Michael believes that a piece of equipment he bought will quickly sculpt his abdominal muscles. what can this belief be best identified as?

a fitness fad

Explanation:

Fad is the term that refers to something that is being very popular and has many consumers, but all this popularity is fleeting and the object that is being victimized by fashion is not very important, but everyone wants it because it is popular for a while. The fad can be observed in many different areas and even with regard to physical exercise, the so-called fitness fad. Fitness fad represents a type of exercise or equipment that is so popular that everyone will want to have it, however the excitement to position the product will pass quickly and the product is not even as good for what it promises.

An example of this can be seen in the question above, where Michael believes that purchased equipment will quickly sculpt his abdominal muscles.