• Jennifer Aniston celebrates her 50th birthday on February 11, 2019.
  • Her trainer Leyon Azubuike says she works out three to seven days a week.
  • Jennifer's workouts include boxing, strength training, cardio, and more.

Whether you've stan-ed for Jennifer Aniston since her days on Friends, or you recently jumped on the Jen train after her role in Dumplin, there's no denying the actress is an icon. And today, she celebrates her 50th birthday-although tbh, she doesn't look a day over Rachel. (Seriously, I'll have whatever she's having...)

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Of course, Jen looks incredible on every red carpet she graces, but she works hard to stay fit, strong, and on top of her game. Her personal trainer Leyon Azubuike , co-owner of Gloveworx , tells Women's Health that Jen works out up to seven days a week for an hour and a half each session, depending on where they are in her training cycle.

Azubuike uses a training technique called "periodization" with Jen, which allows him to adjust things based on her schedule. "Depending on where we are in that cycle dictates the duration and intensity of Jens workout," he says. "If I know Jen isnt filming anything, its a different phase than if I know she has something coming up tomorrow. If shes going to be walking up to receive an award, Im not going to destroy her legs in the gym the day before." So, her workouts vary anywhere from three days a week at 45 minute sessions to those monster seven-workout weeks.

Still, her workouts are never easy. Since Azubuike and Jen both have chaotic schedules, they jump on any available time to break a sweat. "She has to respond when I say go," says Azubuike. "If she has a shoot at 3 a.m. and we need to work out before that, lets go...we respect each other in that regard, so its a constant back and forth with mutual respect and understanding." And he admits he's a tough trainer, so "she definitely should be commended, because when I get into go mode, Im in go mode."

View this post on Instagram A post shared by Leyon Azubuike (@leyon) on Aug 16, 2018 at 12:34pm PDT

"We box, we jump rope, we do strength training, we do a lot of work with resistance bands-were big on resistance bands," says Azubuike. "We rotate these things so its always hard, shes consistently being challenged-Im a big fan of switching things up, so the body reacts in a positive way and changes."

Azubuike says Jen loves boxing and core work. "Every core exercise I throw at her, she dominates it," he says. "She can hold a two- or three-minute plank rather easily."

To challenge her, Azubuike has Jen crank out a plank flow where she starts in a standard plank , then moves to a side plank , then moves to plank with shoulder taps , and so forth. "We do a lot of things that stretch the core, so well do things where shes hanging on a pullup bar, then she pulls her knees up and brings them back down." She also loves doing V-ups and using ab wheel. "Well use a situp to shock the body occasionally, but its not a major part of our core regimen."

View this post on Instagram A post shared by Leyon Azubuike (@leyon) on Nov 21, 2018 at 4:22pm PST

But don't worry, Jen isn't a master of everything in the gym-at least, not at first. Azubuike says she didn't love using the jump rope when he first introduced it into her routine because she found it a bit challenging (same). "I just made her keep on doing it, and now shes great at it."

Azubuike says the hardest part of working with Jen is finding new ways to challenge her. "Heres a woman who has always looked amazing, and I'm tasked with keeping it that way and elevating that even further."

Well, based on recent photos from her 50th birthday party, mission accomplished.

View this post on Instagram Love these ladies Celebrated this beauty last night Happy Bday JA! We all love you sooo! A post shared by Kate Hudson (@katehudson) on Feb 10, 2019 at 10:32am PST