If you want your project to be eligible for lots of $$$ and awards, you need to follow the rule of the International Science and Engineering Fair. ISEF rules will not let you do any experiment where anybody gets hurt (including yourself) or even has the potential to get hurt.
Maybe you could do a study of how the size/length of a person's foot relates to something else (besides the obvious thing that everyone thinks of). The human body has lots of interesting relationships, like the distance of the forearm has something to do with predicting intelligence. You will want to do a lot of background research to pick your best topic (google is great for that) and then talk with your teacher about how to best set up the experiment.
Let your mind wander, and have fun!
Science fair sponsor (teacher) who's had kids win trips to the International Fair the past two years.