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Forget 100 crunches.
You don't need to spend ten minutes on the floor counting reps to challenge your abs. You need resistance, muscular tension, and a reason for your core to work.
That's the idea behind the fastest ab workout.
Using a Bullworker, you'll perform three resisted crunches from three different angles:
Forward Resisted Crunch — 7 seconds
Left Resisted Crunch — 7 seconds
Right Resisted Crunch — 7 seconds
That's it.
Three positions. One set. 21 seconds.
The forward crunch challenges the front of your core. The two angled crunches bring your obliques into the equation.
No gym. No endless repetitions. No complicated routine.
Just 21 seconds of deliberate muscular tension.
And while that may sound too short to accomplish anything, the training principle behind it has been studied for decades.
Why Isometric Ab Training Works
Most traditional ab workouts are built around repetitions.
Crunch. Release. Repeat.
Isometric training works differently.
During an isometric exercise, your muscles generate force while maintaining a relatively fixed position. Instead of measuring your workout by the number of repetitions you complete, you create muscular tension and maintain it.
That distinction is important.
Your muscles don't know whether you've completed your 37th crunch.
They respond to tension and demand.
The 2025 systematic review and meta-analysis on isometric resistance training — PubMed analyzed 32 studies involving 621 participants and found significant improvements in strength with isometric resistance training.
Research into this concept stretches back decades. In the 1950s, German researchers Dr. Theodor Hettinger and Dr. Erich A. Müller conducted pioneering research into isometric strength training.
Their work investigated how much muscular tension—and how much time under that tension—was necessary to stimulate increases in strength.
One influential protocol used approximately two-thirds of maximum muscular tension for only about six seconds. Their work helped demonstrate that remarkably brief isometric contractions could produce meaningful strength improvements.
Modern research has continued investigating isometric resistance training, reinforcing its place as a legitimate method for developing strength.
That principle—create meaningful tension without wasting time—is the foundation of the fastest ab workout.
Your Core Does More Than Give You Abs
When people hear "ab workout," appearance is often the first thing that comes to mind.
But your core has a much bigger job.
Your trunk musculature helps stabilize your body and transfer force between your upper and lower body. It contributes whenever you lift, carry, push, pull, twist, throw, run, or change direction.
Even everyday movements depend on it.
Getting out of a chair. Picking something up. Carrying groceries. Playing golf. Working in the yard.
A strong core isn't just something you see.
It's something you use.
That's why this workout doesn't rely on one abdominal position repeated over and over.
We're going to challenge your core from three directions.
The 21-Second Bullworker Ab Workout
Grab your Bullworker and position yourself comfortably.
The goal is not to create as much force as humanly possible. You want strong, controlled resistance that allows you to maintain good positioning throughout the entire seven-second contraction.
Ready?
1. Forward Resisted Crunch — 7 Seconds
Start facing forward.
Position the Bullworker for the resisted crunch and gradually build pressure as you contract your abdominal muscles.
Think about bringing your rib cage toward your pelvis rather than simply pushing down with your arms.
Build the tension.
Hold.
One... two... three... four... five... six... seven.
Then gradually release.
The key is intentional tension.
Don't bounce.
Don't jerk into the movement.
Don't turn the exercise into an arm press.
Make your core do the work.
Seven seconds down.
2. Side Resisted Crunch — 7 Seconds
Now shift your emphasis to one side.
Set your position, gradually increase the resistance, and contract through the side of your core.
Your obliques run along the sides of your abdomen and play important roles in trunk rotation and lateral flexion.
Maintain your position.
Keep breathing.
Hold for seven seconds.
Release gradually.
Fourteen seconds.
One more.
3. Opposite Side Resisted Crunch — 7 Seconds
Switch to the other side.
Same principle.
Build controlled pressure against the Bullworker and focus on creating tension through the opposite side of your core.
Hold.
Seven seconds.
Release.
Done.
You just completed the fastest ab workout.
Forward. Left. Right.
Three positions and 21 seconds of focused core training.
Why Three Angles?
Your core isn't a single muscle.
The rectus abdominis—the familiar "six-pack" muscle—runs along the front of your abdomen and helps flex your trunk.
Your obliques run along the sides and contribute to movements including rotation and lateral flexion while also helping stabilize your trunk.
That's why the fastest ab workout uses more than one position.
The forward resisted crunch creates a strong contraction through the front of your core.
The two angled crunches change the direction of force and bring greater emphasis to the sides.
Rather than doing dozens of identical repetitions, you're deliberately changing the position and challenging your core from three directions.
Front. Side. Side.
Simple by design.
Why Resistance Changes the Ab Workout
Think about another muscle group.
If you wanted stronger biceps, would you perform 100 curls with no resistance?
Probably not.
You'd add resistance.
As you became stronger, you'd progressively increase the challenge.
Yet abdominal training is often treated differently.
People perform dozens—or hundreds—of bodyweight crunches and assume that more repetitions must mean a better workout.
Bullworker gives you another option.
Add resistance instead of simply adding reps.
The Bullworker allows you to control how much force you generate during the exercise. As your core becomes stronger, you can progressively create more resistance.
That means the workout can grow with you.
You aren't trying to win a crunch-counting contest.
You're trying to build a stronger core.
What About Planks?
Planks are themselves a form of isometric exercise, and they can be an excellent way to train your core.
But there's an important difference in how this Bullworker routine approaches isometrics.
A plank generally asks you to maintain a position for an extended period while your body weight provides the resistance.
With the Bullworker, you actively generate resistance and concentrate it into a much shorter contraction.
Neither approach makes the other useless.
They're simply different tools.
The advantage of the fastest ab workout is efficiency: create substantial, deliberate muscular tension without needing to hold a plank for 30, 60, or 90 seconds.
No Momentum. Make Every Second Count.
High-repetition abdominal exercises can get sloppy.
You start with controlled crunches.
Then fatigue sets in.
The repetitions get faster. Your range changes. You start pulling with other parts of your body just to keep the count moving.
Isometric resistance strips away much of that distraction.
There is no race to finish the repetitions.
There is no momentum helping you through the difficult part.
Set the position.
Create tension.
Hold.
Seven deliberate seconds can demand considerably more concentration than 30 rushed repetitions.
That's the point.
How Hard Should You Push?
More resistance isn't automatically better.
Start by gradually building pressure over the first second or two. Find a challenging level of resistance that allows you to maintain your position and breathe normally.
Then hold it.
You should feel your core doing the work—not your neck, shoulders, or lower back.
If you can't maintain your position, reduce the intensity.
If you're new to Bullworker or isometric training, begin conservatively and become familiar with the movement before increasing your effort.
And don't hold your breath.
Controlled breathing is particularly important when performing demanding isometric contractions.
If you have an injury or medical condition that may affect your ability to safely perform resistance exercise, consult an appropriate healthcare professional before beginning a new training program.
Will the Fastest Ab Workout Give You a Six-Pack?
Let's clear up one of fitness's most persistent myths.
Training your abs can make them stronger. It cannot selectively burn the fat covering them.
Visible abdominal definition depends on several factors, including body composition, nutrition, genetics, and the muscular development of your abdominal region.
Doing more crunches doesn't allow you to choose where your body loses fat.
So don't judge an ab exercise solely by whether it promises a six-pack.
Build a stronger core because a stronger core is useful.
Combine resistance training with appropriate nutrition and overall physical activity if changing body composition is also one of your goals.
That's a much better strategy than doing another 100 crunches and hoping they'll somehow melt belly fat.
The Workout You Actually Have Time to Do
There's another reason we like this routine so much.
It's incredibly difficult to claim you don't have time for it.
You don't need to drive anywhere.
You don't need to change the plates on a machine.
You don't need to clear enough floor space for a 15-minute ab circuit.
Grab your Bullworker.
Twenty-one seconds.
Done.
Keep it at home. Put it in your office. Take it on a trip.
Removing the friction around exercise makes consistency easier, and consistency is where an incredibly short workout can become surprisingly powerful.
The fastest ab workout isn't about proving that longer workouts are bad.
It's about proving that useful training doesn't always have to take a long time.
Why Bullworker?
You don't need a dedicated abdominal machine to progressively challenge your core.
You need resistance.
The Bullworker Bow Classic used in this workout gives you a simple way to create that resistance virtually anywhere.
And when your 21 seconds are finished, you're not left with a piece of equipment that only trains your abs.
Use the same Bullworker for your chest.
Your back.
Your shoulders.
Your biceps.
Your triceps.
Your legs.
One compact strength-training tool can give you hundreds of ways to challenge your body without filling a room with equipment.
That's what makes Bullworker different.
It's not about finding more time to work out.
It's about getting more out of the time you already have.
Try the Fastest Ab Workout
Grab your Bullworker.
Forward Resisted Crunch — 7 seconds.
Side Resisted Crunch — 7 seconds.
Opposite Side Resisted Crunch — 7 seconds.
That's the fastest ab workout.
Three angles.
Twenty-one seconds.
One stronger reason to stop telling yourself you don't have enough time to train.
Try it consistently. As you become stronger, progressively increase the resistance while maintaining good positioning.
Then keep going.
Pair it with the Fastest Biceps Workout and the Fastest Triceps Workout. Add another muscle group tomorrow. Or build these remarkably short routines into a complete Bullworker strength program.
Strength training doesn't have to take over your life to become part of it.
Grab your Bullworker and put 21 seconds to work.
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