Often matches are played in hot, humid conditions. In this environment, the body attempts to cool itself by increasing the sweat rate. Unfortunately, the fluid lost through sweat can lead to dehydration. Laboratory research has shown that even mild dehydration can impact physical performance, reducing strength, power and endurance. Researchers from the United Kingdom and Denmark approached the question of heat, dehydration and performance in a different manner. They took their experiment to the pitch and asked if competing in the heat influences post-match physical performance. Their results show that playing elite, competitive matches in a hot environment adversely affect explosive performance and that the change in performance may be linked to dehydration. ...
See the whole story here, from The Science of Soccer Online.
Kicking Back Comments: As we in the North East US have recently experienced, we have gone from winter to full blown summer with temperatures and humidity in the 90's the last few days.
I can not stress enough in how a referee is an active participant in a match as too should consider themselves an endurance athlete.
As such this requires exercice, diet, and hydration concerns to be successful.
While this particular article details the concerns and dangers of dehydration, particular attention should be paid as well to caloric intake and exertion level during a match.
An additional wrinkle in this, is a referee should also be aware of the signs of dehydration, as the referee is not only responsible for themselves and their crew, but for levels that do not have a trainer or medical staff available, a referee can certainly point out to the competent authority (e.g. coach) if they feel a player is in distress.
You always want to finish with 11 a side folks. A good referee, at all levels, works to keep it that way.