You’ll need Acrobat Reader or a browser plug-in to view this file: http://www.dynasplint.com/pdfs/Contracture.pdf
While this paper deals with joints, there is a good section on connective tissue, how it lengthens, and principles concerning lengthening it. There is more, but here is an excerpt:
With any given stretching force, the resulting proportion of plastic to elastic response depends primarily upon two stretching force variables: time and intensity. Research on these variables has produced three significant findings: 10, 16-18
1) Short duration stretching of high intensity favors the elastic response, while prolonged duration stretching of low intensity favors the plastic response.
2) There is a direct correlation between the duration of a stretch and the resulting proportion of plastic, permanent elongation.
3) There is a direct correlation between the intensity of a stretch and the degree of either trauma or weakening of the stretched tissues.
To summarize, the longest period of low force stretch produces the greatest amount of permanent elongation, with the least amount of trauma and structural weakening of the connective tissues. 10, 11, 16-18
These others are tidbits from my notes - just quotations with the source URL’s.
In fact, applying a sudden load to a joint— if the force of that load is kept within the level of strength of that joint — will not permanently change the structure of the joint’s ligaments. After the load is removed, the joint (vertebrae and/or bones) will simply go back to where they were. There will be no permanent postural correction.(4)
So, what needs to be understood is that because of the stiffness factor (viscous property), ligaments can be injured by sudden forceful stretching. However, because of the stretchability factor (elastic property) — a properly directed “constant” load, operating over a proper period of time, repeated often enough — can change the ligament’s form — producing measureable and permanent correction of joint relations and posture.(2)
In order to deform, and then reform a ligament into a more desireable length and form, the applied “constant” load must reach over 40% of that particular ligament’s “ultimate load”. A ligament’s ultimate load is defined as “the final load reached by a structure before failure”. (5,6) So, the force needed to create new ligamentous form is well below the safety limit for loading that ligament, but must be high enough to stretch the ligament such that it only undergoes a partial rebound towards its original length and shape.
It is like pulling a spring out far enough that it doesn’t quite go back to its original length — while being careful not to pull it so far that it breaks. The safety factor for doing this process is increased by doing repetitive loading and unloading cycles before engaging in the traction of the ligaments. These repeated loading/unloading cycles create just enough increased elasticity to reduce the joint’s elastic resistance factor — thus reducing the chances of injury to the joint’s connective tissues (ligaments). (3)
Therapeutic muscle stretching5 and contract/relax techniques should be used for the contractile components while prolonged stretching should be used for the passive structures. Sapega et al.6 discuss the use of “prolonged low-intensity stretching at elevated tissue temperatures and cooling the tissue before releasing the tension.” The patient is instructed to lie supine with the shoulder in as much abduction, extension, and lateral rotation as possible, holding in his hand a one or two pound weight if tolerated (i.e., minimal discomfort, not painful), for up to an hour. During this period moist heat is applied. At the end of this period an ice pack is applied for ten to fifteen minutes while the shoulder is still being stretched.
In a condition such as adhesive capsulitis of the shoulder, in order to achieve plastic deformation, a prolonged stretch appears to be very beneficial. It has been found that rapid application of force to collagenous tissues results in increased stiffness2 and affects primarily the elastic tissue. This explains one reason why patients with adhesive capsulitis of the shoulder do not benefit from joint play adjustment and why prolonged stretch is necessary for increased changes in ranges of motion. Often in adhesive capsulitis of the shoulder a joint play adjustment may tear fibers and perpetuate the inflammatory process.
It has been shown that the use of heat along with stretching relaxes the collagen fibers and allows greater elongation. Besides influencing the collagen, the increased temperature increases the sensitivity of the Golgi tendons aiding muscle relaxation. The temperature should be over 104 F. It has been found that the use of ultrasound during stretching is more effective in lengthening. A procedure that works very well in treating adhesive capsulitis is putting the patient in a supine stretched position with the shoulder in lateral rotation for 20 to 60 minutes, with moist heat applied to the shoulder followed by 15 minutes of ice maintaining the stretched position. The patient can hold a weight if it does not increase pain. Cooling the tissue is thought to allow the collagenous microstructure to restabilize more toward its new stretched length.8
Management of Contractures
It is sometimes difficult to regain lost motion associated with joint contractures. Disuse and immobilization promote atrophy and scar tissue formation after 7 weeks2. Connective tissue dysfunctions, including abnormal collagen cross links and shortened inter-fiber distances are associated with the lack of motion1,5. Low-load, long duration stretching is the most effective means of restoring normal tissue length5.
Sapega et al.6 describe a program designed to lengthen functional connective tissue structures in an atraumatic fashion. They advocate a moderate but tolerable force to stretch contractures for 20-60 minutes, depending on tolerance. The joint is placed at end range. Several 30- second breaks can be used. Superficial heat is also used to elevate tissue temperature. Finally, ice is applied for 15 minutes at the end of the session while maintaining the stretch. It has been suggested that a 3º increase of joint motion per week is an acceptable standard2. Several authors have described the use of elastic resistance in providing low-load stretching3,4,7,8.