During endurance races, it's not uncommon to pass someone stopped on the side of the trail stretching, moaning and sometimes doubled over with leg cramps. Post-race campfire stories inevitably include guys comparing where along the course the cramps started, how long they lasted for, and how those muscles are still tender to touch. So for this post, I decided to look at what can be done to prevent and treat these dreaded leg muscle cramps.
Why do muscles seize up?
There are 2 theories as to why muscles cramp. The first has to do with dehydration-electrolyte imbalance. Because athletes exercising in hot and humid conditions experienced muscle cramps, it was thought that a combination of the heat and resulting dehyrdation/electrolyte loss from sweating might explain why muscles cramp. It is true that a correct electrolyte composition is important for muscle relaxation. Too much potassium, low sodium, low magnesium and low calcium levels can all cause muscle cramps. However, evidence for dehydration-electrolyte imbalance theory is lacking. In studies of runners, fluid losses, sweat rates and blood electrolyte compositions were exactly the same in those runners that cramped and those who did not. Furthermore, when given proper hydration, carbohydrates and electrolytes during exercise, cramps still occurred in 69% of athletes, suggesting that simple hydration and nutrition is not enough to prevent attacks of the cramp monster.
The second theory of why muscles cramp has to do with the communication between your muscles and your nerves (neuromuscular theory). There are 2 main sensors that send feedback to your brain about muscle contraction. The first are called muscle spindles. These sensors are in your muscle and detect muscle length. When you lengthen or stretch your muscle, they send a signal to your brain (via sensory neurons) to immediately contract that muscle so that the muscle doesn't tear. The contraction signal is carried back to your muscle by the motor neurons. The second sensors are called Golgi tendon organs, and these are located in your tendons, which connect the muscle to the bone. These sense muscle tension, so when your muscle is contracted, these sensors are activated and motor neurons from your brain tell the muscle to relax. In short: muscle spindles tell your brain to contract muscles. Gogli tendon organs tell your brain to relax them.
Muscle cramps usually happen when the muscle is contracting in an already-shortened position. For example, bend your knee and point your toes to the floor - this shortens your calf muscle. Now actively contract that muscle. That is the position your calf muscle is most likely to be in when it cramps up. In this position, there is not a lot of tension on the muscle for the Golgi tendon organs to detect, so there are no "relaxing" signals being sent to your brain. In addition, studies have found that fatigue causes the muscle spindles to be more more excitable and the Golgi tendon organs to be inhibited, meaning that your brain receives a lot more "contract, contract" signals and not enough "relaxing" signals. As a result, your muscle seizes up uncontrollably.
Is there a way to treat muscle cramps in a race?
Most of the riders I've talked to recommend just pedaling through the cramps. After 2-3 minutes of excruciating pain, the cramps go away. The experts in the literature recommend stretching. Stretching a contracting muscle puts more tension on it and gets the Gogli tendon organs firing, which tells your brain to relax that muscle. Here are some ways to stretch your muscles without getting off the bike.
For your calf muscle: put the crank in 4-6 o'clock position, slide back in the saddle, lock your knee straight and slowly drop your heel as far as you can get it to go (or think about pointing your toes towards your nose).
For your hamstring muscle: put the crank at 4-5 o'clock position, slide back in the saddle, bend forward at the hip, and lock your knee straight (don't point your toes down, but don't pull them up either). Pull down on the pedal stroke in the 3-4 o'clock range.
For your quad muscles: Unclip, reach down and grasp your ankle or the heel of your shoe. Keep straight at the hip and use your hand to pull your heel to your butt. If you inside thigh is cramping, bring your heel a little to the outside of your thigh. If your outside thigh is cramping, bring your heel up a little to the inside.
Jeff informed me the other day he was going to start taking quinine for his leg cramps. The anti-malarial drug, I asked questioningly? Apparently, quinine was once prescribed off-label for treatment of leg cramps. However, in 2006, the FDA issued a news release on risks of quinine use linking it to serious side effects such as cardiac arrhythmias, low blood counts and 93 deaths. I think I would rather suffer through a couple minutes of leg cramps than risk some of these.
Vitamin E, magnesium sulfate and magnesium citrate have also been studied as possible treatments for leg cramps, but the studies showed no improvement over placebo. There is weak evidence that 30 mg per day of vitamin B6 or 30 mg of a calcium channel blocker, such as diltiazem, may reduce the number of muscle cramps, but these studies included only a small number of patients so more research is really needed before any drug regimen can be recommended.
Is there a way to prevent muscle cramps in the first place?
The best prevention strategies are ones that make common sense. Good conditioning and proper hydration appear to have the best results. If you are going to be racing in the heat, train in the heat. Same for the mountains. And despite the lack of direct evidence, maintaining hydration and adequate electrolyte levels is still important. During training, your body adapts to the work load and the way it processes fluids and electrolytes so that cramps become less of an issue.
Other prevention techniques target the Golgi tendon organs in an effort to delay neuromuscular fatigue. Plyometric exercises may be beneficial for increasing the efficiency of Golgi tendon organ firing and delaying the onset of Golgi tendon organ fatigue. These exercises involve combinations of explosive jumps, squats or short duration all-out sprints on the bike with the goal of having muscles exert maximum force in as short a time as possible. If a particular muscle is prone to cramping, exercises aimed to increase that muscle's strength and flexibility may also help prevent cramps during races.
Finally, there may be a biomechanical cause to leg cramps during cycling. If your bike is not set up correctly, some muscles may have to work harder than others when you are riding, and those muscles may be more prone to cramping. It can't hurt to get a proper bike fit.