Cramps late in XCM

What do you guys do to prevent them?

Depending on the temperature I usually struggle with cramps at XCM races at around the 3-4 hour mark. I always had the assumption that this was because of the intensity at the beginning of the race.

However, this monday I raced a 4 hour XCM at ‘tempo’ pace because I had been sick the week before and still felt that it was not the best idea to go as hard as i usually would. I expected the race to be a ‘walk ik the park’, which it was for my legs… except I still felt the cramps coming up the last 5k of the race.

Note that I drink at least 1 bottle per hour, and my mix has minerals in them. Should I try extra ORS or magnesium? What works for you?

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Excellent question! I had a similar experience in my first XCM race a week ago. Everything felt fine until about 2:45 into the race, and then the cramps began!

I fueled with about 80grams CHO/hr + electrolyte mix
My IF was 0.93 (no long sustained efforts, but very punchy up/down)

Dylan Johnson has a video about cramps and science says it’s rarely electrolytes. The Electrolyte Myth: What Causes Cramping and How Can You Prevent It? - YouTube


How technical are your XCM races?

I find that racing XCM, especially with long and/or technical descents, there’s a very high risk of cramping due to the isometric contractions holding the “squat” position.

It’s definitely something I greatly underestimated when I first got into racing long XC races. Especially now that there are technical/single track races available rather than the typical gravel road races of previous years.

There’s no real “rest” for your muscles.


Maybe you already reviewed the various topics on the forum, but here are many that are worth a look:

This is a big part of it. Especially if you are having them right after technical sections. Happens to me as well.
Discussed here at lenght.
Working on the technical side helps to be smoother and not to stiffen up.
I do not have nearby long and techy descents so can work on it only in races so mine start to go away later in the season.
Having a big difference in q-factor of the mtb and the main volume bike can be the reason as well. I was having cramps inside the upper legs. They went away when I switched to a wider q-factor main bike.

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  • How long is your long ride?
  • How does your typical race cramping point match up with your long ride duration?
  • Do you have any power data for the races? Whats your IF? Time in Zones? Other metrics?

My long rides are around 3 hours usually. When I have time I try to do more but this has not succeeded much lately. The race that I did was actually meant to prepare me for a stage race later next month.

The cramping point does match with my long ride duration I would say. Given that you put it this way I think this is true. I do have to say that a few seasons ago (2018/19) I regularly did 4+ hour training rides. Coming back to racing now after a few years of relatively low volume.

IF for this race was .72, my usual XCM race IF is more around .87

That makes sense, I do have a full suspension and would consider my technical ability to be more than enough for the demands of this particular race.

The Q-factor could play a role too, I run a 55mm chainline now. Working on getting more miles on the bike. Let’s see if this helps.

Dylan Johnsons video more or less concludes that you need to have enough training volume/long rides with similar intensity to avoid cramps. Also, that there is some genetic component to it.

I have a family member who races a lot as has a very big engine, he also suffers from cramps a lot. Especially on hot days. Not sure if this is due to extended fatigue as stated by the video. But he sure sweats a lot more salt than ‘normal’ people. Sometimes his entire bib shorts turn grey.

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If it is true that IF of race * duration should be matched in training than I definitely need to add more hard, long tempo rides in my plan. Trainerroad does not recommend them in their low or mid-volume plans.

My training plan revolves around vo2max on tuesday, threshold on thursday and longer tempo/endurance/technique rides on the weekend. Going to adjust to a 4+ hour ride every now and then to test this.

Just my n=1 but in the past, cramping seemed to be a result of not enough volume nor intensity, especially at higher than endurance pace. I remembered a race pace ride I did with one of my fast friends after roughly 1.5 years off the bike, I cramped around 8 miles in to a 20 mile ride on a steep punchy climb :scream: My buddy just looked at me & said something like “8 miles?? Dude, you gotta ride harder longer more often & get back to where you were”. He was right. If you can extend your rides out a bit, I’m sure it would help as will ratcheting up the IF on your shorter rides.

What stage race are you doing?

Fully agree, going to focus on that now.

My race is the BEMC. I raced it a couple of times already in 2018 and 2019. I’m using it to step up my fitness for later season main target one day event.

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Looks like a great race! Good luck that & the other race you mentioned!

I’ve had to battle cramping issues in the past.

My strategy now is pretty simple - no efforts above threshold until the final 1/3rd of the race (not even for a few seconds), and be extremely diligent about fueling during the first 2 hours.

Also zero hard efforts in training in the week leading up to a long event. No intervals, no sprints, no race openers, no warmup. Maybe some sweet spot efforts and Z2.

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This is a recurring topic here. Used to be an issue for me everytime I hade taken on racing again after a break. Occurence late in races (XCM as well) was pretty much a function training/race volume leading into the cramp race. Over the last 15 years I’ve had plenty of opportunities to learn about this. Non stop training/racing for the last 5 years. Only once cramps during a 12h race. After 6000m of climbing. And it was hot. Not, these were not heat related electrolyte cramps, these were fatigue cramps. However, not as bad as I used to have them after my breaks in racing.


Thanks, I guess volume + intensity just sums up the problem. Will work on that now :wink:

I had terrible cramps in all of my 4 MTB marathon races (40k, 80k) last year.
Today was my first race (55k) without cramps.
What I did differently:

  • hardly any effort above threshold - this is hard at the beginning when you are fresh but it‘s a marathon and not a sprint
  • I had a pacing plan set up with best bike split and I sticked with it
  • I didn‘t tried to catch other riders - I followed my own pace
  • I streched the legs regularly very intensively right from the beginning in every downhill
  • Only two 30min openers this week to have the legs rested for the race
  • 90g carbs per hour mixed with salt
  • I had read Trainer Road forum :wink: