RESUMEN
BACKGROUND: Popular Brazilian medicine uses Heteropterys aphrodisiaca infusion as a tonic or stimulant, for the treatment of nervous debility and breakdown and for muscle and bone weakness. This study investigated the effects of Heteropterys aphrodisiaca infusion on the tendon properties and extracellular matrix of rats under endurance training. METHODS: Wistar rats were grouped as follows: CS- control sedentary, HS- H. aphrodisiaca sedentary, CT-control trained, HT- H. aphrodisiaca trained. The training protocol consisted in running on a motorized treadmill, five times a week, with weekly increase in treadmill speed and duration. Control groups received water while the HS and HT groups received H. aphrodisiaca infusion, daily, by gavage for the 8 weeks of training. Achilles tendons were frozen for biochemical and biomechanical analysis or preserved in Karnovsky's fixative, then processed for histomorphological analysis with light microscopy. RESULTS: Biomechanical analysis showed significant increase in maximum load, maximum stress, modulus of elasticity and stiffness of the HT animals' tendons. The metalloproteinase-2 activity was reduced in the HT group. The compression region of HT animals' tendons had a stronger and more intense metachromasy, which suggests an increase in glycosaminoglycan concentration in this region of the tendon. The most intense birefringence was observed in both compression and tension regions of HT animals' tendons, which may indicate a higher organizational level of collagen bundles. The hydroxyproline content increased in the HT group. CONCLUSIONS: The association of endurance training with H. aphrodisiaca resulted in more organized collagen bundles and more resistant tendons to support higher loads from intense muscle contraction. Despite the clear anabolic effects of Heteropterys aphrodisiaca and the endurance exercise association, no side effects were observed, such as those found for synthetic anabolic androgenic steroids.