Singer-actor Yui reveals swimsuit figure — the workouts behind her 172 cm, 51 kg frame

Singer and actor Yui has drawn fresh attention to the weight-management benefits of swimming and running after sharing footage of herself swimming in the ocean. Both are classic aerobic exercises, but they work the body in different ways. Experts say combining the two can improve cardiovascular endurance and help reduce body fat.

On Thursday, Yui posted vacation photos and videos from Jeju on her SNS, appearing in a swimsuit and swimming freely in the sea, showing off her skills in the water.

Yui competed as a swimmer before debuting with the group After School and is known to exercise consistently. She has recently taken up running alongside swimming. Having shed 8 kilograms in the past, she has since maintained a height of 172 centimeters and a weight of 51 kilograms, managing her physique through exercise and diet rather than restrictive eating.

Swimming engages muscles throughout the body, including the arms, shoulders, back, core, hips and legs. Because the body must push against water resistance, it builds cardiovascular endurance while activating multiple muscle groups at once. Switching between strokes — freestyle, breaststroke and backstroke — targets different muscles, making it easier to achieve a full-body workout.

Swimming can also support weight management. The foundation of weight loss is consistently burning more calories than one consumes, and swimming increases energy expenditure depending on duration and intensity, making it a useful aerobic tool for reducing body fat.

Another advantage of swimming is its low impact on the joints. Buoyancy reduces the load on the body, so the knees, ankles and lower back absorb far less impact than they do during running. That is why swimming is often recommended for people who are overweight, have joint pain or are returning to exercise after a long break.

Ocean swimming places different physical demands on the body than pool swimming. Dealing with waves, currents, water temperature and shifting directions requires greater balance and core stability. Those challenges also bring added risk. Swimmers should avoid venturing far out alone, check current conditions and weather forecasts, and, if inexperienced, stay within zones monitored by lifeguards.

Running, which Yui also enjoys, is equally effective for weight management. It raises the heart rate faster than walking and repeatedly engages the large muscles of the lower body, increasing energy expenditure. Consistent running can improve cardiovascular endurance and help manage body weight and waist circumference.

Running's biggest advantage is accessibility. All it takes is a pair of sneakers, and a session can begin right outside the front door — in a park or on a track. When it comes to weight loss, building a sustainable habit matters more than pushing hard in a single session, and running fits easily into daily life.

Because running involves repeated impact while bearing full body weight, it can strain the knees, ankles and lower back. Beginners should start by alternating brisk walking with light jogging rather than running long distances from the outset. Reducing mileage when pain arises and wearing well-cushioned shoes can also help.

Combining swimming and running adds variety to a fitness routine. Running places weight-bearing stress on the lower body and bones, while swimming uses water resistance to work the whole body with less joint strain. Alternating between the two prevents overloading any single area while maintaining overall training volume.

One approach is to run two to three times a week to build cardiovascular endurance and lower-body strength, then swim on other days to work the full body while easing joint stress. Adding basic strength exercises — squats, lunges, planks and hip bridges — about twice a week can help minimize muscle loss during weight loss and build a leaner physique.

Exercise alone has its limits when it comes to losing weight. Even with regular swimming or running, frequently eating high-calorie foods after workouts can undercut the results. Yui is said to have structured her meals around chicken breast, eggs, salad and sweet potatoes during her weight-loss period. A diet that balances protein, vegetables and an appropriate amount of carbohydrates supports the benefits of exercise.

Staying hydrated before and after swimming and running is also important. Outdoor running and ocean swimming in summer particularly raise the risk of dehydration due to heavy sweating and fluctuating body temperature. Drink enough water before and after exercise, and anyone who feels dizzy, develops a headache or experiences severe fatigue should stop immediately and rest.

Experts emphasize that combining swimming and running, as Yui does, can support weight management and improve fitness — but the key is keeping it up consistently at a level suited to one's own physical condition. Rather than trying to lose weight quickly, protecting the joints, preserving muscle mass and managing diet alongside exercise are what sustain a healthy physique over the long term.