First off this should this question be in Biology.... and the answer this question is weight, height, level of activity and hormone imbalances.
Answer:
Maybe bear-baiting but a human in place of the bear.
Explanation:
Google says that bear-baiting is "is a blood sport involving the worrying or tormenting (baiting) of bears. It may involve pitting a bear against another animal."
I hope you can formulate an idea around this. Good luck with your homework