Players need to be totally committed to their fitness.
"Tennis is a brutal game that takes no prisoners," Serena Williams' fitness coach, Mackie Shilstone, wrote on nola.com. According to Shilstone, playing tennis is enormously demanding on the body because of "the travel, time zone changes, weather delays, and the constant change of direction of the impact on the knees and lumbar spine from playing on three different surfaces - clay, hard court and grass - during the competitive season." Williams is "committed to make the necessary sacrifices - and there are plenty of them - to walk on the court in the best possible physical and mental state to take on mostly younger opponents."
Maria Sharapova agrees, with the Russian once telling Harper's Bazaar: "Playing professional tennis requires major dedication. If you take more than three days off, you start to lose lean muscle."
Get plenty of sleep.
"When I was in my 20s, seven hours of sleep a night was enough, and I would wake up and be ready to go. But in your 40s you definitely need more sleep," Kimiko Date, who played into her 40s, told wtatennis.com. "I liked to sleep a lot, at least eight hours a night and sometimes nine or ten hours, and during tournaments I slept for even longer."
Keep learning about your body.
"Players now have a better understanding of what they should be doing, and also what they shouldn’t be doing," Martina Navratilova told wtatennis.com. "Older players now know more about how to take care of themselves because they've been doing it their whole career so the body's not as beat-up. Even though the tennis is now more physical, the players are playing less, athletic health care is so much better, travel is easier, and the food and drink the athletes consume has been taken to a whole new level. All of this makes a big difference in the long run - it saves the body and the mind, helps you stay hungry and motivated, and before you know it, you’re pushing 40 while still winning major titles."
Sometimes you have to know when to ease off and rest your body.
"I think I’ve paced myself in terms of training," Venus Williams said in an interview with Health magazine. "With the amount of tournaments and the amount of training and also knowing how to push your body, trust me, I’ve pushed my body a lot. But you have to know when to say when, too. And also it’s very draining mentally to keep this level up, so I also like to take mental breaks. I would love to keep playing even more."
Increase the amount of time you spend working out.
"I probably now spend a little more time at the gym," Venus Williams told Health, "[but] I’ve always spent plenty of time at the gym."
You'll need to be even stricter with your diet.
"The older you get, the more you have to think carefully about what you eat, as your body takes longer to recover," Date told wtatennis.com. "So before a match, or before a training day, eat a lot of carbohydrates and afterwards you need a lot of protein. It’s OK to sometimes have chocolate, cake and ice cream, but only occasionally and not when you’re getting ready to compete."