Stretching: pain and no gain?
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Athletic Injuries↗
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Results for “Muscle Stretching Exercises”
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Treatment of spastic flatfoot with procaine-hyaluronidase and stretching.
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Exercise Therapy↗
Iliotibial band syndrome in runners: innovations in treatment.
Iliotibial band syndrome (ITBS) is the most common cause of lateral knee pain in runners. It is an overuse injury that results from repetitive friction of the iliotibial band (ITB) over the lateral femoral epicondyle, with biomechanical studies demonstrating a maximal zone of impingement at approximately 30 degrees of knee flexion. Training factors related to this injury include excessive running in the same direction on a track, greater-than-normal weekly mileage and downhill running. Studies have also demonstrated that weakness or inhibition of the lateral gluteal muscles is a causative factor in this injury. When these muscles do not fire properly throughout the support phase of the running cycle, there is a decreased ability to stabilise the pelvis and eccentrically control femoral abduction. As a result, other muscles must compensate, often leading to excessive soft tissue tightness and myofascial restrictions. Initial treatment should focus on activity modification, therapeutic modalities to decrease local inflammation, nonsteroidal anti-inflammatory medication, and in severe cases, a corticosteroid injection. Stretching exercises can be started once acute inflammation is under control. Identifying and eliminating myofascial restrictions complement the therapy programme and should precede strengthening and muscle re-education. Strengthening exercises should emphasise eccentric muscle contractions, triplanar motions and integrated movement patterns. With this comprehensive treatment approach, most patients will fully recover by 6 weeks. Interestingly, biomechanical studies have shown that faster-paced running is less likely to aggravate ITBS and faster strides are initially recommended over a slower jogging pace. Over time, gradual increases in distance and frequency are permitted. In the rare refractory case, surgery may be required. The most common procedure is releasing or lengthening the posterior aspect of the ITB at the location of peak tension over the lateral femoral condyle.
Cumulative Trauma Disorders↗
Locomotion in patients with spinal cord injuries.
Following central motor lesions, two forms of reorganization can be observed that lead to improved mobility: (1) the development of increased muscle tone and (2) the activation of spinal locomotor centers induced by specific treadmill training. Tension development is different from normal during spastic gait and appears to be independent of exaggerated monosynaptic stretch reflexes. Exaggerated stretch reflexes are associated with an absence or reduction of functionally essential polysynaptic reflexes. Based on observations of the locomotor capacity of the spinal cat, recent studies have indicated that spinal locomotor centers can be activated and trained in patients with complete or incomplete paraplegia when the body is partially unloaded. The level of electromyographic activity in the gastrocnemius muscle, however, is considerably lower in patients with central motor lesions than in persons without neurological impairments. During the course of a daily locomotor training program, the amplitude of gastrocnemius muscle electromyographic activity increases during the stance phase and inappropriate tibialis anterior muscle activity decreases. Such training programs can improve the ability of patients with incomplete paraplegia to walk on stationary surfaces. This article reviews the pathophysiology and functional importance of increased muscle tone and the effects of treadmill training on the locomotor pattern underlying new attempts to improve the mobility of patients with paraplegia.
Animals↗
Regional distribution of blood flow in calf muscles of rat during passive stretch and sustained contraction.
The regional distribution and number of microspheres in the calf muscles of rat has been studied during isometric sustained contraction and in stretched uncontracted muscles in situ. Carbonized microspheres, 15 +/- 5 mum, were injected into the aortic arch and muscle blood flow arrested 6 sec later. The calf muscles were freeze sectioned (12 slices of 40 mum) and the microspheres counted microscopically. The microsphere concentration in the gastrocnemius and plantaris muscles during rest was 4.6 +/- 1.6 spheres/mm3 (mean +/- S.E.). One min after a standardized exercise programme the sphere concentration was increased to 20.5 +/- 3.9 spheres/mm3. At increasing force of contraction following the standard exercise programme, the microsphere concentration fell from 11.6 +/- 2.5 at 25% of maximal force of contraction (MFC) to 2.2 +/- 0.6 spheres/mm3 at 100% MFC (5.6 kg/cm2). Corresponding measurements in stretched, uncontracted muscles showed a similar fall in microsphere concentration in the central inner zone and in the peripheral outer zone was slightly higher than unity (1.08-1.16) in muscles at rest and at light postexercise hyperemia. At 75 and 100% MFC the ratio was 0.76 +/- 0.07 and 0.57 +/- 0.13, significantly lower than unity. Stretching of the uncontracted muscle group to 175% MFC reduced the ratio towards zero. The greater reduction in blood flow to the inner central zone of contracted calf muscles shown by microsphere distribution was confirmed by measurement of 125 I-antipyrine distribution. These results show an increased resistance against blood flow during active contraction or stretching of the calf muscles, most pronounced in the central inner zone at high tensions.
Animals↗
Nerve impulses in the brainstem of the goat; responses with long latencies obtained by stretching the extrinsic eye muscles.
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Action Potentials↗
Effect of stretch on action potential of voluntary muscle.
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Action Potentials↗
Spinal shrinkage in unloaded and loaded drop-jumping.
Plyometric activities, engaging the muscle in a stretch-shortening cycle, are widely used in athletic training. One such plyometric exercise is drop-jumping, where the athlete drops from a raised platform and immediately on landing performs a maximal vertical jump. These actions are also performed with the athlete externally loaded by the addition of weights to provide greater resistance. Exercises which involve repeated impacts have been shown to give rise to a loss of stature (shrinkage) which can be measured by means of a sensitive stadiometer. This study examined the shrinkage induced by unloaded and loaded drop-jumping from a height of 26 cm. Eight male subjects, aged 20-24 years, performed the test protocol three times, at the same time of day on each occasion. Fifty drop-jumps from a height of 26 cm were performed with no additional load and with a load of 8.5 kg carried in a weighted vest. The third condition was a standing trial where the subject stood for 10 min (the time taken to perform the jumps) wearing the weighted vest. Stature was measured before exercise, immediately after exercise and after a 20 min standing recovery. On a separate occasion the regimen was performed and the vertical reaction force was measured using a Kistler force platform. The mean change in stature for the two jump conditions showed shrinkages of 0.62 (+/- 0.43) mm for unloaded and 2.14 (+/- 1.56) mm for the loaded (p < 0.05). The variance in shrinkage was greater in the loaded case compared to the unloaded condition (p < 0.05) indicating a wider range of jumping strategies.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Gene expression in response to muscle stretch.
In studying the way the musculoskeletal system adapts, it is important to consider how the different tissues interact with each other. During growth, and in response to changes in posture, the functional length of muscle is adjusted by altering the number of sarcomeres in series to the optimum for force generation and power output. In some cases, insufficient adaptation gives rise to problems such as muscle contracture. Stretch has marked effects on muscle mass with eccentric contraction being the most effective form of exercise for building muscles. As far as the mechanism is concerned, the current authors have cloned the deoxyribonucleic acid (cDNA) of a splice variant of the insulinlike growth factor gene that is produced by active muscle that seems to be the factor that controls local tissue repair, maintenance, and remodeling. This new growth factor has been called mechanogrowth factor to distinguish it from the liver insulin growth factors, which have a systemic mode of action. The discovery of the locally produced insulinlike growth factor seems to provide the link between the mechanical stimulus and the activation of gene expression.
Adaptation, Physiological↗
Changes in the excitability of soleus muscle short latency stretch reflexes during human hopping after 4 weeks of hopping training.
Changes in the excitability of the human triceps surae muscle short latency stretch reflexes were investigated in six male subjects before and after 4 weeks of progressive two-legged hopping training. During the measurements the subjects performed 2-Hz hopping with: preferred contact time (PCT) and short contact time. The following reflex parameters were examined before and after the training period: the soleus muscle (SOL) Hoffmann-reflex (H-reflex) at rest and during hopping, the short latency electromyogram (EMG) components of the movement induced stretch reflex (MSR) in SOL and medial gastrocnemius muscle (MG), and the EMG amplitude of the SOL and MG tendon reflexes (T-reflexes) elicited at rest. The main results can be summarized as follows: the SOL T-reflex had increased by about 28% (P < 0.05) after training while the MG T-reflex was unchanged; the SOL MSR (always evident) and the MG MSR (when observable) did not change in amplitude with training, and before training the SOL H-reflex in both hopping situations was significantly depressed to about 40% of the reference value at standing rest (P < 0.05). After training the H-reflex during PCT hopping was no longer depressed. As the value of the measured mechanical parameters (the total work rate, joint angular velocity and the ankle joint work rate) was unchanged after training in both hopping situations, the reflex changes observed could not be ascribed to changes in the movement pattern. To explain the observed changes, hypotheses of changes in the excitability of the stretch reflex caused by the training were taken into consideration and discussed.
Adult↗
Pathophysiology of impairment in patients with spasticity and use of stretch as a treatment of spastic hypertonia.
Paralysis, muscle shortening, and muscle overactivity are the three main disabling factors in patients with spasticity. Occurring after most central lesions, muscle overactivity and shortening are not equally spread throughout all muscles of the body. In an agonist-antagonist couple, there is invariably "greater" overactivity and shortening of one versus the other. This is the rationale for the use of targeted local treatments that train the weaker agonist and stretch and partially block the more overactive and shorter antagonist. Central paralysis, muscle shortening, and muscle overactivity are intertwined, and the three corresponding therapies, motor training, stretch, and local partial blocks, should be implemented in combination. This triple treatment is the main condition for any functional recovery. Muscle shortening occurs acutely after a central nervous system lesion; therefore its treatment should be implemented as rapidly as possible.
Casts, Surgical↗
Effects of different dropping intensities on fascicle and tendinous tissue behavior during stretch-shortening cycle exercise.
This study examined whether the elasticity of the tendinous tissues plays an important role in human locomotion by improving the power output and efficiency of skeletal muscle. Ten subjects performed one-leg drop jumps (DJ) from different dropping heights with a constant rebound height. The fascicle length of the vastus lateralis muscle was measured by using real-time ultrasonography during DJ. In the braking phase of the DJ, fascicle lengthening decreased and the tendinous tissue lengthening increased with increased dropping intensity. In the subsequent push-off phase, the shortening of tendinous tissues increased with higher dropping intensity. The averaged electromyographic activities of the preactivation and braking phases increased and those of the push-off phase decreased as the drop height was increased. With higher dropping height but constant submaximal rebound jump, the stretched tendinous tissue length increased with less stretched fascicle during the braking phase. In the subsequent push-off phase, the recoil of tendinous tissues became greater. These results suggest that the increased prestretch intensity has considerable influence on the process of storage and subsequent recoil of the elastic energy during the stretch-shortening cycle action.
Adult↗
Hamstring injuries. Current trends in treatment and prevention.
Pre-exercise stretching and adequate warm-up are important in the prevention of hamstring injuries. A previous mild injury or fatigue may increase the risk of injury. Hamstring muscle tear is typically partial and takes place during eccentric exercise when the muscle develops tension while lengthening, but variation in injury mechanisms is possible. Diagnosis of typical hamstring muscle injury is usually based on typical injury mechanism and clinical findings of local pain and loss of function. Diagnosis of avulsion in the ischial tuberosity, with the need for longer immobilisation, and a complete rupture of the hamstring origin, in which immediate operative treatment is necessary, poses a challenge to the treating physician. X-rays, ultrasonography or magnetic resonance imaging (MRI) may be helpful in differential diagnostics. After first aid with rest, compression, cold and elevation, the treatment of hamstring muscle injury must be tailored to the grade of injury. Conservative treatment is based on a knowledge of the biological background of the healing process of the muscle. Experimental studies have shown that a short period of immobilisation is needed to accelerate formation of the granulation tissue matrix following injury. The length of the immobilisation is, however, dependent on the grade of injury and should be optimised so that the scar can bear the pulling forces operating on it without re-rupture. Mobilisation, on the other hand, is required in order to regain the original strength of the muscle and to achieve good final results in resorption of the connective tissue scar and re-capillarisation of the damaged area. Another important aim of mobilisation--especially in sports medical practice--is to avoid muscle atrophy and loss of strength and extensibility, which rapidly result from prolonged immobilisation. Complete ruptures with loss of function should be operated on, as should cases resistant to conservative therapy in which, in the late phase of repair, the scar and adhesions prevent the normal function of the hamstring muscle.
Athletic Injuries↗
Behaviour of vastus lateralis muscle-tendon during high intensity SSC exercises in vivo.
AIMS: The interaction between fascicle and tendinous tissue of human vastus lateralis muscle was investigated during varying intensity stretch-shortening cycle (SSC) jumps performed on a sledge apparatus. METHODS: Eight subjects performed single leg squat (SJ) and drop jumps (DJ) from a constant dropping height but to different rebound heights. The fascicle length of the vastus lateralis muscle (VL) was determined from real-time ultrasonography during the movement. Tendon length changes were calculated by subtracting the horizontal part of the fascicle length from the muscle-tendon unit (MTU) length. Simultaneously, kinematic, kinetic and electromyographic data were recorded from leg muscles. In addition, the in vivo patella tendon force was measured from one subject during the trials. RESULTS: In all DJs, where MTU was stretched prior to shortening, the fascicle and tendinous tissue of the VL also underwent a SSC. The fascicle lengths decreased and the recoil of tendinous tissue increased with increased rebound intensities (P<0.05). The force-velocity curves obtained from the MTU showed the expected force-velocity relationship for SSC activities, demonstrating performance enhancement. However, the increased MTU power during the shortening phase of the movement was due primarily to the enhancement of the tendon compartment. CONCLUSION: The results of this study show that, at higher rebound intensities, the fascicle is controlled during the braking phase in a distinct manner so that the effective recoil of the tendon is possible during the final push-off phase. In addition, the results suggest that the behaviour of fascicle length change depends on the muscle in question in addition to the movement intensity.
Adult↗
Effects of changes in pH on the afferent impulse activity of isolated cat muscle spindles.
Muscle spindle activity has been shown to decrease in the sustained contracting muscle. The effect has been assumed to result from a declining fusimotor drive. Since accumulation of metabolites including H(+), lactate and CO(2) might also affect the receptor in the fatiguing muscle, the impulse activity of muscle spindles isolated from the cat tenuissimus muscle was characterized under varying degrees of extracellular pH, thus excluding any effect on fusimotor activity, blood supply and extrafusal muscle fibers. The isolated receptor was exposed to bathing fluids of pH 6.4, 7.4 and 8.4, and afferent discharge activity was recorded from the spindle nerve. Both primary and secondary endings responded similarly to changes in pH. Resting discharge frequency usually decreased with decreasing pH and increased with increasing pH. A sudden break-off in activity was observed with about 40% of primary endings and about 30% of secondary endings at pH 6.4. Experiments with slow stretch stimulation indicated that this effect was caused by a rising threshold of firing at the encoder site of the endings. With brief ramp-and-hold stretches, we tested the effects of changes in pH on the dynamic and static sensitivity of primary and secondary endings. When pH was reduced from 7.4 to 6.4, the initial burst activity at the beginning of the ramp phase increased in primary and secondary endings and the dynamic response increased in secondary endings, demonstrating that the dynamic properties of muscle spindle endings were usually augmented in the acidic milieu. The static properties rose as well because the static index of both types of ending increased significantly. By contrast, dynamic and static properties of both primary and secondary endings decreased significantly, when pH was increased from 7.4 to 8.4. The amplitude of tension that was measured during the passive stretch stimuli very slightly decreased in the acidic solution and very slightly increased in the alkaline solution. The decrease in the resting discharge activity at low pH supports those previous observations, which demonstrate a reduced peripheral input from muscle spindle afferents to the spinal motor nuclei during fatigue in the isometric contracting muscle. The present finding indicates that an attenuated afferent discharge is not only caused by a decreasing central activation of gamma-motorneurons, but may additionally be supported by a direct effect of protons on the muscle receptor itself. The accompanying augmentation of stretch sensitivity is suggested to correspond to the well-known increase in physiological tremor during exhaustive exercise.
Animals↗
Acute leg-cycling exercise attenuates the H-reflex recorded in soleus but not flexor carpi radialis.
The amplitude of the Hoffman reflex (H-reflex) in the soleus muscle is attenuated after acute bouts of leg-cycling exercise. The attenuation has been interpreted as a "tranquilizing" effect of exercise controlled by the central nervous system and generalized beyond a single spinal segmental level. If so, the postexercise depression of the H-reflex should occur in both the soleus and the flexor carpi radialis (FCR) muscle, which is not actively involved during leg cycling. This experiment examined the effect of moderate-intensity cycling exercise on the H-reflex recorded in soleus and FCR among 16 men. The H-reflex was measured immediately before and 10 min after 30 min of either moderate-intensity leg cycling (60% VO(2peak)) or quiet rest. The acute bout of cycling exercise reduced the H-reflex in the soleus but not in the FCR. Thus, the attenuation of the H-reflex after leg cycling does not generalize beyond the spinal segmental level that modulates the involved locomotory muscles; it is likely the result of segmental processes associated with the repetitive stretching or activation of the soleus muscle.
Adult↗
The influence of stretching and warm-up exercises on Achilles tendon reflex activity.
The aim of this study was to investigate the acute effects of prior exercise (warm-up and stretching) on the electromyographic and force output of mechanically elicited triceps surae reflexes. Fifty male subjects performed eight reflex experiments under each of three successive conditions in one session: (1) no prior exercise, (2) after static stretching of the passive triceps surae (3 min) and (3) after a 10-min warm-up run on a treadmill. Tendon tap reflex force was elicited in the triceps surae of the right leg by means of a standardized reflex hammer and measured in a custom-built fixture. Electromyographic (EMG) signals were recorded with surface electrodes over the medial head of the gastrocnemius (G) and the soleus (S). Low coefficients of variation within subjects contrasted with high between-subject variations, indicating highly individual reflex characteristics. After stretching, reductions in the peak force (-5%; P < 0.05), the force rise rate (-8%; P < 0.01), the half relaxation rate (-5%; N.S.), the EMG amplitudes (G, -16%; S, -17%; P < 0.01) and integrals (G, -15%; S, -18%; P < 0.01), and an increase in EMG latencies (G, +3%; S, +1%; P < 0.01), were found compared with the values obtained without prior exercise. After running, the peak force reached the values obtained without prior exercise (-2%; N.S.), the force rise rate and half relaxation rate increased by 8 and 12%, respectively (P < 0.01), and the impulse (force-time integral; -12%), EMG amplitudes (G, -20%; S, -23%; P < 0.01), integrals (G, -18%; S, -23%; P < 0.01) and latencies (G, -1%; S, -2%; P < 0.01) decreased significantly. The changes in the force characteristics observed after the stretching treatment indicate improved muscle compliance that might reduce the risk of injury. On the other hand, the changes after the additional warm-up run had a more pronounced influence with regard to improved force development and a decreased EMG activity, which can be viewed as a performance-enhancing effect.
Achilles Tendon↗
Both central command and exercise pressor reflex reset carotid sinus baroreflex.
In decerebrate unanesthetized cats, we determined whether either "central command," the exercise pressor reflex, or the muscle mechanoreceptor reflex reset the carotid baroreflex. Both carotid sinuses were vascularly isolated, and the carotid baroreceptors were stimulated with pulsatile pressure. Carotid baroreflex function curves were determined for aortic pressure, heart rate, and renal vascular conductance. Central command was evoked by electrical stimulation of the mesencephalic locomotor region (MLR) in cats that were paralyzed. The exercise pressor reflex was evoked by statically contracting the triceps surae muscles in cats that were not paralyzed. Likewise, the muscle mechanoreceptor reflex was evoked by stretching the calcaneal tendon in cats that were not paralyzed. We found that each of the three maneuvers shifted upward the linear relationship between carotid sinus pressure and aortic pressure and heart rate. Each of the maneuvers, however, had no effect on the slope of these baroreflex function curves. Our findings show that central command arising from the MLR as well as the exercise pressor reflex are capable of resetting the carotid baroreflex.
Animals↗