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Train like a triathlete, Holland said, because if you only run, you'll be forced by injury to switch to swimming and biking to rehabilitate overuse injuries. Swimming is beneficial because "your posture and body weight is horizontal to gravity, so you work many muscles that receive little attention when running or can become weak and prone to injuries, such as the hamstrings, abdominals and low back," said Michele Olson, a professor of exercise physiology at Auburn University at Montgomery, Ala. "Swimming provides a top-notch cardio challenge for heart health; that's important since heart disease risk increases markedly as we age."
Runners don't necessarily need to drop their hard training days, said Amby Burfoot, 66, who plans to run the Boston Marathon in April on the 45th anniversary of his 1968 title. Burfoot isn't running as far or as fast, and he needs more recovery time. But he still runs vigorous hill repeats several times a week and alternates running with easy spinning on a recumbent bike. He eliminated his long runs — his longest is a 13-miler versus the 20-milers of his youth. "I still run marathons but don't race them," he said.