Heavy resistance training seems to be necessary for anabolic steroids to exert any beneficial effect on physical performance. Most research studies that have demonstrated improved performance with anabolic steroids used experienced weight lifters who were capable of training with heavier weights and producing relatively greater muscle tension during exercise than novice subjects. The effectiveness of anabolic steroids is dependent upon unbound receptor sites in muscle. Intense strength training may increase the number of unbound receptor sites. This would increase the effectiveness of anabolic steroids.