25Sport — Sports Calculators
Swimming Workouts

Improve Anaerobic Threshold — 22-Session Swimming Plan

This plan is designed to improve your ability to resist fatigue at the anaerobic threshold, gradually raise your fitness level, and enhance overall swimming performance.


How It Works

Swimmers are placed into performance groups (Ga, Gb, Gc) based on a 10×50m test with 5″ rest at maximum sustainable pace. Training then uses fixed departure times to keep everyone working at their correct intensity.

Three 400m time trials (sessions 2, 16, and 19) are used to track your progress throughout the plan.

Session Overview

Session 0 — Initial Assessment (2600m)

10×50m time trial to establish your performance group and baseline pace.

Session 1 (2600m)

1000m medium/threshold aerobic work with 5×100m and 10×50m sets.

Session 2 (2800m)

1100m medium aerobic + 400m speed work. Includes 400m time trial — record your time!

Session 3 (3000m)

800m aerobic + 1000m comfortable continuous + 16×25m varied intensity.

Session 4 (2600m)

1500m continuous in 100m blocks + 800m with fins.

Session 5 (3100m)

1200m medium/intense aerobic in 4 paired blocks.

Session 6 (2800m)

600m medium aerobic + 800m intense aerobic at 85% effort.

Session 7 (3400m)

1500m medium aerobic with 10×150m sets.

Session 8 (3000m)

900m aerobic + 800m intense + accelerations with fins.

Session 9 (3400m)

1500m continuous medium aerobic — a benchmark of your base endurance.

Session 10 (3100m)

Progressive 200m sets with increasing intensity + 150m speed work.

Session 11 (3300m)

1800m medium aerobic at 70–75% effort.

Session 12 (3400m)

600m aerobic + 900m intense + 3×(3×100m) at 85%.

Session 13 (3500m)

2000m medium aerobic with 40×50m finishing sets.

Session 14 (3000m)

600m pull medium aerobic + 1000m intense — compare your time vs. session 2.

Session 15 (3200m)

2000m aerobic in 8 different 400m blocks — each block with a different focus or stroke.

Session 16 (3300m)

800m aerobic + 1000m intense. Includes 400m time trial — compare with session 2!

Session 17 (3500m)

1200m medium aerobic with 4×300m intervals.

Session 18 (3000m)

Speed work with mixed stroke blocks — focus on race-pace efforts.

Session 19 (2800m)

400m intense + 400m time trial (third measurement!) + 1000m mixed work with fins.

Session 20 (2500m)

800m medium aerobic + 800m descending progressive set. Begin tapering.

Session 21 — Final Assessment

Repeat the initial 10×50m test and compare with your starting time. You should see clear improvement across all three 400m time trial results!

Glossary

Anaerobic threshold
The intensity where your muscles produce lactic acid faster than your body can clear it. Training at this level teaches your body to handle that burn better and delay fatigue.
Performance groups (Ga, Gb, Gc)
Swimmers sorted by level based on a test — so everyone trains at the right intensity.
Fixed departure times (salida cada)
Everyone leaves at a fixed interval (e.g., every 1:30). Faster swimmers get more rest, slower ones get less — keeps the pace honest.
Time trial (contrarreloj)
Swimming a set distance as fast as possible to measure current fitness.
85% effort
Hard enough that you're breathing heavily and it feels challenging, but you could keep going for a few more minutes.