According to USA Triathlon, one of the fastest-growing age groups for competitive triathlon is 40 to 44 years old. The sport has proven to be a powerful draw for older athletes looking to challenge themselves and stay in top shape. That said, all those years of training and racing take their toll, often resulting in chronic knee, hip and other joint injuries.
In 2005, USA Triathlon began a pilot program to introduce an alternative triathlon discipline known as the aquabike, which removes the final running portion of the race. The aquabike format proved hugely popular with young and old athletes who wanted to experience the unique challenge of a multi-sport endurance race without the relentless pounding of a 13.1-mile (21-kilometer) run. In 2008, USA Triathlon sanctioned 60 such races across the country, with more in the works [source: USA Triathlon].
What's great about the aquabike format is that it can easily be incorporated into a traditional triathlon course. Since the swimming and cycling portions are the first two legs of a traditional triathlon, aquabike participants simply stop before the final running portion. In sanctioned races, awards are given for top finishers.
If you can't take the heat of a traditional triathlon, then you'll like the next non-traditional discipline: the winter triathlon.