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Biomechanical responses of different rat tendons to nandrolone decanoate and load exercise

Abstract

Supra-physiological doses of androgenic anabolic steroids (AAS) have been associated with increased incidence of tendon rupture. The aim of this study was to compare the biomechanical properties of the rat calcaneal tendon (CT), superficial flexor tendon (SFT), and deep flexor tendon (DFT), and to determine the effect of AAS in association with jumping training. Wistar rats were separated into four groups: Sedentary (S), Trained (T), AAS-treated (Deca-Durabolin 5 mg/Kg body weight, twice a week) sedentary rats (AAS), and AAS-treated and trained animals (AAST). To induce jumps, animals were kept in a water column with a 50-80% body weight overload. The tendons were subjected to mechanical testing, and the displacement at maximum load, maximum stress strength, maximum strain, and elastic modulus were calculated. Mechanical testing showed that the CT differed from the DFT and SFT, which showed similar mechanical properties. Training, AAS administration, and AAS administration in conjunction with training affected the three tendons differently. Jump training improved the mechanical properties of the CT (extended toe region and increased resistance to tensional load). In spite of causing little modification of the mechanical properties of the DFT and SFT, the effect of training was counteracted by simultaneous administration of AAS. Combined treatment decreased tendon accommodation in response to load, and caused the tendon to experience rigidity. The results demonstrated that tendons are differently adapted to exercise, but respond equally to AAS, and that increased risk of tendon rupture in AAS consumers is related to the deterioration of tendon mechanical properties. (AU)

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