Anyone who cycles regularly is probably familiar with this problem: the appearance of unpleasant skin irritations after a particularly intensive training session, often on a hot day which has caused heavy sweating.
Caused by two areas of skin rubbing against each other, the effect is aggravated when the skin is also very wet from sweat.
With cycling, these sore spots mostly develop on the upper thigh or on the buttocks.
As the irritated skin would be rubbed again during the next training session, further training is not usually possible.
This is a good reason to try to avoid any such skin irritation.