Rather than using the common energy systems which can be confusing, I use 4 simple concepts in my own training such as “easy – medium – solid – hard”
Note: Warm-up and sprints are not included in the following table as they aren’t endurance paces.
Below is a brief description of how each pace correspond to the commonly known energy systems
Easy pace is the equivalent of aerobic capacity (also called aerobic recovery / moderate)
Steady pace is the equivalent of aerobic development.
Solid pace is the equivalent of the lactate threshold (anaerobic threshold) where the lactate production remains in steady-state (the rate at which lactate appears in the blood is equal to the rate of its disappearance).
Hard pace is the equivalent of aerobic power to Vo2 Max, so close to your theoretical 400 m. race pace
Fast pace is the equivalent of anaerobic system which provides the body with explosive short term energy that lasts from 10 to 90 seconds without the need for oxygen. As a result, waste products such as lactic acid accumulate in the blood and in muscle cells. The burning sensation in the muscle, shortness of breath and fatigue are all symptoms of lactic acid build up and thus impacts the ability to perform.
What should you feel and focus on when swimming at these paces
Easy pace: Can hold this pace for a very long time. Focus on a good technique but in the most relaxing way as possible. Focus on a nice and high elbow position.
Steady pace: You should still feel good and be enjoying a pace that you could use for a long time (e.g. one hour, depending on current fitness). You could be able to maintain an efficient technique without suffering.
Focus on distance per stroke with a stronger catch.
Solid pace: Helps build endurance and strength. This pace requires you to optimize your distance per stroke and stroke rate as best you can. Focus on a very strong catch & pull as well as increasing your stroke rate (frequency) without losing your distance per stroke too much.
The intensity should be high and constant from the first repetition to the last repetition of the set.
The idea is to progressively increase the total distance and duration at that pace towards the competitive season (e.g. from 10 x 100 to 20 x 100 to 30 x 100…).
Hard pace: The goal is to give lots of power and strength in your strokes with a higher stroke rate.
Focus on maintaining a good technique throughout the whole set especially when your body gets tired.
Losing the technical focus at that pace, will lead into an inefficient stroke and consequently, a loss of speed. A good way to control this is to maintain a good D.P.S. or to avoid adding two extra strokes per length.
This pace requires longer rest time / intervals and recovery.
Fast pace: The goal is to give the maximum power and strength over a short distance while keeping your strokes long (avoiding too short strokes). The stroke rate is at its maximum. Maintaining your streamline and a good technique is also crucial at that speed to maintain efficiency and avoid developing injuries.