How Do I Choose the Right Send-Off Interval for a Swim Set?

Choose your swim send-off by adding a realistic repeat time to the rest needed for the set’s purpose, then checking that any pace-clock rounding preserves that rest. For example, a 1:42 repeat plus 18 seconds rest gives a 2:00 send-off; use fixed rest when your repeat times vary too much to preserve recovery.

How do I calculate a realistic swim send-off?

Use repeat time + intended rest = send-off. USMS describes workout timing as stroke pace combined with allocated rest, so start with the distance and stroke you will actually swim rather than borrowing a faster swimmer’s number.

Calculate, then check

Estimate a sustainable repeat time Use recent repeats at the intended effort in the same pool course. Prefer a time you can repeat over your fastest isolated effort. If pace is 1:45 per 100m, the arithmetic estimate for 200m is 3:30; confirm that estimate in the water.
Choose rest to match the task Use the rest prescribed by the set or coach. If none is given, decide whether you need a brief reset for sustained swimming or fuller recovery for speed and form. Do not infer the purpose from distance alone.
Add, round, and subtract again For a worked example, 1:43 swimming + 15 seconds rest = 1:58. A 2:00 departure gives 17 seconds rest. Check the rounded number by subtracting your swim time before accepting it.
Check the later repeats Record your finish times and remaining rest. If the last repeats no longer fit the intended effort and recovery, change the interval or distance rather than forcing a faster start.

Write the result as a departure interval, not a rest instruction. If those terms are still unclear, read the send-off versus rest interval guide before choosing your number.

How much rest should a swim send-off preserve?

There is no single correct rest amount for every swim set. USMS explains that the break can range from seconds to minutes depending on the purpose, including fuller recovery for all-out sprints and very brief breaks for sustained race-pace work.

For an aerobic set, choose an interval that lets you keep the intended steady effort; for threshold work, follow the prescribed pace and recovery rather than making each repeat all-out. For sprints, prioritise enough recovery to repeat the speed; for technique, leave room to refocus on the movement before departing again.

USMS also allows approximate rest to be adjusted to a sensible clock departure. Use that flexibility only when the set allows it: rounding an exact recovery instruction is a change to the set, even if it makes the clock easier to read.

What does a workable swim interval look like?

In this illustrative set, a swimmer finishing each 100m in 1:40–1:45 on a 2:00 send-off receives 20–15 seconds rest. These times are assumptions for demonstrating subtraction, not a tested workout or a recommendation that every aerobic set needs this rest.

Worked example: steady aerobic repeats

Illustrative main set, not a full session · 600m total

6 × 100m Steady freestyle — GA1 · Leave every 2:00 between repeats · Assumed repeat time: 1:40–1:45, giving 15–20 seconds rest. Change the interval if this pace is not comfortably repeatable.

If a later repeat takes 1:55, the same interval leaves only 5 seconds rest. If it takes 2:03, you have already missed the next scheduled departure; for this steady example, try a longer interval or fixed rest before restarting, rather than sprinting to catch up.

How do I scale a swim send-off that does not fit?

Change the prescription around your current ability and the set’s goal. USMS’s adult-training guide explicitly describes different-speed lanes swimming different numbers of repeats while spending the same time on quality work.

Troubleshoot in this order

Too little rest: recalculate from your actual time Worked example: a 1:55 repeat on 2:00 leaves 5 seconds. If the intended rest is 20 seconds, 2:15 is the arithmetic match. Try that interval at the original effort rather than racing the repeat.
Too much rest: check the purpose before shortening Worked example: 1:35 on 2:15 leaves 40 seconds. If you intended 20 seconds, 1:55 matches; if it is a speed set requiring fuller recovery, keep the recovery rather than tightening the clock for its own sake.
Different course: remeasure the repeat Do not copy a 100-yard time into a 100-metre prescription. Use recent swimming in the new course and units, then add the intended rest again. Treat any distance-based conversion as a starting estimate to verify.
Mixed-speed lane: agree the schedule first Discuss distances, departure order, and space at the wall before starting. If a shared interval does not fit, ask about shorter repeats or fewer repetitions with the same goal. Independent fixed-rest departures need coordination in a shared lane.

For a workout written faster than you can hold, consider shortening the repeat distance as well as changing the send-off. Fewer repeats can help fit the available session time; a shorter repeat can help make an individual departure workable. Keep the effort and recovery goal explicit, and recalculate after changing distance.

When should I choose fixed rest instead of a send-off?

Choose fixed rest when preserving recovery matters more than preserving a departure schedule. USMS distinguishes the two clearly: send-offs keep departures fixed while rest changes with speed; rest intervals keep recovery fixed after each finish.

Choose the timing rule

	Send-off	Fixed rest
What stays constant?	Time between departures	Time after each finish
Worked example: 1:45 swim	2:00 interval gives 15 seconds rest	20 seconds rest gives a 2:05 departure cycle
Worked example: 1:55 swim	2:00 interval gives 5 seconds rest	20 seconds rest gives a 2:15 departure cycle
Suggested use	Stable repeat times and an agreed clock schedule	Variable repeat times or recovery-led work

Choose for this set

Use the clock rule that preserves your intended effort and recovery.

Keep a send-off when your repeat times leave appropriate rest throughout the set. Switch to fixed rest when pace varies enough that the same interval removes the recovery you planned; coordinate departures if you share a lane.

How can I plan my next swim intervals with AquaPlan?

Start with your recent pace in the swim pace calculator , or use your current CSS pace as an initial reference for a set specifically written around CSS. Write down the intended effort, estimated repeat time, and planned rest before selecting the send-off.

Open the example above in the builder, or start in the free workout builder , and adjust repeat distance, count, and recovery. For another starting set, browse the free swim workout library ; then check your chosen interval against what you actually swim.

Frequently Asked Questions

How do I calculate a swim send-off interval?

Add the time you expect to swim the repeat to the rest you intend to take. For example, a 1:42 swim plus 18 seconds rest gives a 2:00 send-off. This is worked-example arithmetic, not a universal rest prescription.

Should I round my send-off up or down?

Choose a clock-friendly interval only after checking the resulting rest. In a worked example, 1:43 plus 15 seconds gives 1:58; rounding to 2:00 gives 17 seconds rest, while 1:55 gives 12. If that difference changes the purpose of your set, keep the exact timing or use fixed rest.

What if I cannot make the interval?

Recalculate from a repeat time you can sustain at the intended effort. Try a longer send-off, a shorter repeat distance, or fixed rest. Do not turn an aerobic or technique set into a sprint just to match someone else’s interval.

Does a 2:00 send-off mean two minutes of rest?

No. A send-off is measured from one departure to the next. If you swim in 1:45 on a 2:00 interval, the remaining 15 seconds are rest. Fixed rest instead starts when you finish the repeat.

Sources and editorial process

Sources checked October 9, 2026: the USMS adult-training guide, Workout Library timing glossary, and wall-time article. The formula follows their timing definitions; the numerical examples and troubleshooting sequence are AquaPlan’s illustrative applications, not quoted USMS prescriptions.

Limitations: this article was not tested with individual swimmers and does not establish universal rest ranges or personalised training zones. Pool course, stroke, effort, and repeat consistency can change the interval that fits; verify estimates in your own session.

Automated editorial check (daily-ai-v1): this article was authored using AI and checked through an automated editorial process. No human expert review is claimed.

Article publisher

Published and maintained by AquaPlan. The article above identifies its evidence sources and automated editorial process; no human expert review is claimed.