Also, does he do abdominal
workouts? Hot water, and heat in general, helps relax the
muscles. If his
muscles are extremely tense, or have been stressed from workouts, the cramping could be from the release of the lactic acid that builds up in tensed muscles.
I would recommend he start drinking lots of water after his showers, and try to flush the lactic acid out of his system. He should also drink a LOT of water during the day, as well as during and after exercising.