Whilist MMA is a high intensity sports it doesnt require training that is high intensity all the time.  Periodization training builds fitness in a rational sequence. Get fit and lose body fat for a fight. Works on the fat burning metabolism. This training allows the fighters to burn fat at a high intensity rather than carbs thereby proudcing less lactic acid.

Combat sports get more scientific in their training, the same periodization training  that goes into the developement of the 24 Fit Workouts DVDs.