Photographer David Clifford has captured the world's most dogged runners doing what they love in the most remote and unforgiving environments.
Go wild on a Segway
You're no doubt familiar with the sight of these quirky, two-wheeled electric scooters, controlled by the rider's body weight. Indeed, a growing number of cities worldwide offer eco-friendly tours on Segways, from Florence to Chicago.
But now a new breed of adventure Segway that tackles steeper terrain is opening up all kinds of fresh cross-country experiences to travellers. You can even venture into snow-capped mountains on them, provided you have a helmet and back protector on. One ski resort offering off-road Segway tours is Serfaus-Fiss-Ladis in Austria.