Broken 3000m: Time-Based Intervals for Advanced Pool Swimmers

Session Overview

The broken 3000m session uses a time-based interval structure to reward faster swimming with more rest — which means pacing matters. Cover the full 3,000m distance as six 500m efforts on a rolling interval (your target 500m time plus a fixed rest period), then race your final rep to find out how much fitness you have been holding back. Ideal for Ironman and 70.3 athletes who need to build open-water endurance at pace.

What You’ll Need

• Pool lane — 50m pool preferred, 25m pool works fine
• Pace clock or GPS watch
• Swim fins (optional, for the warm-up only)
• Pull buoy (optional, for pre-set)

Warm-Up (10 Minutes)

400m as: 100m easy freestyle, 100m kick on back, 100m pull buoy, 100m easy freestyle with bilateral breathing. Focus on long strokes and full rotation — save the effort for the main set.

Main Set

Find your target 500m pace by dividing your CSS pace by 5 (or use your last CSS test result). Set your interval as target 500m time plus 20 seconds for reps 1–5, then send off rep 6 on your fastest comfortable interval. The reward for swimming faster is more rest. Aim for even splits across all six reps.

• Reps 1–5: 500m on (target 500m time + 20 seconds). Swim at controlled CSS effort — RPE 7/10.
• Rep 6: 500m all-out race effort. This is your benchmark rep — compare it to rep 1 to gauge how well you paced the session.

Cool-Down (5 Minutes)

200m easy backstroke or catch-up drill to decompress the shoulders and bring heart rate down. Take your time — after 3,000m of main set, your body will thank you for a thorough cool-down.

Coaching Notes

• The most common mistake is going out too fast on rep 1. If your last rep is more than 10 seconds slower than rep 1, you went out too hard — recalibrate your target time.
• This session works best when your 500m target is realistic. If you do not have a recent CSS time, your CSS pace is approximately 5–10 seconds per 100m slower than your maximum 400m pace.
• To make it easier: reduce to 4 × 500m and extend the rest interval to +30 seconds. To make it harder: shorten rest to +10 seconds and add a 7th rep.
• Heart rate at CSS effort should be Zone 3–4. If you are in Zone 5 by rep 2, slow down — you are working anaerobically, not aerobically.