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Chlorine Chronicle (Archive)

NMSC Dec/96 Newsletter

Your Anaerobic Threshold Pace and Its Importance to Fitness

(by Don Clinton)

In this article I will answer some important questions about your AT pace and how it relates to your fitness.

First of all what is your AT pace? Simply stated in swimming terms your anaerobic threshold (AT) pace is the fastest speed you can swim over a long distance (1/2 hour or more) or a measure of your endurance. Your AT pace equates to an equilibrium state where your working muscles are creating lactic acid at the same rate as your body is removing the lactic acid. Without getting into too many details lactic acid is produced as a byproduct of aerobic exercise and high a levels of lactic acid in your blood tend to paralyze your muscles. Your body removes lactic acid from working muscles in several ways some of it is used as a catalyst in the aerobic process itself and some is picked up by red blood cells and carried to other parts of your body for processing. In an equilibrium state low levels of lactic acid are maintained which allow your muscles to continue to work. Interval training allows you to increase the rate at which your body removes lactic acid and thus improves your AT pace and your endurance.

Why do you need to know your AT pace? Your AT pace is like any other measure of fitness such as your flexibility, strength or VO2max and regular measurement allows you to monitor changes in this aspect of your fitness. Knowing your AT pace is also the key to properly assembling training sets and pace times that train all your energy systems (anaerobic, aerobic, anaerobic lactic). Because your AT pace responds well to training (unlike your VO2max which is relatively stable throughout your life) new swimmers can, through regular measurement, receive positive reinforcement by observing a significant improvement over the course of a year. Therefore if you are interested in tracking your fitness you should regularly measure your AT pace.

How do you measure your AT pace? First of all it is important to note that the measurement of your AT pace only applies to the muscle groups employed during the test. In other words if you test yourself doing freestyle the results do not apply to running muscles or even to other swim strokes. If you don't train these other muscle groups they may be AT challenged (as I frequently discover when I run using my leg muscles).

The best method (but lest popular method in NMSC) to measure your AT is through a maximum effort 1/2 hour swim using one stroke (sometimes called a T-30). Following the swim calculate the average time per 100M to determine your AT pace. A less accurate but more popular method of measurement is to use shorter distances (100s, 200s or 400s) with a short rest interval. With this method you have to calculate your average pace time and use a standard correction factor (e.g. for a set of 12 X 100 with 30sec rest between each, men must use a correction factor of 108% and women 106.5%). These correction factors can be found in the book "Swimming Even Faster" on page 147.

Once you establish your AT pace there are several ways to train to improve it. You can improve the lactic acid removal capacity of your body or you can improve you swim technique so that you are going faster with the same amount of work.

I do not need to discuss how to improve stroke technique in this article - our coaches have this well in hand and use a variety of drills and exercises.

To improve your lactic acid handling capacity, you should complete swim sets using one stroke that pushes your lactic acid level slightly higher than your AT and then allows the lactic acid level to decrease during a rest interval (RI) to a level slightly lower than your AT.

Figure 1 shows conceptually how this type of training works. The table below contains some examples of training sets that improve your AT.

3 X 800M FS Rest Interval 2:00
5 X 400M FS Rest Interval 1.00
8 X 200M FS Rest Interval :30
15 X 100M FS Rest Interval :20

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