Swimming, the Ultimate Low-Impact Exercise - The Science of Water Workouts That Are Gentle on Joints and Train the Whole Body

In Water You Barely Have to Support Your Own Weight

The reason swimming is called the ultimate low-impact exercise is buoyancy. When you get into water, buoyancy pushes your body upward, so the load your legs carry from your own weight drops sharply. How much it drops depends on how deep you go: chest deep is lighter than waist deep, and shoulder deep is lighter still. Once the water reaches your shoulders you barely have to support your own weight at all, and no landing impact reaches your knees, hips, or ankles.

When you run, every landing sends an impact of two to three times your body weight through the knee joint. For people with osteoarthritis of the knee or a lumbar disc herniation, land-based aerobic exercise is a fight against pain. In water, though, whole-body exercise is possible without loading the joints.

This benefit of buoyancy is exactly why aquatic exercise is used so widely in orthopedic rehabilitation. In the recovery period after surgery, or with rheumatoid arthritis or fibromyalgia, conditions in which exercising on land is difficult, the body can still be moved safely in water.

Why Swimming Is a Full-Body Exercise

Swimming is one of the few activities that trains the upper body and the lower body at the same time in a single movement. In freestyle, the arm stroke uses the latissimus dorsi, deltoids, and triceps, while the kick uses the quadriceps, hamstrings, and glutes. On top of that, the core muscles work constantly to keep the body stable in the water.

Water is roughly 800 times denser than air. Because the medium you push aside is in a completely different weight class, the resistance you meet is nothing like it is on land. Simply moving an arm through water loads it in a way that the same movement in air, holding nothing, never could. Water resistance also rises steeply as movement gets faster, so the load adjusts itself naturally to your fitness. Move fast and the load increases; move slowly and it falls. This is an advantage unique to swimming that no other exercise offers.

Calorie expenditure is impressive too. A 60kg person swimming freestyle for 30 minutes burns roughly 250 to 300 kcal, about the same as 30 minutes of jogging. The load on the joints is far lighter than in land-based exercise, yet the calorie burn is comparable. That efficiency is swimming’s greatest appeal.

What Swimming Does for Your Heart and Lungs

Swimming is extremely effective at improving cardiorespiratory fitness. Because water pressure acts on the rib cage, the breathing muscles (the diaphragm and the intercostals) have to work harder. This load on breathing raises lung capacity and breathing efficiency. People who swim regularly tend to have a lower resting heart rate and to move more blood with each beat.

Swimming is also useful for managing asthma. The humid air around a pool irritates the airways less, and coughing and breathlessness are said to be less likely than when you run while breathing in dry air. Some respiratory physicians list swimming among the exercise options, but asthma varies a great deal from person to person, so it is reassuring to talk to your own doctor before you start.

Improvements in blood pressure have been reported as well. There are reports of blood pressure falling in people who swam regularly over a period of several months. The likely background is that blood vessels throughout the body dilate more readily and that body weight and body fat come down. Swimming is no substitute for medication, but because it is easy to keep up, it is a strong option for preventing and managing high blood pressure.

Water Walking as an Option

For people who cannot swim, or who feel resistant to the idea of swimming, water walking is a good choice. Simply walking through a pool uses more energy than walking on land at the same speed, because you have to push the water aside. Buoyancy keeps the load on the joints light while the resistance of the water delivers a strength-training effect. You do not have to swim to get the full benefit of aquatic exercise.

The knack of water walking is to take long strides and swing your arms widely. To make the most of the water’s resistance, move slowly and powerfully. Adding sideways and backward walking to forward walking stimulates muscles you do not normally use.

Many public pools set aside lanes or classes specifically for water walking. Plenty of older adults and people in rehabilitation take part, so there is no need to feel self-conscious about not being fit. Start with 20 minutes and stretch it to 30 or 40 minutes once you are used to it.

A Practical Guide to Getting Started

To start swimming you need three things: a swimsuit, goggles, and a swim cap. Beginners should choose a comfortable fitness swimsuit rather than a racing one. Goggles are essential for protecting your eyes and securing your field of view. They prevent chlorine irritation and take the edge off any fear of being underwater.

If you are not confident in your swimming, starting with kick practice on a kickboard is effective. Resting your upper body on the board and moving forward with the kick alone lets you get used to the water while building lower-body strength. Many pools lend kickboards out.

Aim for two or three sessions a week of 30 minutes each. At first it is fine to swim 25m, rest, and repeat. The distance you can cover without stopping will stretch naturally as you keep going. What matters is continuing at your own pace without forcing it.

Precautions and Risk Management

Swimming is a safe form of exercise, but there are a few things to watch. Pool chlorine damages skin and hair, so shower it off as soon as you finish. If your skin dries out easily, apply a moisturizer after swimming.

Water getting into the ear can cause otitis externa, better known as swimmer’s ear. After swimming, tilt your head to let the water out and dry the ear gently with a towel. If you swim often, consider earplugs.

To prevent accidents while swimming, do not swim when you are unwell or after drinking alcohol. Avoid swimming right after a meal as well; waiting at least an hour is safer. If you swim alone, choosing a pool with a lifeguard on duty is another important safety measure.

Swimming Can Be a Lifelong Sport

Swimming’s greatest appeal is that you can keep doing it as you age. Land-based sports put more strain on the joints as the years pass, which makes them hard to continue. Swimming, thanks to buoyancy, can be enjoyed safely into your seventies and eighties.

Masters swimming meets include competitors over the age of 90. Beyond competition, older adults all over the world keep swimming as a way of maintaining their health. Exercise in water slows the decline in muscle strength and balance that comes with age, and helps people stay independent for longer.

It is never too late to start swimming. Even if you cannot swim, you can begin with water walking. The moment you step into the water, your body is wrapped in buoyancy, your joints are released, and your mind grows calm. Aquatic exercise is one of the smartest exercise choices there is: gentle on the body, and dependable in its effects.