The swim warm-up: what it is for and how short it can be

Ask ten adult swimmers what their warm-up is and eight will say "a few hundred easy". Ask what it is for and most will say something about avoiding injury. Both answers are incomplete in a way that costs them the first part of every session.

The three jobs

A warm-up is doing three separate things, and they need different treatment.

Raising muscle temperature. Warm muscle contracts and relaxes faster than cold muscle. This is the part that easy swimming does well, and it is the part everyone already does.

Preparing the shoulder. Swimming asks the shoulder to rotate through a large range, repeatedly, under load. Going from stationary to a hard pull without that joint having moved through its range first is the single most avoidable risk in adult swimming, and it is why the injury discussed in swimmer's shoulder often shows up in people who train sensibly in every other respect.

Finding the water. This is the one nobody names and the one that changes your session. Feel for the water varies day to day — with fatigue, with sleep, with how long since you last swam. The warm-up is where you find out what you have got today, and adjust the session accordingly rather than discovering it halfway through the main set.

Why the slow 400 fails

The default adult warm-up is a continuous easy swim at one speed. It raises temperature, so it is not useless. But it has two holes.

It never approaches the intensity of the set that follows. If the main set is at threshold pace and the warm-up is 40 seconds per 100 slower, the first two repeats of the set become the warm-up — and those are the two you were counting as training.

And it is one stroke, one speed, one breathing pattern. The shoulder moves through the same range, in the same way, for eight minutes, which is preparation for exactly one thing.

The fix is not a longer warm-up. It is a warm-up with a shape.

A structure that works

Four parts, in this order. Scale the volume to the time you have; keep the order.

1. Easy swimming. Two hundred to four hundred metres, relaxed, breathing comfortably. This is the temperature job. Do not make it a race against the swimmer in the next lane.

2. Something that is not freestyle. Fifty to a hundred metres of backstroke, or breaststroke, or a mixture. This moves the shoulder through a different range and breaks up the repetition. Backstroke is particularly useful because it opens the chest, which most of us need after a day at a desk.

3. Drill or technique work. A hundred metres or so of whatever your current focus is — catch, body position, breathing pattern. This is early enough that you are not fatigued and late enough that you are not cold.

4. Builds. Four to six lengths, each starting easy and finishing at or above the pace of your main set, with rest between. This is the part that gets skipped and the part that matters most. It takes you to the intensity you are about to work at, gradually, so the first repeat of the main set is not a shock.

That whole sequence fits in ten to fifteen minutes. If you have five, cut part one and keep the builds.

Before a hard set versus before an easy swim

The right warm-up depends on what follows, which sounds obvious and is routinely ignored.

Before a steady aerobic swim, the first few hundred metres of the swim itself is a perfectly good warm-up. There is no intensity jump to prepare for. Start easy and let it come.

Before a threshold set — the sort prescribed as offsets from a CSS pace, discussed in CSS pace — you need the builds. Otherwise the first two repeats are slower than the rest and the set is not what it says it is.

Before sprint work, more still. Short, fast efforts with long rest, and enough of them that a maximal effort is not the first maximal effort of the day.

Before a time trial, treat it as a race warm-up. This matters more than people think: if the time trial is going to set your training paces for the next two months, a cold trial poisons everything downstream.

Three warm-ups you can copy

Written out, so there is nothing to invent while standing on the tiles.

Short, when you have fifteen minutes total in the water. 200 easy freestyle. 4 × 50 as 25 build, 25 easy. That is it. It contains the only two things you cannot skip: some swimming and some intensity.

Standard, before a threshold session. 300 easy freestyle. 100 backstroke. 4 × 50 drill of your choice with 15 seconds rest. 6 × 50 as build to main-set pace, 20 seconds rest. Around 900 m, twelve to fifteen minutes.

Before a time trial or a race. 400 easy mixed strokes. 200 as 50 drill, 50 swim. 6 × 50 building to faster than trial pace, with 30 seconds rest. 100 easy. Then wait no more than a few minutes before starting, because the benefit fades.

Notice what all three share: they end near the intensity of what follows, not far below it. If the main set that follows runs on send-offs, work them out before you get in with the interval calculator, so the warm-up is not spent doing arithmetic on the tiles. That is the whole design.

What about the pool deck

Land preparation before swimming is genuinely useful, particularly for adults who arrive from an office. A few minutes of arm swings, shoulder circles and thoracic rotation before you get in does something that easy swimming does not, because it moves the joints without load.

What the evidence does not support is long static stretching immediately before hard effort. The general finding across sports is that movement-based preparation is preferable to held stretches when performance follows shortly after, and the same logic applies here.

If you only have two minutes on deck, spend them on shoulder and thoracic movement rather than on hamstrings.

Cooling down, briefly

The other end of the session gets even less attention, and deserves a paragraph.

Two hundred metres of easy swimming after a hard set costs four minutes and makes the next day noticeably better for most people. It is also the least demanding technique practice available, because you are tired enough that only an efficient stroke feels comfortable.

If you are going to cut something from a session for time, cut a repeat from the main set rather than the cool-down. The main set has diminishing returns at the end; the cool-down does not.

When you are the only person in the lane at 6 a.m.

A word for the majority of adult swimmers, who train alone, early, in a shared lane, with a fixed hour on the clock.

The temptation is to treat the warm-up as the thing to sacrifice, because it is the part that is not the session. That is understandable and it is the wrong cut. A shorter main set that you swim properly beats a full main set whose first third is spent warming up by accident.

The practical version: decide before you get in what the session is, and what you will drop if the lane is busy or the clock runs out. If the answer is always "the last repeat", the warm-up survives and so does the quality of the work.

And if the pool is genuinely too crowded to build, do the builds as 25s. A single length is enough to lift the intensity, and you can fit one into almost any traffic. How to leave the wall and let people past without upsetting the lane is in lane etiquette.

The honest summary

A warm-up is not insurance and it is not ritual. It is the part of the session where you get your shoulders ready, find out what kind of day it is, and arrive at the main set already able to swim the pace it asks for.

Ten minutes with a build in it beats twenty minutes of formless easy swimming, every time. And if your session is 45 minutes total, that difference is most of your training.

The sets that follow are in workouts, including four beginner sessions that already have this structure built in. The stroke work is in technique.

This is general training information rather than advice for your body. Persistent shoulder pain is a reason to see a professional rather than to warm up for longer. Spotted an error? Tell us and we will correct it and date the change.