Designing the Main Set in Pool Training: Optimal Combinations of Distance, Intensity, and Repetitions

Introduction

Many swimming enthusiasts jump into the water and simply “swim a few laps,” lacking systematic workout planning, which leaves them stuck at the same level for a long time. In a complete swimming session, the Main Set is the heart of the entire workout—it determines whether the session is aimed at building endurance, speed, or lactate threshold. If the main set is poorly designed, no amount of warm-up or cool-down will make up for it.

This article explains, from a training-science perspective, how distance, intensity, and repetitions in the main set should be combined to help you build an efficient swimming workout plan.

Function and Role of the Main Set

A swimming session typically consists of four parts: Warm-up, Pre-set, Main Set, and Cool-down. The main set usually accounts for 50–65% of the total training volume and is the key segment that determines the purpose of the session.

The core objectives of the main set are threefold:

• Build aerobic base: Long-distance, low-intensity work to train the heart, lungs, and muscles’ oxygen utilization efficiency
• Raise lactate threshold: Mid-distance, mid-to-high intensity to accustom the body to maintaining pace before lactate accumulates
• Improve maximal speed: Short-distance, high-intensity work to stimulate neuromuscular power and stroke rate efficiency

The Logic of Combining Distance, Intensity, and Repetitions

Intensity Zones

The commonly used intensity zones in swimming training are as follows (referenced by percentage of personal best times or heart rate):

Recommended Combinations of Distance and Repetitions

Based on training purpose, the main set design logic is as follows:

Aerobic Endurance Main Set (primarily Z2)

• Distance per repeat: 200–400m
• Number of repeats: 4–8
• Rest between repeats: 10–20 seconds
• Example: 4 × 400m, 20 seconds rest, pace at 70–75% of your personal 1500m time

Threshold Main Set (Z3)

• Distance per repeat: 100–300m
• Number of repeats: 6–10
• Rest between repeats: 15–30 seconds
• Example: 8 × 200m, 20 seconds rest, pace at 90–95% of your personal 400m time

VO₂max Main Set (Z4)

• Distance per repeat: 50–100m
• Number of repeats: 8–16
• Rest between repeats: 30–60 seconds (or controlled by fixed send-off time)
• Example: 12 × 75m, departing every 1:30

Speed Main Set (Z5)

• Distance per repeat: 25–50m
• Number of repeats: 6–12
• Rest between repeats: 1–3 minutes (full recovery required)
• Example: 8 × 25m all-out sprint, 2 minutes rest

Practical Considerations for Pools in Taiwan

Most swimming pools in Taiwan are 25m short-course pools, with only a few venues offering 50m long-course pools. When designing main sets in a 25m pool, special attention should be paid to:

• Turn technique affects intensity: In a 25m pool, there are 3 turns per 100m. Swimmers proficient in flip turns can maintain a higher average pace, while those with weaker turns should adjust their target pace accordingly.
• The start advantage fades quickly: In short-course swimming, the start acceleration segment accounts for a higher proportion. For pure training, it’s recommended to use a “push-off from the wall” instead of a dive start to eliminate the variable of the start.
• Time pressure of midday sessions: Many public pools in Taiwan have midday opening hours of only 1–1.5 hours. The main set distance is recommended to be kept within 1500–2500m, leaving enough time for warm-up and cool-down.

Common Design Mistakes and Corrections

Many self-coached swimmers frequently make the following mistakes:

• Using the same main set every time: Lacking periodized variation, the body adapts and progress stalls. It’s recommended to adjust the main set structure every 2–3 weeks.
• Intensity too low—volume without quality: Staying below Z2 the entire time fails to stimulate threshold improvement. It’s recommended to include at least 1–2 main sets at Z3 or above per week.
• Rest between repeats too long: Turning the session into a series of personal-best sprints loses the training effect of accumulated fatigue. Rest during threshold training should be kept at a level where you “depart again before fully recovering.”
• Excessive total volume: When the main set exceeds 70% of total training volume at high intensity, insufficient recovery leads to overtraining.

Practical Recommendations

1. Establish the primary purpose of each session before deciding the distance and intensity of the main set, rather than combining elements arbitrarily.
2. Use fixed send-off times (intervals) instead of free rest to control intensity more precisely—for example, “depart every 2:00.”
3. Record split times for each repeat to track pace consistency. If pace drops more than 5% in the latter half of the set, the intensity setting is too high.
4. Beginners should start with Z2 aerobic main sets, first building a stable weekly training volume of 3000–4000m, then gradually incorporating Z3–Z4 training.
5. Periodize your training: A basic rhythm of “3 weeks of progressive intensity + 1 week of reduced-volume recovery” can be adopted.

Conclusion

Main set design is not just about filling up swimming distance—it’s about precisely combining distance, intensity, and repetitions so that every session has a clear physiological stimulus goal. Starting today, get in the water with the question “What is this main set meant to train?” in mind, and you’ll find that training efficiency improves dramatically, and the pace of your progress will exceed expectations.

Related Reading

• Swimming Main Set Design: The Complete Structure of Warm-up → Technique Set → Main Set → Cool-down
• Lane Grouping Strategies for Pool Training: Workout Design Differences Across Fast, Medium, and Slow Lanes
• Swimming Drill Sets: Optimal Proportions and Design Methods in a Workout Plan
• Swimming Interval Training Design: Workout Configurations for 100m×10 Sets and 200m×5 Sets