Just realized how much water you actually lose during a full Ironman swim

I was reading a forum post about open water swimming and saw a stat that said you can lose up to 1.5 liters of water just from the swim alone, which blew my mind because I always thought the bike and run were where you really sweat, has anyone else been shocked by a random training fact like that?

2 comments

2 Comments

miawalker17d ago

Man that seems like one of those stats that sounds scary but doesn't really matter in practice. I mean yeah you're moving in cold water for an hour or two, not exactly sweating buckets like on the run. Most of that "loss" is probably just water you swallowed or splashed out. I've done a bunch of open water swims and never felt dehydrated after. The bike and run are where you actually bake in the sun and lose real fluid. I'd take that number with a grain of salt personally.

richardk269d ago

That "grain of salt" you mentioned is exactly right, but I'd actually flip it the other way. I've learned the hard way that even in cool water, your body is working hard and you're still losing fluids through respiration and cold-induced diuresis. The real trick is to start hydrating well before the swim, not just waiting until you're on the bike. What works for me is downing about 500ml of an electrolyte drink about an hour before the start, then sipping a little right up to the gun. That way my tank is topped off before I even hit the water, and I'm not playing catch up all day.