To get ready to climb Everest, I did a lot of hill running with a daypack on and a lot of underwater swimming. I would swim a couple of lengths underwater and then a couple above. It gets your body going with limited oxygen.
Bear GryllsI exercise about 40 minutes a day, and I'll run one day and do circuit training the next day. I live in an area where there are brilliant hills and mountains, so I get a good hill run with my dog. At home, I'll do the circuit training with old weights, along with pull-ups in the trees and that sort of stuff.
Bear Grylls