A retired Navy SEAL commander who wakes up at 4:30 a.m. to work out shares his weekly fitness routine

Regardless of when you read this, Jocko Willink woke up today before dawn to get in a hard workout.

As a Navy SEAL, Willink learned the extent to which the human body and mind can be pushed. And after he retired in 2010, after commanding the most decorated US special-operations unit of the Iraq War, he decided to share with the public some of the lessons he learned about discipline.

His new book, "Discipline Equals Freedom: Field Manual," is a practical collection of the leadership philosophy he has taught with his former platoon leader, Leif Babin, through their leadership consulting firm Echelon Front, as well as exercise and diet routines he's discussed on his hit podcast.

The book contains three detailed sets of four-day exercise routines for beginner, intermediate, and advanced skill levels. Willink, who has a decked-out home gym in his garage and a black belt in Brazilian jiu-jitsu, typically will stick with the advanced exercises, but he'll work in some lighter basics when he's traveling or recovering from a string of heavy workouts.

Business Insider recently asked Willink about his overall workout philosophy and broke down his approach into components that could be adapted for any fitness level.

Get out of bed while everyone else sleeps.

Willink shares an image of his digital wristwatch with his thousands of Twitter followers every morning, and it always reads about 4:30 a.m. It's a habit he picked up in the SEALs after noticing that the highest performers woke up the earliest.

As a civilian, it can be easy to have your entire day filled, and exercise usually doesn't get top priority. Willink's advice is simple: Start going to bed earlier, get your gym clothes ready before you go to sleep, get up while the rest of your coworkers are sleeping, and jump into your gym shorts.

Warm up.

You need to get your blood flowing and your muscles loosened up before you begin working out. Willink's typical warm-up is as follows:

• Hang on a pull-up bar or equivalent for 10 to 15 seconds.

• Hold a push-up position for 10 to 15 seconds.

• Get on the ground, face down, and stretch your hips, arching your head to ceiling to stretch abs.

• Raise hips to the sky and stretch your back (aka the downward dog pose in yoga).

• Do a slow squat and hold at bottom for 10 to 15 seconds.

• Do a burpee.

• Do a few jumping jacks.

• Do a pull-up, do a push-up, do a "dive-bomber push-up" (aka "chaturanga dandasana" in yoga), do a slow squat to the ground and up, do a burpee. End this cycle with five jumping jacks; repeat the cycle, now doing two repetitions of each exercise, each set followed by 10 jumping jacks; repeat the cycle, now doing three repetitions of each exercise, each set followed by 15 jumping jacks; repeat the cycle with this pattern until reaching five repetitions and 25 jumping jacks.

After warming up, consider doing very light movements of the exercises you're about to do, for the purpose of loosening up while also working on muscle memory.

Day 1: Pull.

Pulling exercises that Willink does are based on the standard pull-up motion. "And all you need to do pull-ups is a set of rings or a pull-up bar and you can handle that workout."

Willink is a fan of weighted kipping pull-ups, wherein you use a swinging motion with your shoulders and hips while adding weight to your body through a vest or other means, but it's important to first master standard pull-ups with various grips.

Day 2: Push.

Push day "is based on push-ups and dips, and all the exercises that are associated with those types of movements," Willink said.

On his push day, Willink may put on a weight vest or belt with about 20% of his body weight and do five sets of ring dips.

Day 3: Lift.

Plenty of people say they're "going to go lift," but when Willink uses that term, he specifically means all exercises in which he's lifting weight off the ground and over his head or when he's doing deadlifts.

Power lifting exercises Willink likes, like the clean-and-jerk and snatch movements, are very dangerous when done improperly, and Willink recommends in his book that no one attempt them without first building a foundation and learning proper lifting techniques from someone who knows what they're doing.

If you don't have experience with a barbell, Willink recommends mastering the handstand motion, building up endurance by holding the position until you get tired. You can use a wall as support to start.

Day 4: Squat.

Bodybuilders and athletes love squats because even though they're primarily a leg exercise, they require a full use of your body and can yield big results.

Willink likes to do a variety of squats, including overhead squats, back squats, and front squats. Beginners should first build a base with body weight lunges and then move on to standard squats.

Work that gut.

On each of these four days, Willink incorporates a few minutes of working out his "gut" — "which is what we call in the SEAL teams when you're working your 'core,'" he said.

This is pretty basic across all skill levels, and includes exercises like crunches and hanging leg raises.

Get in some cardio each day.

Each of the four days also has a "MetCon" component, which is short for Metabolic Conditioning, and that's just what's popularly called "cardio." For Willink, this means getting his "heart rate up for very intense short periods of time."

For all skill levels, this essentially means pushing yourself after your main exercises with either a few sets of sprints or a hard one- to two-mile run. Pushing yourself on a stationary bike or rowing machine also works.

Have fun.

Willink is adamant that he's sharing his workouts as a way to help get people started or try something new, and isn't declaring his way is the best. He just took a particular approach based on exercises he learned improved his functional athleticism required of him as a SEAL, and which now help him in Brazilian jiu-jitsu (he's a black belt and instructor at the gym he owns in San Diego).

"Some people, they take their form of working out as a religion that they think is better than everyone else's," he said. "I'm not like that. If you have a better way to work out and you can teach it to me, and I find it to be useful, and gets me in better shape, I'm all about."

Also, it's important to build in recovery days into this four-day cycle, and give yourself time to do some lighter exercise, like a jog or calisthenics.

The point is, he said, is do something early every morning that activates both your body and mind, and enjoy yourself. The point is to get up and, as Willink says, "Get some."