One hour on the treadmill or one hour in the pool – which does more for your heart, circulation and fat burning? We looked at the key studies: large observational studies with more than 120,000 people, controlled training trials and the official tables of energy use. The answer is more interesting than “swimming is always better”.
- Heart and circulation: swimming does very well in studies. In a British study of 80,306 adults, swimmers had a 41 % lower risk of dying from cardiovascular disease (Oja 2017).
- Blood pressure: 12 weeks of swimming training lowered the upper blood pressure value in people over 50 from 131 to 122 mmHg on average (Nualnim 2012).
- Calories: one hour of front crawl at a moderate pace uses clearly more energy than leisurely walking on a treadmill and about as much as easy jogging (Compendium 2024).
- Fat loss: the studies are mixed. Swimming can help you lose fat, but it is no miracle – consistency, intensity and diet make the difference.
Heart and circulation: what the large studies show
Two large observational studies compared swimmers with people who run, walk or hardly exercise:
- 80,306 adults from England and Scotland (Oja et al., 2017): after an average of 9 years, people who swam regularly had a 28 % lower risk of death overall and a 41 % lower risk of dying from cardiovascular disease. For running, the link was no longer statistically clear once age, smoking, weight and other factors were taken into account.
- 40,547 men from the USA (Chase, Sui & Blair, 2008): swimmers had a 53 % lower risk of death than men who did no exercise, 50 % lower than walkers and 49 % lower than runners – also after accounting for age, weight, smoking, alcohol and family history.
The honest view: both are observational studies. They show a link but do not prove that swimming is the cause. People who swim may also live more healthily in other ways. The researchers adjusted for many factors, but not all. What is certain: in these studies swimming does at least as well as running and walking.
Blood pressure and blood vessels: training trials with swimmers
Stronger than observations are trials in which people are randomly assigned to a training group:
- People over 50 with slightly raised blood pressure (Nualnim et al., 2012): 43 participants not taking blood pressure medication swam for 12 weeks or did relaxation exercises. In the swimming group, the upper blood pressure value fell from 131 to 122 mmHg. The elasticity of the carotid artery rose by 21 %, and vessel function improved too. Nothing important changed in the comparison group.
- Women with mild high blood pressure (Mohr et al., 2014): 62 women trained for 15 weeks, about three times a week. One group swam 6–10 short 30-second sprints, the other swam for an hour at an easy pace. The upper blood pressure value fell by 6 and 4 mmHg, and resting heart rate dropped by 5 beats per minute in both groups.
What is interesting about the second study: the sprint group trained for only 15–25 minutes per session and achieved heart effects similar to the group that swam for a full hour.
Calories: one hour of swimming against one hour on the treadmill
Energy use is measured in METs (1 MET is roughly the energy you use at rest). The Compendium of Physical Activities, updated in 2024, lists these values:
- Front crawl, slow and easy: 5.8 METs
- Front crawl, moderate pace: 8.0 METs
- Front crawl, fast and hard: 9.8 METs
- Breaststroke, leisurely: 5.3 METs
- Leisurely walking: 3.5 METs
- Running at about 10 km/h: 9.3 METs
As a rough rule, a person uses about METs × body weight in kg kilocalories per hour. For someone weighing 75 kg, one hour of front crawl at a moderate pace is about 600 kcal, one hour of leisurely walking about 260 kcal and one hour of running at 10 km/h about 700 kcal. These are averages – individual values can differ a lot.
In other words: against an hour of leisurely walking on the treadmill, front crawl clearly wins. Against jogging it is roughly level. And: if your technique is not good, you will not manage an hour of front crawl – in swimming, technique is the key to burning energy.
Fat burning: what the studies really say
To be honest, the picture here is mixed:
- Swimming better than walking (Cox et al., 2010): about 120 previously inactive women aged 50 to 70 swam or walked for 40 minutes three times a week for 12 months. In the short term, swimming improved fat distribution and insulin more than walking; in the long term, body weight and blood fats.
- Less fat through swimming training (Mohr et al., 2014): in the study mentioned above, fat mass fell by 2.2 kg (one hour of easy swimming) and 1.1 kg (sprints) after 15 weeks.
- No weight loss (Gwinup, 1987): in an older study of young women with overweight, the walking and cycling groups lost about 10–12 % of their weight after 6 months, while the swimming group lost none. The study is small and methodologically weak, but it is still often quoted.
Our conclusion: swimming can help with fat loss, but the evidence is less clear than for the heart. Treadmill or pool – you lose fat by training regularly, increasing the challenge and watching what you eat.
Where swimming clearly beats the treadmill
- Joints: in water, buoyancy carries much of your body weight. Knees, hips and back are spared – ideal with overweight or joint problems, when an hour on the treadmill hurts.
- Whole-body training: in front crawl, arms, shoulders, core and legs all work at the same time. On the treadmill it is mainly the legs.
- Sticking with it: what is gentle and fun is what you keep doing. In the Cox study, the weight benefits showed up over the whole year.
Read more about the effects of front crawl in our article Front crawl for adults: what the research says about health.
Getting more out of your hour in the water
- Technique first: with clean front crawl technique and calm breathing you swim longer and faster – and use more energy.
- Add intervals: short, fast lengths with breaks work about as well on heart and blood pressure as a long, easy session (Mohr 2014).
- Stay regular: two to three times a week, week after week, does more than one long session.
- Don’t forget your diet: training alone is rarely enough for clear fat loss.
Learn front crawl in Graz and Gratkorn
Many adults can swim but cannot do front crawl for long – and that is exactly where the biggest gain for the heart and calorie use lies. In private 1:1 or two-person lessons at Bad zur Sonne in Graz, you learn breathing, body position and arm stroke step by step (our courses). From March 2027 there is also the evening course “Learn front crawl” at the Gratkorn indoor pool (courses in Gratkorn).
Frequently asked questions
Is swimming better for the heart than running?
In large observational studies swimming does at least as well as running: in the British study by Oja (2017), swimmers had a 41 % lower risk of dying from cardiovascular disease. Such studies show links, not proof.
Does one hour of swimming burn more calories than one hour on the treadmill?
Compared with leisurely walking on a treadmill: yes, clearly. Moderate front crawl is 8.0 METs, leisurely walking 3.5 METs. Compared with jogging at 10 km/h (9.3 METs), front crawl is roughly level.
Can you lose weight by swimming?
It can help: in the study by Cox (2010), swimming improved body weight more than walking in the long term. An older study, however, found no weight loss. Consistency, intensity and diet are what count.
How often should I swim?
Two to three times a week worked well in the training studies. Even 15–25 minutes with short, fast sections can improve blood pressure and resting heart rate.
Sources
- Oja P, Kelly P, Pedisic Z, et al.: Associations of specific types of sports and exercise with all-cause and cardiovascular-disease mortality: a cohort study of 80 306 British adults. British Journal of Sports Medicine 51(10), 812–817 (2017)
- Chase NL, Sui X, Blair SN: Swimming and All-Cause Mortality Risk Compared With Running, Walking, and Sedentary Habits in Men. International Journal of Aquatic Research and Education 2(3) (2008)
- Nualnim N, Parkhurst K, Dhindsa M, et al.: Effects of swimming training on blood pressure and vascular function in adults >50 years of age. American Journal of Cardiology (2012) – report on Medical Xpress
- Mohr M, Nordsborg NB, Lindenskov A, et al.: High-Intensity Intermittent Swimming Improves Cardiovascular Health Status for Women with Mild Hypertension. BioMed Research International (2014)
- Cox KL, Burke V, Beilin LJ, Puddey IB: A comparison of the effects of swimming and walking on body weight, fat distribution, lipids, glucose, and insulin in older women. Metabolism 59(11), 1562–1573 (2010) – University of Western Australia media statement
- Gwinup G: Weight loss without dietary restriction: efficacy of different forms of aerobic exercise. American Journal of Sports Medicine 15(3), 275–279 (1987)
- Herrmann SD, Willis EA, Ainsworth BE, et al.: 2024 Adult Compendium of Physical Activities. Journal of Sport and Health Science 13(1), 6–12 (2024) – values for water activities
This article does not replace medical advice. If you have health concerns, please speak to your paediatrician or GP.
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