When discussing the effects of exercise and anabolic steroid hormones on receptor concentration, a strong synergistic relationship may exist between the two. This is supported by a recent study that examined the impact of steroids and exercise on the skeletal muscles of adult and elderly rats. The study administered nandrolone phenylpropionate at a dose of 6 mg per kilogram of body weight per week, with control groups either left untreated or subjected to overload stimulation (surgically removing supportive muscle tissue to force the muscle to bear a greater load). In the adult plantaris muscle (composed primarily of fast-twitch fibers), the combined use of overload stimulation and steroids resulted in androgen receptor concentration three times higher than that of nandrolone alone (nine times that of the control animals).

Significant Findings

The most striking result of this study was observed in the soleus muscle of elderly rats (composed primarily of slow-twitch fibers), where the combined effect of overload and nandrolone increased androgen receptor concentration to 27 times that of the control group. There is no doubt that a 27-fold or even 9-fold increase in AR density would have a direct and significant impact on the rate of muscle growth.

Summary

As you can see, the control of androgen receptor density is a critical aspect of the "other half of the puzzle" regarding anabolic steroids. The effectiveness of a particular drug and the actual blood levels of the substance are crucial variables often overlooked.

Studies on androgen receptor proliferation show that both exercise and steroid doses positively affect receptor density. Both substances significantly increase cells' sensitivity to steroid metabolism. Further evidence suggests a powerful synergistic relationship between the two, resulting in a greater increase in androgen receptor cell concentration than either alone.

This might explain why training is essential for significant growth and why steroid use is so effective. The dramatic (seemingly unnatural) changes in body composition are often due to the intense resistance training combined with the use of anabolic steroids.