Sunrise Pool Intervals: Beat-the-Heat Swim Session

Session Overview

This 45-minute session is built for early mornings when the pool is quiet, the water hasn’t warmed up under the sun, and you can bank quality training before the day’s heat makes any outdoor session harder work than it needs to be. The main set uses threshold-pace intervals to build swim fitness without needing the recovery load of a full hot-weather brick session later in the day.

What You’ll Need

• Pace clock or waterproof watch
• Pull buoy (optional, for one recovery set)
• Water bottle at poolside — you still dehydrate in the water, especially in a warm pool

Warm-Up (10 minutes)

400m easy freestyle, mixing in 100m of choice stroke or drill if you swim one regularly. Finish with 4x25m building from easy to brisk, 15 seconds rest between each, to wake up your stroke rate before the main set.

Main Set

The main set targets your threshold pace — roughly the pace you could hold for a hard 20-30 minute effort, similar to your CSS (critical swim speed) pace if you’ve tested it. Aim for consistent, even splits across all ten reps rather than fading in the back half.

• 10 x 150m at threshold pace, 20 seconds rest between each
• Every 4th rep (reps 4 and 8), swim easy pace instead to break up the set and check your effort is sustainable
• Total main set: 1500m of work

Cool-Down (8 minutes)

300m easy swimming, mixing freestyle with backstroke or breaststroke to loosen different muscle groups. Finish with a few lengths of easy pull-buoy swimming if your shoulders need it.

Coaching Notes

• Even pacing matters more than speed here — if your first three reps are noticeably faster than your last three, you’ve started too hard; aim for splits within 2-3 seconds of each other across the set.
• Common mistake: treating the “easy” reps (4 and 8) as another hard effort out of habit. Use them as genuine recovery so your threshold reps stay high quality.
• Scaling option: if 150m reps feel too long to hold pace consistently, drop to 10x100m at the same threshold effort, or reduce to 8 reps total.
• Early sessions in a cooler pool are also a good opportunity to dial in open water sighting drills afterwards if you have time, since you’ll be fresher than after a hot-weather session later in the day.

See also: threshold swim: CSS pace work · heat acclimatisation for triathletes.