July 3, 2011
Muscle Cramps in Athletes and Exercisers
This month a study from the University of Cape Town, South Africa
showed that the athlete who is most likely to suffer muscle cramps is the one
who runs the fastest and the one who has had previous muscle cramps (British
Journal of Sports Medicine, June 2011). Of 210 triathletes competing in an
Ironman triathlon, 43 developed severe muscle cramps, while 166 did not.
There were no significant differences between groups in any pre-race or post-
race blood mineral levels or body weight changes (a measure of dehydration).
This supports many other studies that show that the most likely cause of
muscle cramps in conditioned athletes is muscle damage. The most likely
causes of muscle cramps in out-of-shape exercisers are lack of salt or water
(1).
CRAMPS IN ATHLETES OCCUR MOST COMMONLY DURING INTENSE EXERCISE. Cramps
occur far less often during less-intense training, because the most common
cause of muscle cramps in exercisers is muscle damage from all-out pressure
on the muscles.
MUSCLE DAMAGE: Most muscle cramps in serious exercisers and athletes
are caused by an exaggerated "stretch reflex" triggered by muscle damage.
When you stretch a muscle, it pulls on its tendon. Stretch reflex nerves in
that tendon send a message back to the spinal cord (not the brain), and then
the "stretch reflex" in the spinal cord sends a message along nerves from the
spine to cause the muscle to contract. During extreme pressure on the
muscles, muscles are damaged causing sustained contractions. A study from
South Africa showed that the most likely causes of cramps are muscle fatigue
or tearing of the muscle itself (2). Electromyograph (EMG) studies measure
increased electrical activity from damaged muscles. EMGs show markedly
elevated electrical activity of the nerves controlling cramped muscles.
Furthermore, a review of the scientific literature shows the most common
cause of muscle cramps appears to be muscle damage (3).
WARNING SIGNS: Before athletic cramps come on full force, you will
usually feel the muscle pulling and tightening. If you slow down, the pulling
lessens, but if you continue to push the pace, the muscle goes into a
sustained cramp and you have to stop exercising to work the cramp out.
Further evidence that muscle damage is the cause of the cramp is that the
muscle often hurts for hours or days afterwards.
WHEN A CRAMP STRIKES: Muscle cramps during endurance events can be
prevented by slowing down when you feel excessive soreness in one muscle
group or straining in a muscle. You do this by switching pressure from the
cramped leg to the uncramped one. A bicycle racer moves most of his pressure
to the pedal of the uncramped leg. A runner shortens the stride of the
cramped leg. Continuing to put pressure on the cramped muscle can rupture the
muscle.
PREVENTION: You may be able to prevent cramps by exercising more
frequently but less intensely and for shorter periods of time, but most
racers do not want to do this.
OTHER CAUSES IN NON-ATHLETES: Known medical causes of muscle cramps
are extremely rare. If you suffer from recurrent muscle cramps, you may need
special tests for pinched nerves, Parkinson's disease, low thyroid, diabetes,
narrowed arteries from arteriosclerosis, low blood mineral levels, metabolic
diseases that cause muscle damage, or side effects of drugs used for high
cholesterol, high blood pressure or diabetes, diuretics, oral contraceptives
or alcohol (4).
DEHYDRATION OR LACK OF MINERALS LESS COMMON. Some cramps are caused by
low mineral or fluid levels (5). However, for the vast majority of trained
athletes who suffer exercise- associated muscle cramps, blood levels of
sodium, potassium, calcium and magnesium are normal. Research in athletes
after they ran in 52-mile races showed that the runners who suffered cramps
had the same level of dehydration and blood minerals as those who did not get
muscle cramps.
ATHLETES SHOULD TAKE EXTRA SALT ANYWAY. Athletes need more salt than
people who do not exercise. They lose a lot of salt through sweat. The most
common mineral cause of muscle cramps in untrained people who exercise is
lack of salt, according to a report from the University of Oklahoma (6). The
authors found that intravenous saline can reverse cramping in exercisers, and
that more salt in the diet or in sports drinks can help to prevent heat-
associated cramping.
If you are concerned about excess salt raising your blood pressure, get
a wrist cuff monitor and check your blood pressure every night before you go
to bed. If your blood pressure rises above 120, you may need to restrict
salt. (Excess salt can raise systolic blood pressure. Excess body fat, not
salt, raises diastolic pressure,
TREATMENTS THAT USUALLY DO NOT WORK: Nobody has shown consistent
benefit for trained athletes from any of the most common treatments:
multivitamin pills; mineral pills with calcium, zinc, magnesium, salt and/or
potassium; massage or chiropractic manipulation; drinking large amounts of
water; dietary manipulations; or bio-mechanical stretching and strengthening.
MEDICATIONS: Quinine has been reported to help relieve muscle cramps
in non athletes, but it can burst red blood cells. Some studies show that
gabapentin (an anticonvulsant), diltiazem ( a blood pressure medication), or
B-complex vitamins may help to relieve muscle cramps in some people (7).
SUGAR: There is some evidence that taking sugared drinks or foods
during prolonged exercise helps to maintain endurance and muscle integrity
which helps to prevent cramps. Take a source of sugar frequently during
vigorous workouts or races, and back off if you feel a group of muscles
pulling or tightening during exercise.
LACK OF VITAMIN D: A leading cause of muscle damage, soreness and
slow-healing injuries in athletes is lack of vitamin D. If you suffer
frequent cramping and your muscles feel sore or you keep on being injured
when you exercise, get a blood test called D3. If it is below 75 nmol/L, your
problems may be caused by lack of vitamin D and be cured by getting some
sunshine or taking at least 2000 IU each day of the very inexpensive vitamin
D3.
OCCASIONAL CRAMPS ARE NOT HARMFUL: Most racers and serious exercisers
accept that occasional cramps will occur, and rarely cause serious injuries.
References:
1. Sports Medicine, April-May 2007
2. Medicine & Science in Sports & Exercise, July 2005
3. Journal of the American Academy of Orthopaedic Surgeons, July 2007.
4. Neurology 2010; 74: 691-96
5. The Japanese Journal of Clinical Pathology, November 2007
6. Sports Medicine, April-May 2007
7. Journal of Clinical Pharmacology, 1998;38:1151
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Reports from DrMirkin.com
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http://www.drmirkin.com/joints/partial_knee_replacement.html
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Dear Dr. Mirkin: Can sudden memory loss be caused by medications?
Yes; a recent long-term study on 13,000 men and women, aged 65 and
older, shows that many drugs can impair memory (Journal of the American
Geriatrics Society, published online June 24, 2011). Those drugs most
likely to do this are called anticholinergics, taken for insomnia, allergies,
incontinence, high blood pressure, heart failure, or excess stomach acid.
Anticholinergics affect the brain by blocking acetylcholine, the chemical
that transmits a message from one nerve to another.
Over-the-counter drugs on the list include diphenhydramine (Benadryl®),
Dramamine®, Excedrin PM®, Nytol®, Sominex®, Tylenol PM®, and Unisom®, and
prescription drugs: Paxil®, Detrol®, Demerol® and Elavil®. A more complete
list can be found at:
http://www.indydiscoverynetwork.org/AnticholienrgicCognitiveBurdenScale.html
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Dear Dr. Mirkin: Recently you wrote that nitrates improve cyclists' race
times and help to prevent heart attacks. Should I take nitrate pills?
No! Nitrates in vegetables appear to be safe and healthful, but
nitrates in pills can harm you. Diabetics with heart disease who were given
long-term nitrates (Isosorbide mononitrate) were four times more likely to
suffer heart attacks (Cardiovascular Diabetology. June 13, 2011).
***********************************************
Recipe of the Week:
Cuban Mango Salad
http://www.drmirkin.com/recipes/cubansalad.html
You'll find lots of recipes and helpful tips in
The Good Food Book
http://www.drmirkin.com/goodfood/index.html
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