Tennis Wellness See all topics Follow

As seven-time grand slam singles champion Venus Williams said upon her comeback to the sport late last month: “Do you know how hard it is to play tennis? … You’re running the whole time, lifting weights and just, like, dying. And then you repeat it the next day.”

Fellow American Frances Tiafoe voiced a similar belief last year: “It’s the hardest sport in the world,” he told Sky Sports.

So, what is it that makes tennis so challenging? Are singles tennis players the fittest of all athletes in any sport?

Sports scientist Dr. Mark Kovacs believes so, heartily agreeing with Tiafoe. The former tennis player has dedicated years to researching fitness, training and recovery methods across sports and has worked with athletes from the NBA, MLB, US women’s national soccer team (USWNT) and WTA and ATP Tours.

Speaking to CNN Sports, Kovacs admits he’s slightly biased due to his affinity for the game he grew up playing, but also has decades of research experience to back his belief that tennis players are among the fittest – and toughest – athletes in the world.

Technical and physical attributes

It’s hard to think of a sport that requires such an extreme spectrum of skills as tennis.

Maximum oxygen uptake (VO2 max), maximum heart rate, resting heart rate and heart rate variability to analyze recovery are usually t