Bent-Knee Hip Raise
A floor reverse crunch with the knees held at roughly 75 degrees. The rep is not lifting the legs — it is peeling the tailbone off the floor by rolling the pelvis backwards, which is a range of about 10 centimetres and the reason most people never actually perform one.
Own the movement
Set up first, then execute. Every cue below is something you can check on your next set.
Before the first rep
- Lie flat with your arms alongside your body, palms down. Do not grip the floor or a bench behind your head.
- Bend the knees to roughly 75 degrees — a little more open than a right angle.
- Lift the feet about 5 cm off the floor and hold them there. That is the start, not the floor.
- Flatten your lower back into the ground before the first rep, so the range starts from a neutral pelvis.
Every rep
Breathing & tempo — Exhale hard as the hips roll up — the exhale is what drives the pelvis under. Inhale on the way down. Two seconds up, one-second hold, two to three seconds down.
Sets, reps & load
Where to start, and what to change when it stops being hard.
Bodyweight, and it stays bodyweight for a long time. Progress by adding the top hold first, then by lowering the feet closer to the floor at the bottom, then by slowing the eccentric to four seconds. Only once you can do 15 strict hip lifts with a one-second pause is it worth moving to hanging or decline versions rather than loading this one.
What goes wrong
The errors that show up most often, and the cue that fixes each one.
Slow the rep to two seconds up, two down, and stop the set the moment your tailbone stays glued to the floor. Half the range is the whole exercise.
Turn your palms up, or rest your hands on your ribs. If the hips will not lift without arm drive, you are not ready for the full range yet — reduce the range and build the tilt.
Fix the angle at 75 degrees and treat the legs as one rigid block from hip to ankle. Film one set from the side and check the shin angle does not change.
Stop the descent higher — at the point where you can still keep your lumbar spine pressed down — and only lengthen the bottom range as your control improves.
Why bother
The rectus abdominis pulls the pubic bone towards the ribs. A standard crunch does that from the top end; this does it from the bottom, with the ribs pinned by the floor and the pelvis doing the travelling. Same muscle, opposite anchor, and far harder to fake once the hip flexors are taken out of it.
Locking the knees at about 75 degrees is what removes the psoas. With straight legs, hip flexion does most of the work and the lower back arches to compensate. With the shins parked and the angle unchanged through the rep, the only thing that can raise your hips is posterior pelvic tilt.
Where it fits
End of a session, two or three times a week, 2-3 sets taken to a point where the tilt still happens cleanly. It pairs sensibly with an anti-extension drill like a dead bug or a rollout rather than with more crunches — you do not need three flexion exercises in one week.
If this one isn't it
No kit, too hard, or too easy — here's where to go instead.
Same job, different kit
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Asked and answered
What is the difference between this and a leg raise?
A leg raise mostly flexes the hip — the psoas moves the femur while the abs work statically to stop the back arching. The bent-knee hip raise deliberately parks the hip angle so the abs have to move the pelvis instead. If your hips never leave the floor, you have done a leg raise, not this.
Why 75 degrees and not 90?
A slightly open angle keeps the thighs from stacking vertically over the hips at the start, so the abs stay under tension from the first centimetre rather than resting at the top of a stack. It is a small detail, but it is the difference between constant tension and a free ride at the top.
Does this hit the lower abs specifically?
It biases them, but it does not isolate them. The rectus abdominis is one sheet and contracts along its length; what changes is where the tension is highest. Pelvic-tilt work like this loads the lower portion harder than a crunch does, which is worth doing — just do not expect a separate muscle to appear.
My hip flexors burn more than my abs. What is wrong?
Either your legs are straightening during the rep, or you are stopping before the pelvis tilts. Reset the knee angle, shorten the range to the top third, and chase the tailbone lift rather than knee height until the burn moves where it belongs.