Newsgroup: it.sport.ciclismo
Titolo: Crampi in Pista

Per Andrea Costa, soprattutto.
Cosa succede se a un pistard viene un crampo lancinante mentre viaggia
a 60 km/h con quegli attrezzi dove non si puo' semplicemente smettere
di mulinare le gambe?
Mi fa male solo a pensarci.
Sergio
Pisa


le gare in pista sono estremamente brevi, un crampo dovrebbe essere un 
evento assai remoto, di solito è causato da disidratazione.
se non hai di meglio da fare:
What are the types and causes of muscle cramps?
Skeletal muscle cramps can be categorized into four major types. These 
include "true" cramps, tetany, contractures, and dystonic cramps. Cramps are 
categorized according to their different causes and the muscle groups they 
affect.
"True" cramps
"True" cramps involve part or all of a single muscle or a group of muscles 
that generally act together, such as the muscles that flex several adjacent 
fingers. Most authorities agree that "true" cramps are caused by 
hyperexcitability of the nerves that stimulate the muscles. They are 
overwhelmingly the most common type of skeletal muscle cramps. "True" cramps 
can occur in a variety of circumstances as follows:
Injury: Persistent muscle spasm may occur as a protective mechanism 
following an injury, such as a broken bone. In this instance, the spasm 
tends to minimize movement and stabilize the area of injury. Injury of the 
muscle alone may cause the muscle to spasm.
Vigorous activity: "True" cramps are commonly associated with the vigorous 
use of muscles and muscle fatigue (in sports or with unaccustomed 
activities). Such cramps may come during the activity or later, sometimes 
many hours later. Likewise, muscle fatigue from sitting or lying for an 
extended period in an awkward position, or any repetitive use can cause 
cramps. Older adults are at risk for cramps when performing vigorous or 
strenuous physical activities.
Rest cramps: Cramps at rest are very common, especially in older adults, but 
may be experienced at any age, including childhood. Rest cramps often occur 
during the night. While not life-threatening, night cramps (commonly known 
as nocturnal cramps) can be painful, disruptive of sleep, and they can recur 
frequently (that is, many times a night, and/or many nights each week). The 
actual cause of night cramps is unknown. Sometimes, such cramps are 
initiated by making a movement that shortens the muscle. An example is 
pointing the toe down while lying in bed, which shortens the calf muscle, a 
common site of cramps.
Dehydration: Sports and other vigorous activities can cause excessive fluid 
loss from perspiration. This kind of dehydration increases the likelihood of 
"true" cramps. These cramps are more likely in warm weather and can be an 
early sign of heat stroke. Chronic volume depletion of body fluids from 
diuretics (medicine that promote urination) and poor fluid intake may act 
similarly to predispose to cramps in seniors. Sodium depletion has also been 
associated with cramps. Loss of sodium, the most abundant chemical 
constituent of body fluids outside the cell, is usually a function of 
dehydration.
Body fluid shifts: "True" cramps also may be experienced in other conditions 
that feature an unusual distribution of body fluids. An example is cirrhosis 
of the liver, with fluid in the abdominal cavity (ascites). Similarly, 
cramps are a relatively frequent complication of the rapid body fluid 
changes that occur during artificial kidney treatment (hemodialysis).
Low blood calcium, magnesium: Low blood levels of either calcium or 
magnesium directly increase the excitability of both the nerve endings and 
the muscles they stimulate. This may be a predisposing factor for the 
spontaneous "true" cramps experienced by many older adults, as well as for 
those that are commonly noted during pregnancy. Low levels of calcium and 
magnesium are common in a normal pregnancy unless these minerals are 
supplemented to the diet. Cramps are seen in any circumstance that decreases 
the availability of calcium or magnesium in body fluids, such as from 
diuretics, hyperventilation (overbreathing), excessive vomiting, inadequate 
calcium and/or magnesium in the diet, inadequate calcium absorption due to 
vitamin D deficiency, poor function of the parathyroid gland (a tiny gland 
in the neck that regulates calcium balance), and other conditions.
Low potassium: Low potassium levels occasionally cause muscle cramps, 
although it is more common for low potassium to be associated with muscle 
weakness.
Tetany
In tetany, all of the nerve cells in the body are activated, which then 
stimulate the muscles. This reaction causes spasms or cramps throughout the 
body. The name tetany is derived from the effect of the tetanus toxin on the 
nerves. However, the name is now commonly applied to muscle cramping from 
other conditions, such as low blood levels of calcium and magnesium. Low 
calcium and low magnesium, which increase the activity of nerve tissue 
nonspecifically, also can produce tetanic cramps. Often, such cramps are 
accompanied by evidence of hyperactivity of other nerve functions in 
addition to muscle stimulation. For instance, low blood calcium not only 
causes spasm of the muscles of the hands and wrists, but it can also cause a 
sensation of numbness and tingling around the mouth and other areas.
Sometimes, tetanic cramps are indistinguishable from "true" cramps. The 
accompanying changes of sensation or other nerve functions that occurs with 
tetany may not be apparent because the cramp pain is masking or distracting 
from it.
Contractures
Contractures result when the muscles are unable to relax. The constant 
spasms are caused by a depletion of adenosine triphosphate (ATP), an energy 
chemical within the cell. This prevents muscle fiber relaxation. The nerves 
are inactive in this form of muscle spasm.
Contractures can be inherited (for example, McArdle's disease, which is a 
defect of the breakdown of glycogen to sugar within the muscle cell) or 
acquired (for example, hyperthyroid myopathy, which is a muscle disease that 
is associated with an overactive thyroid). Cramps of this category are 
uncommon.
Dystonic cramps
The final category is dystonic cramps, in which muscles that are not needed 
for the intended movement are stimulated to contract. Muscles that are 
affected by this type of cramping include those that ordinarily work in the 
opposite direction of the intended movement, and/or others that exaggerate 
the movement. Some dystonic cramps usually affect small groups of muscles 
(eyelids, jaws, neck, larynx, etc.). The hands and arms may be affected 
during the performance of repetitive activities such as those associated 
with handwriting (writer's cramp), typing, playing certain musical 
instruments, and many others. Each of these repetitive activities may also 
produce "true" cramps from muscle fatigue. Dystonic cramps are not as common 
as "true" cramps.
-- 
WNC2 - World Nutrition Center 2 - Integratori per lo sport
ONLINE STORE: 
http://www.wnc2.biz
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 evento assai remoto, di solito č causato da disidratazione.
In effetti in tanti anni non ne ho neanche mai sentito parlare......
Neanche dai seigiornisti, la cui percorrenza in giornate particolari si 
aggira a piů di 200 km !
Andy 

 si aggira a piů di 200 km !
penso sia piů facile uno stiramento o addirittura uno strappo durante uno 
sforzo massimale, che un crampo


sforzo massimale, che un crampo
Anche questo porterebbe un problema a chi sta mulinando a 200 rpm
Henry


credo molto dolore ma se non contrai il muscolo il danno č fatto ma non 
dovrebbe peggiorare


 dovrebbe peggiorare
In ogni caso non ne ho visti ne sentiti neanche di questi....
Di catene rotte alla partenza del km e palle sul tubo orizzontale sě....
;-)
Andy