Descending 100m Swim Set: Speed and Efficiency Pool Session

Session Overview

This descending 100m swim set is designed for intermediate triathletes looking to build speed and sharpen race-pace awareness. You start each 100m rep at a controlled effort and progressively get faster through the set, training your body to negative-split and finishing each rep quicker than the last. It is an excellent pre-season speed session before your first open water races.

What You’ll Need

• 25m or 50m swimming pool
• Swim goggles and cap
• Kickboard (optional for warm-up)
• Fins (optional for cool-down)

Warm-Up (10 minutes)

Swim 400m easy freestyle with no pace target, focusing on long strokes and relaxed breathing. Include 2 x 50m with alternating 25m freestyle / 25m backstroke to loosen your shoulders. Finish with 4 x 25m build (each 25m progressively faster, from easy to threshold effort).

Main Set

Complete 3 rounds of the descending 100m set below. For each round, each 100m rep must be faster than the previous — aim to drop 2–4 seconds per rep. Take 20 seconds rest between reps and 60 seconds rest between rounds.

• 100m at RPE 6/10 (aerobic, conversational pace) — 20 sec rest
• 100m at RPE 7/10 (comfortably hard, controlled breathing) — 20 sec rest
• 100m at RPE 8/10 (threshold pace, at or near CSS pace) — 20 sec rest
• 100m at RPE 9/10 (near-sprint, maximum sustainable effort) — 60 sec rest between rounds

Cool-Down (5 minutes)

Swim 200m easy backstroke or easy freestyle, focusing purely on relaxed breathing and letting your heart rate drop naturally. Shake out your arms and shoulders at the pool wall before exiting.

Coaching Notes

• Do not go out too fast on the first rep — if you max out early you will not have the speed reserves to descend properly
• Focus on maintaining stroke rate rather than lengthening your stroke as you fatigue; cadence holds speed better than reach
• Beginners: reduce to 2 rounds and add 30 seconds rest between reps; advanced swimmers can add a fourth round with a 90-second all-out 100m finisher
• Target heart rate: RPE 7–8 on the hard reps; HR should recover to Zone 2 during rest before the next effort