Could Circuit Training make a come back? 
Circuit training has been around for a while and used to be popular in schools, the Armed Forces and sports clubs. Recently, this has not been the case for various reasons, one of them being a perceived lack of specificity. It is also due to the fact that certain fitness qualifications or accreditations focus on barbell platform lifts, and so the people who pass those courses tend to do those type of exercises with other people.However, as part of the Long Term Athlete Development Process whereby generalisation of motor skills is essential before specialisation, and as an easy to use, cheap, and very varied exercise mode, circuit training should be considered with the right populations at the right time.
A recent study from Turkey (http://journals.lww.com/nsca-jscr/Fulltext/2009/09000/Effect_of_Circuit_Training_on_the_Sprint_Agility.25.aspx)
showed an improvement in sprint agility and anaerobic endurance following a circuit training protocol of 3 days a week for 10 weeks. The subjects were healthy PE students, average age 24, so may not have been that fit to start with.
This information is useful for all most intermittent type field sports as an improvement in sprint agility and anaerobic endurance could prove useful.
A good book to read that shows how circuit training fits into the overall training plan is John Jesse's "Wrestling Physical Conditioning Encyclopedia ".
Enhancing Sports Performance
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