Okay here it is:
Proponents of weightlifting claim that lifting weights can make weak muscles become strong. The problem with this claim is its obvious circular reasoning. For the ability to lift weights presupposes muscular strength to begin with. Thus one would need to be strong already to become strong. But this is clearly begging the question. Thus the notion of weight training has been shown to be logically incoherent.
The question is how would you respond to this? Is there any merit to the argument?