Most ab exercises try to take the hip fexors out of the equation so that the abs have to work without assistance. But ignoring the hip fexors can lead to injury if you lift heavy, run, or play sports. The spread-eagle jackknife allows you to strengthen both the abs and the hips without sacrificing development in either area. But be warned: This is an advanced move.

Having your legs spread apart makes it difficult to sit up, and that forces the abs and hip fexors to engage to raise your torso. Strong hip fexors help your hamstrings stabilize heavy squats and deadlifts, and they also enhance running speed and explosiveness.

If raising your legs off the floor is too difficult, it’s OK to do this move as just a torso situp. You can also secure your feet inside the support beams of a power rack, or have a partner hold them down for more stability. For a greater challenge, do spread-eagle jackknifes (or situps) while holding a medicine ball overhead.

How to Do It

  1. Lie on your back on the floor with your legs spread to form a “V” shape and your arms extended behind your head.
  2. Sit up explosively while simultaneously raising your legs and hips off the floor. As you come up, reach your hands between your legs.

Quick Tips

Perform the spread-eagle jacknife at the end of a lower-body day. Aim for 2-4 sets of 10.