The 5 Hardest Ab Exercises Known to Man

The following five ab exercises are like circus tricks—they're visually impressive and only fitness freaks can perform them. Go ahead and try them for yourself. If you nail them, you have bragging rights for a lifetime. If you fall short, don't worry: Master the moves by following our trainers' advice, then add them to your ab workout.

If these are too hard (and that's likely), refresh your workout with these 25 Awesome Abs Exercises today!

Human flag sightings are rare. The reason: Only the fittest of the fit can do it.

"This is the master of all core moves because you have to be strong enough to hold your own weight," says Sam Stauffer, a trainer with Men’s Health Thrive in Philadelphia. "Your arms, shoulders, back, and abs are all responsible for holding up your long body."

In order to pull it off, you'll need a high strength-to-mass ratio, and a ridiculous amount of upper-body strength, core stability, and total-body muscle control, he says. It also takes a ton of practice and lots of ab workouts.

WANT TO TRY IT? Find a vertical pole. It should be sturdy enough to hold your body weight but thin enough to grasp securely. Grab it toward the bottom with your nondominant hand using an underhand grip, and higher up with your dominant hand using an overhand grip. Lock your bottom elbow, leaning your body away from the pole. Press hard with your bottom arm, squeeze tightly with your top arm, and lift your legs up with your knees bent. Contract your core and extend one leg at a time until your body is perpendicular to the pole. Your goal: Hold for 10 seconds.

Can't do it? No problem. Head to the next slide to learn how to master the move.
 

If your human flag isn't jaw-dropping quite yet, add the vertical pushup plank row to your ab workouts. It trains your entire body to stabilize, but it also hit your deltoids and lats, which are heavily involved when your arms are pushing and pulling on the pole.

DO THIS: Anchor a resistance band to a vertical pole about 2 feet off the floor. Assume a pushup position facing the pole, about 4 to 6 feet away from it. Lift your right arm straight out in front of you, grabbing the resistance band. Bend your elbow and pull the band to the side of your chest. Pause, and then release your arm straight in front of you. That's 1 rep. Do 8 to 12 reps with your right hand, and then switch sides. Perform 2 to 3 sets.

Add this move to your routine 3 to 5 times per week. Along the way, keep attempting the human flag. How long will it take to nail the flag? "It's different for everyone, so you'll need patience," says Stauffer. "It's something you have to keep practicing." So take pride in the small improvements—like getting your body more perpendicular to the floor or holding it for one second longer. Eventually, the work will pay off and your flag will fly.
 

You'll not only need a strong core to perform even one rep of toes to bar, but also a vise-like grip, great hip flexibility, and total-body strength, says Craig Ballantyne, C.S.C.S., author of Turbulence Training. "Most guys won't be able to do one rep."

The move draws out the eccentric phase—or the lowering phase—of the move, requiring you to recruit more muscle fibers. You can't let gravity do the work, says Ballantyne. Your abs have to control the movement and speed.

WANT TO TRY IT? Grab a pull-up bar with an overhand grip. Pull your shoulders down and away from your ears and hold them there. Create tension in your arms and throughout your core by pulling down on the bar as hard as possible. Contract your glutes and lift your toes to the bar. Your legs should be straight (a slight knee bend is fine). Once your toes reach the bar, slowly lower your legs back down to the start position for two seconds. Do as many reps as you can.

Can't do it? No problem. Head to the next slide to learn how to master the move.
 

The hanging knee raise is a regression of the move, but it's still tough, says Ballantyne. It'll engage the same muscles as toes to bar, but the load will feel lighter since your legs are closer to your body.

DO THIS: Grab a pullup bar with an overhand grip. Pull your shoulders down and away from your ears and hold them there. Create tension in your arms and throughout your core by pulling down on the bar as hard as possible. Bend your knees and curl them up toward your chest. Pace yourself: Lift for two seconds and lower for two seconds. Do 10 reps—or as many as you can—for 3 sets.

Once you master the hanging knee raise, try the hanging leg raise in an ab workout. Follow the directions above, but with only a slight bend in your knees. Take two seconds to raise your legs until they are parallel to the floor, and then two seconds to lower them. Perform as many reps as you can for 3 sets.

Follow this routine three times a week for two to four weeks, says Ballantyne. By that time, you should be able to do one or more reps of the toes to bar.
 

The single-side bird dog might look too easy to belong on this list, but it's a serious core challenge. In fact, about 90 percent of people can't do it, says Stauffer. That's because picking up an arm and a leg on the same side forces your core stabilizers to work overtime to keep you from tipping over or flexing or extending your back. "Most of us don't train for this type of of core stability, so we can't hold the position," says Stauffer.

WANT TO TRY IT? Get down on your hands and knees and lift your right arm and right leg off the floor. Touch your elbow to your knee, and then fully extend your arm and leg until they're in line with your body. Pause, and then bring your elbow and knee together again. That's one rep. Do 8 to 12 reps on the right side, and then repeat on the left side, as part of your abs workout.

Can't do it? No problem. Head to the next slide to learn how to master the move.
 

The pushup-position row trains your midsection to resist movement when you lift up a base of support and increases your core endurance.

DO THIS: Assume a pushup position with a heavy dumbbell in your right hand. Pull the dumbbell up to the side of your chest, pause, and then lower it back down. That's 1 rep. Do 8 to 12 reps, then repeat on the left side. 

Do this routine 2 or 3 times a week, and you should notice a significant improvement in your ability to do the single-side bird dog in about 4 weeks.
 

This ab exercise is an absolute screamer. The "hollow body" position is a fundamental position for gymnasts. To do it, you must hold your upper and lower body a couple of inches off the floor by clenching every muscle from your fingers to your toes.

But unlike the regular hold, this version requires you to also keep a 3- to 6-pound medicine ball between your feet. "If you're new to this move, you'll only be able to hold it for 15 seconds before your abs will feel as if they're on fire and you'll start to shake," Stauffer says. 

WANT TO TRY IT? Grab a 3-to-6-pound medicine ball duirng your next abs workout. Place the ball between your ankles, and lie on your back with hands by your side and your legs straight. Press your tongue to the roof of your mouth. Keep your mouth closed as you brace your core, point your toes, and squeeze the medicine ball. Lift your head, shoulders, and legs about 12 inches off the floor. Extend your arms toward your feet. Hold this position for 30 to 45 seconds.

Can't do it? No problem. Head to the next slide to learn how to master the move.
 

Build up the core strength and endurance you'll need by practicing without the medicine ball.

DO THIS: Lie on your back with your legs straight and hands in fists in front of your face, as if you're a boxer protecting yourself. Press your tongue to the roof of your mouth. Keep your mouth closed as you brace your core, point your toes, and squeeze your quads, knees, and ankles together. Lift your head, shoulders, and legs about 2 inches off the floor. If that feels too easy, extend your arms overhead. Hold this position for as long as you can, aiming for 30 to 60 seconds. Do 3 to 5 sets.

Perform this move 3 to 5 times a week. After two weeks, the regression should start to feel easier. When you can perform the 60-second hold for 5 sets, begin adding weight, says Stauffer. Start with a one-pound medicine ball and slowly increase the weight.
 

A regular pushup engages your abs, but the Valslide pushup hammers your obliques, rectus abdominus (a.k.a. your six-pack muscles), shoulders, upper back, pecs, and triceps, says Tony Gentilcore, C.S.C.S., strength coach at Cressey Perfomance in Hudson, Massachussetts. 

The reason: As you lower down into a pushup, one hand glides forward on a Valslide—a slippery disk that lets your hands slide over a gym floor or carpet—or a paper plate. It's almost like you're doing an assisted one-arm pushup, says Gentilcore. Your sliding arm can't handle as much of your bodyweight as it travels away from your body. This puts more stress on your opposite arm and makes it more difficult for your core to remain straight throughout the move, he explains. It's tough to get more than a few reps with perfect form.

WANT TO TRY IT? Begin in a pushup position with your right hand on a Valslide or paper plate. As you lower your chest to the floor, slide your right arm out in front of you. Your spine should remain in a neutral position the entire time. If your lower back and hips bow, you've reached too far forward. On your next rep, keep your arm closer to your torso, says Gentilcore. Perform 5 to 8 reps with your right hand sliding forward, then switch sides. Do 3 to 4 sets.

Can't do it? No problem. Head to the next slide to learn how to master the move.
 

The plank arm march forces you to engage the muscles in your lower back and hips while reaching with an arm—just like the Valslide pushup. However, it doesn't take the upper-body brawn needed in the Valslide pushup, so you can concentrate solely on your core strength.

DO THIS: Start in plank position with your forearms on the floor. Your body should be a straight line from your head to your toes. Maintain that straight line as you extend your right arm out in front of you, as if you were shaking someone's hand. Hold this position for 2 seconds, and the return to the starting position. Switch arms. That's 1 rep. Do 4 sets of 5 to 8 reps.

Do this routine 2 to 3 times per week. Make the move harder by holding out your arm longer or by lifting your opposite foot at the same time, Gentilcore says. After a month, attempt the Valslide pushup again.

If these proved too hard (no shame there), refresh your workout with these 25 Awesome Abs Moves today!