Prolonged mechanical passive stretching A. A low-intensity external force (5 to 15 lb or 5 to 10 percent of body weight) is applied to shortened tissues over a prolonged period with mechanical equipment. B. The streth force is applied through positioning of the patient, with weighted traction and pulley systems or with dynamic splints or serial casts. C. The prolonged stretch may be maintained for 20 to 30 minutes or as long as several hours. 1. Several authors have suggested that a period of 20 minutes or longer is necessary for a stretch to be effective and increase range of motion when low-intensity prolonged mechanical stretch is used. Bohannon evaluated the effectiveness of an 8-minute stretch of the hamstrings in comparision to a 20-minute or longer stretch using an overhead cable-pulley system. The 8-minute stretch resulted in only a small increase in hamstring flexibility, which was lost within 24 hours. It was suggested that a 20-minute or longer streth is necessary to effectively increase range of motion on a more permanent basis. Significant increases in range of motion in subjects who were healthy but had tight lower extremity musculature have also been reported using only 10 minutes of low-intensity prolonged mechanical stretch. 2. Bohannon and larkin also used a regimen of tilt table-wedge board standing for 30 minutes daily to increase the range of ankle dorsiflexion in patients with neurologic disorders. 3. Prolonged, low-intensity stretch and an increase in range can also be accomplished with a dynamic splint such as the dynasplint. The splint is applied for 8 to 10 hours. Units are available for the elbow, wrist, knee, and ankle. D. Low-intensity prolonged stretch (5- to 12-lb stretch force applied 1 hour per day) has been shown to be significantly more effective than manual passive stretching over a 4-week period in patient with long-standing bilateral knee flexion xcontractures. The patients also reported that the prolonged mechanical stretch was more comfortable than the manual stretching procedure. E. Plastic changes in noncontractile and contractile tissues may be tha basis of "permanent" or long-term improvements in flexibility. 1. When muscle are held in a lengthened position for several weeks, sarcomeres are added in series. 2. When noncontractile connective tissue are stretched with a low-intensity prolonged stretch force, plastic deformation occurs and the length of the tissue increases. Note: the term permanent lengthening means that length is maintained after the stretch force is removed. The increase in length will be "permanent" only if the new length is used regularly.
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Stretching Mobility and flexibility of the soft tissues that surround a joint, that is, muscles, connective tissue, and skin, in conjunction with adequate joint mobility are neccessary for normal range of motion. Unrestricted, pain-free range of motion (Rom) is often required to perform many functional daily living tasks as well as occupational or recreational activities. Adequate mobility of soft tissue and joint is also thought to be a important factor in prevention of injury or reainjury to soft tissue. Conditions that may produce adaptive shortening of soft tissues around a joint and subsequent loss of range of motion include 1 prolonged immobilization, 2restricted mobility, 3 connective tissue or neuromuscular diseases, 4 tissue pathology due to trauma, and 5 congenital and acquired bony deformities.