The Ab-Building Trick Nobody Told You About

Up to 46 Percent Better Results

Categorized under Training

Fun Fact

Activating your hamstrings and glutes will force your abdominals to work harder. Doing so limits hip flexor recruitment, which is the area that often takes over during ab training. And while meaty hip flexors can look impressive, that’s not the point of working the abs.

Professor Vladimir Janda popularized the concept of reciprocal inhibition, which basically states that when one muscle contracts, the antagonist relaxes. So when you activate your glutes and hamstrings, your hip flexors will somewhat switch off.

By inhibiting your hip flexors (via hamstring and glute engagement), you isolate your abs better and take some strain off your lower back. You’ll also increase the level of difficulty of your regular ab exercises. Your abs will fatigue first, which is the entire point of the exercise.

Need proof? A 2007 study compared a regular crunch to a modified version with hamstring activation. With hammy engagement, the research showed 26 percent more activation of the lower rectus abdominis fibers and 46 percent more activation of external oblique fibers (1).

Now that we know why it works, let’s apply it. Remember, the goal is to activate your hamstrings and glutes as much as possible to get more out of your abs.

The Exercises

Unfortunately, just thinking about contracting your hams and glutes isn’t enough. It helps somewhat, but there are smarter ways to set up your regular ab exercises to create more tension in them. Here’s how.

Rollout With a Medicine Ball

Crushing a medball between your calves and hamstrings during roll-outs is an effective way to get your hammies firing. You’ll instantly feel how this small upgrade can completely change the feel of your regular rollouts. As a bonus, it’ll also add a small amount of resistance at the bottom of the movement.

How to do it…

  • Crush the medicine ball with your hamstrings. Squeeze your glutes. Imagine trying to crack a walnut with your butt cheeks throughout the rollout.
  • Brace hard in the bottom position.
  • Exhale fully at the top, pulling your ribs to your pelvis and flexing your spine at the top.

Foam Roller Reverse Crunch

Use your hamstrings to squeeze a foam roller. Providing you don’t have twig legs or sweaty calves, a foam roller should clamp nicely between your calves and hamstrings, encouraging some activation.

Use this method for knee raise and reverse crunch variations to help switch off your hip flexors. Doing so will make these exercises particularly effective at hitting the lower fibers of your rectus abdominis.

How to do it…

  • Place the foam roller between your calves and hamstrings. If it slips, try wrapping it in a towel.
  • Tense your hamstrings while making a conscious effort to engage your glutes at the same time. This will make the exercise significantly harder.
  • Hold onto a plate or sturdy object for stability.
  • Raise your knees and focus on tilting your pelvis. Lift your hips off the floor at the top without momentum.
  • Exhale fully at the top to get maximum abdominal engagement.

The Janda Sit-Up

The Janda crunch is known for removing the hip flexors from a traditional ab exercise. Professor Janda originally described a process of performing a crunch while actively driving your heels into the ground. This is somewhat similar but you’ll be coming up fully to the top, the way you would for a sit-up.

Pavel Tsatsouline recommends coming up fully to the top with these. If starting from the floor is too difficult, you can practice partial reps from the top down. The key is to maximally engage your glutes and hamstrings, which make even the simplest of sit-ups a whole different beast.

How to do it…

  • Drive your heels into the edge of a platform to activate your hamstrings. You can also pile up a few thick mats to lay on and wedge your heels against.
  • As you sit up, think about closing the space between your ribs and pelvis to fully shorten your rectus abdominis.
  • Get rid of all of your air as you reach the top.
  • Accentuate the eccentric, taking at least 2-3 seconds to lower.
  • To make these easier, start from the top and go down further over time.

The Banded Janda Sit-Up

Janda sit-ups can also be done using a resistance band. In this case, an NT Loop is a comfortable setup to pull your heels against. Use the band to activate your hamstrings while working hard to keep cracking that imaginary walnut between your butt cheeks.

How to do it…

  • Thread a band around a piece of equipment that’s not going to move anywhere, then place each end of the band around your ankles. This will create just enough tension to lock you into position and continue pulling your heels against.
  • As you sit up, think about closing the space between your ribs and pelvis to maximally shorten your abdominal fibers.
  • Exhale fully as you reach the top.
  • Squeeze your glutes and hamstrings throughout.
  • Lower slowly. Take at least 2-3 seconds to lower yourself back down to the floor.
  • To make it harder, stretch your arms up overhead on the way down to overload the eccentric.

Banded Swiss Ball Crunch

This might look silly with both a band and a ball, but the setup is worth the pay off.

While crunches tend to reduce hip flexor activation (compared to sit-ups) they still recruit them somewhat. And on top of that, the standard crunch has such a low resistance that experienced lifters often get bored with it. This variation solves both problems.

Hamstring-activated crunches help inhibit hip flexor involvement while making the basic crunch harder. Doing these on a Swiss (stability) ball places you in an ideal position to “close the space” between your pelvis and ribs. This way you can fully shorten and activate your transverse abdominis.

How to do it…

  • Sit on a ball and place the band around your ankles.
  • Lay back and position the peak of the ball in your lumbar curve.
  • While getting settled, make sure you can create enough tension with your hams and glutes (through the band) to create stability.
  • Try placing your thumb at the bottom of your ribcage and your forefinger on your pelvis. As you crunch up, just think about your thumb and forefinger getting closer together. As you come down they’ll move further apart.
  • Try to squeeze your glutes throughout, and use your hamstrings to maintain tension on the band.
  • Exhale fully as you reach the top.
  • Try not to flex your neck excessively. If you do, you can use the trick of putting a tennis ball under your chin. It works. But fear of looking like an ass with a ball under you chin is incentive enough for keeping your neck in check anyway!


  1. Larson et. al. (2007). The Effect of Hamstring Contractions in the Activation of the Abdominal Muscles during a Standard Abdominal Crunch. Doctoral dissertation, University of North Dakota.