Actress Kim Hye-soo recently showcased her impressive fitness routine, revealing how she maintains her sculpted physique through high-intensity water workouts.
On Oct. 28, Kim shared several workout videos on social media without additional captions, offering fans a glimpse into her aquatic training regimen.
The footage showed Kim exercising in an "Endless Pool," which generates a powerful artificial countercurrent. She completed a high-intensity swim session, performing stationary freestyle sprints directly against the current.
Kim then transitioned to a floating mat anchored on the water’s surface, executing challenging core exercises—including twist planks and bicycle crunches—set to fast-paced music. Her core stability stood out as she maintained form atop the constantly shifting surface.
Kim is well known for utilizing diverse aquatic workouts to stay in shape. She previously shared videos of herself "water running" in a full-body swimsuit, as well as performing underwater cycling and snorkeling drills.
So, what physiological benefits do Kim’s signature water workouts offer compared to conventional land-based exercise?
Caloric Burn and Low-Impact Conditioning
Swimming combines aerobic conditioning with resistance training, making it exceptionally effective for burning body fat and toning muscle throughout the body. Moving against water resistance—which is denser than air—burns more calories in the same duration. A 70 kg (154 lb) adult burns approximately 360 to 500 calories during an hour of swimming.
The continuous propulsion of arms and legs engages major muscle groups, including the glutes and quadriceps, effectively building lower-body strength.
Another major advantage of aquatic exercise is its minimal joint impact. On land, high-impact activities put substantial stress on weight-bearing joints, increasing the risk of strain or injury for individuals with back or knee vulnerabilities. In water, buoyancy neutralizes gravity, significantly reducing the load on the spine and knees. This allows individuals recovering from injuries or managing arthritis and joint pain to train safely and effectively.
Core Activation on Unstable Surfaces
The twist planks and bicycle crunches Kim performed on the floating mat are comprehensive full-body movements targeting the abdominal and core muscles.
Executing these exercises on a floating mat rather than a rigid floor dramatically amplifies their effectiveness. Constantly adjusting balance to avoid falling into the water engages not only the visible rectus abdominis and side obliques, but also deep stabilizing muscles like the transverse abdominis, which are difficult to activate during standard floor routines.
Training on an unstable surface also enhances neuromuscular coordination and balance. As the water shifts beneath the mat, the nervous system rapidly coordinates fine adjustments across the wrists, shoulders, and pelvis. Furthermore, because momentum can easily tilt the mat, movements must be controlled entirely through deliberate muscle contraction, maximizing workout intensity.
On average, a 30-minute high-intensity core session on a floating mat burns between 300 and 400 calories—1.5 to more than double the caloric expenditure of performing the same movements on a terrestrial mat.
