You should be doing more than just running, Dr. Steinberg said. For one, cross-training with cycling, swimming, and weights adds variety and makes your schedule of runs, which some might perceive as "boring," more fun. "In addition, cross-training may be beneficial for recovery, flexibility, endurance, and strength, depending on the activity," he explained.
For example, he noted, swimming is a low-impact aerobic exercise that works many muscle groups used in distance running. If you're injured and can't run, swimming is a great option (just ask Olympian Colleen Quigley). On the other hand, working muscles that running doesn't target can help prevent overuse during runs. Yoga, he said, is an activity that's good for developing core strength and flexibility.