In a condition by tradition philosophy of physical preparation, trainers would separate physiological parameters and train them sequentially as per the tenets of periodisation. To this end an athlete would move from aerobic to anaerobic to speed and agility over a period of time. I believe this method for teams sports preparation to be outdated in that since team sports are an integrated metabolic amalgam you should train for all things at all times following a Conjugate method of training.  This will allow you to emphahise various components of fitness along the way but to continue to train all elements concurrently. As the founder of the modern Westside method of strength training would state “ what you do not train you lose” so train all elements concurrently and not sequentially for the complete athletic preparation.   With this in mind you can train agility whilst at the same time train the metabolic systems. Exercise physiology tells us that the phosphate energy systems is most involved in activities of less than 15 seconds duration and becomes less involved as the time moves out further where the anaerobic lactate systems contributes more and if the time of effort continues the aerobic system dominates. Although not one energy system is mutually exclusive the time of effort will dictate the most dominant contributor. If we were to set up a series of coloured ladders or the cross ladder, we could construct an agility pattern of many different footwork elements.  If you were to run through it once and then rest, the time would be quite short and hence the emphasis is on the phosphate system of a one off event with maximal rest in between. If instead you continued the patter for 45 – 60 seconds you would be challenging energy production via the lactate system and also a by product would be to challenge your footwork under fatigue. Further increases in time would greatly increase the fatigue factor whilst challenging you aerobically at the same time. An example program to assist in planning is in the table below, again this is just a guide so work with your athletes and see what works best and gives you what you need to condition the athlete for the demands placed on them in the game.     Energy System Time Rest Time between Example Work : Rest Phosphate  1 – 15  seconds 3 – 5 : 1  20 x 15 secs every 1 minute Work 15 seconds : Rest 45 seconds Lactate 15 – 60 seconds 2 – 3 : 1 10 x 45 secs every 135 seconds Work 45 seconds : Rest 90 seconds Aerobic 60 - 180 seconds 1 – ½ : 1 5 x 3 minutes every 4 ½ minutes Work 3 minutes : Rest 1.5 minutes Ashley Jones