One recent study found that people were able to burn up an extra 450 calories a day with one hour of moderate exercise. That can include walking briskly, biking or swimming.

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Some patients describe chronic fatigue syndrome as feeling like an "unrelenting flu." iStockphoto.com hide caption

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Many people with sleep apnea wear a CPAP machine mask in bed to help them breathe. Amy Walters/iStockphoto.com hide caption

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Keratoconus is an eye condition in which the normally round cornea thins, causing a cone-like bulge to develop. Courtesy of JirehDesign.com hide caption

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Peggy O'Brien-Murphy receives a massage from therapist Loretta Lanz. O'Brien-Murphy was among the participants in a study that found both relaxation and deep tissue massage are effective treatments for lower back pain. /Group Health Research Institute hide caption

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Artificial hips have been a big advancement in treating debilitating arthritis. But there have been reports of medical issues — some serious — in patients with all-metal implants. iStockphoto.com hide caption

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