Many athletes complain of muscle cramps throughout their training and performance. While there are many causes of muscle cramps, there are two main categories. First, there are movement related muscle cramps and second, there are nutritionally related muscle cramps. Movement related muscle cramps can happen when the muscle is overexerted or fatigued. The muscles can be over stimulated and fail to relax. Most cramps that are movement related can be easily remedied by altering movement patterns, massage, and stretching.
Those cramps that are not movement related are often nutritionally related. This can come in form of a fluid imbalance or electrolyte imbalance. The first thing to check is if the athlete is dehydrated. Athletes should consider their hydration status if they are experiencing cramping. A simple and effective way to check hydration status is checking the color of your urine. It sounds silly, but it is a visible cue that you may be dehydrated if your urine is darker than pale straw! Athletes can check individual hydration recommendations with a registered dietitian or they can consult this fact sheet from SCAN.
Athletes may also experience cramping from electrolyte imbalances such as a lack of calcium, potassium, sodium, or magnesium. Calcium is a vital mineral when it comes to muscle contractions. Consuming at least two servings of dairy products a day (or calcium fortified orange juice or soy milk) will ensure adequate calcium consumption. Potassium is lost in sweat and can lead to cramping. Good sources of potassium include fruits, vegetables, whole grain products, legumes, beans, nuts and proteins. Sodium losses are a result of sweating just like potassium losses. Athletes who are predisposed to low sodium are those who exercise in heat for over four hours (tennis players, triathletes, ultrarunners). All athletes should be consuming adequate sodium. Endurance drinks such as Gatorade and Powerade contain sodium. Magnesium is also being further studied in exercise related cramping. Many people do not consume enough magnesium. The RDA for women is 320 mg per day and for men is 420 mg per day. Sources of magnesium include leafy green vegetables, whole grains, nuts, beans, and legumes.
All athletes should consult their trainers about proper technique in their sport to prevent movement related cramping. If you are experiencing cramping that is not thought to be movement related, a session with a Registered Dietitian may help discover where you might be lacking nutritionally. Make sure that you are getting in enough hydration and electrolytes as you train!
This and other great information can be found in Nancy Clark’s Sports Nutrition Guidebook.
Julie DuBois, RD 
February 2nd, 2011 at 6:55 am
Great timing. Tuesday my calf started cramping on a treadmill run — I NEVER have cramping issues. I attributed it to lower body strength training on Sunday. I kept running and today my leg is pretty sore. I’ll have to see what happens on my Thursday run and will consider analyzing my calcium intake (I’m vegan) if I cramp again.
February 2nd, 2011 at 12:59 pm
Sorry to hear you’re having cramping problems! Make sure you’re hydrated enough as well. It may be movement related but make sure to eat your leafy green veggies for calcium!
February 2nd, 2011 at 2:27 pm
Love the post. I often have foot cramps while lying in bed or when I am driving, especially my right foot (accelerator) Any ideas. Thanks
February 2nd, 2011 at 5:39 pm
Have y’all ever woke up in the middle of the night with a cramp? That is the worst!
February 3rd, 2011 at 4:24 pm
I assume driving is movement related. The night cramps I am not sure about, could be hydration or nutritionally related since you’re not moving. I will look further into it!