Abstract
ABSTRACT Introduction: Both laser therapy and eccentric exercises are used in tendon injuries. However, the association of these physiotherapeutic modalities is yet little investigated. Objective: To evaluate the effect of low-level laser therapy associated to eccentric exercise (downhill walking) on Achilles tendinopathy of Wistar rats. Method: Eighteen Achilles tendon from 15 adult male Wistar rats were used. Tendons were distributed in six groups (laser, eccentric exercise, laser and eccentric exercise, rest, contralateral tendon, and healthy tendon). Unilateral tendinopathy was surgically induced by transversal compression followed by scarification of tendon fibers. The treatments laser therapy (904 nm, 3J/cm²) and/or eccentric exercise (downhill walking; 12 m/min; 50 min/day; 15o inclination treadmill) began 24 hours after surgery and remained for 20 days. Clinical and biomechanical analyzes were conducted. Achilles tendon was macroscopically evaluated and the transversal diameter measured. Euthanasia was performed 21 days after lesion induction. Tendons of both limbs were collected and frozen at -20°C until biomechanical analysis, on which the characteristic of maximum load (N), stress at ultimate (MPa) and maximum extension (mm) were analyzed. Results: Swelling was observed within 72 hours postoperative. No fibrous adhesions were observed nor increase in transversal diameter of tendons. Animals with the exercised tendons, but not treated with laser therapy, presented lower (p=0.0000) locomotor capacity. No difference occurred be-tween groups for the biomechanical characteristics maximum load (p=0.4379), stress at ultimate (p=0.4605) and maximum extension (p=0.3820) evaluated, even considering healthy and contralateral tendons. Conclusion: The concomitant use of low-level laser and the eccentric exercise of downhill walking, starting 24 hours after surgically induced tendinopathy, do not result in a tendon with the same biomechanical resistance or elasticity as a healthy tendon. On the other hand, it also does not influence negatively the structure and function of the Achilles tendon.
Highlights
Both laser therapy and eccentric exercises are used in tendon injuries
In the first evaluation, carried out 12 hours after tendinopathy induction, discrete intensity swelling in injured limbs was observed, which was maintained up to 72 hours
This fast tendinopathy recovery was confirmed by biomechanical analysis, which revealed no difference between groups
Summary
Both laser therapy and eccentric exercises are used in tendon injuries. the association of these physiotherapeutic modalities is yet little investigated. Objective: To evaluate the effect of low-level laser therapy associated to eccentric exercise (downhill walking) on Achilles tendinopathy of Wistar rats. Euthanasia was performed 21 days after lesion induction Tendons of both limbs were collected and frozen at -20°C until biomechanical analysis, on which the characteristic of maximum load (N), stress at ultimate (MPa) and maximum extension (mm) were analyzed. Conclusion: The concomitant use of low-level laser and the eccentric exercise of downhill walking, starting 24 hours after surgically induced tendinopathy, do not result in a tendon with the same biomechanical resistance or elasticity as a healthy tendon. Tendons play an important role in musculoskeletal system by transferring tensile loads from muscle stabilizing joints and, allowing appropriate movement of the limbs[1] They have the ability to undergo mechanical adaptation in response to forces by change their structure, composition and mechanical properties. The therapy allows faster tissue healing[7], with appropriate structural organization of collagen fibers[8]
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