Most articles on the benefits of swimming read like a brochure. Full-body workout, burns loads of calories, great for your joints, fixes your back, good for everything. Some of that is true, some of it is half true, and a bit of it is just made up.

I’ve been teaching swimming since 1994, so you’d expect me to call it the best exercise there is. It isn’t, for everyone. It’s a very good one, with specific strengths and real gaps.

This article keeps three things apart, the same way the backstroke guide does: what the guidelines say, what research has measured (with the sample sizes and the catches), and what I see at the poolside, labelled as my experience so you know which is which.

The benefits of swimming, the short honest version

  • It’s cardio. Properly. At a steady lap pace it counts as moderate or vigorous aerobic exercise under the official definitions. More on that below.
  • It’s low impact. You can train your heart and lungs without your joints taking a pounding. HPB describes it as suitable for people recovering from injuries, and in my experience heavier adults who find running painful often do well in the pool.
  • Swimmers in large studies tend to live longer. But those are observational studies, and they can’t prove swimming is the cause.
  • It can help with weight and body fat, a bit. Not as much as people think, and not more than other exercise.
  • It doesn’t build bone the way impact sports do. And it doesn’t fix posture or scoliosis.
  • It’s the only exercise that might save your life in the water. No other workout does that.

What the guidelines say

The WHO’s 2020 guidelines on physical activity, as published in the British Journal of Sports Medicine, say:

“Adults should do at least 150–300 min of moderate-intensity aerobic physical activity, or at least 75–150 min of vigorous-intensity aerobic physical activity…”

That’s a strong recommendation, based on what WHO rates as moderate-certainty evidence. They also want muscle-strengthening work on two or more days a week. For children and teenagers aged 5–17 it’s “at least an average of 60 min/day of moderate-to-vigorous intensity, mostly aerobic, physical activity, across the week”, plus vigorous activity and activities that strengthen muscle and bone at least three days a week.

And the line I’d put on every pool noticeboard:

“For all populations, doing some physical activity is better than doing none.”

Singapore’s own guidelines, revised by Sport Singapore and the Health Promotion Board on 12 June 2022, use the same 150–300 minute range for adults and name swimming directly. HealthHub lists “brisk walking, jogging, swimming, and cycling” as examples of aerobic activity, and an HPB article on HealthHub (last reviewed 7 January 2026) describes it like this:

“Swimming is a low-impact aerobic physical activity that reduces stress on your skeletal system…”

So swimming counts. Neither body says it beats the other options. It’s one way of hitting the target, not a special one.

Is swimming cardio?

Yes. Swimming is a cardiovascular exercise, and at most lap-swimming paces it’s moderate to vigorous intensity.

The standard reference for this is the Compendium of Physical Activities, which gives activities a MET value: how hard they are compared with sitting still. In the 2024 Adult Compendium, moderate intensity is 3.0–5.9 METs and vigorous is 6.0 METs or more. Here’s where swimming lands:

Activity (2024 Adult Compendium) METs
Treading water, moderate effort 3.5
Backstroke, recreational 4.8
Breaststroke, recreational 5.3
Freestyle laps, slow, recreational 5.8
Leisurely swimming, not lap swimming 6.0
Freestyle laps, fast, vigorous effort 9.8
Breaststroke, training or competition 10.3
Butterfly, general 13.8

Easy lap swimming sits near the top of moderate. Push the pace and you’re well into vigorous, which matters because WHO’s vigorous target (75–150 minutes) is half the moderate one.

One caveat, and the Compendium’s authors make it themselves: these are averages for adults aged 19–59, not for children. They say the Compendium “does not reflect precise individual EE values.” A smooth, efficient swimmer and a beginner fighting the water get very different workouts from the same “breaststroke”.

Does it actually make you fitter? A 2018 systematic review and meta-analysis in Sports Medicine (Lahart and Metsios) looked at 29 controlled studies of swim training in non-elite swimmers. In healthy adults, swimming raised VO₂max, the standard measure of aerobic fitness, by 5.87 mL/kg/min compared with not training (95% CI 2.93–8.81). The authors call that “clinically meaningful”. Their conclusion is careful, though: effects “may be comparable to other exercise modes”, and they say more randomised trials are still needed.

So yes, it’s cardio. It’s not magic cardio.

Is swimming a good workout?

For your heart and lungs, yes, as above. For the rest, it depends what you want from it.

Where it’s strong: arms, legs and trunk work together, the water supports your weight, and the impact is close to zero.

Where it’s weak: it doesn’t load your bones (see below), and it doesn’t replace the twice-weekly muscle-strengthening work WHO asks for.

Coach Kes’s experience: what decides whether swimming is a good workout is technique. An adult who stops to gasp after every length is doing intervals by accident, with long rests at the wall. Once someone can swim steadily for 20 minutes, the pool becomes a proper training tool. Until then, the stroke is the limit, not their fitness. That’s most of what our adult lessons work on.

What the research measured: swimming and living longer

This is the claim behind a lot of “swimmers live longer” headlines, so it’s worth reading closely.

The big cohort study. Oja and colleagues (British Journal of Sports Medicine, 2017) followed 80,306 British adults for an average of 9.2 years, during which 8,790 people died. After adjusting for age, sex, smoking, alcohol, BMI, education, existing illness and other physical activity, people who swam had:

  • 28% lower risk of death from any cause (HR 0.72, 95% CI 0.65–0.80)
  • 41% lower risk of cardiovascular death (HR 0.59, 95% CI 0.46–0.75)

That’s a big effect. Now the catches, several of which the authors list themselves:

  • Swimming was measured with a few questions about the previous four weeks (how many days, how long, how hard), asked once. The authors note this short recall period “may have led to additional misclassification”.
  • It’s observational. People who swim may differ from people who don’t in ways a questionnaire doesn’t capture. The authors say they “cannot discount the possibility of residual confounding.”
  • In the same study, running showed no significant link once everything was adjusted for. The authors think that’s a quirk of their data, not proof running doesn’t help. One cohort doesn’t rank sports.

The later meta-analysis. In 2024, an overlapping team pooled the evidence across sports (Sports Medicine – Open, 76 studies, 2.6 million participants in total). For swimming and all-cause mortality they pooled 4 studies with about 371,000 participants: a 24% lower risk (HR 0.76, 95% CI 0.63–0.92). They rated the certainty of that evidence as “low”, because of high heterogeneity between studies. Running came out at 23% and cycling at 21%, which is basically the same ballpark.

My honest reading: regular swimmers do well, and swimming is very plausibly part of the reason. But nothing here shows it beats other regular aerobic exercise. If you’d rather cycle or run, the research supports that too.

Is swimming good for weight loss?

Swimming can help you lose some weight and body fat, but it isn’t especially good for weight loss, and in at least one trial it did worse than walking or cycling. What you eat matters more than which exercise you choose.

The modest good news. The 2018 Lahart and Metsios meta-analysis found swim training reduced body mass by 2.90 kg compared with controls (95% CI 0.78–5.02 kg) and body fat by about 1.9 percentage points. But in the small amount of data comparing swimming with running in healthy adults, the swimmers’ BMI after training was higher than the runners’.

The awkward trial. A 1987 randomised study (Gwinup, American Journal of Sports Medicine) gave young women with mild to moderate obesity up to 60 minutes a day of walking, stationary cycling or lap swimming, with no dietary restrictions. After about six months, the walkers had lost 10% of their starting weight, the cyclists 12%, and the swimmers nothing. It’s one old trial in one group of people, and the abstract doesn’t give group sizes, so don’t treat it as the final word. But it’s the trial everyone selling swimming for weight loss conveniently leaves out.

The “swimming makes you hungry” idea. The evidence here is thinner than the internet suggests:

  • In a 2005 study, 11 men did 45 minutes of exercise in water at 20°C or 33°C. After the cold session they ate 44% more than after the neutral one. But that was cycling on an underwater bike, not swimming.
  • In a 2011 Loughborough study, 14 men swam for 60 minutes. Their appetite went up in the hours afterwards, but they didn’t actually eat more at the buffet meals (9,749 kJ vs 9,161 kJ on the rest day, not a statistically significant difference).

So “swimming makes you hungry” is plausible but unproven. Overall, the evidence for swimming as a weight-loss tool is weaker than most people assume.

What a session actually burns. The 2024 Compendium defines 1 MET as roughly 1 kcal per kg of body weight per hour. So for a 70 kg adult, 30 minutes of recreational breaststroke at 5.3 METs comes to about 5.3 × 70 × 0.5 ≈ 185 kcal, and about 35 of those you’d have burned at rest anyway. That’s a rough estimate, not a measurement.

Coach Kes’s experience: the adults who change shape through swimming are the ones who swim three or four times a week for months, not the ones who swim hard once a week and reward themselves afterwards. Choose swimming because you’ll keep doing it, not because you think it burns more.

What swimming won’t do

It won’t build your bones. A 2016 meta-analysis of 14 studies on children and teenagers (Sports Medicine) found young swimmers had bone mineral density similar to sedentary children and lower than kids in high-impact sports. The authors concluded swimming “does not appear to be an effective sport for improving BMD”. A 2018 meta-analysis of young adults found the same pattern. An earlier review stressed that swimming “does not seem to negatively affect bone mass”, so it’s not harmful, just not bone-building. If bone health matters to you, or you’re a parent thinking long-term, add something with impact or resistance: running, jumping, or resistance training.

It won’t fix your posture or scoliosis. I’ve covered this in the backstroke guide: the evidence is mixed at best, swimming isn’t a treatment for a structural spinal condition, and you should be wary of anyone selling lessons on that basis.

Blood pressure: probably helps, with a footnote. A 2018 meta-analysis of 14 randomised trials (452 people) found regular aquatic exercise lowered systolic blood pressure by 8.4 mmHg and diastolic by 3.3 mmHg. But “aquatic exercise” includes water aerobics, results varied a lot between trials, and the abstract reports significant drops only for people with high blood pressure, for endurance exercise, and for aquatic exercise other than swimming. It gives no significant result for swimming on its own. The authors’ verdict: “Like exercise on land”. Good, not special.

Benefits of swimming breaststroke

In my experience, breaststroke is the stroke most Singapore adults learn first, so it gets its own section.

The numbers: recreational breaststroke is 5.3 METs in the 2024 Compendium, squarely moderate intensity, so it counts towards your 150 minutes. Training-pace breaststroke is 10.3 METs, about the same as fast freestyle in the same table. So “breaststroke is the lazy stroke” isn’t true. It’s only lazy when it’s swum slowly.

Coach Kes’s experience: breaststroke’s real advantages are that you can see where you’re going and breathe every stroke, which is why nervous adults settle into it. The fault I see most is the head-up version, face out of the water the whole time. It strains the neck, drops the hips, and makes the stroke far harder work than it needs to be. Learning to put your face in and breathe on the pull is usually the biggest single improvement. For balance, add backstroke; for distance, the front crawl guide is the next step.

The benefit no other exercise gives you

Running makes you a better runner. Swimming is the only exercise that also makes you safer around water, and that matters most for children.

I’ve gone through the drowning figures, and the five skills that actually keep someone alive, in What Water Competency Actually Means. Short version: swimming a few laps in goggles and surviving an unexpected fall into deep water are not the same thing, and the second is the benefit worth paying for.

So, should you swim?

If you enjoy it, your joints don’t like running, or you want exercise that also keeps your family safer near water: yes. It counts fully towards your WHO and HPB targets.

If your main goal is weight loss, swim because you’ll stick with it, and fix your diet. If your main goal is bone health or strength, swim and do something else.

And if the thing stopping you is that you can’t swim a continuous 20 minutes yet, that’s a technique problem, and it’s very fixable. WhatsApp me with where you’re at and I’ll tell you honestly how far you are from it.

Sources