It is likely in these cases that they are suffering from serious dehydration. When the body becomes dehydrated it suffers from a condition known as hyperthermia, or over heating. A lot of blood is diverted to the skin in an attempt to cool down, and as a result the brain is deprived of oxygen. When this happens the body's safety mechanism cuts in and tries to stop the exercise and get the brain down to the level of the rest of the body as soon as possible so that blood can pour back to where it is required. The vast majority of marathon injuries are low level skin abrasions, caused by areas such as the armpits and the groin rubbing together.
Joggers nipple is also a problem in women.
The best way to avoid chaffng of this sort is to use vaseline. Muscle strains are unlikely as most people who run a marathon do not overstretch. It is important to make sure that running shoes are well broken in before taking part in a long distance race. Hard shoes may rub into the achille's tendon at the back of the heel. In almost every marathon that includes part-time runners, somebody will suffer from a heart attack.