Re-Evaluation of the Effects of Anabolic Steroids on Tendons

Question: “I’ve read that testosterone usage impairs tendon growth, Deca Durabolin and Equipoise promote it, and Winstrol makes tendons brittle. I really don’t know what to do as rat studies may not tell the whole stories. I love testosterone and am no fan of Deca or Equipoise, and am pretty fond of Winstrol as well. However, the last thing I need is a tendon tear, particularly as I like mostly on low rep work. What is the actual situation with anabolic steroids and tendon growth and strength or brittleness?”

Answer: The results of animal studies in this instance are indeed questionable. There’s the obvious reason that results in humans often differ from results in a given animal, but a further reason as well.

Namely, researchers failed to control estrogen level of the subject animals. This, despite it being a known fact that high estrogen impairs tendon growth, and abnormally low estrogen promotes tendon brittleness.

Nearly any bodybuilder could have told the researchers that estrogen levels will increase when testosterone is administered in supraphysiological doses, estrogen levels may remain normal when injecting Deca Durabolin or Equipoise (boldenone undecylenate) at effective doses, and estrogen levels will drop to subnormal when Winstrol alone is used at effective doses.

The studies, therefore, provide no information as to the effect of the androgens themselves. The results could be explained entirely from higher amounts of estrogen suppressing tendon growth, abnormally low amounts promoting brittleness, without their necessarily having been any difference between the androgens themselves in terms of direct effect.

Provided estrogen levels are kept in the normal range, I do not at all believe that tendon problems result from using testosterone. Joint improvements seen with Deca or Equipoise use may not be the result of any greater tendon strength than would be achieved with testosterone use and normal estrogen levels.

Winstrol may not be harmful to tendon elasticity when estrogen levels remain normal. But nonetheless for caution I would avoid using Winstrol a large number of weeks per year. Just because low estrogen levels could have been the full explanation for the animal results does not mean that Winstrol (stanozolol) may not have contributed brittleness as well. A differing in vitro study shows stanozolol to affect collagen production of skin fibroblasts differently than nandrolone does. That suggests that there could be more to the difference between Winstrol and other androgens than simply different effect on estrogen levels.