“The transverse abdominis, or TVA muscle, is the deepest ab muscle, attaching to the anterior lumbar spine and wrapping around the midsection from back to front like a corset or pair of Spanx,” says Ali Handley, founder of Bodylove Pilates in New York City. “When correctly engaged, the TVA cinches the waist, lengthens the torso, flattens the belly, and supports the spine and pelvis.” Just because the transverse abdominis is hard to see and reach doesn’t mean it’s not crucial to keeping you strong, toned, and pain-free. This super-deep muscle often referred to as the corset muscle, does everything from stabilizing your lumbar spine to holding your organs in place. That’s a huge job. And according to Handley, if you have a weak or disengaged TVA, back pain likely isn’t far behind. “A strong TVA supports the pelvis in a neutral position, which lets you correctly target and strengthen your lower body,” she says. “Therefore, someone with a weak TVA will likely have weak butt and leg muscles too.” Unlike the rectus abdominis (or visible six-pack muscles), the TVA muscle fibers run horizontally, Handley says. A strong transverse abdominis compresses and flattens the belly, whereas the rectus muscle fibers run vertically and grow outward. Good news if you’re sick of crunches: Forget about them—they won’t help strengthen your TVA. “If you have a weak TVA, you may have a low belly pooch, and no matter how many crunches you do, it won’t go away,” Handley says. So if crunches don’t do the trick, how exactly can you work this muscle? “The TVA is a thinking muscle, which means you don’t have to move to activate it,” Handley says. “Instead you have to find a mind-body connection to the action of the muscle. Just by breathing and thinking about how it wraps around your body will engage it.” Here are some of the best ab workouts you can do at home (or literally in your chair at work) to engage the transverse abdominis muscle.

TVA Counting

  1. Sit comfortably on a physioball, yoga block, or chair with a neutral spine and weight evenly distributed between both sitting bones.
  2. Inhale through your nose, allowing your belly to fill up with air and your stomach muscles to relax completely.
  3. Exhale a long, slow, even breath through your mouth and imagine your TVA wrapping around your midsection, pulling your belly button in all the way to the spine.
  4. Keep your belly button on your spine and begin to count out loud. Start by holding and counting to 10 and build to 25.

Bird Dogs

  1. Start on all fours with your spine in a neutral position.
  2. Inhale through your nose, allowing your belly to fill up with air and your stomach muscles to relax completely.
  3. Exhale a long, slow, even breath through your mouth as you imagine your TVA wrapping around your midsection, pulling your belly button in all the way to the spine, and knitting the two sides of the abs together.
  4. Keeping your abs engaged and spine completely neutral, reach your left arm and right leg out away from the body. Inhale through your nose again and bring the arm and leg back to the start position.
  5. Exhale through your mouth again and extend the opposite arm and leg. Aim for eight reps on each side.

Knee Hovers

  1. Start on all fours with your spine in a neutral position.
  2. Inhale through your nose, allowing your belly to fill up with air and your stomach muscles to relax completely.
  3. Exhale a long, slow, even breath through your mouth as you imagine you’re zipping a pair of high-waisted jeans up and over your belly button.
  4. Keeping your abs engaged and spine completely neutral, hold this connection as you lift and hover both knees up off of the mat.
  5. Inhale as you lower the knees with control. Aim for eight reps. Core challenge: Hold the connection and hover the knees for one minute.