Dear Sports Doc, My children suffer from muscle cramps during their early season training and often during their fall sports. Can you help me understand why this happens?
Muscle cramping is an unpleasant side effect of training in the hot, humid weather common in North Carolina. Let’s review some of the causes of exercise-related muscle cramping and discuss how to avoid or manage them.
What Is a Muscle Cramp?
Cramping is an abnormality in muscle relaxation, which leads to an involuntary contraction of one or more muscles. The causes of exercise-associated muscle cramping are varied and often debated.
Cramping can be a result of electrolyte deficiency or dehydration or can be a result of central muscle fatigue. Cramps also may be a result of other unidentified causes related to existing medical conditions or medications that have been taken.
Because we do not know exactly what the cause of every cramp is, let’s focus on some of the possible causes and how to best avoid them:
Sweating the Details
One popular explanation is that cramping happens as a result of an excessive loss of electrolytes and fluids during activity. When we sweat, we lose water and many of the electrolytes that are required for normal muscle function. We attempt to replete these by consuming water or sport drinks, but often the amount lost is not balanced with what is replaced. There are research studies that support this theory, demonstrating that cramping is more common during the hot months.
In the Triangle, the summer and early fall can be extremely hot and humid. Even athletes who drink a lot may not be replacing nearly enough of what is being lost in terms of water and electrolytes. Some athletic training staff, coaches and providers consider exercise-associated muscle cramping as a warning sign for impending dehydration.
What are we really losing during activity? Sweat primarily consists of water and electrolytes. The most important electrolytes lost in sweat are sodium-chloride, potassium and magnesium. The average person sweats about 1 to 2.5 liters per hour with some people losing as much as 3.5 liters per hour in extreme cases. To calculate how much you sweat, weigh yourself without clothes before and after your workout, noting also how much fluid you consumed during the workout.
Sweat rate also depends on weather conditions, clothing worn, exercise intensity and how well adapted someone is to a particular climate. In hotter climates, athletes will begin to develop less concentrated sweat once they have adapted to the environment.
Maintaining hydration is important for the obvious reasons, but there are also some less apparent reasons. When we become dehydrated during exercise, the rate we can digest consumed fluids is reduced. One study found if someone is 5 percent dehydrated (meaning 5 percent of body weight) there is a reduction in the gastric (stomach) emptying rate of 20 to 25 percent. This affects how efficient one can be in replacing fluids and electrolytes during exercise.
In severe cases, sports teams and medical staff may use intravenous fluids to help an athlete catch up with lost volume. Although there may be debate about the degree to which dehydration causes cramping, the infusion of fluids very often can help an athlete struggling with cramps, particularly those suffering from multiple muscle or persistent cramps. Please note this is reserved for extreme cases and only should be done by trained medical staff.
In addition to water, we need to replace the electrolytes lost during and after exercise. Sodium appears to be one of the most important electrolytes to replete; it is an important element in initiating signals from nerves that lead to movement in the muscles. A sodium deficit makes muscles irritable and may cause the muscle to contract and twitch uncontrollably.
Although potassium and magnesium have also been associated with cramping, their connection is less clear. Similar to water, the amount of sodium and other electrolytes lost during activity is variable. Some people are salty sweaters. You will recognize them as people who often look crusty after they dry off following a hard workout. These athletes can lose grams rather than milligrams of salt with each workout, and that amount is not easily replaceable during activity.
So how do you replace electrolytes? Most commonly athletes will consume sport drinks. These drinks provide fluid, carbohydrate and electrolytes. They taste good and are accessible to everyone. These products can be bought in liquid or powder form and come in a variety of flavors.
It is important to keep in mind that while these drinks replace water and electrolytes, they do have limitations. Primarily, though they were designed to replenish fluid and electrolytes in exercising athletes, the concentrations of electrolytes present and the volume an athlete is able to consume is often significantly lower than what is lost during sport. In addition, these products frequently contain a lot of sugar, which is not always easily digestible for athletes during a workout.
An alternative to sport drinks are electrolyte supplement tablets, capsules or powder. Athletes can replace lost electrolytes with the supplements and take in water separately. These products may contain only sodium, potassium, magnesium and can even be buffered to help digestion.
The quantity of sodium, potassium and other electrolytes within them varies greatly and the best strategy for use varies by athlete and the brand of the product. The best recommendation is to use and experiment with these products during practice to determine the strategy that best works for you. Each individual athlete can figure out the best balance for him/her whether it is to use sport drinks, water, electrolyte supplements or a com- bination of these to help reduce or prevent cramping during activity.
Beyond hydration and electrolytes, there are theories that cramping may be caused by central muscle fatigue. This theory is supported by the fact that when muscles fatigue, feedback loops are inhibited at the cellular level and cramps begin to occur. This is very important for athletes, coaches and athletic trainers to understand because if it is recognized as a potential cause, a successful treatment strategy can be implemented.
When a cramp begins, a simple solution is to stretch the cramped muscle. By stretching the cramping muscle, the neuronal activity decreases within 15 seconds of starting a passive stretch. This is a simple intervention that can be started immediately and often alleviates the cramp. Immediate stretching of the cramped muscle can possibly arrest those long debilitating cramps that not only take an athlete out of practice, but can lead to muscle soreness for days afterward.
Lastly, there are the genetic causes of cramping. In athletes who are African-American, Caribbean, some Central Americans, Indian, Mediterranean and Middle Eastern, there is a medical condition called sickle cell anemia. For those with this condition, there is a gene that alters the shape of the red blood cells. This genetic variation evolved as a protective adaptation to malaria. Unfortunately for the athletes who carry this gene, it also makes them more susceptible to the effects of dehydration. This can lead to cramping and other more serious medical issues.
It is critical to understand that having the sickle cell trait or disease does not in any way disqualify any athlete from participation. It merely requires a greater attention to heat and hydration status during activity, particularly in warm climates. If you are unsure of whether or not you are a carrier of this trait, reach out to your pediatrician, primary care doctor or sports medicine provider. Nearly every child born in the U.S. will have a series of blood tests at birth that include a sickle cell screen.
To summarize: Cramping is multifactorial and understanding the causes and how to best manage these can help keep our children having fun and staying healthy while practicing and competing in the heat. Remember: stretch the muscle that is cramping until it releases, hydrate early and often and take in electrolytes in a manner that works for you and your body. If you are unsure what to do with your cramping, reach out to your coach, certified athletic trainer or local sports medicine physician for help and guidance.
What Are Electrolytes?
We hear the term all the time associated with sport drinks, but what are electrolytes? An electrolyte is a substance that produces an electrically conducting solution when dissolved in
a polar solvent, such as water. In the human body, primary electrolytes include chloride, magnesium, potassium and sodium.