Gerald Lefon has a very concise and well considered article on warm ups posted on the Judo America site.
Here is an excerpt:
It is generally accepted that prior to any type of athletic performance a warm up period precede the actual training phase. As with much of what occurs in Judo training, the warm up has all too often become a ritual performed without any clear purpose or goal. Traditionally, warm ups have been viewed primarily as a method to prevent injuries or lessen their severity. While this article will not cover flexibility training or debate whether warm ups prevent injuries- research by sports scientists can’t empirically validate this claim nor do they refute it- it will address issues pertaining to the purposes, goals and training parameters of warm ups.
Purpose of warm ups
Leaving aside the issue of whether warm ups are preventive medicine or not, one of the main purposes of this period is to physiologically prepare the body for the strenuous workout that follows by making it more efficient. In many ways the human body operates like a car. High and efficient performance can’t be expected from a car with a cold engine any more than from a cold body. Research in automotive fuel efficiency indicates that cars will operate at their most economical level after about fifteen minutes of warming up the engine. While there are no standard time frames for humans, efficient performance also is contingent upon adequate warm up.
Note: Many authors state that an athlete is properly warmed up after he breaks into a light sweat. It should also be noted that flexibility training, a separate but closely related training unit, should not take place until after the core temperature of the muscles has been raised at least one degree. Contrary to popular belief, flexibility training doesn’t precede the warm up period but rather follows it!
A second purpose of warm ups piggy backs the need to physiologically prepare the body. The warm up period presents the coach with an opportunity to teach participants basic psychomotor skills and kinesthetic awareness so necessary in the performance of Judo and yet undeniably ignored in many clubs. It’s a two for one deal that prepares the body for the strenuous workout while it develops and expands the inventory of athletic skills. Finally, a third purpose for warm ups is to add variety and fun to the Judo class which under traditional leanings can be quite repetitive and boring to participants.
Read the rest here.