What happens when you get cramps?

Generally you start cramping when you push harder than your fitness allows.  Heat, hydration, and salt levels are factors into how hard you can push and for how long, but the biggest issue is usually pacing and fitness.

IOW, if you can run a half marathon in 1:40 in 65 degree weather and 40% humidity, you shouldn't expect to run that same time in 95 degree weather and 80% humidity just because you drink more water and take in more salt.  You need to slow down or increase your fitness is you expect to maintain that pace in hotter conditions.

Edited by Jason N 2016-09-30 2:41 PM

My hypothesis is that cramps are caused by not enough oxygen. I started to wonder because the only time I get cramps is during a swim--during anything else, my muscles just fatigue and stop, they don't cramp. I have also noticed that when I trail race at high altitude, a lot of people get muscle cramps in the first half mile or so, but I never see that when I race near sea level (which is much more common).

During the run of the last race I did, some guy was being very theatrical about his quads cramping. I was running at a steady pace, and he would run ahead of me then stop and yell and whine. After about the third time I passed him, I told him to take slow, deep, deliberate breaths. He did and he passed me one more time. At the end of the race, he found me and told me that the breathing had gotten rid of the cramps.

I'm assuming the same thing applies on the bike (% of FTP needs to be adjusted for the heat). I probably pushed that.

I train and race a lot in those conditions and actually have very rarely cramped in them. Where I tend to get them is actually in cooler races where I have pushed the bike really hard, either due to going after ambitious time goals and/or the course being tough due to wind or hills. I have a tendency to ride in too high a gear/low cadence on those and it comes back to bite me on the run. That has been true across the board, from sprint to HIM, and at races with temps in the 50's to the 90's. Another issue is my approach to transition. Cramps are much more likely to be a problem on the run if I don't ease off in the final kilometer or so and get into an easier gear. The other possible trigger is my running form. I tend to run on the balls of my feet and in a long race, that sometimes does a number on the muscles at the sides of my shins, particularly if I then go up on my toes to run up a hill. For me it is very much a muscular fatigue issue. I am really careful about hydration and electrolytes as that can be a life-or-death matter in extreme conditions, and I don't think I've had cramps triggered specifically by dehydration or electrolyte issues. But you do have to slow down a bit in those conditions. How much varies on how adapted you are to them, but even someone who lives most of the year in the tropics like me is just not as fast as in cooler conditions.

Case in point--I had hard efforts and good placing at two HIM about 10 weeks apart (Vietnam and Calgary) this year. Vietnam was a flat, "fast" course (except for heat) and I did 5:31 with temps in the mid-80's to low 90's and high humidity. Calgary was a much more challenging bike course, and I did 5:16. (Probably more like 5:18 on a standard course as swim was a bit short.), with temps ranging from low 50's to mid 60's There was roughly a five-minute difference for both bike and run splits, at a similar effort level. (The rest would be due to long transitions at the Vietnam race.) And I cramped at Calgary (beginning and end of run), not Vietnam. I would attribute that to incorrect gearing and high effort on the bike, and not easing off at all as I approached T2.

Suffice to say, there are a lot of possible causes, and not all of them have to do with hydration an electrolyte balance.

I would definitely back off the effort in hot, humid conditions. I was using times above but realize that's not valid to compare across courses. My normalized power (using that as there was more variability at Calgary due to hills and wind) was 70% of FTP at the Vietnam race, 78% in Calgary. I think particularly if the run conditions will be very hot, you need to be conservative on the bike, or you may have issues not only with hydration but muscular fatigue and energy levels in general, since the circulatory system is working harder to both cool the body and keep you moving forward.

Jason pretty much summed it up, but I do think there a few individual nuances from time to time. I do get fiesty hammies when running hard or long off a hard bike session. And not necessarily at a cusp of fitness level pace per se. If I run the equivalent as a solo effort they really won't "act up", but off a hard bike effort they start talking

When I get cramps. I fall down. Then I roll around in the dirt. Probably holler some. Caught the cramps at a spartan race. Made it back to the truck only to lock up again. Must have been loud. Someone came and rubbed my calf, never opened my eyes to look.

But, that's me