For cardiovascular exercise, weight-bearing, higher-impact activities such as walking, jogging and aerobics are better than nonweight-bearing or lower-impact exercise such as swimming, cycling and elliptical machines, which put less strain on your muscles and bones.

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Participants were asked about activities such as walking, hiking, jogging, swimming and sport, but also about the number of stairs they climbed each day.

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Many websites such as FitLink, My Sports Partner, BuddyUp, and Jogging Buddy, act as matchmakers for solo exercisers.

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