In his teens and 20s, he’d train for as many as five hours a day. “Now that I’m older, I can’t work out like that,” he says. “The intensity is the same, but the training is smarter and more specific.” These days, his time in the gym is devoted to mobility, agility and isometric exercises.

During lockdown, he had a workout bubble with his cousins who kept him on his toes and in his garage gym. But for the first time in over a decade, he was apart from both his fitness coach, Joan Forcades, and his physiotherapist, Rafael Maymo, whom he credits with prepping his body for workouts and matches—and putting it back together after.

Jumping back into a grueling tournament schedule after a six-month hiatus hasn’t been easy. A lower-back injury plagued Mr. Nadal during the Australian Open in February and sidelined him from two tournaments.

“My goal is to play better every time I step on the court,” he says. “I’ve been off-pace, but it takes one or two key matches to get back the rhythm.” Mr. Nadal said his back was feeling better before his first matches in the Italian Open, which began May 8, and his performance has been back to top form. On May 14 he defeated Alexander Zverev to reach his 12th semifinal in Rome. He will defend his title at the French Open, which kicks off May 30.

The Workout

In recent years, Mr. Nadal moved away from heavy cardio and weight training. He now focuses on high-intensity workouts that emphasize agility and speed and exercises that strengthen the stabilizing muscles around his knees and shoulders.

He’s scaled back his on-court training to a still-daunting 2 to 2½ hours almost daily. For cardio, he alternates between intervals on the elliptical, rowing machine or treadmill with a 15% incline. Other days he does a circuit workout that mixes jump rope and ladder drills with five or six strength exercises.

Twice a day he runs through a series of shoulder exercises. “If the small muscles around the shoulder fail, your game is dead,” he says. To strengthen the four muscles of the rotator cuff that help move and stabilize the shoulder, he uses resistance cables on a Technogym Kinesis machine to perform internal and external rotations.

To strengthen his quads, he performs leg extensions on a machine. He does five reps with 10 kilograms (22 pounds) and holds for 45 seconds at the bottom of each rep. He then performs 15 dynamic reps using 30 kilograms. Bosu ball squats and calf raises are also staples. He uses a resistance band for glute exercises such as clamshells, bridges and lateral lunges. “Getting my glutes strong and firing has really helped with my back,” he says.

The Diet

Wiser in time: “My diet was 100% a disaster when I was younger,” he says. “I don’t follow any crazy diet, but I have adopted better eating habits with age.”

Breakfast: Bread with olive oil and orange juice.

Post-workout recovery: A vanilla protein shake.

Dinner: When he has time, which isn’t often, he loves to cook. His go-to dish is seafood pasta. Before a match he typically has rice with fish and vegetables.

Indulgences: Mr. Nadal enjoys chocolate and red wine from Spanish producer Bodegas El Nido in small amounts.

Essential Gear

Mr. Nadal’s carry-on bag always contains a set of resistance bands.

Playlist

Mr. Nadal listens to music before matches and the playlist depends on his mood. “Sometimes I’ll put on opera,” he says. “Sometimes punk rock or reggae. But never heavy metal.” Bon Jovi and Julio Iglesias are two favorites.

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