leg cramps marathon

If you have ever suffered from leg cramping at the end of a marathon, there is a simple (although not easy!) solution.

prevent leg cramping marathon

Imagine that you are at mile 20 of the marathon.  You’ve been running well, you’ve been hydrating and fueling according to the plan that you’ve practiced in training.  You know that you just need to get through the next 6.2 miles and you’ll cross the finish line faster than you have ever done before.

And then it hits you a massive stab in your calf that gets worse and worse as you run.  Maybe you are tough enough to suffer through it, but your pace certainly will slow.  But for many runners, the cramps are intense enough to stop you in your tracks.

What causes leg cramping and more importantly, how can you prevent this from ever happening again?

In this article, I’m going to go into the science of leg cramping.  I’ll equip you with an action plan that you can start today to cramp-proof your legs, so you can crush your next race, cramp-free.

The Science of Leg Cramping

One popular theory of leg cramping is that it is caused by a fluid or electrolyte imbalance.  When your body’s electrical system is out of whack, the muscles can misfire causing painful cramping.  For some lucky runners, changing their hydration plan has made a significant difference in the occurrence of late race cramping, but for many, many others, the cramps return again despite what they eat or drink.

For most cramp sufferers, the problem is actually a muscle fatigue issue. As a muscle get tired, your body doesn’t completely shut that muscle down; it transfers the work to another area.

For example, if a cramp happens in your calf, it’s usually an issue with your hips or your glutes getting too tired to do their job of powering your running. In order to maintain the pace your brain wants to run, the body recruits the much smaller calf muscle to help.

The problem with that is that the calf was not designed to power most of your running, so at some point it protests with a powerful cramp.

Muscle Overloading and Leg Cramping

So what’s going on inside your leg with these “muscle overloading” or fatigue cramps? The neural mechanisms that are supposed to inhibit muscle contraction become depressed and the chemical and electrical synapses that fire the muscle fibers become enhanced. The result? An intense, sustained involuntary muscle contraction that can derail all your hard work on race day.

So why is this happening now at mile 20 of the race and not happening during all those long runs and hard tempos you ran during training?

prevent leg cramping marathon

The Breakdown of Your Form Breaking Down

Let’s break down the form break down in a little more detail.  Many runners begin to slouch or lean at the waist as we get tired.  When we are fresh, many runners are conscious of relaxing the shoulders down and back, keeping the spine straight, and running light and tall.  But in order to do that, you need to have a strong set of core muscles holding the spine in that position for 3, 4, or 5 hours or more.

Eventually, perhaps without even noticing it, that supportive core starts to tire and relax.  The spine starts to curve, causing the head to drop forward.  This creates a “bowling ball on a broomstick” effect, over stressing the lower back.  For many runners, this then causes them to counterbalance the weight by shifting the pelvis backwards.  In this position, it becomes easier to over-stride, which dramatically increases the impact forces that travel up the leg as the foot lands.

Over striding also puts the hamstrings in a vulnerable position at ground contact and forces them to do more work to pull the leg through since the glutes can’t be activated as efficiently. If you suffer from frequent hamstring cramps during the marathon, I contend this is the likely cause.

So it’s not just the calves that are prone to cramping late in a race.  Those bigger muscles, like the hamstrings and the quads can be susceptible, when they get recruited for more load than they have been trained for.

quad cramping marathon

Hip Extension is Also Key

Another culprit of cramping is lack of hip extension.

Hip extension is extending the leg backwards after your foot contacts the ground. This bigger the push, the longer the stride and the faster you run.  The hip and glutes power this movement and it is perhaps the single most important factor in your ability to run faster. 

As the miles pile up in a race, the hip and glute muscles may struggle to maintain the forceful contractions required for good hip extension. This will become even more obvious if you went out too fast and fatigued your intermediate muscle fibers early on. To compensate for the hip and glute fatigue, the body recruits the calf and quad to help generate the power needed to maintain marathon pace. Since the calf and quad aren’t accustomed to such a large workload, they quickly fatigue and soon the cramps begin.

But interestingly, not all runners suffer from cramps even though we all get tired in a marathon.  For example, I’ve never suffered from cramping, and my form certainly has broken down late in a race.  This could be simply genetics, but more likely it’s because I’ve unknowingly been preventing cramps with my strength sessions.

Three Ways to Lower Your Risk of Leg Cramping

The first way to help cramp-proof your legs is simply to run more. The more volume you can handle, the lower the chance of cramping in your race, because you are better trained to handle fatigue.

But not every runner can run more miles.

The next place to look is improving your form. Take a look at photos of you early and late in a race. What weaknesses do you see? If you are hunched over and shuffling, it could mean that your core and your hip extension need some help. Make sure to spend time strengthening and stretching those areas several times a week. You’ll also want to mentally prepare to focus late race and during long runs on the areas you know know start to breakdown.

The third approach is to improve your strength training with a specific focus on the core, abs, glutes, hips, as well as the muscle where you suffer cramping most often. Here’s exactly how:

Lift Heavy on Tired Legs

This is the part that’s simple, but not easy. The goal is to simulate late-race fatigue by lifting heavy when you’re already tired from running. And then do a second session later in the day.

Right after your long run, lift heavy with compound movements like lunges, squats, and deadlifts. The weight should be heavy enough that you can only do 4-5 reps per set, for about 3-6 sets. Between sets, get a full rest for 3-5 minutes. Be sure to focus on form, because you will be tired. That is the whole point.

Later in day, when you are slightly more recovered, do the same exercises but with lighter weights or just body weight for about 10-20 reps. This session reinforces the movements and further strengthens the neurological pathways between the brain and your running muscles.

Yes, lifting twice on your long run day is tough. But can be the key to runners that struggle with race-crushing cramps.

When to Begin

Start this routine once a week early in your race cycle about 14-16 weeks out. If all goes well the first few weeks, add another double strength day after a speed run until 3 weeks out from race day.

One thing to clarify is that you don’t want to simply focus on the area that cramps in your strength work.  You can do all the calf raises in the world during training, but if you don’t get your core, glutes, and hips solidly strong, your giant calves are still going to get cramps late in the race, because they are not designed to drive your entire leg alone.

If weakness in your calf was really the main issue of cramping, you would get cramps in training, which is not what typically happens.

So if you’ve tried changing up your fluids and electrolyte plan, you are running better than ever and still are suffering from leg cramping late in the race, consider bumping up your strength sessions and working on your hip extension.  It could make the difference between a painful stumble to the finish line and a triumphant race, entirely cramp-free.

Prefer to listen to the podcast version of this article? Check it out on my show, The Run to the Top Podcast!

When you are ready to transform your running, nutrition, and mental strength, with truly personalized coaching to reach your potential, reach out!



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About Claire

Coach Claire has helped hundreds of runners chase their dreams and conquer big goals. Her coaching philosophy combines science-based training, plant-based nutrition, and mindset techniques to unlock every runner's true potential. She's an ASFA certified running coach, sports nutrition specialist, a 2:58 marathoner, mom, and borderline obsessive plant lover.

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  • If you have cramps and you are well hydrated, you are not properly trained. Way too often, weekend warriors decide to run a marathon off 30 mpw. How on Earth you think your body will handle 26 continuous miles when you barely do 30 a week?! I don't have any science backing my claims, but running more miles not only reduces the chances of cramping but you will also feel not so beaten up after goal race. As you get better prepared for the start line and the demands of the race, your body knows what to expect and if you are running 50 mpw with a long run in the 15-18 mi range, 26 isn't such a shock for the body. I had only 2 races where I cramped. I was training for short races, 3K-5K, I decided to go 3 workouts per week with no long runs. My biggest day was maybe 11 miles. Then club coach asked me if I can run the marathon for the team, 3 weeks out. I knew it will be a bad idea, my hydration was a bit sub-par (race was not properly hosted and some refreshment points were missing) and got some cramps around 35K. The 2nd race was a few weeks before this one, a HM in the mountains, about +4000 feet elevation. I live in a pancake city and the race is like 40% only uphill, then 25% downhill, 5% uphill, 10% downhill, 5% uphill, 15% downhill. Quite a jigsaw! My quads were overwhelmed by the downhill and cramped hard, used uphills for walking breaks then pounded some more downhill. I knew I was in for a really good time and pushed past the cramps, so maybe it was a bit mental, too?! Finished just 1 minute over 3 hours and you can tell I was so disappointed despite everybody congratulating me. I promised myself that when I'll be back, I will go there to smash the 3h barrier, sub 2h40m, do or die.
    • Thanks for sharing, Silviu. I don't disagree with you, but I work with a top master's athlete that runs 100-120km/week, has run 2:29 for the marathon at age 47, and still gets calf cramps at 35km. I would not say he was undertrained, but we are changing up his strength work to what I described in this post to toughen up his legs further. It's definitely not a hydration issue for him, it's muscular. Hope you get your sub-3 soon!
  • So informative! A lot of runners get muscle cramps in long distance races. I've been fortunate not to have, but I always wondered why, since my husband does. I think it's my regular high mileage compared to his. Also, I go very easy on easy days and focus on form those days. He does a lot of great strength training, but I think his body doesn't know what's up when he exceeds his normal distances. Thanks for the insight!
  • I did my first double leg weight workout after my long run, and then followed by a light leg weight workout in the late afternoon. I missed the part where you said to repeat the same lifts, so I did different lifts and worked some of the smaller muscles (e.g. hip adductors/abductors). My Sunday recovery was a bit of a shuffle due to soreness, but it was a good challenge. I will repeat this workout again in the coming weeks but repeat the morning lifts in the afternoon. Thanks for the workout! Living in a super flat area of TX, I think lifting heavy will help me with the hills in Boston this fall.
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