Rest times vs. send-offs: how to read and swim a set
A send-off tells you when to push off the wall. A rest interval tells you how long to stand there. For anyone not swimming in a squad with a big clock, rest is the more honest instruction — and it is what every SwimSwimSwim set gives you.
The two notations
Send-off (@1:40): you leave every 1:40 regardless of how fast you swam. Swim a 1:25 and you get 15 seconds rest; swim a 1:35 and you get 5. It is precise, it is brutal, and it needs a pace clock and a lane that agrees on it.
Rest (R:20"): you swim, you look at the clock, you push off 20 seconds later. The effort stays where it should be even on a day when you are slower than usual, and it works in a busy public lane.
Every set in the library is written with rest — R: or P: followed by seconds. Where the original coached session did not state a rest, we suggest one that fits the zone and the length.
How much rest belongs where
Rest is part of the training stimulus, not a break from it. Too much and a threshold set turns into intervals; too little and a sprint set turns into slow swimming.
| Zone | What it is | Typical rest | Why |
|---|---|---|---|
| Z1–Z2 | Recovery, easy aerobic | 10–15" | Just enough to see the clock; the swimming should stay continuous in feel |
| Z3 | Aerobic, intensive | 15–20" | Keeps heart rate up across long repeats |
| Z4 | Threshold / CSS | 15–25" | Short enough that the set stays a threshold set, not a sequence of hard swims |
| Z5 | VO2 / anaerobic development | 30–60" | You need to be able to repeat the pace, not survive it |
| Z7–Z8 | Speed endurance, max speed | 45"–2:00 | Real speed needs real recovery; without it you are training something else |
Longer repeats take the upper end of the range, 25s and 50s the lower — except at true sprint speed.
Reading a set line
8x100 free Z4 R:20" means eight repeats of 100 m front crawl at threshold pace, resting 20 seconds after each. If the whole block is prefixed with a multiplier — 2 × above the lines — you swim the entire block twice. Abbreviations such as DPS, drill, scull, build or negative split are explained in the glossary.
Keeping a set honest
- Take the same rest on the first repeat as on the last. Creeping rest is how a set quietly gets easier.
- If you cannot hold the pace by repeat five, the pace was wrong, not your character. Slow it a second or two.
- Do not race the first repeat. Threshold sets are won at the end.
- Know what the pace should be: with your CSS saved, each rep prints the time you should be hitting.
When send-offs are better
If you swim with a squad, a functioning pace clock and swimmers of similar speed, send-offs keep the lane together and add useful pressure. If you swim alone, rest wins on almost every count. You can always convert: target time plus rest equals send-off.