Dave Legeno became known for his character name, Fenrir Greyback, after the final 3 Harry Potter installments were released. Off-screen Legeno was a 50-year-old martial artist who enjoyed the outdoors in his spare time. In 2014, the Harry Potter died of a heat stroke while hiking in Death Valley.
Staying fit is certainly a commitment. Besides doing the physical training, there are some other factors to consider, like nutrition