6x500m Descending Pace CSS Pool Session

Session Overview

This 45-minute pool session uses six descending 500m reps to challenge your pacing, push your CSS threshold, and build the race-specific speed endurance that makes the difference in triathlon swim splits. It’s ideal for intermediate and advanced swimmers ready to race the clock.

What You’ll Need

• 25m or 50m pool
• Swim watch or poolside clock
• Pull buoy (optional, for warm-up)

Warm-Up (10 minutes)

Start with 400m easy freestyle, focusing on long strokes and full rotation. Follow with 4x25m build swims, starting easy and arriving at threshold pace on the final rep. Take 20 seconds rest between each 25m.

Main Set

The goal of this session is to swim each 500m slightly faster than the last. Start around CSS+5-7 seconds per 100m pace and aim to hit CSS pace or faster by the final rep. Take 60-90 seconds rest between each effort.

• 500m at CSS + 6 sec per 100m (controlled, sustainable)
• 500m at CSS + 4 sec per 100m (settling in)
• 500m at CSS + 2 sec per 100m (building effort)
• 500m at CSS pace (race tempo)
• 500m at CSS – 1 sec per 100m (strong push)
• 500m at CSS – 2 to -3 sec per 100m (all out finish)

Cool-Down (5 minutes)

Swim 200m easy backstroke or mixed strokes, focusing on relaxed breathing and slow turnover. Let your heart rate drop naturally and shake out your arms gently to reduce post-swim stiffness.

Coaching Notes

• If you don’t know your CSS pace, swim a 400m and 200m time trial with 10 minutes rest, then use a CSS calculator to find your number.
• Avoid going out too fast on rep one — patience early makes the final two reps possible.
• Beginner option: cut to 4x400m descending at the same pace structure.
• RPE guide: reps 1-2 at 6/10, reps 3-4 at 7-8/10, reps 5-6 at 8-9/10.