Mary Jennings has a regular column in The Irish Times in which she encourages people to take up running.
She now has a new book, Get Running: Forget the Gym, Get Fit, Have Fun!
Mary says that running is a great option for people who want to get fit, but who feel the gym isn't for them.
"A lot of people have an impression that they have to be in a gym, but a lot of people find that quite intimidating."
For Mary, running provides her with "freedom and release, plenty of energy and headspace."
Although she wasn't a sporty person at school, she has embraced running partly because of the mental health benefits as well as the physical ones.
For those who find running difficult, Mary says the problem is often a lack of proper technique. She says that, although running can be physically demanding, it's all about balance.
"It's how much of an impact you let it be. The enjoyment factor for most people far outweighs the fact that they need to spend five or ten minutes stretching or loosening out afterwards."