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An increase in the capacity of athletic performance depends on adequate nutrition, which ensures optimal function of the musculoskeletal system, including tendon stability. However, little is known about the status of tendons and extracellular matrix modifications during malnutrition and nutritional recovery when leucine is used in response to exercise conditioning. The purpose of this study was to evaluate the collagen content and biomechanical aspects of the deep digital flexor tendon (DDFT) in malnourished rats submitted to nutritional recovery (control diet or leucine-rich diet) and aerobic physical activity. After 60 days of undernourishment (6% protein diet), the malnourished rats were subsequently nutritionally recovered with a control diet or leucine-rich diet and trained or not (swimming, without overload) for 5 weeks. The biomechanical analysis and quantification of hydroxyproline were assessed in the DDFT in all experimental groups. The leucine-rich diet increased hydroxyproline content in the tension region, independently of the training. In the compression region, hydroxyproline content was higher in the malnourished and leucine-trained groups. Biomechanical analysis showed a lower load in the malnourished and all-trained groups. The lowest stress was observed with control-trained animals. The nutritional-recovered groups showed higher strain values corresponding to control group, while the lowest values were observed in malnourished and trained groups. The results suggest that a leucine-rich diet stimulates collagen synthesis of the DDFT, especially when in combination with physical exercise, and seems to determine the increase of resistance and the biomechanical characteristics of tendons.

Objective: The present study compared the effects of gallium-aluminum-arsenide diode laser and healing oil on fibroblasts, blood vessels, and collagen maturation of skin wounds in Wistar rats., Materials and Methods: Twenty-four male rats weighing 325 ± 27 g were used. Five wounds, 12 mm in diameter, were made on the animals' backs. The rats were randomly divided into four groups with six animals in each group., Control Group: saline solution; L30 group: 30 J/cm(2) laser; L60 group: 60 J/cm(2) laser; Oil group: healing oil. Histomorphometric analysis was performed on the scar tissue removed from the different wounds every 4 d for 20 d., Results: On day 4, there were significantly more fibroblasts in the wounds treated with the laser and the healing oil compared to the controls. On day 8, there were significantly more fibroblasts in the oil group compared to the L30 and L60 groups. On the same day, the quantity of vessels was significantly greater in the L60 group compared to the other groups. On day 16, there was a significant increase in the number of blood vessels in the wounds treated with the 60 J/cm(2) laser compared to the other groups. Analysis of the collagen maturation index throughout the experiment showed significantly higher values in the L60 group compared to the other groups at all time points., Conclusion: The healing oil exerted a greater effect on fibroblast proliferation, whereas the 60 J/cm(2) laser was more effective in stimulating angiogenesis and scar-tissue maturation.

This study determined the effects of gallium-aluminum-arsenide laser (GaAlAs), gallium-arsenide laser (GaAs) and Dersani healing ointment on skin wounds in Wistar rats. The parameters analyzed were: type I and III collagen fiber concentrations as well as the rate of wound closure. Five wounds, 12 mm in diameter, were made on the animals' backs. The depth of the surgical incision was controlled by removing the epithelial tissue until the dorsal muscular fascia was exposed. The animals were anesthetized with ketamine and xylazine via intraperitoneal injection. The rats were randomly divided into five groups of 6 animals each, according to the treatment received. Group 1 (L4): GaAs laser (4 J/cm(2)); group 2 (L30): GaAlAs laser (30 J/cm(2)); group 3 (L60): GaAlAs laser (60 J/cm(2)); group 4 (D): Dersani ointment; group 5 (control): 0.9% saline. The applications were made daily over a period of 20 days. Tissue fragments were stained with picrosirius to distinguish type I collagen from type III collagen. The collagen fibers were photo-documented and analyzed using the Quantum software based on the primary color spectrum (red, yellow and blue). Significant results for wound closing rate were obtained for group 1 (L4), 7.37 mm/day. The highest concentration of type III collagen fibers was observed in group 2 (L30; 37.80 + or - 7.10%), which differed from control (29.86 + or - 5.15%) on the 20th day of treatment. The type I collagen fibers of group 1 (L4; 2.67 + or - 2.23%) and group 2 (L30; 2.87 + or - 2.40%) differed significantly from control (1.77 + or - 2.97%) on the 20th day of the experiment.

This study investigated if nonforced active exercise alters the biomechanical and biochemical properties of calcaneal tendon during maturation. Chickens at 1, 5, and 8 months old were divided into two groups: caged and penned. Intact tendons were used for biomechanical analysis, but they were divided into tensile and compressive regions for quantification of hydroxyproline and glycosaminoglycans. The exercise increased tendon strength after the fifth month, energy absorption in the eighth month, and ultimate tensile stress in the first month. Age increased tendon strength and energy storage and reduced stiffness but did not alter stress. There was an increase in collagen content in the fifth month. Glycosaminoglycans showed a progressive decline in the tensile region. Thus, some biomechanical and biochemical changes depend on the maturation process itself and also are influenced by spontaneous exercise, showing that mechanical stimulation of low intensity may help to improve the quality of the tendon.