According to research submitted to the 2009 annual meeting of the American College of Sports Medicine (abstracts 851 and 852), consuming tart cherry juice can reduce pain from exercise. Healthy runners between the ages of 18 and 50 were randomly selected to receive either tart cherry juice or a placebo to drink one week before the race. The group with the cherry reported less pain. Another study had 14 women with fibromyalgia drinking either tart cherry juice or a placebo for 10 days to see its effect on muscle pain and strength after exercise. Once again, the group receiving the cherry juice had less pain and more strength.
It makes sense, according to an article appearing in the Journal of Natural Products (1999;62(2):294-296), substances in tart cherries, called anthocyanins and cyanidin are both antioxidant and anti-inflammatory. Another article in the Clinical Journal of Pain (January/February 2004;20(1):19-26) mentions that substances in tart cherry juice are anti-inflammatory.