Fuel and Flow with Jess
A Run Vault series on nutrition and hydration for performance

Why Do I Cramp During a Run? Causes, Prevention, and Tips from a Sports Nutritionist

By Jesikah Ings, Run Vault Nutritionist

You're feeling strong, moving smoothly, and then it happens.

Your calf tightens, your stride shortens, and your pace slips away. What felt comfortable moments ago suddenly becomes hard work.

Muscle cramps are one of the most common (and frustrating) issues runners experience. While they are often blamed on dehydration and electrolytes alone, the reality is more complex.

As a Sports Nutritionist, here is what runners need to know about why cramps occur and how to reduce the risk.

What Causes Muscle Cramps While Running?

Muscle Fatigue Is the Primary Driver

The biggest predictor of cramping is not dehydration. It is not low electrolytes. It is fatigue.

As your muscles tire, the signals between your nerves and muscles start to misfire. That smooth rhythm you had for kilometres breaks down, and suddenly your muscle locks up in a painful, involuntary spasm.

Cramps are more likely when:

• You increase mileage too quickly
• You push pace beyond what your training supports
• Your strength training is not keeping up with your running demands
• Fatigue accumulates late in long runs or races

That is why cramps often appear when you are just about to hit your stride, or the finish line.

Running Low on Fuel Can Make It Worse

Carbohydrates are your muscles’ favourite fuel. When your glycogen stores run low:

• Muscles fatigue faster
• Coordination declines
• Cramping becomes more likely

This is common in runners who train fasted, under fuel long runs, or do not eat enough day to day. Your muscles are working harder with less fuel, and they let you know.

Electrolytes and Hydration Help, but They Are Not the Whole Story

Electrolytes like sodium, potassium, magnesium, and calcium support muscle function and nerve signalling. Losing too many through sweat can increase the risk of cramping, especially on hot, long runs.

For some runners, electrolyte drinks, gels, or powders can help maintain balance. But remember, these strategies work best when your training, pacing, and fuelling are already on point.

If you are looking to support your hydration and fuelling strategy, explore:

• Electrolytes
• Gels and Nutrition
• Hydration

Pacing: Don’t Let Your Nervous System Fall Behind

Starting too fast places early stress on your muscles. As fatigue builds, your nervous system struggles to control muscle contractions and cramps can strike.

Practising race pace and fuelling in training helps your body adapt so your muscles can handle the load when it matters most.

Will Supplements Help With Running Cramps?

Supplements are not a magic fix, but they can support your performance. Electrolyte products help replace minerals lost in sweat, while carbohydrate supplements help maintain energy during long runs.

Some runners also experiment with pickle juice or cramp specific gels such as CrampFix, which may provide rapid relief when cramps hit late in a session. Research is still emerging, but anecdotal evidence suggests they can be useful tools in the right context.

Used alongside smart training, fuelling, and pacing, supplements can help reduce cramping risk and keep you moving.

Quick Tips to Prevent Cramping While Running

• Progress your training gradually
• Include strength training specific to running
• Eat enough carbohydrates to support your workload
• Fuel runs longer than 60 to 90 minutes
• Replace fluids and electrolytes when needed
• Practise pacing and fuelling in training

The Takeaway

Cramps are not random, and they do not mean something is wrong with you. They are your body’s way of signalling fatigue, insufficient fuel, or excess stress.

By combining smart training, proper fuelling, hydration, and pacing, you can make cramps far less likely and far less disruptive, so your runs feel smooth, powerful, and enjoyable.

Need Help Building Your Plan?

If cramps are showing up regularly, it is often a sign that training load, pacing, fuelling, or hydration needs a small adjustment. If you would like help tightening up your approach, come in and chat with the Run Vault team. We can help you dial in a plan that supports your running goals with the right gear, fuelling options, and coaching support.

Jesikah Ings
Resident Nutritionist — Fuel & Hydration, Run Vault