by Kat Kaihoi, ATC
It is not uncommon to be watching a sporting event and witness an athlete hobble off to the sideline to be promptly stretched by an athletic trainer. Most of us have experienced the uncomfortable sensation of a cramped muscle as well, and we often associate these cramps with hard workouts or with poor water intake ahead of time. In situations like this, what do you do? What is the cause of muscle cramping associated with exercise, and what can be done to treat and prevent it?
Exercise-associated muscle cramps (EAMC) often occur towards the end of a hard workout or immediately following exercise. This type of cramping occurs most often in single muscles that cross multiple joints, such as the hamstrings or quadriceps muscles in the thigh, or gastrocnemius muscle in the calf. The hallmark of these cramps is a prolonged, involuntary contraction of the muscle that is often painful, and which can produce muscle soreness that persists for hours or days. Despite the common occurrence of muscle cramps, solid scientific evidence is largely lacking when it comes to explaining their cause. This results in a variety of suggestions for treating and preventing cramps.
Why am I cramping?
There are two primary theories that explain the cause of exercise-associated muscle cramps. The first is the dehydration-electrolyte imbalance theory. In order to sustain exercise, the body requires both adequate fluids and electrolytes. Electrolytes such as sodium and potassium are essential for skeletal muscle contraction and relaxation. The dehydration-electrolyte imbalance theory argues that cramping occurs when an exercising individual depletes the body’s fluid and electrolytes through sweating. The loss of fluid and electrolytes causes nerve endings to be sensitized and decreases the space between muscle cells, resulting in muscle cramping.
Support of this theory mainly lies in evidence that muscle cramping occurs more frequently with exercise in hot and humid environments, where increased sweating and dehydration occur. However, this theory does not explain why muscle cramping still occurs when individuals exercise in cooler environments. Studies also do not consistently indicate a correlation between fluid loss and muscle cramping. Furthermore, if dehydration and electrolyte depletion were the cause of muscle cramping, replacement of fluids and electrolytes should adequately treat muscle cramping, and this is not consistently the case.
The second theory attempting to explain the cause of muscle cramping is neuromuscular in nature. This theory proposes that overload and fatigue of muscles and nerves causes a “glitch” in the communication system between the nerves and muscle fibers, especially when the muscle contracts in an already shortened position. Essentially, an imbalance occurs, with an increase in the amount of impulses stimulating contraction and not enough impulses stimulating relaxation. As a result, an isolated muscle cramp occurs.
The quality of research regarding the neuromuscular cause of muscle cramping is slightly better than those regarding dehydration. Measurements of nerve activity in some animal studies do seem to indicate this phenomenon may take place with neuromuscular fatigue. This theory also seems to apply to humans for two reasons. First, exercise-associated muscle cramping occurs more frequently when a muscle is very fatigued. Second, stretching a cramped muscle can be an effective treatment. This supports the neuromuscular theory, because stretching a muscle decreases tension in that muscle’s tendon, which in turn stimulates reflexive relaxation in the muscle. That’s what the athletic trainer on the television is doing!
Pickle juice, anyone?
A plethora of suggested remedies for muscle cramping exist. These are mostly anecdotal, but include drinking pickle juice, ingesting salty substances, drinking sports beverages, ice, massage, stretching, IV fluids, etc. Despite the lack of understanding of their cause, health professionals do have general recommendations to attempt prevention of muscle cramping during exercise. Assuming the dehydration theory to be accurate, the National Athletic Trainers’ Association recommends supplementing 0.3 to 0.7 grams of salt per liter of fluids for ingestion, which most sports drinks provide. Keep in mind that it takes at least 13 minutes for the body to absorb ingested fluids, so even if effective, this method takes time. Theoretically, intravenous fluids remove this delay, and may help those who experience intense cramping that does not resolve. There is stronger evidence that stretching is the best remedy for isolated muscle cramps, and so moderate stretching of the involved muscle group is recommended. Keep in mind this may be ineffective for “heat cramps.”
How do I prevent cramps in the first place?
Even though evidence is lacking regarding the dehydration theory, maintaining hydration and adequate electrolytes is still an accepted prevention strategy. You can be confident that drinking a liter of water or sports drink one hour before competition will make those fluid and electrolytes available for your body to use. Make sure to rehydrate periodically throughout exercise; it is best to prevent losing more than 2% of your body weight during activity. Keep in mind that a balanced diet that includes carbohydrates, protein, fruits, and vegetables will be the best way to maintain adequate hydration and electrolyte levels between bouts of exercise.
There is also a theoretical basis for neuromuscular training that may help delay the onset of muscle fatigue, and therefore possibly exercise-induced muscle cramping. Exercises such as plyometrics may cause adaptations in nerves responsible for neuromuscular control. An individual’s level of conditioning may play a role in the onset of muscle cramping.
Finally, some cramping is not normal. Cramping with exercise that is severe and generalized, coming on early into exercise when body temperatures have not yet risen should be worked up. Patients who carry a gene for sickle cell trait have a tendency to cramp, while other people who carry a gene for cystic fibrosis have an increased tendency to sweat out higher levels of salt, increasing salt depletion and a tendency for cramping and heat-related illness. If you are concerned that the cramping you are experiencing is not normal, or if hydration and stretching isn’t addressing it, give us a call.