Muscle Cramps While Running: Causes, Prevention & Solutions

Why most advice about cramps is wrong

If you have ever suffered a cramp mid-race, you know how frustrating it is. That sharp, unexpected pain that forces you to stop when you are at your most motivated. And if you search for solutions, most articles will tell you the same thing: eat a banana, drink more water, do not forget your electrolytes.

The problem is that science has advanced significantly in recent years and most of those recommendations are incomplete or outright wrong. Dehydration and lack of electrolytes are not the main cause of running cramps. Current research points to a very different mechanism: neuromuscular fatigue.

In this guide we will explain what real science says, what types of cramps exist, how to truly prevent them and what to do when they catch you in the middle of a workout or race.

Types of cramps in runners

Not all cramps are equal. Understanding what type of cramp you suffer is the first step toward solving it.

Muscle cramps (calves, hamstrings, quadriceps)

These are the most common in runners. They occur when a muscle contracts involuntarily and does not relax. The calves are the most frequently affected muscle, followed by the hamstrings and quadriceps. They tend to appear in the second half of a race or long workout, when muscle fatigue accumulates.

• Calves: the classic runner cramp. It appears as an intense contraction in the back of the lower leg.
• Hamstrings: common in runners who increase pace or distance too quickly. It is felt in the back of the thigh.
• Quadriceps: more common in races with elevation gain or in runners with weakness in the posterior chain.

Side stitch (side pain)

Technically called “exercise-related transient abdominal pain” (ETAP), a side stitch is not a muscle cramp in the strict sense. It is a sharp pain in the lateral area of the abdomen, generally below the ribs. It especially affects beginner runners and is usually related to eating or drinking too close to training, irregular breathing or a lack of diaphragm conditioning.

EAMC (Exercise-Associated Muscle Cramps)

This is the scientific term that encompasses cramps that occur during or immediately after exercise. EAMCs are different from nighttime cramps or cramps caused by underlying diseases. Their main characteristic is that they affect muscles that are being actively used and are already in a shortened position.

Real causes according to modern science

For decades, the dominant theory was that cramps were caused by dehydration and electrolyte loss. But research over the last 15 years has shown that this theory has significant holes.

Neuromuscular fatigue: the main cause

The most supported theory currently is that of “altered neuromuscular control.” When a muscle fatigues, the nerve signals that control its contraction and relaxation become dysregulated. Muscle spindles (which detect stretching) become hyperactive, while Golgi tendon organs (which inhibit excessive contraction) become hypoactive. The result is a muscle that contracts without control.

This explains why cramps appear in the final stages of races, when fatigue is at its peak, and why they affect the muscles that work hardest during the run.

It is not just dehydration: debunking the myth

Several studies have shown that runners who suffer cramps are not more dehydrated nor do they have lower electrolyte levels than those who do not. A study with Ironman runners found no significant difference in sodium, potassium or magnesium levels between athletes who cramped and those who did not. Hydration matters for overall performance, but it is probably not the determining factor in cramps.

Pace too fast for fitness level

Running at a pace your muscles are not adapted to dramatically accelerates neuromuscular fatigue. This is the reason many runners suffer cramps in races but not in training: they go out faster than they have practiced. If your training pace is 5:30/km and you go out at 4:50/km on race day, your muscles are not prepared to sustain that effort.

Insufficient training for the distance

If your longest long run has been 25 km and you run a marathon, the last 17 km are uncharted territory for your muscles. The accumulated fatigue over those untrained distances exceeds your neuromuscular system's ability to maintain control, and cramps appear. The solution is simple: train the distance. Check our guide on how to increase your running endurance.

Risk factors

Some runners are more prone to cramps than others. Knowing the risk factors helps you take specific preventive measures.

• Previous cramp history: the most reliable predictor. If you have had cramps in previous races, you are 4 to 6 times more likely to have them again. This suggests an individual neuromuscular predisposition.
• Running faster than trained: going out in a race at a significantly faster pace than your training pace is one of the most direct causes of cramps. Race day enthusiasm is a real enemy.
• Heat and humidity: hot environmental conditions accelerate overall muscle fatigue and increase thermoregulation demands, which indirectly contributes to neuromuscular fatigue. It is not the heat itself that causes the cramp, but the accelerated fatigue.
• Inadequate nutrition: running with low glycogen stores accelerates muscle fatigue. Poor pre-workout nutrition can be an indirect trigger.
• Lack of muscle strength: weak muscles fatigue sooner, reaching the neuromuscular dysregulation threshold faster.
• Age: runners over 40 have a greater tendency toward cramps, probably due to natural loss of muscle mass and reduced neuromuscular efficiency.

Prevention strategies

Now that we know neuromuscular fatigue is the main cause, prevention strategies make sense. It is not just about drinking more water, but about preparing your muscles for the effort they will undertake.

1. Progressive training (the most important)

The best prevention against cramps is training that prepares your muscles for the demands of the race. This means:

• Respecting the 10% rule: do not increase weekly mileage by more than 10% compared to the previous week.
• Doing long runs that approach race distance (at least 75-80% for a marathon).
• Including race-pace workouts in your training plan so your muscles are used to that effort.
• Cycling load with recovery weeks every 3-4 weeks to allow adaptation.

2. Smart pacing

Start more conservatively than you think you need to, especially in the first half of the race. Running the first kilometers 10-15 seconds per kilometer slower than your goal is an investment that pays off massively in the final kilometers. Negative splits (second half faster than the first) not only improve your finishing time but dramatically reduce the risk of cramps.

3. Electrolytes: useful but not magic

Although dehydration is not the main cause, maintaining good electrolyte levels is still important for overall performance and can help delay fatigue:

• Sodium: the electrolyte most lost through sweat. In long races or in heat, 300-600 mg per hour is a reasonable reference.
• Magnesium: essential for muscle function and nerve conduction. Many runners have suboptimal levels.
• Potassium: important for normal muscle contraction. Easily obtained through a diet rich in fruits and vegetables.

4. Proper hydration (without overdoing it)

Hydrate enough, but not in excess. Overhydration (hyponatremia) is more dangerous than mild dehydration and can cause its own muscle problems. A practical guide: drink according to thirst and aim for pale straw-colored urine. For more details, check our complete hydration guide for runners.

5. Strength training

Stronger muscles fatigue later. Including 2 weekly strength sessions focused on the lower body significantly reduces the probability of cramps:

• Squats and deadlifts: strengthen quadriceps, glutes and hamstrings.
• Calf raises: specific to the calves, the muscle most prone to cramps.
• Lunges: work unilateral strength and balance, replicating the running pattern.
• Glute bridges: strengthen the posterior chain and stabilize the pelvis.

What to do when cramps strike

No matter how much you prepare, cramps can appear. Knowing how to act in the moment makes the difference between dropping out of a race or finishing it.

Reduce pace or stop completely

The first thing is to reduce the demand on the affected muscle. If you can, slow down significantly. If the cramp is intense, stop and walk. Trying to “run through the cramp” almost never works and can cause a real muscle injury (tear).

Stretch gently

A gentle, sustained stretch of the cramping muscle can help restore neuromuscular signaling. The key word is “gentle”: stretching a muscle in spasm forcefully can make it worse. Hold the stretch for 15-30 seconds, breathe deeply and release slowly.

• Calf: place the ball of your foot on an elevated surface (curb, rock) and gently drop your heel.
• Quadriceps: standing, bring your heel to your glute, holding your ankle. Lean on something if you need balance.
• Hamstring: extend the affected leg forward, toe pointing up, and lean your torso slightly forward from the hip.

Pickle juice: the science behind it

It may sound strange, but pickle juice has scientific backing. A study published in Medicine & Science in Sports & Exercise showed that it reduces cramp duration significantly faster than drinking water. The mechanism has nothing to do with hydration: the sour taste stimulates oropharyngeal receptors that send signals to the nervous system to inhibit motor neuron hyperactivity. Basically, the strong taste “resets” the nerve signal causing the spasm.

Mustard, vinegar and very acidic drinks also work through the same mechanism. If you compete in long races, carrying a small container of pickle juice or mustard can be your best insurance against cramps.

Walk, then resume

After the cramp subsides, do not immediately return to your previous pace. Walk for 2-3 minutes, then jog gently. If you can maintain the jog without the cramp returning, gradually increase your pace over the next 5-10 minutes. If the cramp comes back, walk longer and accept that today you need to finish at a more conservative pace.

Nutrition for cramp prevention

Although nutrition is not the direct cause of cramps, an adequate diet helps delay muscle fatigue and maintain optimal neuromuscular function.

Magnesium: the forgotten mineral

Magnesium participates in over 300 enzymatic reactions, including muscle contraction and relaxation. Many runners have suboptimal levels because intense exercise increases losses through sweat and urine. The recommended intake is 400-420 mg/day for men and 310-320 mg/day for women. Magnesium-rich foods: pumpkin seeds, almonds, spinach, dark chocolate and avocado.

Potassium: beyond the banana

Potassium is essential for nerve impulse transmission and muscle contraction. Although the banana is the most famous food for its potassium content, it is not the richest. Potatoes, sweet potatoes, spinach, white beans and avocado contain more potassium per serving. Aim for 3,500-4,700 mg daily through food.

Sodium: strategic loading before races

If you compete in long races or in hot weather, sodium loading 24-48 hours before can improve your fluid retention and delay sweat losses. This does not mean eating bags of chips: adding a bit more salt to your meals and having salty broths is enough. During the race, sports drinks with electrolytes or salt capsules can supplement.

Frequently asked questions