A man who started running at 55 has completed 50 marathons. Here are 3 things that made getting fit easier.

Dennis Beggs

Dennis Beggs hated his first run. He was 55 years old and had been walking a lot to clear his mind while caring for his mom, who had Alzheimer's disease. He wanted to start running instead to "waste less time," he told Business Insider, so ran a quarter of a mile in spring 2017 — and thought he'd never do it again.