This is a cardio-vascular training that we will be doing daily at practice thru at least the beginning of our season.  Ethan Harris sent this research and training to me.  It is called 30-30.   It is simple to do and will not be easy IF you do this correctly.  The training last for 10 to 30 minutes and consists of a 30 second jog and then a 30 second sprint and you alternate without stopping until the time has passed.  The research on this training was done on soccer players and the results showed that the players increased their cardio-vascular fitness thereby increasing their energy levels during the last half of the 2nd halfs of the matches they played.  In otherwords, they did not run out gas so quickly and were able to run more and with more speed late in the matches.  I share this in hopes that the committed dedicated players will start this training now.  

www.pponline.co.uk/encyc/soccer-fitness.htm