Jim Dreeben, 83, works out outdoors all year round.Jim DreebenJim Dreeben, 83, took up CrossFit in his 80s and got hooked.He does 100 push-ups and also planks six days a week, and his doctor told him to keep going.Dreeben's active lifestyle includes kayaking, walking, and push-ups, boosting longevity.Jim Dreeben has always been active, but it wasn't until he was in his 80s that he took up CrossFit.Dreeben, a retiree in Riverhead, New York, now does weekly CrossFit sessions and 100 push-ups six days a week, he told Business Insider.That's alongside walking, kayaking, battle rope workouts, sea swimming, planking, and paddling on a prone board.He is one of the many keeping up serious fitness regimes into old age, in the hope of staying healthy as long as possible."I enjoy working out and you sort of get hooked on it after a while," said Dreeben, who is 83.CrossFit is an intense sport designed to help people build strength, fitness, power, and endurance across a range of disciplines.