Before tennis fans get the wrong idea, three of the top players appear in an issue of Sports Illustrated, and it’s not the Swim Suit edition. Serena Williams, Caroline Wozniacki and Novak Djokovic have made the magazine’s Fittest 50 issue.

Sports Illustrated, with a panel of training and performance experts, have picked the top 25 fittest female and male athletes in various sports. Over the last year, the experts considered the demands and risks, durability, training regimens of the respective sports. They also looked at other factors including power, speed, strength, agility, endurance, and flexibility.

Serena Williams

Serena Williams made it to number 10 even after 14-month maternity leave and being bed ridden for six weeks following pregnancy complications. Williams managed two runner-up finishes in three major appearances.

Caroline Wozniacki

Caroline Wozniacki was the only other female tennis player to make the list at 23rd. The marathon running Dane has always been in superior fitness, but her challenge increased after being diagnosed with rheumatoid arthritis. In response, Wozniacki’s workout, which consists of speed training, boxing, and yoga, has also added more mobility exercises.

Novak Djokovic

The lone male player to make the list at number 4 was Novak Djokovic. The number one Serb lost a part of 2017 to an elbow injury. He returned to form in 2018 by claiming back-to-back championships at Wimbledon and the U.S. Open. Always lean and Limber, the 31-year-old Djokovic owes much of his comeback to injury rehabilitation, conditioning, diet, and strong mental health.

Overall, tennis has some of the fittest athletes in the world. There are many other players that could have been included in Sports Illustrated’ Fittest 50 list, but Williams, Wozniacki, and Djokovic are great proof of the success due to their workouts and conditioning.