A swimming workout: an easy warm-up, short repeats with rests, and an easy finish

A swim session has the same three parts as any other cardio session: a warm-up, the main work, and an easy finish. The main work for a beginner is short repeats of swimming with a rest at the wall between them, because swimming a continuous 20 minutes is easier to build up to than to start with (a practical view).

This page gives two sessions, labelled practical, and the research they lean on: what heart rate does in the water, what the Compendium of Physical Activities rates swimming at, and what the trials of swim training measured. It's not a promise about what swimming will do for you, and it's about the session, not the stroke: if you can't swim a length comfortably yet, learn with an instructor in a pool with a lifeguard first. Swimming compared with running is on swimming vs running.

1. Leave the running heart-rate numbers on land

In one study, peak heart rate was lower swimming than running. In 34 college-age fitness swimmers tested to their maximum on a treadmill and swimming against a tether, peak swimming heart rate was 11 beats a minute lower than running's, and the authors suggested taking about 12 beats off a running or age-predicted maximum to estimate a swimming one.¹ They were fitness swimmers swimming against a tether, so a beginner's numbers will differ; the authors' suggestion was to subtract, so a zone built on a running maximum would sit too high for them. For a first session, go by effort: steady swimming at a pace you could keep up for a few lengths, and recovery at the wall until your breathing settles. The heart-rate zone calculator takes whatever maximum you give it.

2. Short repeats with rests

The one trial here in recreational swimmers used intervals: 15 male college-age recreational swimmers used interval swim training for an hour a day, 3 days a week, for 10 weeks, and their swimming VO2 max rose significantly, by 380 mL/min; their VO2 max on a treadmill running test didn't improve significantly.² That was in men who already swam, an hour at a time, in 1975, so it supports the shape of the session, not its length. From a sedentary start, a trial of 37 men aged 28 to 35 found 11.5 weeks of swim training or run training, 3 days a week at a heart rate matching 75% of their treadmill VO2 max, raised treadmill VO2 max by 25% and 28%, against 5% in the controls, and the two training groups didn't differ significantly.³

3. How hard swimming rates

The Compendium rates swimming in METs, a measure of energy cost; one MET is about 1.0 kcal per kilogram of body weight per hour.⁴ The ratings depend on the stroke and the effort:⁵

These are group averages from the Compendium's sources, an estimate of the stroke and not a measurement of you.

4. Warm up in the water

A 2014 review of the studies on warm-up in competitive swimming found a positive effect on swimming performance, especially for distances over 200 m, and noted that studies on warm-up in swimming are scarce.⁶ That's about competitive swimmers before a race; the sessions below use a few minutes of easy swimming, which is a practical choice, not a protocol from a trial.

Two sessions to try

Practical, not protocols from a trial. A "length" is one length of your pool. Swim easy enough that you could say a sentence at the wall. Rest at the wall until your breathing settles, about 30 seconds to start.

When a session is easy, change one thing: more repeats, a longer repeat or a shorter rest, not all three. Write the session down (the workout log).

How often

The World Health Organization asks adults for 150 to 300 minutes of moderate aerobic activity a week, or 75 to 150 vigorous, and advises starting with small amounts and gradually increasing frequency, intensity and duration.⁷ The two sessions above are a start toward that, not all of it. In a 16-week trial of 80 volunteers aged 60 to 70, a free-swimming group trained twice a week, and their 6-minute walk test was up 19.4%, significantly better than the control group's; the trial's other groups did aquatic resistance training, alone or with the swimming.⁸ It's older adults, and it's a walk test, not a swim test, but it shows what two sessions a week looked like in a trial. The WHO also asks for muscle-strengthening on 2 or more days a week:⁷ strength training for swimmers has what the studies say for people who swim, and cardio and lifting how the two share a week.

Common questions

How long should a swimming workout be?

The sessions above are roughly 20 to 30 minutes, and that's a practical choice. The hour-long sessions in the recreational-swimmer trial were in men who already swam.² Add time gradually, as the WHO advises.⁷

Is swimming good cardio?

By the studies cited here, swim training raised VO2 max in sedentary men about as much as run training did (25% and 28% against 5% for controls).³ In men who already swam, it raised swimming fitness but not treadmill fitness.² Both are men, and the details are on swimming vs running.

Do I need to know all four strokes?

No. The Compendium rates recreational backstroke at 4.8, breaststroke at 5.3 and slow freestyle at 5.8,⁵ so a stroke you're comfortable with is a workable stroke. Use two if you like, one for the main set and one for the finish.

How fast should I swim?

At a pace you could say a sentence at the wall. The Compendium's vigorous ratings, 8.0 and 9.8,⁵ are for the effort level above that, and you can add it to a repeat or two once the sessions feel easy.

What about calories?

Only as an estimate. For the Compendium's ratings turned into calories, see the calories section of swimming vs running.

If you'd rather have the week planned

Swim days, lifting days and a week that moves around only work when they land in the right order, and that's a scheduling problem as much as a training one. Coaching is the version where your workouts are built around the days you actually have, and a weekly call looks at the week you just had and rebuilds the next one around what's coming. Coaching for a week that doesn't hold still explains how that works, and apply is the first step. Otherwise: do Session A twice this week.