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About Training Categories

Each workout set specifies a training category, which identifies the intensity of effort for that set. Based on your Critical Swimming Speed, there are three endurance training categories: Endurance, Threshold, and Overload. In addition, there is a single Recovery category that is used for just that.

The Recovery Training Category

The recovery training category is always used during the Cool Down phase of the workout, and sometimes between higher intensity sets. It is simply relaxed, easy and slow swimming. The objective is to flush lactate from your muscle fibers, replenish oxygen and nutrients, and lower your heart rate. Although recovery swimming is slow, it is not standing still. You need to move the muscles you have just used! Do not skip or cut short your Cool Down sets at the end of a hard workout. If you must cut a key workout short, eliminate main sets or repeats rather than Cool Down sets.

The Endurance Training Categories

The three endurance training categories - referred to as EN1, EN2, and EN3 in the workouts - are all based on Critical Swimming Speed (CSS). For a description of how to determine your CSS, see About Critical Swimming Speed.

CategoryYour Pace per 100 ydsDescription, Training Objectives, and Cautions

Add 5 seconds if your CSS pace for 100 yards is 1:30 or more

Add 3 seconds if your CSS pace for 100 yards is less than 1:30

This pace is used primarily for drilling and longer repeats. You should feel that you could maintain this pace indefinitely. Swimming here may feel effortless, but it improves virtually all aspects of cardio-vascular performance. Training here increases the capillaries around your slow-twitch muscle fibers, which facilitates the delivery of oxygen and nutrients, and the removal of lactate. Long-course triathletes should spend most of their training time here. Short-course triathletes need to work here, but must not swim here exclusively, because that will cause some fast-twitch muscle fibers to start acting like slow-twitch fibers (resulting in reduced speed for the shorter events).


This is your swimming velocity at your maximal lactate steady state. Swimming at this pace builds strength and speed by increasing capillaries around both slow and fast-twitch fibers, with the same benefits as described above. Short course triathletes should be spending up to half of their swimming training time here. Do not be tempted to spend all of your training time here. Your body will adapt and your test times (and hence your lactate steady state and CSS) will decline.

CSS minus 3 seconds per 100 yards (regardless of your CSS)

This is an anaerobic pace that you can maintain for only a short period of time. The primary training benefit is the improved ability to remove lactate from both types of muscle fiber. This is used used sparingly for endurance swimmers, to build overall speed and strength. Too much time in this category causes a decrease in muscle endurance, and requires longer recovery times.

For detailed information about these training categories, see Ernie Maglischo's book, Swimming Fastest, 2003, Human Kinetics.


Regarding paces based on CSS: The above method works well for swimmers who can maintain good swimming form long enough to complete the tests on which their CSS is based. If you cannot do that, your CSS will not be a valid measure of your lactate steady state, so you should not base your pace times on CSS. In this case use your perceived exertion: easy for EN1, hard for EN2, and too hard for very long for EN3.

Regarding the categories: Note that these are endurance training categories. If you are a sprinter, you may enjoy performing these workouts in the off season. In fact, there may be physiological advantages to doing that if you train hard as a sprinter for part of the year.

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