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.