EFFECTS OF HEATING AND EXERCISE IN THE BIOMECHANICAL AND HISTOLOGICAL PROPERTIES OF THE CALCANEAL TENDON OF RATS

Objectives: The purpose of the present study is to show the biomechanical and histological alterations in the calcaneal tendon of rats submitted to stresses through physical exercise and heating in a thermal bath. Methods: We used 35 rats divided into seven groups: Baseline (BL), group not submitted to any intervention, (C), group not submitted to either heating or exercise, (Ex), group with no heating and with exercise, (H42), group with heating at 42°C and without exercise, (ExH42), group with heating at 42°C and with exercise, (H45), group with heating at 45°C and without exercise, and (ExH45), group with heating at 45°C and with exercise. The exercises consisted of water jumps performed 10 times in 4 sets, interspersed with the thermal bath. Heating was performed by immersing the lower limbs in warm water for 10 minutes. The tendons were removed and submitted to the traction test, histological analysis, and quantification by means of fractal analysis. Statistical analysis was performed, with a significance level of 5%. Results: Heating at 45°C significantly decreased maximum strength, stiffness, energy absorbed, and mature collagen (p<0.05), and simultaneously increased the amount of immature collagen (p<0.05). Heating and exercise promoted inflammation and disarrangement of tendinous tissue. Conclusion: We conclude that heating to 45°C caused injury and a decrease in mature collagen, leading to weakening of the biomechanical properties. In addition,exercise also caused tendon damage and intensified the effects of heating.