The body's three energy systems

Today I did five laps of the February strength circuit and paddled for 90 minutes.  It's warmed up into the mid-50s here, and I paddled without pogies.

To elaborate a little on what I was talking about in Tuesday's post, I've put together a summary of the three systems by which our body produces energy (with substantial help from William T. Endicott's books The Ultimate Run and The Danger Zone):

1.  The aerobic system.  This is the one I was talking about on Tuesday.  This is the system by which our bodies produce energy in the presence of oxygen breathed in with the air.  In Tuesday's post I offered a very basic description of how it works; one of the things I didn't mention is that the product of this (and the other two) systems is adenosine triphosphate (ATP), a compound necessary for muscle contraction to occur.  In the case of the aerobic system, the mitochondria produce ATP from glycogen in the muscles and liver.  The glycogen comes from the food we eat.

The aerobic system takes the longest to develop of the three systems--three or four months.  So athletes start on it early in the season with long aerobic sessions such as the long paddles I'm doing these days.  In a long-distance endurance sport like the one I do, the body uses the aerobic system to produce its energy a great majority of the time.

2.  The anaerobic system.  You're probably familiar with the point, once you reach a certain level of exertion, at which you start to feel that burning in your muscles or, if you're really out of shape, the muscles tie up completely.  What's happened is that the oxygen supply from the air is no longer adequate for producing the energy for what you're doing, and the body is now converting glycogen to ATP anaerobically.  The by-product of this reaction is lactic acid, and that's what causes the burning sensation in your muscles as well as the soreness you feel after a hard workout.

The anaerobic system takes some six to eight weeks to develop.  My most intense races are scheduled for the first half of June, so I'll start doing some workouts that specifically target this system  around the end of March.

3.  The ATP-CP system.  This system uses the ATP stored in the muscles along with creatine phosphate (CP) to enable muscle contractions.  The system is depleted after about only 15 seconds, so in a sport like flatwater/open water canoe and kayak racing, it get used up in the sprint off the starting line.  The ATP-CP system can be developed very quickly.  I typically work on it in the week or two leading up to a big race, doing short (maximum 15 seconds) sprints with full recovery in between.


So that's my very basic understanding of the physiological principles of training.  I've probably made some mistakes in my summary above, so feel free to offer corrections in the comments section.  Meanwhile, I'll refer back to this post in the future when I explain some of the workouts I'm doing.