Effects of long-term exercise on the biomechanical properties of the Achilles tendon of guinea fowl

The purpose of this study wasto determine the effect of long-term exercise on tendon compliance andto ascertain whether tendons adapt differently to downhill running vs.running on a level surface. We carried out this investigation on thegastrocnemius tendon of helmeted guinea fowl (Numidameleagris) that were trained for 8-12 wk before commencingexperimental procedures. We used an in situ technique to measure tendonstiffness. The animals were deeply anesthetized with isofluorane duringall in situ procedures. Our results indicate that long-term exerciseincreased tendon stiffness. This finding held true after normalizationfor the cross-sectional area of the free tendon, likely reflecting achange in the material properties of the exercised tendons. Whethertraining consisted of level or downhill running did not appear toinfluence response of the tendon to exercise. We hypothesize that theincreased stiffness observed in tendons after a long-term runningprogram may be a response to repeated stress and may function as amechanism to resist tendon damage due to mechanical fatigue.