I'd think the first one would be correct. To determine whether or not athletes have an increase in vertical leap when wearing the shoes.
I'm not totally sure but this answer just seems the most correct. It would prove if the manufacturers clam is valid. You would have to other brand and models of shoes. You would also have to test the same kind of shoes ie, gym shoe vrs gym shoe instead of gym shoe vrs flip flop.
You would also have to use the different shoe on the same test group of users/athletes to keep a constant.
