Muscle Cramps While Running: Causes, Treatments, and Prevention
Almost every runner has experienced a muscle cramp at one time or another, especially during the marathon or on hot summer days.
I’ve heard countless stories from friends, family, and clients about cramping up in the last few miles of a marathon and barely being able to even walk. Sometimes the cramps can be worked out, but often they persist and can ruin an entire race and training segment.
The most frustrating thing about muscle cramps may be that they can come out of nowhere, without warning, and the cause often cannot be determined.
My readings and research on cramping have unveiled two distinct types muscle cramps that are associated with exercise.
The first type is due to muscle overloading and fatigue. This type of cramp can often be attributed to overuse and the cramping is localized to the muscle group that is being overworked.
The second type of cramp is due to an electrolyte deficit that develops due to extensive sweating and consequent loss of sodium. These cramps may occur even if there is no muscle overuse and cramping may occur in multiple muscle groups.
It is important to determine which type of cramp you are experiencing or are prone to getting so that you can appropriately respond to the cramping. In this article, we will take a closer look at the two types of cramping and recommend treatment and prevention strategies that can keep you cramp-free.
Muscle Overloading and Fatigue Cramps
This type of muscle cramp occurs from repeated or extended loading of a particular muscle group and muscles that are in a shortened position (e.g. the calf while running). These muscles that remain in a shortened position while running are the most vulnerable.
The true physiological explanation for how the cramping develops is a bit complex, but basically the neural mechanisms that are supposed to inhibit muscle contraction are depressed and excitatory activity (chemical and electrical synapses that fire the muscle) of the muscle fibers is enhanced. The result is an intense, sustained involuntary muscle contraction.
Common Symptoms
- Sudden onset and constant cramping (vs. intermittent)
- Localized and asymmetric (e.g. only in the left calf)
- Responds to passive stretching and massage
Risk Factors
- Older age
- Poor stretching practices
- Poor or insufficient conditioning
- Excessive exercise intensity and duration
- History of cramping
Treatment and Prevention
As mentioned earlier, muscle overloading and fatigue cramps remain localized to the muscles that are being overworked. Immediate treatment of these types of cramps include:
- Passive stretching and massage
- Active contraction of antagonist muscle group (e.g. contracting hamstring to stretch quadriceps)
- Icing affected muscle group
Prevention tips:
- Reducing exercise intensity and duration
- Improving conditioning and range of motion
- Making biomechanical adjustments
- Practicing relaxation while exercising
Nutritionally, there isn’t much you can do to prevent overload and fatigue cramps. Typically, these types of cramps are training related, so you’ll need to incorporate some innovative workouts to help prevent the possibility of fatigue cramps.
My advice is to do more workouts where you challenge the body to run faster as it gets tired or practice running on tired legs. This will help prepare the muscles for the fatigue they will experience during the race and be better prepared to run relaxed.
Some examples include running steady runs the day before a long run, which will simulate running the last half of the race as opposed to starting a long run with fresh legs. I also recommend what we call combo workouts. Combo workouts basically entail doing some type of tempo run or hilly run to tire they legs and running a set of fast 400 or 800 meter repeats the latter part of the workout to practice generating explosive muscle contractions when the muscles are fatigues. Finally, I definitely recommend including more strength work into your training to increase you efficiency, which means your muscles will need to contract fewer muscle fibers to perform at the same level of effort/pace.
Electrolyte Deficit Cramps
This type of cramp is typically due to extensive sweating and significant electrolyte losses, especially sodium and chloride.
As the duration of exercise increases and sweating continues, a whole body sodium deficit may develop, especially if the sodium and chloride lost in sweat are not replaced promptly. These electrolyte changes and the accompanying fluid shifts in the body can cause certain neuromuscular junctions to become hyperexcitable, resulting in cramping. Dehydration is very often an underlying cause.
Common Symptoms
- Gradual onset that typically begins with fasciculations- small muscle contractions (“twitches”) that are just barely visible under the skin
- Usually begins in the more highly active muscle groups like the hamstrings and quadriceps
- Cramping often spreads or jumps around and is usually bilateral
- Cramping is intermittent (vs. constant)
Risk Factors
- High sweat rate, high sweat sodium concentration, or both
- Poor hydration and/or salt intake before and during exercise
- Poor daily intake of fluids and electrolytes
Treatment
- Immediate electrolyte replacement at first sign of muscle twitches/ cramps
- Ingestions of a high-salt sports drink or 3 grams of salt mixed into 0.5 L of a regular carbohydrate sports drink
- Massage and icing to help relax the muscles
- If muscle cramping is severe or hyponatremia is present, IV fluids and electrolytes may be needed
- Note: potassium, calcium and magnesium supplements are not recommended. These minerals and foods that are rich in them will typically not provide and relief for this type of cramp
Prevention
- Maintenance of hydration AND electrolyte balance before and during exercise
- Maintenance of overall daily salt and fluid intake
- Not overdrinking fluids, especially low- or no-sodium fluids
- Try to match sodium intake closely with individual sodium losses through sweat.
If you frequently struggle with the electrolyte deficit cramps, consider changing up your pre and during run fluid choice.
Most sports drinks on the market are what sports scientists call isotonic, which means they contain a carbohydrate solution that is at 6-8% concentration. Because the sugar concentration of most sports drinks is higher than that of most body fluid, they are not readily absorbed into the blood stream and are thus not optimal for hydration.
Accordingly, your best choice before and during your run would be a heavily diluted sports beverage or water with electrolyte tablets.
By diluting your sports drink or using electrolyte substitutes, you provide your body with the best combination of electrolyte replacement and immediate absorption. Likewise, electrolytes, especially sodium and potassium, reduce urine output, speed the rate at which fluids empty the stomach, promote absorption from the small intestine, and encourage fluid retention.
Resources:
Emily Brown
Emily Brown is the resident nutritionist at Runners Connect. She graduated as a four-time All-American from the University of Minnesota while earning her Bachelors in Nutrition Science. After graduating, Emily pursued her Master’s in Public Health Nutrition (MPH) and began to specialize in the area of sports nutrition, specifically working with runners. Emily is a 15:19 5k runner and Olympic Trials qualifier. She offers 
I’ve had a few cramps while running, but they were quickly gone. Still, I wouldn’t want to risk a bigger one the next time I take my exercise to the next level. Thanks a lot for sharing this article.