| Heat Application in Physiotherapy | ||
| Limitation of motion is a major area
of concern in rehabilitation. Thus, one of the most relevant and important
goals in Physiotherapy is the restoration of the client's full range
of motion (ROM) in an attempt to maximize function. The shortening
of connective tissue or the formation of new connective tissue often
causes decreased motion. Superficial heat has been proven advantageous
in the remodeling of connective tissue. Connective tissue shortening or formation will result in several problematic conditions. Provided full ROM exercises are not performed following injury, connective tissue will gradually shorten with time and joint contractures will develop. In addition, adhesion formation, which is an abnormal adherence of collagen fibers to surrounding structures, restricts normal elasticity of the structures involved by preventing these structures form gliding past one another. Further limitations of mobility are due to formation of scar tissue from lacerations, burns and crush injuries.9 There are definite advantages to applying superficial heat to remodel connective tissue. Perhaps the most important is an increase in joint mobility. This is caused by three mechanisms. First, heat creates several physiologic changes through subsequent vascular changes, causing vasodilation. This dilation gives an analgesic effect which increases the client's pain threshold and results in greater tolerance of connective tissue stretching. Another physiologic effect of heat is an alteration of the viscous flow properties of collagen which results in the relief of joint stiffness.3 Lastly, there is an increase in the extensibility of collagen tissue, a major component of connective tissue, through changes in its viscoelastic properties following the application of heat. This is an important effect of heat due to the long-term remodelling of connective tissue.7,9 The main goal in the clinical treatment of adhesions, contractures, scar tissue or other connective tissue problems is the production of permanent collagenous tissue elongation. Numerous studies have concluded that the most effective means of attaining this result is through the combination of temperature elevation and the application of prolonged stretch thus altering the viscoelastic properties of connective tissue. 5,9,16 Collagen has viscous properties which allow a residual elongation after a load is applied then released. This phenomenon is known as plastic deformation. Furthermore, its elastic properties allow for recoverable deformation which is a return to its original length after stretch is applied then released. As mentioned above, elevated temperatures increase the extensibility of collagen. Therefore, when a load is applied to heated tissue then released, greater plastic deformation results (increased residual length) and thus permanent elongation of the connective tissue.9 Lehman and associates (1970) studied the effects of heat and stretching on rat tail tendons.6 The results indicated that heating alone produced no significant elongation and that stretching alone produced no residual elongation. Significant elongation occurred if heat and stretch were combined. A greater increase in length was maintained if the stretch was held during the period of cooling since “reorganization of the tissues is thought to occur during the cooling period.”6 Overall, the most effective method of producing a plastic deformation of connective tissue was to apply a sustained stretch during the application of heat and to maintain the stretch during the period of cooling. Similar experiments using rat tail tendons have been conducted by Warren et al (1976) regarding permanent elongation of connective tissue at various temperatures.16 The data showed that the application of low force over a long duration was very effective in producing slow elongation in the viscous elements, resulting in increased residual elongation. Furthermore, elevating tissue temperature and maintaining it prior to applying force was found to cause significantly less tissue damage. Lastly, the lower loads applied at elevated temperatures for prolonged periods were found to produce significantly greater residual elongation.16 The clinical implications of this study are three fold: first, stretches used to increase ROM should be held for prolonged periods; second, warming tissue prior to ROM exercises will cause less tissue damage; and third, stretching should be accompanied with the highest possible therapeutic temperature for prolonged periods to most effectively increase joint mobility. Although these therapeutic effects are beneficial, special consideration should be given to patients with rheumatoid arthritis. As Harris and McCroskery (1974) note, “excessive heat therapy harms joints by [increasing intrarticular temperature and thus] increasing the rate of collagen breakdown by specific collagenases.”1 It is for this reason that Oosterveld et al (1992, 1994) recommend that cold applications are most effective in the treatment of arthritis.10,11 They advise that if the patient nevertheless prefers heat, it should last no more than 5 to 10 minutes.10 It is evident that superficial heat is an effective modality that Physiotherapists can use in the remodelling of connective tissue. Studies have effectively shown that superficial heat therapy increases connective tissue elongation. Hence, its use is recommended to assist a patient maximize his or her mobility and functional capacity. Reference List |
Physiotherapy
Heat Application in Physiotherapy |
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