Pushing too hard
If you have cramped up during a race, or experienced leg cramps at night, you’ve probably tried to stop them with the most common and intuitive solution: stretching. This actually one of the few effective remedies that you will find recommended on most websites, but it does have one downside: you have to stop to do it. While that’s not such a big deal if you’re lying in bed, it can mean months of training down the drain if you’re in the middle of a big race or sporting event. Worse yet, it seems nearly impossible to predict when a cramp is going to strike, making it difficult to plan for.
In previous posts we’ve discussed the neuromuscular fatigue theory for muscle cramps. The premise is that muscle cramps develop when muscles are extremely fatigued, which causes the nerves that control the muscles to become over-excited, and misfire. Dr.’s Tucker and Dugas elaborate in their book, Runner’s World the Runner’s Body:
“Anything you can do to prevent muscle fatigue should help prevent cramps. This is why runners often find that they can handle long training runs, yet shorter-length races cause severe cramps - the difference is the higher intensity of the race, leading to fatigue… athletes who had a goal time that far exceeded what their historical performances suggested they were capable of were more likely to cramp. This is because these athletes would start out at a pace that was simply too fast for their physiology, leading to premature fatigue.”
In 2010, University of Cape Town Professor Martin Schwellnus also attempted to identify the factors that could predict muscle cramping. In his study of 210 triathletes, Schwellnus and his team concluded, “faster overall race time (and cycling time) and a history of cramping (in the last 10 races) as the only two independent risk factors for EAMC [exercise-associated muscle cramps].”
(As a side note, his final report also stated, “The results from this study add to the evidence that dehydration and altered serum electrolyte balance are not causes for EAMC”)
In 2011, Professor Schwellnus followed this up with another study of 433 triathletes. Again, he found that EAMC was associated with exercising at a higher intensity during a race than accustomed, an inherited risk of muscle cramps through family history, and tendon or ligament injuries. He also made an observation that has since been studied more thoroughly, “Compared with the CON [control] group, triathletes in the EAMC [exercise-associated muscle cramp] group were significantly taller and heavier.”
The information above suggests that muscle fatigue is a significant factor in cramping, particularly if an athlete is exerting more energy at a higher intensity than he or she is accustomed. And there is one last factor that contributes to muscle cramps: heat… but not in the way that you’ve probably been taught.
Does body size matter?
Almost every website and muscle cramping resource will identify heat or temperature as a risk factor. The logic is that it causes athletes to sweat more, thus dehydrating them. We’ve already discussed why this is incorrect, but it doesn’t mean that heat is irrelevant.
In general, humans can only perform with a body temperature up to 104 degrees. Every species seems to have a specific temperature - antelope can handle up to 107 degrees, and rats 106 degrees. One of the most extreme examples is the Sahara Desert Ant, who can still forage with body temperatures at 122-degrees. When a body’s temperature reaches these extremes, the brain literally prevents your muscles from exerting as much force as they were. It is believed that this decreased brain function also degrades neuron activity, which leads to muscle cramps.
You may have noticed that marathon runners and endurance athletes tend to be small. This is where body temperature, body size, and muscle cramps come into play. In an interview with podcast EconTalk, David Epstein - former Sports Illustrated writer and author of the “The Sports Gene” - explains:
“One major limiting factor in endurance is your ability to dissipate heat quickly. So at about 104 degrees core temperature, you will slow down or stop… the greater the surface area of your body is compared to your volume, the quicker you unload heat… Smaller people also: because as you grow in height, your volume increases in 3 dimensions, while your surface area only in two. So you actually become sort of heavier for your size, which can be a disadvantage for running economy as well.”
So while dehydration may not be as dangerous as advertised, body temperature control is. Unfortunately, if you’re a bigger person, it’s physically harder to dissipate heat, which puts you at higher risk for muscle cramps, heat stroke, and heat related illness.