Passive Mechanical Properties Of Muscle Research Articles

The Structure and Role of Intramuscular Connective Tissue in Muscle Function.

Extracellular matrix (ECM) structures within skeletal muscle play an important, but under-appreciated, role in muscle development, function and adaptation. Each individual muscle is surrounded by epimysial connective tissue and within the muscle there are two distinct extracellular matrix (ECM) structures, the perimysium and endomysium. Together, these three ECM structures make up the intramuscular connective tissue (IMCT). There are large variations in the amount and composition of IMCT between functionally different muscles. Although IMCT acts as a scaffold for muscle fiber development and growth and acts as a carrier for blood vessels and nerves to the muscle cells, the variability in IMCT between different muscles points to a role in the variations in active and passive mechanical properties of muscles. Some traditional measures of the contribution of endomysial IMCT to passive muscle elasticity relied upon tensile measurements on single fiber preparations. These types of measurements may now be thought to be missing the important point that endomysial IMCT networks within a muscle fascicle coordinate forces and displacements between adjacent muscle cells by shear and that active contractile forces can be transmitted by this route (myofascial force transmission). The amount and geometry of the perimysial ECM network separating muscle fascicles varies more between different muscle than does the amount of endomysium. While there is some evidence for myofascial force transmission between fascicles via the perimysium, the variations in this ECM network appears to be linked to the amount of shear displacements between fascicles that must necessarily occur when the whole muscle contracts and changes shape. Fast growth of muscle by fiber hypertrophy is not always associated with a high turnover of ECM components, but slower rates of growth and muscle wasting may be associated with IMCT remodeling. A hypothesis arising from this observation is that the level of cell signaling via shear between integrin and dystroglycan linkages on the surface of the muscle cells and the overlying endomysium may be the controlling factor for IMCT turnover, although this idea is yet to be tested.

The Passive Mechanical Properties of Muscles and Tendons in Children Affected by Osgood-Schlatter Disease

Osgood-Schlatter disease (OSD) is a sports-related disorder involving apophysitis, which affects the tibial tuberosity. The identification of factors related to OSD is important for its prevention and early recovery from the disease. This study aimed to compare the passive mechanical properties of the muscle-tendon unit in children affected by an OSD and healthy children, by using ultrasound real-time tissue elastography. Eighteen legs affected by OSD (OSD group) and 42 healthy legs (control: CON group) were assessed. The elasticity was obtained from the quadriceps muscles and patella tendon (PT) using real-time tissue elastography. The strain ratio (SR; muscle or tendon/reference ratio: strain rate of the muscle or tendon divided by that of the reference material) was calculated as an indicator of the elasticity of the tissue of interest. The SR of the PT in the OSD group was significantly lower than that in the CON group (P<0.05). We found no significant difference between the groups in terms of the SR value of all muscles (P>0.05). The results suggest that a PT with a lower SR may be associated with an OSD and that the passive mechanical properties of the quadriceps muscles have limited association with an OSD. Level IV.

The passive mechanical properties of muscle.

The passive mechanical properties of muscle.

The desmin network is a determinant of the cytoplasmic stiffness of myoblasts.

The mechanical properties of cells are essential to maintain their proper functions, and mainly rely on their cytoskeleton. A lot of attention has been paid to actin filaments, demonstrating their central role in the cells mechanical properties, but much less is known about the participation of intermediate filament (IF) networks. Indeed the contribution of IFs, such as vimentin, keratins and lamins, to cell mechanics has only been assessed recently. We study here the involvement of desmin, an IF specifically expressed in muscle cells, in the rheology of immature muscle cells. Desmin can carry mutations responsible for a class of muscle pathologies named desminopathies. In this study, using three types of cell rheometers, we assess the consequences of expressing wild-type (WT) or mutated desmin on the rheological properties of single myoblasts. We find that the mechanical properties of the cell cortex are not correlated to the quantity, nor the quality of desmin expressed. On the contrary, the overall cell stiffness increases when the amount of WT or mutated desmin polymerised in cytoplasmic networks increases. However, myoblasts become softer when the desmin network is partially depleted by the formation of aggregates induced by the expression of a desmin mutant. We demonstrate that desmin plays a negligible role in the mechanical properties of the cell cortex but is a determinant of the overall cell stiffness. More particularly, desmin participates to the cytoplasm viscoelasticity. Desminopathies are associated with muscular weaknesses attributed to a disorganisation of the structure of striated muscle that impairs the active force generation. The present study evidences for the first time the key role of desmin in the rheological properties of myoblasts, raising the hypothesis that desmin mutations could also alter the passive mechanical properties of muscles, thus participating to the lack of force build up in muscle tissue.

Investigation of the passive mechanical properties of spine muscles following disruption of the thoracolumbar fascia and erector spinae aponeurosis, as well as facet injury in a rat

Background ContextMuscle tissue is known to remodel in response to changes to its mechanical environment. Alterations in passive mechanical properties of muscles can influence spine stiffness and stability. PurposeThis study aimed to determine whether passive muscle elastic moduli and passive muscle stresses increased 28 days following mechanical disruption of the thoracolumbar fascia and erector spinae aponeurosis, and injury induced by facet joint compression. Study DesignMale Sprague Dawley rats were randomly assigned to three groups (Incision n=8; Injury n=8; and Control n=6). MethodsThe thoracolumbar fascia and erector spinae aponeurosis were incised in the Incision and Injury groups to expose the left L5–L6 facet joint. In the Injury group, this facet was additionally compressed for three minutes to induce facet injury and cartilage degeneration. Twenty-eight days after surgery, rats were sacrificed and muscle samples were harvested from lumbar and thoracic erector spinae and multifidus for mechanical testing. ResultsHistologic staining revealed mild cartilage degeneration and boney remodeling in the Injury group. However, the hypotheses that either (1) disruption of the thoracolumbar fascia and erector spinae aponeurosis (Incision group) or (2) the addition of facet compression (Injury group) would increase the passive elastic modulus and stress of surrounding muscles were rejected. There was no effect of surgery (Incision or Injury) on the passive elastic modulus (p=.6597). Passive muscle stresses were also not different at any sarcomere length between surgical groups (p>.7043). ConclusionDisruption of the thoracolumbar fascia and erector spinae aponeurosis and mild facet damage do not lead to measurable changes in passive muscle mechanical properties within 28 days. These findings contribute to our understanding of how spine muscles are affected by injury and fundamental aspects of the initial stages of spine surgery.

Effect of Cryopreserved Amniotic Membrane on the Mechanical Properties of Skeletal Muscle after Strabismus Surgery in Rabbits

ABSTRACTPurpose: To study the functional recovery of the superior rectus muscle (SRM) after its partial resection in a rabbit model with and without cryopreserved amniotic membrane (AM).Material and methods: Resection of the right and left SRMs of 30 rabbits was performed. On the left eyes, a single sheet of equine cryopreserved AM was placed covering the muscle edge sutured. Active and passive mechanical properties of muscles operated with and without AM were monitored over time at 30 (n = 10), 60 (n = 10), and 90 (n = 10) days after surgery. Muscle samples were extracted and electrically stimulated to register the force exerted by the samples, characterizing its active behavior. They were, then, subjected to stretching test to obtain its resistance to deformation, known as passive behavior. Moreover, right and left eyes of a control group (n = 5) were equally subjected to active and passive tests to characterize the physiological behavior of SRM muscles.Results: On active function examination, statistically significant differences were documented between the following: control vs AM and no AM at 30 days (p = 0.002 and p = 0.04, respectively). All other comparisons were insignificant (p > 0.05). On passive function analysis, significant differences were only found between control vs. no AM at 30 days (p = 0.004) and between AM vs. no AM at 30 days (p = 0.002). Indeed, muscle operated without AM did not recover a normal passive function until 60 days after surgery.Conclusion: Cryopreserved AM is effective in accelerating recovery of SRM passive function in rabbits. Nevertheless, AM produced no significant effect on recovery of SRM active function.

Force-controlled ultrasound to measure passive mechanical properties of muscle in Duchenne muscular dystrophy.

The purpose of this study is to assess differences in skeletal muscle compressibility between patients with Duchenne muscular dystrophy (DMD) and normal subjects. The transverse passive mechanical properties of muscle, particularly those related to stiffness and elasticity, can be measured using force-controlled ultrasound. We acquired ultrasound videos of muscle compression under known pressures in the biceps and quadriceps in 23 boys with DMD and 20 age-matched healthy controls. We calculated the bulk linear spring constant, nonlinear stress-strain response, and average Young's modulus for each. Young's modulus was found to be significantly higher in the DMD population in both the biceps (normal: 33 ± 6 kPa, DMD: 45 ± 14, p <; .01) and quadriceps (normal: 42 ± 6, DMD: 58 ± 14, p <; .0001). Muscle compressibility measured by force-controlled ultrasound is an objective and robust technique to quantitatively monitor the effects of DMD and distinguish from normal subjects.

Evaluation of Muscle Function of the Extensor Digitorum Longus Muscle &lt;em&gt;Ex vivo&lt;/em&gt; and Tibialis Anterior Muscle &lt;em&gt;In situ&lt;/em&gt; in Mice

Body movements are mainly provided by mechanical function of skeletal muscle. Skeletal muscle is composed of numerous bundles of myofibers that are sheathed by intramuscular connective tissues. Each myofiber contains many myofibrils that run longitudinally along the length of the myofiber. Myofibrils are the contractile apparatus of muscle and they are composed of repeated contractile units known as sarcomeres. A sarcomere unit contains actin and myosin filaments that are spaced by the Z discs and titin protein. Mechanical function of skeletal muscle is defined by the contractile and passive properties of muscle. The contractile properties are used to characterize the amount of force generated during muscle contraction, time of force generation and time of muscle relaxation. Any factor that affects muscle contraction (such as interaction between actin and myosin filaments, homeostasis of calcium, ATP/ADP ratio, etc.) influences the contractile properties. The passive properties refer to the elastic and viscous properties (stiffness and viscosity) of the muscle in the absence of contraction. These properties are determined by the extracellular and the intracellular structural components (such as titin) and connective tissues (mainly collagen) 1-2. The contractile and passive properties are two inseparable aspects of muscle function. For example, elbow flexion is accomplished by contraction of muscles in the anterior compartment of the upper arm and passive stretch of muscles in the posterior compartment of the upper arm. To truly understand muscle function, both contractile and passive properties should be studied. The contractile and/or passive mechanical properties of muscle are often compromised in muscle diseases. A good example is Duchenne muscular dystrophy (DMD), a severe muscle wasting disease caused by dystrophin deficiency 3. Dystrophin is a cytoskeletal protein that stabilizes the muscle cell membrane (sarcolemma) during muscle contraction 4. In the absence of dystrophin, the sarcolemma is damaged by the shearing force generated during force transmission. This membrane tearing initiates a chain reaction which leads to muscle cell death and loss of contractile machinery. As a consequence, muscle force is reduced and dead myofibers are replaced by fibrotic tissues 5. This later change increases muscle stiffness 6. Accurate measurement of these changes provides important guide to evaluate disease progression and to determine therapeutic efficacy of novel gene/cell/pharmacological interventions. Here, we present two methods to evaluate both contractile and passive mechanical properties of the extensor digitorum longus (EDL) muscle and the contractile properties of the tibialis anterior (TA) muscle.

Evaluation of Muscle Function of the Extensor Digitorum Longus Muscle &lt;em&gt;Ex vivo&lt;/em&gt; and Tibialis Anterior Muscle &lt;em&gt;In situ&lt;/em&gt; in Mice

Body movements are mainly provided by mechanical function of skeletal muscle. Skeletal muscle is composed of numerous bundles of myofibers that are sheathed by intramuscular connective tissues. Each myofiber contains many myofibrils that run longitudinally along the length of the myofiber. Myofibrils are the contractile apparatus of muscle and they are composed of repeated contractile units known as sarcomeres. A sarcomere unit contains actin and myosin filaments that are spaced by the Z discs and titin protein. Mechanical function of skeletal muscle is defined by the contractile and passive properties of muscle. The contractile properties are used to characterize the amount of force generated during muscle contraction, time of force generation and time of muscle relaxation. Any factor that affects muscle contraction (such as interaction between actin and myosin filaments, homeostasis of calcium, ATP/ADP ratio, etc.) influences the contractile properties. The passive properties refer to the elastic and viscous properties (stiffness and viscosity) of the muscle in the absence of contraction. These properties are determined by the extracellular and the intracellular structural components (such as titin) and connective tissues (mainly collagen) 1-2. The contractile and passive properties are two inseparable aspects of muscle function. For example, elbow flexion is accomplished by contraction of muscles in the anterior compartment of the upper arm and passive stretch of muscles in the posterior compartment of the upper arm. To truly understand muscle function, both contractile and passive properties should be studied.The contractile and/or passive mechanical properties of muscle are often compromised in muscle diseases. A good example is Duchenne muscular dystrophy (DMD), a severe muscle wasting disease caused by dystrophin deficiency 3. Dystrophin is a cytoskeletal protein that stabilizes the muscle cell membrane (sarcolemma) during muscle contraction 4. In the absence of dystrophin, the sarcolemma is damaged by the shearing force generated during force transmission. This membrane tearing initiates a chain reaction which leads to muscle cell death and loss of contractile machinery. As a consequence, muscle force is reduced and dead myofibers are replaced by fibrotic tissues 5. This later change increases muscle stiffness 6. Accurate measurement of these changes provides important guide to evaluate disease progression and to determine therapeutic efficacy of novel gene/cell/pharmacological interventions. Here, we present two methods to evaluate both contractile and passive mechanical properties of the extensor digitorum longus (EDL) muscle and the contractile properties of the tibialis anterior (TA) muscle.

THE EFFECT OF PHYSIOTHERAPY ON THE SYMMETRY OF PASSIVE MECHANICAL PROPERTIES OF MUSCLES OF CHILDREN WITH AND WITHOUT CEREBRAL PALSY

The aim of the research is to investigate whether physiotherapy exercises can decrease asymmetry of passive mechanical properties of skeletal pair muscles. In this research, 17 schoolchildren from 8 to 16 years of age participated. In the first group, 7 children had cerebral palsy. In the second group, there were 10 children without physical and movement impairments. The subjects were treated with 10 sessions of physiotherapy on the therapeutic ball. Passive mechanical properties of the muscles were measence between children with and without CP was observed. The research showed that exercises of physiotherapy on the therapeutic ball imitating horseman’s movements decreased asymmetry of stiffness and tone of gluteus medius muscles of children with and without CP and only partially decreased asymmetry of stiffness and tone of their lumbar erector spinae.DOI: http://dx.doi.org/10.5755/j01.mech.18.6.3162

Discrete Reversible Transitions in Titin at Low Forces

Titin is a giant filamentous protein which, due to its sarcomeric arrangement, molecular structure and elasticity, determines the passive mechanical properties of muscle. At low, physiologically relevant passive forces (<30 pN/molecule) titin is thought to extend continuously at the expense of reducing the configurational entropy of its tandem-Ig regions and PEVK domain. Structural transitions, such as Ig-domain unfolding, are thought to begin only at forces well exceeding the physiological regime, typically above 100 pN. To investigate the detail in the mechanical behavior of titin in the low-force regime, we manipulated individual native skeletal-muscle titin molecules by using custom-built optical tweezers operating at high spatial and temporal resolution in the constant-velocity or constant-force (force-clamp) mode.Titin molecules, purified from rabbit longissimus dorsi, were captured with two beads, one coated with the T12 sequence-specific antibody, and the other with the photoreactive cross-linker sulfo-SANPAH. One of the beads was captured in the optical trap, while the other with a micropipette, the position of which was either moved with a constant rate or adjusted rapidly so as to maintain constant force. At constant, physiologically relevant stretch rates (200-500 nm/s) we observed discrete, step-like (∼20-60 nm) structural changes at forces well below 30 pN, prior to the onset of globular-domain unfolding. In force-clamp stretch experiments these transitions decayed with a high-rate kinetic component. The low-force discrete transitions disappeared in the immediately subsequent mechanical cycle but reappeared after a rest period, indicating that they contribute to titin's mechanical fatigue. This fatigue, previously attributed to the PEVK domain, thus occurs by mechanically wearing out distinct structural elements, suggesting that long-range interactions stabilize this putative random domain. The time- and force-scales suggest that the observed discrete structural transitions may play an important role in sarcomeric stress adaptation.

Passive mechanical properties of rat abdominal wall muscles suggest an important role of the extracellular connective tissue matrix

Abdominal wall muscles have a unique morphology suggesting a complex role in generating and transferring force to the spinal column. Studying passive mechanical properties of these muscles may provide insights into their ability to transfer force among structures. Biopsies from rectus abdominis (RA), external oblique (EO), internal oblique (IO), and transverse abdominis (TrA) were harvested from male Sprague-Dawley rats, and single muscle fibers and fiber bundles (4-8 fibers ensheathed in their connective tissue matrix) were isolated and mechanically stretched in a passive state. Slack sarcomere lengths were measured and elastic moduli were calculated from stress-strain data. Titin molecular mass was also measured from single muscle fibers. No significant differences were found among the four abdominal wall muscles in terms of slack sarcomere length or elastic modulus. Interestingly, across all four muscles, slack sarcomere lengths were quite long in individual muscle fibers (>2.4 µm), and demonstrated a significantly longer slack length in comparison to fiber bundles (p < 0.0001). Also, the extracellular connective tissue matrix provided a stiffening effect and enhanced the resistance to lengthening at long muscle lengths. Titin molecular mass was significantly less in TrA compared to each of the other three muscles (p < 0.0009), but this difference did not correspond to hypothesized differences in stiffness.

In vivo passive mechanical behaviour of muscle fascicles and tendons in human gastrocnemius muscle–tendon units

Ultrasound imaging was used to measure the length of muscle fascicles in human gastrocnemius muscles while the muscle was passively lengthened and shortened by moving the ankle. In some subjects the muscle belly 'buckled' at short lengths. When the gastrocnemius muscle-tendon unit was passively lengthened from its shortest in vivo length by dorsiflexing the ankle, increases in muscle-tendon length were not initially accompanied by increases in muscle fascicle lengths (fascicle length remained constant), indicating muscle fascicles were slack at short muscle-tendon lengths. The muscle-tendon length at which slack is taken up differs among fascicles: some fascicles begin to lengthen at very short muscle-tendon lengths whereas other fascicles remain slack over a large range of muscle-tendon lengths. This suggests muscle fascicles are progressively 'recruited' and contribute sequentially to muscle-tendon stiffness during passive lengthening of the muscle-tendon unit. Even above their slack lengths muscle fascicles contribute only a small part (<~30%) of the total change in muscle-tendon length. The contribution of muscle fascicles to muscle-tendon length increases with muscle length. The novelty of this work is that it reveals a previously unrecognised phenomenon (buckling at short lengths), posits a new mechanism of passive mechanical properties of muscle (recruitment of muscle fascicles), and confirms with high-resolution measurements that the passive compliance of human gastrocnemius muscle-tendon units is due largely to the tendon. It would be interesting to investigate if adaptations of passive properties of muscles are associated with changes in the distribution of muscle lengths at which fascicles fall slack.

What are the long-term consequences of botulinum toxin injections in spastic cerebral palsy?

Muscle spasticity, defined as a velocity dependent resistance to stretch, is the primary impairment of spastic cerebral palsy (CP) and is neural in origin. However, spastic muscle also undergoes significant morphological and structural alterations secondary to spasticity which contribute to muscle weakness, muscle stiffness, restricted joint range of motion, and skeletal deformity. These secondary alterations can progress with age and contribute to a gradual loss of functional capacity during development, including the ability to ambulate independently. There is consensus that intra-muscular botulinum toxin A (BoNT-A) injections can be effective in the management of lower limb spasticity in children with spastic CP. BoNT-A injections can improve gait and delay and reduce the requirement for surgical interventions to treat musculoskeletal deformities when combined with conservative treatments. The study by Alhusaini et al. is one of the first that begins to address the important clinical question of how BoNT-A injections influence the secondary effects of spasticity on joint-level mechanical properties in children with spastic CP. An attractive feature of the study was that the authors assessed ankle joint stiffness and not just joint range of motion. Alhusaini et al. showed that BoNT-A has relatively minor effects on passive mechanical properties of the ankle plantar-flexor muscles at 6-weeks post injection in children with spastic CP aged 4– 10 years with high ankle joint stiffness. This study therefore does not support the efficacy of BoNT-A for treating contractures. What remains unclear at the present time is how BoNT-A might influence other structural and neuro-mechanical properties of the muscle and ⁄or tendon, especially in the longer term. For example, how does BoNT-A affect muscle size, strength, force-length-velocity behaviour, moment arms, co-activation, and tendon compliance? Of increasing concern is evidence from animal studies that intra-muscular BoNT-A injections adversely influence muscle growth in the injected muscle as well as muscles remote from the injection site. For example, Fortuna et al. recently reported up to 95% reductions in rabbit hind limb quadriceps muscle strength following 6 months of repeated BoNT-A injections, which was accompanied by up to 60% reductions in muscle mass. Reductions in strength and mass were also reported for quadriceps muscles in the contralateral limb. These findings point to the possibility that the short-term functional benefits of BoNT-A injections reported in clinical studies in spastic CP may be offset by accelerated structural weakening of muscle. This is important because children aged 2–5 years with spastic CP that have not undergone orthopaedic surgery or commenced BoNT-A injections already have significantly lower calf muscle volume relative to their typically developed peers. BoNT-A is routinely administered to children in this age group and is often repeated over many cycles. Further muscle weakening by BoNT-A would therefore be expected to adversely influence functional capacity. BoNT-A acts to weaken overactive muscles through chemical blockade of the neuromuscular junction. It might be expected that any associated muscle atrophy could contribute to observed improvements in gait following BoNT-A injections. However, during maturation in childhood and adolescence, muscles must increase in size to cope with the increased mechanical loading associated with motor function in activities such as gait. Muscle weakening from BoNT-A could therefore be beneficial in the short-term but detrimental in the longerterm because of impeded muscle growth. Aside from the study by Alhusaini et al., to our knowledge no detailed in vivo studies of the effects of BoNT-A on the active and passive mechanical properties of muscle in children with spastic CP have been conducted. In spite of the widespread use of BoNT-A injections in children with spastic CP for almost two decades, the long-term efficacy of this treatment for improving functional outcomes in children with spastic CP remain relatively unknown. In using a short-term solution we may be creating a long-term problem which could lead to increased costs of care in spastic CP. Long-term trials of the structural and neuro-mechanical responses of muscle to BoNT-A and their consequences for motor function in spastic CP are required. New developments in musculoskeletal modeling and simulation may prove fruitful in linking muscletendon adaptation with gait function in spastic CP.

Quasi-static compression on dog muscles at high strain

The knowledge about passive mechanical properties of muscles is quite limited. Even if a lot of studies have been done on longitudinal muscle properties (Davis et al. 2003; Bensamoun et al. 2006), ...

In vivo passive mechanical properties of the human gastrocnemius muscle belly

The purpose of the present study was to determine the in vivo passive mechanical properties, including the length below the slack length, of the gastrocnemius muscle (GAS) belly in humans. Transverse ultrasound images of the medial head of the GAS were taken in 11 subjects during passive knee extension from 80°to 5°with a constant ankle joint angle of 10°(0°is the neutral ankle position: positive values for dorsiflexion). The change in passive ankle joint moment (Mp), which is produced only by the GAS length change, was also measured during passive knee extension. The onset of Mp during passive knee extension was found to be 43±8°(mean±SD) when the baseline of the Mp was set at the average Mp in the range of 55–60°where the Mp was almost constant (SD<0.03Nm). At this onset, the muscle fascicle length of the GAS (Lf) was 46±7mm (slack length; Lfs). Lf at 80°was 6±4mm (13±6%) less than the Lfs, and Lf at 5°was 12±5mm (27±11%) greater than the Lfs. The passive force-resisting compression of the GAS did not produce a dorsiflexion moment in the joint angle range adopted. The passive ankle joint moment increased linearly with Lf (coefficient of determination (R2)=0.85–0.96), and the slopes of the relationships between Lf and Mp, and between the relative Lf to Lfs and Mp were 0.093±0.038Nm/mm and 0.043±0.021Nm/%Lfs. The findings of the present study can be implemented in musculoskeletal modeling, which would provide a more accurate evaluation of the passive mechanical properties of muscle during movement.

Structural and functional changes in spastic skeletal muscle.

This review summarizes current information regarding the changes in structure or function that occur in skeletal muscle secondary to spasticity. Most published studies have reported an increase in fiber size variability in spastic muscle. There is no general agreement regarding any shift in fiber type distribution secondary to spasticity. Mechanical studies in whole limbs as well as in isolated single cells support the notion of an intrinsic change in the passive mechanical properties of muscle after spasticity in addition to the more widely reported neural changes that occur. Evidence is presented for changes within both the muscle cell and extracellular matrix that contribute to the overall changes in the tissue. Taken together, the literature supports the notion that, although spasticity is multifactorial and neural in origin, significant structural alterations in muscle also occur. An understanding of the specific changes that occur in the muscle and extracellular matrix may facilitate the development of new conservative or surgical therapies for this problem.

The Passive Mechanical Properties of Muscle and Their Adaptations to Altered Patterns of Use

The length and stiffness of a relaxed muscle are determined by the mechanical properties of its intramuscular connective tissue and/or intracellular structures. Viscous deformation of these components of muscle is responsible for the increase in muscle length seen immediately after stretching, but this increase is transient. Lasting changes in muscle length can only be brought about by adaptations of the structure of muscle. An understanding of the nature of the stimulus for muscle to adapt can provide therapists with a theoretical basis for therapeutic intervention aimed at producing changes in muscle length.

Protocollagen proline hydroxylase activity in work-induced hypertrophy of rat muscle.

ARTICLESProtocollagen proline hydroxylase activity in work-induced hypertrophy of rat muscleH Turto, S Lindy, and J HalmeH Turto, S Lindy, and J HalmePublished Online:01 Jan 1974https://doi.org/10.1152/ajplegacy.1974.226.1.63MoreSectionsPDF (736 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByMechanische Belastung und Bindegewebe17 August 2017Regulation of synthesis of fibrillar collagens in rat skeletal muscle during immobilization in shortened and lengthened positions20 December 2001 | Acta Physiologica Scandinavica, Vol. 172, No. 2Effects of prolonged exposure to and physical training in hypobaric conditions on skeletal muscle morphology and metabolic enzymes in ratsPflügers Archiv - European Journal of Physiology, Vol. 432, No. 1Effects of streptozotocin-induced diabetes, physical training and their combination on collagen biosynthesis in rat skeletal muscleActa Physiologica Scandinavica, Vol. 155, No. 1Extracellular matrix arrangement in the papillary muscles of the adult rat heart. Alterations after doxorubicin administration and experimental hypertensionBasic Research in Cardiology, Vol. 89, No. 4Quadriceps Exercises for Osteo-arthritis of the Knee — A Single Case Study Comparing Short-term versus Long-term Training EffectsPhysiotherapy, Vol. 80, No. 4Collagens in the injured porcine intervertebral disc18 February 2005 | Journal of Orthopaedic Research, Vol. 12, No. 1Enhanced prolylhydroxylase activity in the posterior annulus fibrosus of canine intervertebral discs following long-term running exerciseEuropean Spine Journal, Vol. 2, No. 3The effects of anabolic steroids on collagen synthesis in rat skeletal muscle and tendon23 April 2016 | The American Journal of Sports Medicine, Vol. 20, No. 3Alterations in collagen cross-linking impair myocardial contractility in the mouse heart.Circulation Research, Vol. 65, No. 6Cardiac interstitium in health and disease: The fibrillar collagen networkJournal of the American College of Cardiology, Vol. 13, No. 7Resistance Training: Physiological Responses and Adaptations (Part 2 of 4)12 July 2016 | The Physician and Sportsmedicine, Vol. 16, No. 4Collagen remodeling of the pressure-overloaded, hypertrophied nonhuman primate myocardium.Circulation Research, Vol. 62, No. 4The Passive Mechanical Properties of Muscle and Their Adaptations to Altered Patterns of UseAustralian Journal of Physiotherapy, Vol. 34, No. 3Collagen metabolism of mouse skeletal muscle during the repair of exercise injuriesPfl�gers Archiv European Journal of Physiology, Vol. 407, No. 1Collagen of slow twitch and fast twitch muscle fibres in different types of rat skeletal muscleEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 52, No. 2Skeletal Muscle Adaptability: Significance for Metabolism and Performance1 January 2011Increased activities of prolyl 4-hydroxylase and galactosylhydroxylysyl glucosyltransferase, enzymes of collagen biosynthesis, in skeletal muscle of endurance-trained micePfl�gers Archiv European Journal of Physiology, Vol. 399, No. 4Biomechanics of the Musculotendinous Unit: Relation to Athletic Performance and InjuryClinics in Sports Medicine, Vol. 2, No. 1Muscle ultrastructural characteristics of elite powerlifters and bodybuildersEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 48, No. 1Relationship between Muscle Hypertrophy and the Composition of Skeletal MusclesConnective tissue changes in surgically overloaded muscleCell And Tissue Research, Vol. 221, No. 2Connective tissue of “fast” and “slow” skeletal muscle in rats…effects of endurance trainingActa Physiologica Scandinavica, Vol. 108, No. 2Protein and collagen synthesis in rat diaphragm muscle incubated in vitro: The effect of alterations in tension produced by electrical or mechanical meansInternational Journal of Biochemistry, Vol. 11, No. 1Effects of physical training on metabolism of connective tissues in young miceActa Physiologica Scandinavica, Vol. 108, No. 1Effects of the inhibition of DNA synthesis on hypertrophying skeletal muscle.Journal of Biological Chemistry, Vol. 253, No. 9Oxidative metabolism of hypertrophic skeletal muscle in the ratExperimental Neurology, Vol. 48, No. 2Effect of Prolonged Physical Training on the Development of Connective Tissues in Growing MiceEnzyme activities in muscle and connective tissue of M. vastus lateralis in habitually training and sedentary 33 to 70-year-old menEuropean Journal of Applied Physiology and Occupational Physiology, Vol. 34, No. 1 More from this issue > Volume 226Issue 1January 1974Pages 63-65 Copyright & PermissionsCopyright © 1974 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1974.226.1.63PubMed4358853History Published online 1 January 1974 Published in print 1 January 1974 Metrics