If you’re an intermediate or competitive swimmer, or a triathlete looking to improve your swim performance, Project Sub-6: The 400m Swim Plan is a focused 4-week training block designed to help bring your 400m swim time down towards 6 minutes.

This plan provides a structured, progressive approach to building the specific fitness needed for a faster 400m. Rather than simply adding more volume, the sessions are designed to be purposeful, targeting threshold speed, race pace familiarity, aerobic endurance, and speed under fatigue so you can hold a strong, efficient pace across the full distance.

Who’s it for?
This plan is aimed at intermediate or competitive swimmers and triathletes who already have a solid swim base and want a clear, targeted block of training to improve their 400m performance.

Is it for you?
If you’re already comfortable swimming regularly, can swim approximately 6min30 for 400m, can handle structured sessions, and want to become a faster, more efficient swimmer over 400m, this plan is for you.

What’s involved?
Across the 4 weeks, the training develops progressively with a mix of pace work, aerobic support, and controlled speed endurance sessions. The goal is to improve both your swim fitness and your ability to sustain race-relevant pace with good form, even when fatigue starts to build.

The bigger picture
The aim of this plan is simple: to help you become sharper, fitter, and better prepared to attack the 400m with confidence and move closer to that sub-6 benchmark.