They tested natural watermelon juice, watermelon juice enriched in L-citrulline (ABOVE STRUCTURE) and a control drink containing no L-citrulline on volunteers an hour before exercise. Both the natural juice and the enriched juice relieved muscle soreness in the volunteers. L-citrulline in the natural juice (unpasteurized), however, seemed to be more bioavailable -- in a form the body could better use, the study found.