Long Course Swim: 2500m Pool Endurance Session for Triathletes

Session Overview

This 60-minute pool endurance session is designed to build the aerobic base for long-course triathlon swimming — bridging the gap between sprint distance and 70.3 or IRONMAN swim volumes. Intermediate swimmers will develop sustained stroke efficiency and threshold pace over a structured 2,500m set.

What You Will Need

  • 25m or 50m pool with lane availability
  • Swim goggles and cap
  • Pull buoy (optional for main set variation)
  • Pace clock or waterproof watch

Warm-Up (10 minutes)

400m easy at RPE 4/10, alternating 50m freestyle with 50m backstroke or choice stroke. Focus on long, relaxed strokes and comfortable breathing rhythm. Finish with 4 x 25m build swims (gradually increasing from 50% to 80% effort), with 20-second rest between each.

Main Set

Complete the following structured blocks with short rests as indicated. The goal is to maintain consistent pace throughout — this is an endurance session, not a speed session, so start conservatively.

  • 600m continuous at aerobic pace (RPE 6/10) — 15 seconds rest
  • 4 x 200m at CSS (Critical Swim Speed) pace — 20 seconds rest between each
  • 400m continuous at aerobic pace — 15 seconds rest
  • 4 x 100m at slightly above CSS pace — 15 seconds rest between each
  • 200m easy, focusing on long strokes and full body rotation

Cool-Down (10 minutes)

300m easy at RPE 3/10, alternating between freestyle and backstroke. Focus entirely on stroke mechanics rather than pace. Finish with 2 x 25m kick-only drills, focusing on ankle flexibility and hip-driven kick rather than knee-driven bending.

Coaching Notes

  • If you do not know your CSS pace, a rough guide is the pace you could sustain for a 400m time trial minus 2-3 seconds per 100m
  • Common mistake: treating the 4 x 200m CSS blocks as sprint sets. These are controlled threshold efforts, not maximal efforts.
  • Scale down: Replace the 600m opener with 400m and the 4 x 200m with 4 x 150m for swimmers new to this volume
  • Scale up: Add a second 400m continuous block before the cool-down for athletes building towards 3.8km IRONMAN swim preparation

Training at your own risk. The information provided is for general guidance only and is not a substitute for professional medical advice. Please consult a doctor before starting any new exercise programme, especially if you have any pre-existing health conditions.