reckonerLying leg raise
Flat on the floor, legs straight, lift them and lower them. Most of the movement here belongs to the hip flexors, and the abdominal work is the part nobody watches: stopping the lower back arching off the floor as the legs go down.
Lower back stays flat on the floor.
- Pattern
- Core flexion
- Trains
- Abs, hip flexors
- Kit
- Bodyweight, floor
- Loading
- Your own bodyweight
- Reckoner prescribes
- 3 sets of 10 to 15 reps at RPE 8
- Progression step
- Nothing to add, so the sets climb instead
- Skill
- Some technique
- Recovery cost
- Low
- Not prescribed if you have declared
- Lower back
Muscles worked
How to do it
Get the lower back flat and keep it there
Lie down with your hands under your backside or flat beside you, and press the small of your back into the floor. That contact is the reference for the whole set.
Raise the legs with the knees soft
Take them up to roughly vertical, together, with a slight bend in the knees rather than locked out. Going higher than vertical adds nothing unless you also curl the pelvis up.
Lower only as far as the back stays down
The way down is the work. Go slowly, and stop the descent at the exact point where the back begins to lift. For most people that is a lot higher off the floor than they think.
End the set on the first arch
One arched rep is the signal, not a reason to grind out three more. Log the reps you controlled, because the ones after that trained something else.
What goes wrong
Letting the back bridge on the way down
A gap opens under the small of the back and the legs get lower, which feels like more range. What actually happened is that the abs let go and the lower back took over holding the legs up.
Dropping the legs and bouncing them back
The legs fall, the floor and momentum return them, and the count climbs. Speed here removes the only part of the movement the abs were doing.
Treating it as a lower ab exercise
The name suggests you are picking a region and you are not. What separates this from a knee raise is lever length, not which part of the muscle works.
How Reckoner progresses this lift
Six weeks of this lift, run through the real engine. Nothing below was typed in: the prescription, the decision and the sentence beside it all come from the same code that writes your week.
| Week | Prescribed | What it did |
|---|---|---|
| 1 | 3 x 10 | More reps 10 → 11 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 2 | 3 x 11 | More reps 11 → 12 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 3 | 3 x 12 | More reps 12 → 13 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 4 | 3 x 13 | More reps 13 → 14 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 5 | 3 x 14 | Deload 40% of sets offFive weeks of building, then one week lighter. About 40% of the sets come off. The load holds and your reps stay where you earned them, so you keep the strength and lose the fatigue. |
| 6 | 2 x 14 | More reps 14 → 15 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. The lighter week is over, so this is back to three sets. |
Real engine output, not an illustration. Every row was produced by running the engine itself when this page was generated.
The full rule, and why the reps move before the load does, is in how Reckoner decides to add weight.
Questions people ask
Why do I feel this in my hip flexors?
Because they are doing a lot of it, and that is not a fault in your technique. Exercises built around raising the legs or the hips have been measured producing high rectus femoris activity alongside the abdominal work, which the authors flag as a reason to be careful with them if your low back is unhappy1. The abdominal share is the bracing, not the lifting.
Leg raise or hanging knee raise?
The hanging version is the harder one and Reckoner treats them as alternatives, so alternating keeps your history in one line. The floor version is the one to use when there is no bar, or when the hanging version has turned into a swing.
How do I make this harder without arching?
Slow the lowering down before you lengthen anything. Straightening the knees fully, taking the arms overhead, or adding a pause near the floor all raise the difficulty while the back can still stay down, and any of the three beats adding reps you cannot control.
Similar movements
There is no load to ease on this lift, so Reckoner offers one of these the first time it stalls. Each of them has a page.
Sources
- Escamilla and colleagues, Physical Therapy, 2006. Electromyographic analysis of traditional and nontraditional abdominal exercises: implications for rehabilitation and training twenty-one healthy adults across traditional and nontraditional abdominal exercises, with the wheel roll-out, the pike, the knee-up, the hanging knee-up on straps and the inclined reverse crunch highest for upper and lower rectus abdominis, internal oblique and latissimus dorsi, and with the wheel pike and knee-up, the inclined reverse crunch and the bent-knee sit-up also highest for rectus femoris, which the authors note may be a problem for some people with low back trouble