Does placebo effect applies in bodybuilding?

Maybe: For athletes, there is a matter of confidence and drive. The placebo effect may provide the motivation to stay committed to the program, follow the necessary diet, and stress the muscles enough to build them to the desired size. The placebo will not cause the muscles to bulk up, but the psychological effect may be just as effective.

And placebo use is?: You are assuming that placebo works by lying. Having a daily routine of medical care, having a doctor relationship, having any daily routine. all are Incredibly useful and all are reinforced by a daily routine of supplements Whether or Not the supplement does anything. This is especially true when keeping a routine matters (weightlifting).

Placebo: Effect may apply in bodybuilding when the bodybuilder believes in the supplements and perform extra weight lifting or body toning exercise resulting in more muscles

Relation to what ?: It is likely true that most supplements end up in the pee & poop every day they are taken so their true effect is minimal. It is likely true that someone taking supplements will focus on their workout (investment /placebo effect). Since they focus on their workout they may improve their performance. When you post a question is would be good to clarify what you are talking about.