Zac Efron’s Dirty Grandpa Workout Revealed

Zac Efron’s 2016 buddy road-trip movie Dirty Grandpa sees him teaming up with a Hollywood legend. In the process he displays his body – a lot! To keep the audience, many of whom flood to the theater just to gaze at his physique, satisfied, he had to train his butt off. See his full diet plan here.

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Zac team


Zac stars along Robert de Niro in the comedy flick about a debauched grandfather and his grandson who take a car journey from Georgia to Florida. As he always does, Zac formulated his training plan by scrutinizing the script of the movie. He scanned the pages for his scenes, taking note of any shots where he’s shirtless or in a tank-top / t-shirt.

Zac’s script analysis identified the areas that he needed to put his main energies into:

  • Chest
  • Shoulders
  • Biceps
  • Triceps
  • Abs

Density Training

Zac hand on hipIn order to achieve the look he needed, Zac introduced a new style of workout. It’s called density training. Here’s a quick run-down of how it works:

Most of our workouts are based round sets and reps. Our workout is done when we’ve finished our prescribed number. Your muscles, however, don’t count reps. All they know is how much tension they are under and how long that tension lasts for. If that tension is maintained for long enough it will lead to a host of chemical reactions within the cell that triggers muscle growth.

The problem with the traditional 8-10 rep system is that it simply doesn’t last long enough to elicit this response. Most people do their reps too quickly, meaning that the average guy’s set lasts for just 12-18 seconds.

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The reality in most gyms is that almost no-one counts the time under tension. The fixation on reps is actually robbing most people of the time under tension that is vital to eliciting an anabolic response.


Escalated Density Training (EDT) goes counter to this model by focusing on total time working out and total reps performed. Popularized by Dr. Charles Staley, EDT is based on the principle that the workout protocol that encourages you to do the most amount of work in a set amount of time will lead to maximum muscle growth. So, if you are able to do more work in the same amount of time than you did it in the last time you trained, you will build muscle.


Escalating Density Training allows you to know exactly what you are doing each workout and gives you a fail-proof way to determine whether or not you are making progress. It also allows you to zero in on a specific goal each and every workout – to hit more reps than you did in the last timed workout.

How Zac Used Density Training

  • His workout consisted of twenty-minute phases that were separated by a 5-10 minute recovery period.
  • During each twenty-minute phase he performed two exercises for opposing muscle groups.
  • He moved from one exercise to the next without any rest.
  • He tallied the total number of reps performed in each exercises.
  • In the next workout, his goal was to perform more reps than he did this time.
  • He rested for 5-10 minutes, then performed another 20-minute phase with opposing exercises for two other body parts.

These are the exact phase training combinations that Zac used in his Dirty Grandpa Density Training workouts:

Day One Workout

Lats / Triceps

Phase One:

Chin Ups (Palms Facing)

Lying EZ Bar Triceps Extensions

 Phase Two:

Seated Rowing

Reverse Grip Triceps Pushdowns (Palms Up)

 Day Two Workout

Legs / Core

Phase One:


Swiss Ball Crunches

Phase Two:

Leg Extensions

Leg Curls

 Day Three Workout

Chest / Biceps

Phase One:

Dumbbell Bench Press

Low Cable Curl

Phase Two:

Barbell Incline Press

Hanging Leg Raises

The Ab Workout

Zac Efron six packZac is well aware that the key focal point of the physique is the abdominals. That’s where the viewer’s eyes settle when he’s shirtless on screen. As a result, he knows he needs to hit his abs regularly and hard. The following lower ab centric routine was performed four times per week to allow him to bring a six pack to the set:

  • Hip Rocks: Lying on your back with your feet together and the soles touching, place your hands behind your head, bend your knees and splay them out. Now simply rock your hips up and down. Drop the weight of your head into your hands, keep your elbows wide and keep your feet off the ground throughout.
  • Thumbs Together: Maintain the same position as the last exercise but, this time, place your hands under your butt, with the thumbs together. Your head should be up and your knees slightly bent with feet just off the ground. Now, keeping your legs locked in position, lift up and down from the hips. You should be moving about 12 inches. Make sure not to kick from the knees and keep your feet off the ground at all times.
  • Bicycle: Place your hands behind your head with legs extended and your head and shoulders off the ground. Now alternate your arms and shoulders to simulate a circular bicycling motion. Focus on feeling the twisting motion in your abs throughout the motion.
  • Isolation Crunches: Lying on your back with your knees bent, feet on the floor and hands clasped behind your head, forcefully contract your abs. This will give you a movement of just a few inches toward your pelvis. Your shoulders should be just lifting from the floor but the rest of your back should stay down. This small movement will isolate your abdominal wall – go too high and the focus transfers to your back.
  • Full Body Crunches: Start in the same position as for the isolation crunch except that your legs are extended and just off the floor. This time, as you bring your upper body towards your abs, draw your knees back towards your mid-section. Return them to an extended position as you crunch back down. Make sure that your feet stay off the floor at all times. Focus on a tight ab squeeze in the top position.
  • In and Outs: Sit with your legs extended in front of you and slightly off the ground. With knees together pull your legs into your chest and them immediately extend them back out. Your hands should be supporting you on the ground.
  • Mason Twists: Sit with your back arched and knees slightly bent. Your feet should be just off the floor. Now grasp your hands together in front of your knees. Use a twisting motion to touch your hands to the floor on either side of you in a fast paced motion. Be sure to make solid contact on each side and keep your feet up throughout. Both sides counts as one rep.

The Complete Package

Zac’s combination of Density Training and ab focused core work allowed him to, once again, bring an impressive physique to the set. He looks great in this movie, with lean, sinewy muscles and a tight, defined mid-section. Let’s hope he passed on a few training tips to DeNiro!

Related: Zac Efron Muscle Supplements

Zac with DeNiro

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