Bar backs help. Wrist-rests (Crampbusters) help. Keeping weight off wrists helps. And, keeping loose rather than riding with tension in the arms makes a lot of difference. Tensing up puts strain on the wrists and is probably the worst of the causes. Having BMW's cruise control on the bike is a real help too because every so often, you can take your hand off the throttle and relax it with no diminution of speed. Throttlemeisters are handy in that regard too, the trouble with them being that they simply set the throttle at one position, rather than automatically adjusting it to compensate terrain that would cause variances in speed (uphills/downhills).