8×150m Build Swim: Progressive Pool Intervals

Session Overview

This 45-minute progressive pool session builds your ability to hold pace under fatigue. Eight 150m repeats progress from easy Zone 2 effort through to near-race pace, developing lactate threshold and pace judgment. Ideal for intermediate swimmers targeting sprint or Olympic-distance triathlon.

What You’ll Need

• Pool access (25m or 50m)
• Swim goggles
• Pull buoy (optional, for warm-up)
• Pace clock or waterproof watch

Warm-Up (10 minutes)

Swim 400m at easy choice pace — no specific stroke or drill, just get moving and loosen up. Focus on long, relaxed strokes and controlled breathing. Finish with 4×25m as 15m catch-up drill into 10m full stroke build. Rest 20 seconds between each.

Main Set

Eight 150m repeats with 20 seconds rest between each. Progress through four effort zones — two reps per zone, each pair pushing harder than the last:

• Reps 1–2: Zone 2 — comfortable, conversational effort (~75–80% max heart rate)
• Reps 3–4: CSS pace — your Critical Swim Speed, steady and sustainable
• Reps 5–6: 5K effort — noticeably harder, breathing elevated but controlled
• Reps 7–8: Race effort — close to maximum, maintain stroke length as fatigue builds

Cool-Down (5 minutes)

Swim 200m easy backstroke or breaststroke to flush lactic acid and bring your heart rate down. Focus on relaxed breathing and gentle kick — this is recovery, not training.

Coaching Notes

• Record your split time for each 150m rep — you should see clear progression across the set
• Don’t go too hard on reps 1–2; resist the urge to sprint early or you’ll pay on reps 7–8
• If you’re struggling to hold stroke technique on the final reps, reduce to 6 reps and build to 8 over subsequent weeks
• Target RPE: reps 1–2 = 5/10, reps 3–4 = 6–7/10, reps 5–6 = 7–8/10, reps 7–8 = 9/10