What's causing cramping?

I went on a long ride (4 hours) a few days ago and experienced cramping in both legs the last 45 minutes or so of the ride. After I got home and had a recovery drink and shower, I continued to cramp for the next couple of hours, including in my fingers and feet! I’m trying to figure out what caused this-- Not enough fluids? Not enough electrolytes? Not enough nutrition while on bike? Lack of fitness? All of the above?

Some context:

  • My longest ride of the season before this was 3 hours (once). Before that most of my rides were 1-2 hours with a mix of intervals close to LT 1 and VO2 Max
  • I lost 3 lbs pre-post ride. (I weigh around 176 lbs)
  • I had 3.5 bottles with Skratch hydration plus an electrolye pill (Hammer Endurolytes) in each bottle
  • I had 2 bags of skratch chews on bike and a GU gel or two

I am hoping to do a 5 hour gravel race/ride in a couple of weeks and would like to figure out what’s going on before that as it likely will be a hot day. Any advice is most welcome!


I used to suspect lack of hydration and salts was the cause of cramps after a certain period on long rides. But experimentation in the pandemic period showed that it was actually not taking on enough fuel / food. I upped my carbohydrates intake on longer rides and the cramps have gone away.

Subsequently I did read a scientific paper about low glycogen in the muscles can cause them to malfunction and cramp etc.


This is an unknown for me, but happy to share what I’ve been through, or what I’ve seen.

Over the years, I’ve cramped a few times while racing (never during training), running, playing golf, football (aka soccer) and sometimes laying in bed. With the exception of the occasional cramps while in bed, it was all towards the end of the race, run, round or match. So I would put it down to extended duration that was at a higher intensity compared to training, with possible outside influence from the weather conditions.

One race, where I hadn’t been on the bike for a full year. Possibly too high intensity for the duration. Fueling was coke and water and a couple gels. This was when I knew very little other than just riding.

Another 2-3 races, age group (35-39) where I was chasing almost every break. Eventually cramped at 101km of 116Km. Again, possibly due to the higher intensity relative to the training so had done. Fueling was adequate (60-75g/hr).

A 21.1km in very hot and humid conditions. Pace was probably too high in the beginning, and fueling was done at every water table. Hydration was well below par.

was on a day when playing 36 holes in one day. Was close to the end of the second round. Also on a hot day. Fueling was a burger and fries at halfway (18 holes), and probably a Powerade or two.

Happened more often when trying to do static stretching. Why? Because the pros did it on TV.

As far as what I’ve seen.
Besides the outside factors, like weather conditions, I always look to see other cyclists bottle and pockets. Of those that have cramped, they all seemed to have bottles that were hardly used, or back pockets with food. Their riding skills also indicate they are holding on at the back of the bunch, which could mean they are riding at a higher intensity.

I think this is your answer. You haven’t been training enough for a long ride. Sure, you still need to eat plenty before and during a 4-5 hour ride.


I’ll second that. It’s a fitness thing. Once you can progressively build up to longer rides you will adapt to the stress and cramping will go away. Nutrition and hydration play a large role, but you have to start from the perspective of also having the capacity to just do the amount of work required for that length of ride.

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Yes, I cramped often when I began to ride, less so as I got fitter, despite ingesting plenty of the usual suspects, and now only cramp once in a while if I go past my usual effort. If your urine is fairly clear, and eating well, it’s likely just the fitness.


yes to ‘all of the above’ potentially.
Cramping is just a reduction in the ability to produce ATP, and that can be caused by ‘any’ of the factors related to fatigue/stress, and deficiencies.


iMHO, this visual explains very well the complexity of the topic, ans it is even more complex if you think about combinations of causes, and not read it as various isolated causes…