Why Do I Get Muscle Cramps? – A Runner’s Guide

Why Do I Get Muscle Cramps? – A Runner’s Guide

The Dreaded Cramp

Many, if not most runners will have experienced cramp, either during or perhaps after a race.  It can appear at anytime, although more often than not will be in the back half of your run or after/during an increase of physical exertion. They can sometimes start with a slight tightening of the muscle then slowly develop. Or they can hit you hard and fast, which stops you in your tracks.


My research has unveiled two distinct types of cramps:

Muscle Overload Cramp

Electrolyte Imbalance Cramp

A word on Magnesium before we go ahead….

While there is a link between magnesium deficiency and muscle cramps, there is no conclusive evidence to suggest taking a magnesium supplement will help alleviate cramps. Magnesium is a mineral involved in hundreds of the body’s biomechanical processes, including muscle contraction and nerve transmission.

As magnesium is both safe to use and beneficial for a number of things (including athletic performance) it would certainly not hurt to include it in your supplementation program.

Muscle Overload Cramp

This type of muscle cramp occurs when there is an over-loading to a particular muscle.

The muscles that are in a shortened position while running are the most vulnerable.

When these muscles are in a stressed state, the neural mechanisms that make the muscle contract are depressed. Excitatory activity (chemical and electrical synapses that fire the muscle) of the muscle fibers is enhanced.

The result is an intense, involuntary muscle contraction.


Muscle Overload Cramp Symptoms

Sudden onset of intense cramping.

Generally in a specific muscle.

It can be settled with stretching and massage.


What Can Cause Muscle Overload Cramps?

Poor stretching practices.

Not conditioning the muscle in training.

To much exercise intensity and duration for what the body has been prepared for.

Some people are prone to cramping more than others.

Old age.

How to Treat Muscle Overload Cramps

  • Stretching and massage
  • Icing affected muscle group



How to prevent muscle cramps

Keeping  exercise intensity and duration within your limits

Slowly improving conditioning when training so you can extend your limits

Stretching so you have adequate range of motion

Trying to relax while exercising



What Type of Training is Best for Preventing Muscle Cramps in Races?

So, the overloading muscle cramp occurs when you push your body too far, for what it has been conditioned for.  For example when you pick a pace on race day that is greater than your body can handle, or run a lot further than you have practised for. 

By conditioning your body for strength, duration and speed it will lessen the chance of this type of cramp happening.



Strength work in your training is a must  to help increase your strength and therefore efficiency. By doing this your muscles will need to contract fewer muscle fibers to perform at your race pace.



Although we do not all have the want to be speedsters on race day, some speed training will condition your body for when you get excited in a race and push your body that little harder than you intended.

So bringing these two types of training together along with longer runs is a good way to prep your body against overload cramps. I suggest 2 key sessions that you can perform to overcome this problem.

Pre-Fatiguing your Legs

Doing leg exercises to fatigue your legs before you go out on your long run is a good way to ward off muscle overload on race day. This method not only strengthens your legs but also conditions your body to run on tired legs. Which is similar to being tired on race day.


Speed Drills at the End of a Long Run

Straight after your long run is a good time to sneak in some speed drills to condition your muscles for a change of intensity while racing. By doing this it will accustom your muscle so they can deal with any changes of intensity and not spasm due to not been trained to perform in this way.

These drills can be as easy as 5-0 x 100m run throughs at faster than race pace, (does not need to be at sprint pace).

5 x 200m can also be good, or if you are feeling really energetic you can throw in some 400m. These drills will basically teach your muscles to perform when in a tired state without freaking out by screaming: “I’m not coping with this stress, and I’m going to close this down on you on race day”.

So by training smarter by conditioning your muscles so they are properly prepared will help you overcome any unwanted surprises on race day.


Electrolyte Imbalance Muscle Cramps

This type of cramp is caused by an imbalance of electrolytes in the body. Most of us sweat when running, and we excrete a degree of sodium. This disturbs the delicate balance in our bodies, leading to cramp. This type of cramp is typically due to extensive sweating and significant electrolyte losses, especially sodium and chloride.

 Some people sweat a lot more sodium than others, and thus are particularly susceptible to cramp.

As the duration of exercise increases or intensifies, sweating develops a deficit, in particular sodium and chloride. This results in muscle cramping if it is not replaced promptly.

These electrolyte changes and the accompanying fluid shifts in the body can cause certain neuromuscular junctions to become hyperexcitable, which triggers cramping. The lack of fluid intake can also be a contributing cause.

Electrolyte Muscle Cramp Symptoms

Gradual onset of small muscle contractions (“twitches”) that can go unnoticed.

Usually develops in the more highly active muscle groups like the hamstrings and quadriceps.

Cramping can jump to different muscles.

Cramps are generally intermittent and not constant.


What Causes Electrolyte Muscle Cramps?

  • High sweat rate, high sweat sodium concentration, or both.
  • Poor hydration practices and/or salt intake before and during exercise.


Ways to Treat Electrolyte Muscle Cramps

Drink an electrolyte replacement straight after noticing first signs of cramp, (muscle twitching).

Take salt tablets like SaltStik Capsules or SaltStik Chews with 0.5 L of water or preferably sports drink.

Massage and icing to help relax the muscles.

In severe cases IV fluids and electrolytes may be needed.


How to Prevent Electrolyte Muscle Cramps

  • Adequate hydration and electrolyte/salt  balance before and during exercise.
  • Not over-drinking especially non-electrolyte fluids.


For more information check out my post on Salt Intake for Endurance Athletes here.

Like most things, this is always best to trial in training and not on race day. Everybody is different in the amounts they sweat, so tailor an electrolyte plan to your personal needs. Being properly prepared is key.

Any questions, please leave in comments below and I will do my best to answer. Please note that I am not a medical or nutritional professional and these approaches are formed from extensive research and my own experiences as an endurance athlete.

Happy Running,





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