture. Disturbance in the activity of these receptors may occur through faulty posture, shortened muscle length, intense exercise and exercise to fatigue, resulting in increased motor neuron activity and motor unit recruitment. The relaxation phase of muscle contraction is prolonged in a fatigued muscle, raising the likelihood of fused summation of action potentials if motor neuron activity delivers a sustained high firing frequency. Treatment of cramp is directed at reducing muscle spindle and motor neuron activity by reflex inhibition and afferent stimulation. There are no proven strategies for the prevention of exercise-induced muscle cramp but regular muscle stretching using post-isometric relaxation techniques, correction of muscle balance and posture, adequate conditioning for the activity, mental preparation for competition and avoiding provocative drugs may be beneficial. Other strategies such as incorporating plyometrics or eccentric muscle strengthening into training programmes, maintaining adequate carbohydrate reserves during competition or treating myofascial trigger points are speculative and require investigation.
Two-thirds of all adults age 65 or older are either irregularly active or completely sedentary. With this inactivity comes an increased risk of chronic diseases, including coronary heart disease, hypertension, diabetes, osteoporosis, and depression. Adequate aerobic exercise--even when started as late as age 60--is associated with a 1- to 2-year increase in life expectancy, as well as increased functional independence. Even chairbound patients can benefit from a program of simple exercises. To help prevent injuries, your exercise prescription should include stretching exercises and exercises to strengthen the muscles surrounding weak joints.
The stretch-shortening cycle (SSC) is an effective and natural form of muscle function but, when repeated with sufficient intensity or duration, it may lead to muscle damage and functional defects. A reduced tolerance to impact has been reported, which may be partly attributed to a reduced stretch-reflex potentiation. The aim of the present study was to examine the influence of SSC-induced metabolic fatigue and muscle damage on the efficacy of stretch reflexes, as judged by the electromyograph (EMG) response of two shank muscles (lateral gastrocnemius LG, soleus SOL) to controlled ramp stretches. These EMG responses were recorded before and immediately after exhausting SSC-type leg exercise and 2 h, 2 days and 4 days later. Serum concentrations of creatine kinase ([CK]), myoglobin and lactate were measured repetitively along the protocol. Two maximal vertical drop jumps and counter-movement jumps were performed after each reflex test. The exhausting SSC-type exercise induced an immediate reduction (P < 0.05) with a delayed short-term recovery of the LG peak-to-peak reflex amplitude. This was not accompanied by significant changes in the reflex latency. The drop jump performance remained slightly but significantly reduced (P < 0.05) until the 2nd day postexercise. Peak [CK] appeared for all the subjects on the 2nd day, suggesting the presence of muscle damage. The increase in [CK] between the 2nd h and the 2nd day postexercise was found to be negatively related (P < 0.001) to the relative changes in the drop jump height. Furthermore, a significant relationship (P < 0.05) was found between recovery of the stretch reflex in LG and the decrease of [CK] between the 2nd and the 4th day. These findings support the hypothesis of a reduced stretch-reflex sensitivity. While the exact mechanisms of the reflex inhibition remain unclear, it is emphasized that the delayed recovery of the reflex sensitivity could have resulted from the progressive inflammation that develops in cases of muscle damage.
Ascending vasodilatation is integral to blood flow control in exercising skeletal muscle and is attributable to conduction from intramuscular arterioles into proximal feed arteries. Passive stretch of skeletal muscle can impair muscle blood flow but the mechanism is not well understood. We hypothesized that the conduction of vasodilatation along feed arteries can be modulated by changes in muscle length. In anaesthetized hamsters, acetylcholine (ACh) microiontophoresis triggered conducted vasodilatation along feed arteries (diameter, 50-70 microm) of the retractor muscle secured at 100 % resting length or stretched by 30 %. At 100 % length, ACh evoked local dilatation (> 30 microm) and this response conducted rapidly along the feed artery (14 +/- 1 microm dilatation at 1600 microm upstream). During muscle stretch, feed arteries constricted approximately 10 microm (P < 0.05) and local vasodilatation to ACh was maintained while conducted vasodilatation was reduced by half (P < 0.01). Resting diameter and conduction recovered upon restoring 100 % length. Sympathetic nerve stimulation (4-8 Hz) produced vasoconstriction and attenuated conduction in the manner observed during muscle stretch, as did noradrenaline or phenylephrine (10 nM). Inhibiting nitric oxide production (Nomega-nitro-L-arginine, 50 microM) produced similar vasoconstriction yet had no effect on conduction. Phentolamine, prazosin, or tetrodotoxin (1 microM) during muscle stretch abolished vasoconstriction and restored conduction. Inactivation of sensory nerves with capsaicin had no effect on vasomotor responses. Thus, muscle stretch can attenuate conducted vasodilatation by activating alpha-adrenoreceptors on feed arteries through noradrenaline released from perivascular sympathetic nerves. This autonomic feedback mechanism can restrict muscle blood flow during passive stretch.
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We have studied 35 patients (25 female and 10 male) with low-back pain who were managed with aquatic exercises after an appropriate period of treatment for their condition in the medical institution. The exercises employed consisted of strengthening exercises for the abdominal, gluteal, and leg muscles, stretching of the back, hip, hamstrings, and calf muscles, walking in water, and swimming. All the patients had been participating in the exercise program for more than 6 months. The frequency of performing exercises was once a week for 7 patients, twice a week for 19, and 3 or more times a week for the remaining patients. The method used in this study was a survey questionnaire which was composed of questions about the patient's physical and psychological condition. Those patients who had performed exercises twice or more in a week showed a more significant improvement in the physical score than those who performed exercises only once a week. More than 90% of the patients felt they had improved after 6 months of participation in the program. The improvement in physical score was independent of the initial ability in swimming. The results obtained suggested that exercises in water may be one of the most useful modes of exercise for a patient with low-back pain.
Congenital muscular torticollis (wry neck) results from shortening of the sternocleidomastoid muscle and may lead to limitation of neck movement and craniofacial deformity. If conservative treatment is started early, with a regimen of passive stretching exercises and active strengthening of the contralateral muscle, about 95% of patients achieve an acceptable range of neck movement. The surgical management of patients who do not respond to physiotherapy remains controversial. Its aim is to provide a long-term, cosmetic restoration of neck mobility while minimizing the development of craniofacial deformity and upper cervical scoliosis; few previously advocated techniques achieve both these goals. We describe a technique that combines subperiosteal lengthening of the sternocleidomastoid muscle at its mastoid insertion, and division of lower fibrotic bands with minimal postoperative fibrosis. As the sternomastoid muscle is reattached lower down on the mastoid process, the lengthening of the muscle is stable, because the tendency to fibrosis and shortening is minimized. Comparison of the results with previous series shows that this technique provides immediate benefit and good long-term results.
One hundred drop jumps were performed at maximal intensity every 20 s in 12 untrained subjects (UT), 9 sprinters (S) and 10 long-distance runners (LDR). Muscle contraction force (P20, P50) induced by percutaneous electrical stimulation (20 Hz and 50 Hz, respectively) as well as maximal voluntary contraction force and the height of vertical jumps performed in different ways decreased (P<0.05) and was not restored to the initial value 20 min post exercise. There was a marked increase in low frequency fatigue (LFF) in all the groups studied as substantiated by a significant decrease in the ratio of P20/P50 immediately after exercise as well as 20 min post exercise compared to pre exercise values (P<0.05). However, low frequency fatigue was similar in UT, S and LDR. The jump height of the sprinters during counter-movement jump and drop jump at 90 degrees decreased to a smaller extent compared to jumps performed by LDR and UT. Muscle pain did not differ between UT, S and LDR at 24 h post exercise. The present data indicate that endurance training status as well as prevalence of muscle fibres of the slow type does not decrease muscle resistance to LFF nor accelerate the recovery of muscle contraction force following maximal, intermittent stretch-shortening cycle exercise.
Congenital muscular torticollis is a painless condition usually presenting during infancy with a tight sternocleidomastoid muscle causing the child's head to be tilted to the tightened side. Limited neck motion and a palpable tumor within the muscle are often present. A regimen of stretching exercises is the most common form of treatment with positive outcomes for over 90% of the identified cases. Rarely children require surgical intervention to release the tightened muscle. Botox injections to relax the tight muscle is a new form of treatment being used by some practitioners. Torticollis also presents as a symptom for a variety of muscular, bony, and neurologic conditions, which are briefly reviewed in this article.
The purpose of this study was to determine the effect of different durations of static stretching exercises on coxo-femoral (hip) flexibility. The experimental group, consisting of 20 sedentary women (20-30 years of age), participated in an exercise programme of static stretching exercises with emphasis on the hamstring muscles. The programme lasted for 10 weeks and consisted of two 50-min sessions per week. A control group of 15 sedentary women did not participate in the programme. Hip flexibility was determined before, during and at the end of the programme by means of a goniometric measuring technique developed by us and described elsewhere. Three sub-groups were formed, each following the same programme except that the duration of the static stretch differed (group 1, 10 s; group 2, 20 s; group 3, 30 s). The ANOVA tests showed that for all groups - the control group excepted - the hip flexibility had improved significantly after 10 weeks (P less than 0.05). No significant differences in hip flexibility were noted between the three subgroups at the end of the programme. This finding suggests that a duration of 10 s static stretching is sufficient for improving coxo-femoral flexibility.