I've never had a problem on the bike, it's the run part that concerns me the most, and not only because of cramping. For some reason, I get super dehydrated, no matter how much fluid I take in. I lose between 4-7 pounds of water weight (and gain it right back) in a span of 2 or 3 days. At <110 lbs, it's a significant weight crash. My OB-GYN doesn't seem to make much of it, but it's definitely a performance-downer.