How to do a proper hanging knee raise

Here is the thing nobody tells beginners. Your abs, the rectus abdominis, do not lift your legs. That muscle runs from your ribs to your pelvis, and its job is to pull those two toward each other, rounding your spine. Lifting your thigh is done by the hip flexors, a separate set of muscles at the front of your hip. So when you hang and swing your knees up, the muscles doing the lifting are mostly your hip flexors.

This is why people do endless hanging knee raises and never feel their abs. The knees go up, the hip flexors work, the abs come along for the ride but never really contract. To bring the abs in, you have to add a movement they actually cause: curling your pelvis up toward your rib cage at the top, which rounds your lower back. That is the move that turns a hip flexor swing into an ab exercise.

Picture a normal knee raise. You bring your knees up to around hip height and your thighs are parallel to the floor. For most people, that is where the rep ends and the knees drop back down. That whole range was mostly hip flexor work. The ab part is what happens next, and most people never do it.

At the top, keep going. Tuck your tailbone up and forward, curling your pelvis toward your rib cage so your lower back rounds and your hips lift up and away from the bar. Your knees travel toward your chest and, more importantly, your hips roll up. That final curl is your abs contracting. It is a small movement and it feels awkward at first, but it is the entire point of the exercise. Then lower under control, un-curling the pelvis first, then letting the knees drop back down slowly.

1. Hang from the bar. Grip a pull up bar a little wider than shoulder width, arms straight, and let yourself hang. Pull your shoulder blades down slightly so you are not dead hanging limp from the joints.
2. Set a still, braced body. Brace your midsection and stop any swinging before you start. The goal is a controlled hang, not a pendulum. If you are swinging, you have not started the rep yet.
3. Raise your knees. Bend your knees and lift them up toward your chest. This part is mostly hip flexors, and that is fine. Bring them to about hip height smoothly.
4. Curl your pelvis at the top. This is the key rep. Tuck your tailbone up, round your lower back, and lift your hips so your knees come toward your chest and your pelvis rolls up. This is your abs working. Pause and squeeze for a beat.
5. Lower under control. Reverse it slowly. Un-curl the pelvis, then let the knees lower back down over a couple of seconds. Do not just drop and swing into the next rep.

The two big themes are the pelvic curl and killing the swing. Add the curl and you turn on the abs. Kill the swing and you make the muscles, not momentum, do the work. Get both and the humble knee raise becomes a serious ab builder.

The hanging knee raise is a natural home base for ab and core work. It costs nothing but a bar, it builds grip alongside abs, and it scales in clear steps as you get stronger.

• Sets and reps: 3 to 4 sets of 8 to 15 controlled reps, each finished with a real pelvic curl. Quality over quantity here.
• Progress the leverage. Once bent knee raises with a full pelvic curl feel easy, move toward straighter legs, which makes the same movement much harder. Straight leg raises are the next step up.
• Kill the swing to make it harder. Slowing down and removing momentum increases the difficulty far more than adding reps. A slow, swing free knee raise humbles most people.
• Pair it with a spinal flexion move. Something like a cable crunch trains the abs through rounding the spine from the top down, while the knee raise works them from the pelvis up. Together they cover the full ab.