Swimming benefits the heart and eases pressure on the joints, which places it among the endurance activities most recommended after age 50. Practiced in a pool or in open water, it engages the whole body without the ground impact of running. Large cohort studies and several randomized trials have measured its effects on blood pressure, cardiovascular mortality, and joint pain. This article details five proven effects, with the studies that document them.
In brief – Swimming benefits include measurable improvements in cardiovascular health and a reduced mechanical load on the joints, thanks to the buoyancy of water, which offsets most of the body’s weight during exercise. A British cohort of 80,306 adults links regular swimming with a 28% lower all-cause mortality risk and a 41% lower cardiovascular mortality risk, compared with no regular sport (Oja et al., 2017). A randomized trial in adults over 50 found that twelve weeks of swimming lowered systolic blood pressure from 131 to 122 mmHg and raised carotid artery compliance by 21% (Nualnim et al., 2012). A meta-analysis of 13 trials in 746 patients with knee osteoarthritis confirms that aquatic exercise reduces pain and improves joint function compared with no exercise (Xu et al., 2023). Water’s buoyancy explains much of this joint protection, since it offsets a large share of body weight during effort.
Definition: swimming, a buoyant, low-impact activity
Swimming covers any style of swimming in a pool, the sea, or open water, at a moderate to vigorous intensity, done to maintain health rather than purely for performance. Unlike running or tennis, water supports roughly 90% of body weight when a person is immersed to shoulder height, which removes most of the impact the knees, hips, and lower back would otherwise absorb with every movement. This trait makes it, along with walking, one of the activities recommended by French health authorities for early-stage osteoarthritis.
The effort remains real on a cardiorespiratory level, though. Water’s hydrostatic pressure eases venous return to the heart, and the horizontal body position shifts how blood volume is distributed, two features that explain part of the vascular effects measured specifically in regular swimmers.
Mechanism: how swimming acts on the heart and joints
Two distinct mechanisms explain the effects observed in swimmers.
- On the cardiovascular system: horizontal immersion increases venous return and cardiac stroke volume, which, with regular training, leads to improved endothelial function and arterial compliance.
- On the joints: buoyant force reduces the compressive load carried by cartilage, while still allowing active muscle work around the joint, which helps preserve mobility without stressing it.
Water resistance, roughly 800 times greater than air resistance, continuously engages the stabilizing muscles of the trunk and limbs, a demand that running or cycling do not place on the body to the same extent.
The swimming benefits for the heart and joints, according to the science
A cohort of 80,306 British adults links regular swimming with a 28% lower risk of all-cause mortality (HR 0.72, 95% CI 0.65 to 0.80), compared with no regular sporting activity. Cardiovascular mortality risk falls by 41% in the same cohort (HR 0.59, 95% CI 0.46 to 0.75) (Oja et al., 2017). This is an observational association, not proof of direct causation, but the effect size exceeds the one measured for cycling in the same cohort.
On blood pressure, a randomized controlled trial in 43 adults over 50 with prehypertension or stage 1 hypertension found that twelve weeks of swimming lowered average systolic pressure from 131 to 122 mmHg. Carotid artery compliance increased by 21%, and cardiovagal baroreflex sensitivity also improved (Nualnim et al., 2012).
A landmark review published in Sports Medicine confirms that the coronary risk profile of regular swimmers is more favorable than that of sedentary people. The effect is sometimes smaller than that of land-based sports on certain markers, though, a reminder not to overrate any single type of exercise (Tanaka, 2009).
On the joint side, a meta-analysis of 13 randomized trials in 746 patients with knee osteoarthritis shows that aquatic exercise significantly improves pain, stiffness, and physical function compared with no exercise. This benefit on pain persists at three months (Xu et al., 2023).
The fifth documented effect is a direct reduction in mechanical load. When immersed to shoulder height, the body’s apparent weight drops by about 90%, which is why walking and swimming remain the two activities the NHS recommends for early-stage osteoarthritis.
In practice: when and how to add swimming
Swimming suits most profiles, including people who are overweight, older adults, or those with early-stage osteoarthritis of the knee or hip. It is less well suited, however, to building bone strength. Unlike running, the absence of ground loading limits its effect on bone mineral density, a point worth knowing when building a complete program, as detailed in our physical activity and longevity guide.
The table below compares it with other endurance activities on the criteria that matter most for the heart and joints.
| Activity | Joint impact | Measured cardiovascular benefit | Recommended frequency |
|---|---|---|---|
| Swimming | Very low, buoyancy supports about 90% of body weight | CV mortality -41% in cohort, systolic pressure -9 mmHg in 12 weeks | 2 to 3 sessions per week, 30 min |
| Running | High, repeated ground impact | Improved VO2 max and lipid profile | 2 to 4 sessions per week |
| Cycling | Low to moderate | Reduced CV mortality in cohort, smaller effect than swimming in the same study | 2 to 3 sessions per week |
| Brisk walking | Low | Dose-dependent cardiovascular benefit, widely documented | Daily, 30 min |
To place swimming within a broader cardio program, our article on running and cardiovascular health details the effects specific to impact exercise, to alternate according to joint tolerance. People already living with osteoarthritis will find further guidance in our article on osteoarthritis and longevity, as well as on the pillar page dedicated to mitochondrial dysfunction, a central mechanism of cardiorespiratory endurance.
Protocol: how much to swim for a measurable effect
Studies that measure a cardiovascular or joint effect nearly all rely on a similar format: two to three weekly sessions of 30 to 45 minutes, swum continuously at a moderate to vigorous pace. It takes at least 8 to 12 weeks to observe a measurable change in blood pressure or joint pain.
- Start with 20 to 30 minutes of continuous swimming, freestyle or backstroke, twice a week.
- Alternate swimming strokes to spread out the muscular effort and limit shoulder pain linked to repetitive freestyle.
- Increase duration before intensity, gradually, over several weeks.
- Add dry-land strength training: swimming alone is not enough to preserve bone density.
- Warm up the shoulders before every session, the joint most heavily used and most often injured among regular swimmers.
Medical advice beforehand remains useful for anyone with a known heart condition, before resuming an endurance activity after a long period of inactivity.
Frequently asked questions about swimming benefits
Does swimming build as much muscle as running?
Swimming engages more muscle groups in a single session, especially the upper body, than running does. It builds less bone density, though, because water removes the ground loading that stimulus requires. For complete strength gains, pairing swimming with dry-land resistance training remains the best-documented combination.
How much should you swim each week for a measurable cardiovascular effect?
The randomized trials that measured an effect on blood pressure or vascular function used two to three weekly sessions of 30 to 45 minutes, over at least 8 to 12 weeks. Below that volume, no study reliably supports a measurable cardiovascular benefit.
Is swimming suitable for knee or hip osteoarthritis?
Yes. Walking and swimming are among the activities French health authorities recommend for early-stage osteoarthritis, since water’s buoyancy sharply reduces the load on cartilage. A meta-analysis of 13 trials confirms improved pain and joint function among knee osteoarthritis patients doing aquatic exercise, one of the clearest swimming benefits for this group.
Which stroke is best for protecting the shoulders?
Excessive repetition of freestyle raises the risk of shoulder pain linked to subacromial impingement, the joint most heavily used in swimming. Alternating freestyle, backstroke, and breaststroke spreads the load across different muscle groups. A specific warm-up before each session also limits this well-documented risk among regular swimmers.
Does swimming lower blood pressure as quickly as walking?
Both activities lower blood pressure, but on different timelines and under different study protocols. The reference randomized trial on swimming measures a clear effect after twelve weeks, at three sessions a week, in adults with prehypertension. No direct comparison between the two has established which acts faster.
Medical disclaimer. The information provided here is for informational purposes only and does not constitute medical advice. It does not replace a consultation. Ask a healthcare professional before changing your diet, taking dietary supplements or starting a new practice, especially if you have a medical condition, are pregnant or are under treatment. Dietary supplements do not replace a balanced diet or medical follow-up.
