Stretching Exercises II By Dr. Michael Banoub
PROPERTIES OF SOFT TISSUE RESPONSE TO IMMOBILIZATION AND STRETCH • the soft tissues that can become restricted and impair mobility are muscles with their contractile and noncontractile elements and various types of connective tissue (tendons, ligaments, joint capsules, fascia, skin).
PROPERTIES OF SOFT TISSUE RESPONSE TO IMMOBILIZATION AND STRETCH • For the most part, decreased extensibility of connective tissue, not the contractile elements of muscle tissue, is the primary cause of restricted ROM in both healthy individuals and patients with impaired mobility
PROPERTIES OF SOFT TISSUE RESPONSE TO IMMOBILIZATION AND STRETCH • Each type of soft tissue has unique properties that affect its response to immobilization and its ability to regain extensibility after immobilization. • When stretching procedures are applied to these soft tissues, the direction, velocity, intensity (magnitude), duration, and frequency of the stretch force as well as tissue temperature affect the responses of the various types of soft tissue.
PROPERTIES OF SOFT TISSUE RESPONSE TO IMMOBILIZATION AND STRETCH • When soft tissue is stretched, elastic, viscoelastic, or plastic changes occur. • Elasticity is the ability of soft tissue to return to its prestretch resting length directly after a short-duration stretch force has been removed
Viscoelasticity • is a time-dependent property of soft tissue that initially resists deformation, such as a change in length, of the tissue when a stretch force is first applied. If a stretch force is sustained, viscoelasticity allows a change in the length of the tissue and then enables the tissue to return gradually to its prestretch state after the stretch force has been removed.
Plasticity • the tendency of soft tissue to assume a new and greater length after the stretch force has been removed. • Both contractile and noncontractile tissues have elastic and plastic qualities; however, only connective tissues, not the contractile elements of muscle, have viscoelasticproperites.
Response to Immobilization and Remobilization , Morphological changes • If a muscle is immobilized for a prolonged period of time, the muscle is not used during functional activities, This results in decay of contractile protein in the immobilized muscle, a decrease in muscle fiber diameter, a decrease in the number of myofibrils, and a decrease in intramuscular capillary density, • the outcome of which is muscle atrophy and weakness (decreased muscle force). As the immobilized muscle atrophies, an increase in fibrous and fatty tissue in muscle also occurs.
Muscle Spindle The muscle spindle is the major sensory organ of muscle and is senstive to quick and sustained (tonic) stretch. The main function of muscle spindles is to receive and convey information about changes in the length of a muscle and the velocity of the length changes. Muscle spindles are small, encapsulated receptors composed of afferent sensory fiber endings, efferent motor fiber endings, and specialized muscle fibers called intrafusal fibers. Intrafusal muscle fibers are bundled together and lie between and parallel to extrafusal muscle fibers that make up the main body of a skeletal muscleS
Neurophysiological Response of Muscle to Stretch • To minimize activation of the stretch reflex and the subsequent increase in muscle tension and reflexive resistance to muscle lengthening during stretching procedures, a slow applied, low-intensity, prolonged stretch is considered prefereablely to a quickly applied, short-duration stretch.
Neurophysiological Response of Muscle to Stretch • In contrast, the The Golgi tendon organ (GTO) , as it monitors tension in the muscle fibers being stretched, has an inhibitory impact on the level of muscle tension, particularly if the stretch force is prolonged. • This effect is called autogenic inhibition. • Inhibition of the contractile components of muscle by the GTO contributes to reflexive muscle relaxation during a stretching maneuver, enabling a muscle to be elongated against less muscle tension.
Neurophysiological Response of Muscle to Stretch • It is thought that if a low-intensity, slow stretch force is applied to muscle, the stretch reflex is less likely to be activated as the GTO fires and inhibits tension in the muscle, allowing the parallel elastic component (the sarcomeres) of the muscle to remain relaxed and to lengthen.
Mechanical Properties ofNoncontractile Soft Tissue • Connective tissue is composed of three types of fiber: collagen, elastin and reticulin, and nonfibrousground substance • Collagen fibers are responsible for the strength and stiffness of tissue and resist tensile deformation.
Mechanical Properties ofNoncontractile Soft Tissue • Elastin fibers provide extensibility.They show a great deal of elongation with small loads. Tissues with greater amounts of elastin have greater flexibility. • Reticulin fibers provide tissue with bulk. • The Ground Substance is mostly an organic gel containing water that reduces friction between fibers, transports nutrients and metabolites, and may help prevent excessive cross-linking between fibers by maintaining space between fibers.
Mechanical Behavior of Noncontractile Tissue • Those high in collagen and low in PGs are designed to resist high tensile loads; those tissues that withstand greater compressive loads have greater concentrations of PGs • Collagen is the structural element that absorbs most of the tensile stress. Collagen fibers elongate quickly under light loads (wavy fibers). With increased loads, tension in the fibers increases, and the fibers stiffen.
Mechanical Behavior of Noncontractile Tissue • The fibers strongly resist the tensile force, but with continued loading the bonds between collagen fibers begin to break. When a substantial number of bonds are broken, the fibers fail. • When tensile forces are applied the maximum elongation of collagen is less than 10%, whereas elastin may lengthen 150% and return to its original configuration. Collagen is five times as strong as elastin.
Creep • When a load is applied for an extended period of time, the tissue elongates, resulting in permanent deformation • Low-magnitude loads, usually in the elastic range and applied for long periods, increase the deformation of connective tissue and allow gradual rearrangement of collagen fiber bonds (remodeling) and redistribution of water to surrounding tissues
Stress-relaxation • When a force (load) is applied to stretch a tissue and the length of the tissue is kept constant, after the initial creep there is a decrease in the force required to maintain that length, and the tension in the tissue decreases