Posted : April 2014
Author : Dr. B. Green
This is an article from TheMedicineJournal’s Dr. B. Green.
Cramps come in four categories: True cramps, Rest cramps,
Tetanic cramps, and Dystonic cramps. The most common of these is the True
cramp. While there are different causes of muscle cramps, like the
involuntary contractions associated with seizures, we’ll focus on muscle
cramping related to athletics, as this is the most common.
Our bodies are composed of over 700 muscles that work
together. Occasionally, involuntary contractions of one or more of these
muscles will cause a cramp or spasm. A muscle cramp may involve a single
muscle, part of a muscle or a number of muscles that work in synergy. Although
most skeletal muscle cramps occur in foot and calf muscles, other muscles such
as the thighs, arms, hands, and abdomen are also prone to spasms. No one knows for sure the exact mechanism that causes people
to cramp during exercise, but there are two main theories, the second of which
is generally accepted as the principle cause, though not definitively proven
yet.
Although not supported by scientific evidence, dehydration
is often given as an explanation for why muscle cramps occur in athletes. The
lack of evidence might seem difficult to believe because every high-school sports
coach preaches hydration as a way to ward them off. The truth is, the
only studies showing dehydration, and by extension some of the electrolyte
abnormalities associated with dehydration, is the cause of cramps have all been
called in to question due to small sample sizes, or that they relied on
anecdotal clinical observations. In fact, several studies have shown
athletes who cramped during events have the same levels of dehydration, and the
same levels of electrolyte concentrations, as those who didn’t cramp.
Even though dehydration and electrolyte problems, as a cause
of cramping, is not well accepted in the medical field, due to the fact no one
has definitively shown the exact cause, this can’t be ruled out altogether. Further, sodium depletion and low blood levels of either calcium or magnesium
have been associated with an increased risk of cramping. A quick online
search will yield several medical professionals who still hold fast to this
line of thinking and some have suggested, even though electrolyte abnormalities
may not be the main cause of the cramp, it might predispose you to getting a
cramp.
The second, and arguably most accepted, theory behind why we
cramp during exercise involves muscle fatigue and spinal reflexes. In
1997, Professor Mortin Schwellnus and colleagues proposed this new theory after
an extensive review of the studies involved in cramping did not yield any clear
cause. Normally when you want your muscles to contract, like when
you choose to push down on your bike pedal, the signal comes from a grouping of
nerves called your alpha motor neurons. These neurons can be stimulated
in three ways. The first is voluntary, and the second is caused by
signals from what are known as spinal inter-neurones. The third, and
arguably most important when it comes to cramping, involves involuntary
reflexes.
Muscles have within them tiny structures known as muscle
spindles. The main purpose of these spindles is to prevent damage from
our muscles being stretched too far. Every time your muscle is stretched,
the spindle activity increases with the level of stretching, and causes the
muscle to contract when that stretching reaches a certain point. When we doctors hit you in the knee with a tiny
hammer-of-torture, this is the cause of the reflex contraction. Your
doctor stretches your quadriceps with the hammer, the spindles cause your alpha
motor neuron to fire, and your leg muscles contract, and you kick your doctor
in the shin!
The second reflex involved with cramping comes from what is
known as your Golgi tendon organ. This organ is responsible for keeping
your muscles from contracting too forcefully, preventing tearing. When
this organ is stimulated, it causes the alpha motor neurons to stop firing,
forcing your muscle to relax. If you prevent the Golgi tendon organ from
working, like in a marathon when you want your legs to continually churn out
the miles, the result will be increased firing from your alpha motor neuron,
and increased contraction.
So knowing how your alpha motor neurons cause your muscles
to contract, the theory of cramping goes a little something like this: you’re
running a marathon, your alpha motor nerves are consistently fired off by you
telling your legs to keep churning. Due to the fact your muscle is
fatigued, and your control over it decreasing, this causes the involuntary
reaction of your muscle spindles to increase, while simultaneously causing the
Golgi tendon organ activity to decrease. The net result of these two
reflexes is increased involuntary firing of your alpha motor neurons. You
then start jumping around like you’re on hot coals because your calf muscle is
contracting like a uterus in labor!
Giving credence to this theory as the main cause of cramping
is what relieves the cramp. Every athlete knows that stretching will help
the contraction. Passive stretching has been shown to decrease Alpha
motor neuron activity, thereby relieving the contraction. If electrolyte
abnormalities were the cause, stretching would not change the concentration of
electrolytes, thus not affect the cramp. Whether you subscribe to the less-accepted dehydration and
electrolyte abnormalities theory, or the increased alpha motor neuron proposal,
we do know some people are more prone to cramping than others. This
suggests a genetic predisposition. Although it’s true no one has ever
identified a specific gene that causes you to be a ‘Cramper’, family history of
cramping does increase your risk of being one who cramps more than others.
Other risk factors for cramping include: increases in
intensity and duration of exercises; inadequate conditioning for the activity;
and previous occurrences of cramping during or after exercise. In the end, if you want to prevent cramping, time honored
practices like a cool down period after the exercise; stretching and warming up
well before the activity; and knowing you body’s limits while performing have
all been shown to help prevent cramps. If you count yourself one of the unlucky who seem to get
cramps more often than a woman in labor, sleep a little more uneasy knowing
you’re also more likely to get the dreaded leg-cramp-while-sleeping!
~Blog Admin~
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