What does 4×100 @1:30 mean in swimming?
4×100 @1:30 means four reps of 100 yards or meters, leaving every 1 minute 30 seconds. The @ number is a send-off interval, not a rest period — it covers swim time plus whatever rest is left over. If a swimmer swims each 100 in 1:12, they get 18 seconds of rest before the next one starts. Swim slower, rest less. This is the core idea behind almost every swim set you'll ever read.
The basic format: reps × distance
Every set starts with two numbers separated by an x. The first is how many times you do something. The second is how far each one goes.
4×100 free is four reps of 100, freestyle. If the stroke isn't named, assume free. 4×100 IM means each 100 is a full individual medley — fly, back, breast, free, 25 of each.
Distance can be broken down further. 8×50 is not the same as 4×100 even though total volume is equal. Shorter reps mean more starts and turns, and usually a faster per-100 pace than the longer version.
What does the @ symbol mean?
The @ sign tells you when the next rep starts — not how long you get to rest. This is the part that trips up parents and new assistants most.
4×100 free @1:30 means a swimmer leaves on 0:00, 1:30, 3:00, 4:30. The interval is the total time allotted for one rep, swim plus rest combined.
Coaches use send-off intervals instead of flat rest because the interval controls pace and recovery at the same time, and it self-corrects. Swim faster, get more rest. Swim slower, get squeezed. That squeeze is often the point — it's what makes a set aerobic-threshold work instead of pure sprint work, even at a moderate pace.
Some boards write @1:30 SO (send-off) to be explicit, or use :30 R to mean 30 seconds of pure rest with no set send-off. If you see 1:30 R, that's rest, not an interval — the next rep starts 90 seconds after the swimmer finishes, regardless of their time.
How do I figure out the rest if I only see the interval?
Subtract the swim time from the interval. On 4×100 @1:30, a 1:12 swimmer gets 18 seconds rest; a 1:25 swimmer gets 5 seconds. If a swimmer can't hold enough pace to get at least a few seconds of rest most rounds, the interval is too tight for that swimmer on that day — loosen it or shorten the rep, don't just let them grind through with zero recovery every time.
What do rounds and brackets mean?
Sets often stack smaller pieces into rounds using brackets or parentheses.
3 rounds: (4×50 @0:45 + 200 @3:00)
Do the bracket three times through: four 50s on 45 seconds, then one 200 on 3:00, then repeat that whole block two more times. Total volume: 3 × (200 + 200) = 1200.
A number in front of the bracket, or the word "rounds," tells you how many times to repeat everything inside it. Nested sets are how coaches build variety and mixed-energy work into one line instead of writing out forty individual reps.
What do common instruction words mean?
- Hold — keep the same pace across every rep. "Hold best average" means find a pace you can repeat for all four reps without falling apart on the last one. It's not about swimming the fastest possible first rep — it's about picking a sustainable number and hitting it every time.
- Descend 1-4 — each rep gets faster than the one before, across four reps. Rep 1 easy-moderate, rep 4 fastest. A common mistake is descending too hard on reps 1-2 and having nothing left for 3-4.
- Build — get faster within a single rep. "Build 100" means start controlled and finish strong, inside one rep, not across multiple reps.
- Negative split — swim the second half of a rep faster than the first half. On a 200, the 100-150 and 150-200 should be quicker than the opening 100. Worth drilling directly, since most swimmers naturally go out too fast.
- DPS — distance per stroke. A DPS set asks for fewer strokes per length, not necessarily a faster time. Used to reinforce technique under low fatigue, often on easier intervals.
- RP — race pace. "3×100 free @2:00, RP" means swim each 100 at the pace the swimmer would hold in an actual 100 race, with enough rest for full recovery between reps.
- ! or max — all-out effort. No pacing strategy, just go. Usually reserved for short reps (25s, 50s) with generous rest so quality doesn't erode.
How do I read a full whiteboard set?
Put it together and a line like this stops looking like code:
3 rounds: (4×50 free @0:45, descend 1-4) + (1×100 free @1:45, RP) + 0:20 rest
That's three trips through a block. Each trip: four 50s on 45 seconds, getting progressively faster; one 100 on 1:45 at race pace; a short breather before the block repeats. A coach reading this knows the energy system target (mostly aerobic-to-threshold, with a race-pace touch), the volume (900 total), and where to watch for breakdown — usually rep 4 of the descend series or the RP 100 once fatigue builds.
Once you can parse reps, interval, rounds, and instruction words, you can read any board in any pool, not just the ones you wrote yourself.
SwimIQ handles this translation for you when you're building sets, not just reading them — speak, type, or photograph a practice and it structures the reps, intervals, and instructions automatically, and checks the result against training literature so you can confirm the set trains the energy system you actually intended before it goes on the board.