Thermomonitoring of the Achilles tendon during Isometric and Eccentric exercise associated with Photobiomodulation

Introduction: Prior knowledge of physiological and thermal adaptations of the tendon to different types of exercise, as well as its association with photobiomodulation (PBM) are essential for establishing effective protocols for the prevention and treatment of calcaneal tendinopathies. Objective: To analyze the thermal pattern of the skin over the Achilles Tendon (CT) of healthy individuals submitted to FBM in association with isometric and isotonic exercises. Method: This is an experimental, randomized, single-blind study. The sample consisted of 32 healthy, physically active volunteers, equally distributed between two independent groups (n= 16 subjects, eight men and eight women), submitted to evaluation by thermographic video; assessment of isometric muscle strength of the triceps surae; subjective perception of effort and pain. The experiment consisted of performing two different exercise protocols (1. Isometric and 2. Isotonic) of the sural triceps performed only by the dominant limb, with the contralateral limb serving as a control. Preceded by the application of FBM (real and sham) using a total energy dose of 20.3 J distributed in four points on the CT, with a washout of one week between the two interventions. Data were processed using SPSS version 20.0, adopting a significance level of 5% and a confidence interval of 95%. A paired t test was used to compare the pre and post strength measurements and an Anova of repeated measures was applied to compare the mean temperatures over the evaluation time. Pain and perceived exertion were compared using the Man Whitney test and partial eta (?2) was used to interpret the effect size. Results: Significant interactions were verified in the time x exercise analysis (p=0.001), in which the eccentric group presented higher temperatures than the isometric group during the execution of the exercise protocol. Strength measurements showed good reproducibility (ICC=0.859; p=0.001) and prior application of FBM did not cause significant changes. The isotonic group had a greater perception of exertion (p=0.001) and pain (p=0.001) than the isometric group. Conclusions: Isotonic exercise presents a greater thermal amplitude over the exercised CT, and may act in a preventive way and in the rehabilitation of tendinopathies. On the other hand, isometric exercise can be indicated in the early stages of rehabilitation of tendon ruptures, as it can be better tolerated since they present less perceived exertion and discomfort. FBM at the dose applied in this study did not cause immediate changes in the subjects' muscle strength.