CSS repeats break the continuous CSS swim into chunks — 4 to 6 efforts of 4 to 6 minutes each at critical swim speed, separated by 30–60 seconds of easy swimming. The same threshold pace, but more accumulated time at that quality because the short recovery resets just enough to hold form.
This is the swim parallel to running's threshold intervals. The session lets a swimmer push more total threshold minutes per session than a continuous CSS swim would allow, with cleaner stroke quality throughout.
What the Effort Feels Like
During reps: Comfortably hard. RPE 7. Same effort as the continuous CSS swim — not harder. The short recovery is what makes it sustainable, not a higher pace.
During recovery: Easy swim or rest at the wall. The shoulders soften, breathing settles enough to attack the next rep at quality. Don't fully recover — the partial recovery is the point.
Across the set: The first rep should feel manageable. The last should be earned but achievable at the same pace. If the final rep falls apart, the early ones were too aggressive — pull back next time.
Session Structure
Warmup (10–15 minutes). Easy swimming. Build the last 100m to prime the body for threshold work.
Repeats (4–6 × 4–6 minutes at CSS). Each rep at RPE 7 with 30 seconds to 1 minute of easy swim recovery. Freestyle throughout. Pace consistency across reps matters more than speed on any single rep.
Cooldown (10 minutes). Easy swimming. Let the system wind down.
When to Use CSS Repeats vs. CSS Swim
The continuous CSS swim teaches sustained pace discipline — one effort, no breaks. CSS repeats teach quality under fatigue with rebuilds — more total minutes, cleaner form.
Use the continuous swim earlier in build, when sustained pacing is the priority. Use repeats in peak, when accumulating more threshold time without form breakdown matters most. Some weeks will alternate. They're complementary, not interchangeable.
Practical Guidelines
- Duration: 40 to 55 minutes total. Repeat block is 20–35 minutes including recovery.
- Reps: 4 to 6 repetitions of 4 to 6 minutes each.
- Effort: RPE 7 during reps. RPE 3 during recovery.
- Recovery: 30 seconds to 1 minute easy swim between reps.
- Stroke: Freestyle. Switch only if form breaks down.
- Frequency: Once per week at most. Don't stack on the same week as a CSS swim — pick one.
- Progression: Start with 4 reps at 4 minutes. Add a rep before lengthening each one.