Day 2: Base 400s Swim

This 30 to 60-minute workout by coach Marilyn Chychota is designed to build endurance and your aerobic base as a swimmer.

Enjoy this Base 400s swim.

The Base 400s Workout

Warm Up

200 swim-scull-swim-kick

4x 50 as 25 fast, 25easy on 15 seconds rest

4x 50 descend 1-5 (the first one is the slowest, then get a little faster each one after that) on 10 seconds rest

Base 400s Aerobic Set

3-8 x 5 minutes (or 400s, whichever comes first)

Do each 5-minute (or 400) segment at an even split and low aerobic heart rate. Just feel the “shape” of the set. It should not be too hard, but you will feel a load on your arms. Stroke rate and heart rate should stay consistent throughout each segment.

How many sets should you do? It depends on the time you have and your fitness. Just do 3 or 4 if you only have half an hour, or if you haven’t been swimming in a while. If you’re feeling strong, go for more!

Cool Down

8 x 25 as:

Evens: Stream line as far as possible and then swim easy smooth to finish

Odds: Kick on your back stretched out

10 seconds rest in between 25s

Extra Credit 

Check your stroke rate during the first 50 of each 5-minute segment (or 400) and the last 50. Your goal is to keep your stroke rate consistent both within each segment and throughout the entire set.

How to integrate this base 400s workout into a training plan

 “I like this set on a Monday after a hard weekend of training,” Chychota says. “This session can also aid in recovery while working on aerobic conditioning in the water.”

Meet Your Coach 

Marilyn Chychota is a high-performance coach who’s been in the sport since 1999. She’s worked with a broad range of triathletes, from beginners to professionals—sending athletes to world championships in iron-distance, 70.3, USAT short-course, and XTERRA. Her own athletic resume includes professional competition in three different sports: equestrian show jumping, cycling, and triathlon. Chychota became a professional triathlete in 2003, racing to podium positions at Ironman events around the world, including a win at Ironman Malaysia in 2004. For more, check out