Muscle cramps are something most people have experienced at one time or another. I often have clients ask me if there is something that can be done to stop them or to prevent them. If I'm being entirely honest, I have always dreaded having to respond to this question because the answer is really quite unclear. So today we'll explore the topic of muscle cramps, and take our understanding from entirely opaque to clear as mud.
What is a Cramp?
A muscle cramp can be defined as a temporary and involuntary contraction of skeletal muscle, which causes intense pain. Cramping can happen in many different situations, but the most common complaints documented are hand cramps due to writing, nocturnal leg cramps in older populations, and exercise related calf cramps. For the purposes of this post, we will focus on exercise related muscle cramps.
Cramping is a difficult topic to study, as the onset is relatively unpredictable and even in cases where electrical stimulation is used to provoke cramping, only select people will cramp following its use. Research shows that exercise related cramping most often happens in endurance type sports, affecting 67% of triathletes, 18-70% of marathoners and cyclists, and 30-53% of soccer players. Duration of repetitive muscle contraction also appears to play a role, as most athletes experience cramping in the later stages of races or games. Theories as to what causes cramping include dehydration and electrolyte imbalance as well as abnormal nerve activation.
Dehydration and electrolyte imbalance theory stems from the science behind the cross-bridging cycle which creates muscle contraction. In order for the actin and myosin filaments in the muscles to create movement, the body must release calcium, which allows for binding and activation of filament shortening. To release, the body must produce ATP (an energy source) which requires the use of the sodium-potassium pump system. It is theorized that without adequate amounts of sodium, potassium or calcium that the body cannot perform a normal cross-bridging cycle, and that the muscles become stuck in the shortened position. When we are dehydrated, we lose the proper balance of electrolytes, which impacts concentration gradients at the cellular level, and may impact muscle cramping.
Although at face value this theory seems to make sense, in formal studies dehydration and electrolyte imbalance does not have an effect on the presence of muscle cramps. Research has not been able to reliably determine a connection between electrolyte imbalance and cramping. As previously stated, some studies have shown that cramping typically occurs during the end stages of endurance type activities which may lead us to assume that athletes are dehydrated. Other research has shown that 95% of cramping in American football players occurred during bouts of hot weather, which would increase sweating and impact electrolyte balance. Following a training camp, there was a 37% incidence of cramping during week one, with incidence rates dropping to 27%, 18% and 4% in the weeks to follow. The source mentioned acclimation to weather over the weeks, but is this enough information to cite heat and dehydration as a causation of muscle cramping? In my opinion, we need to take into consideration fitness levels and exposure to repetitive muscle contraction, which takes us to our next theory.
As we've talked about, we often see exercise related muscle cramping in populations participating in endurance sports. If we use running as an example, we are seeing people performing the same contraction over and over and over typically without stopping. As the muscles fatigue, the nerves controlling them may fatigue as well. The neuromuscular system is controlled through a series of input and output mechanisms which involve the brain and the nervous system. Stretch receptors and tension receptors allow the brain to create nerve impulses which control contraction and relaxation, allowing the body to move. So what happens when the nervous system becomes fatigued? In theory, it may lead to muscle cramping.
As the muscles activate and contract over and over, the muscle spindles which tell the brain to create contraction send out an enormous amount of output. But in order for the muscles to contract, the Golgi Tendon organs which control relaxation must be inhibited at the same magnitude. It is theorized that with fatigue, eventually there is no room for relaxation signals to be received, resulting in a painful and involuntary contraction. The peripheral nerve system theory seems to be a more believable explanation to muscle cramping, as we often see increased rates of cramping in older populations, those with COPD, people with diabetes and pregnant women. Each of these populations has an association with neuropathy, decreased sensation or impeded peripheral nerve function. Another example that supports this theory, is when we experience cramping when we are training muscles that we have forgotten how to use involuntarily. Sometimes when we start training new activation patterns, the underuse of peripheral nerves requires a large amount of input to create contraction, again creating a contraction biased feedback system and resulting in cramps. Since we have not been able to nail down a correlation between electrolyte imbalance and incidence of cramping, I think that our focus should shift to the peripheral nerve theory.
How do we prevent Cramps?
I'm sure that at some time or another you've heard a remedy or two related to muscle cramps. Drink enough water, eat a banana, drink a Gatorade. But what does the research say? Unfortunately, all it tells us is that no methods involving consumption of electrolytes or liquids can be reliably used as a preventative measure. Our best bet for mitigating the onset of exercise related muscle cramps, is to make sure that we get in a good stretch before our activity. This all goes back to the peripheral nerve fatigue theory. When we stretch, we use the Golgi Tendon organs to produce relaxation and muscle lengthening. Consistent relaxation stimulus before repetitive contractile activity may help to prevent overload of contraction stimulus during activity, and may help to prevent cramping. In relation to calf cramping, make sure to stretch the calf with both a straight leg and bent knee to address both large muscles of the lower leg, and hold for 30 seconds at the very least!
Clear as Mud
As I alluded to at the start, cramping is not well understood and involves a whole lot of maybes. Although we have not been able to confirm a cause of the painful condition, stretching seems to be the most useful method for preventing and alleviating muscle cramps. But this isn't to say that hydration and nutrition isn't important! Make sure that before activity you fuel your body well, rest, stretch and make sure to acclimatize to weather or altitude if competition takes place somewhere different from your home. As much as I'd love to have a clear answer for you, it's not really a possibility when it comes to this topic. At the very least, I hope that you've learned something about muscle cramps and now understand why I dread the cramping questions.
Kristen Huber BaKin, CAT(C)
Owner, the Gentle Athletic Therapist
References
Bordoni B, Sugumar K, Varacallo M. Muscle Cramps. [Updated 2022 Feb 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499895/
Maughan, R. J., & Shirreffs, S. M. (2019). Muscle Cramping During Exercise: Causes, Solutions, and Questions Remaining. Sports medicine (Auckland, N.Z.), 49(Suppl 2), 115–124. https://doi.org/10.1007/s40279-019-01162-1