reckonerDecline crunch
The crunch on a decline bench: feet hooked, shoulders curling up toward your hips, lower back staying on the pad. It is the short version of the decline sit-up, and the shortness is the point. Keeping the movement in the spine and out of the hips is the first thing a synthesis of abdominal research names in choosing an exercise, and it names a slope as a way to make one harder2.
Curl the ribs up, lower back stays down.
- Pattern
- Core flexion
- Trains
- Abs
- Kit
- Bodyweight, decline bench
- Loading
- Your own bodyweight
- Reckoner prescribes
- 2 sets of 10 to 15 reps at RPE 8
- Progression step
- Nothing to add, so the sets climb instead
- Skill
- Some technique
- Recovery cost
- Very low
- Not prescribed if you have declared
- Lower back
Muscles worked
How to do it
Hook your feet and lie back
Set the bench at a gentle slope to start, hook your feet under the pad and lie back with your lower back flat on the bench. Cross your arms over your chest.
Curl your ribs up
Curl your shoulders up toward your hips by bringing your ribs toward your pelvis. Lift your shoulder blades off the bench, no higher.
Keep your lower back down
Your lower back stays on the bench for the whole rep. The moment it lifts, your hips have started folding and the rep has become a sit-up.
Lower slowly back to the bench
Uncurl under control until your shoulders are back on the bench, then start the next rep without a rest at the bottom.
What goes wrong
Turning it into a sit-up
When the set gets hard it feels natural to keep coming up. The hooked feet let the hip flexors take over from there3, which is a different exercise. Stop at the shoulder blades.
Pulling on your head
Hands laced behind the head pull the chin toward the chest and move the effort into the neck. Keep the arms across the chest, and if you cannot curl up without them, the bench is too steep.
Rushing the way down
On a slope you fall back faster than you curled up, and the abs miss the slow half of the rep. Lower at least as slowly as you came up.
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 | 2 x 10 | More reps 10 → 11 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. |
| 2 | 2 x 11 | More reps 11 → 12 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. |
| 3 | 2 x 12 | More reps 12 → 13 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. |
| 4 | 2 x 13 | More reps 13 → 14 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. |
| 5 | 2 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 | 1 x 14 | More reps 14 → 15 repsYou finished every set with three reps left in the tank (RPE 7) and room left in the range, so the reps climb before the load does. The lighter week is over, so this is back to two 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
Decline crunch or decline sit-up?
For the abs, the crunch. The crunch measured among the highest exercises for both halves of the rectus abdominis and for both obliques, and kept the hip flexors quieter than the sit-up1. The sit-up is the bigger movement and asks more of the hips.
How steep should the bench be?
Start at a slope where you can curl and lower slowly for every rep you are asked for. A steeper slope or added load is how abdominal work is made harder2, so tilt the bench once the reps feel easy at the top of your range.
How does Reckoner progress it?
It only reaches your plan if you choose it, in the movement picker, a swap offer or search, and a swap offer shows you the other crunches and sit-ups in the library. With no weight to add, Reckoner moves you up through the rep range, then adds a working set once you top it at the effort it asked for, up to a ceiling.
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, Journal of Orthopaedic and Sports Physical Therapy, 2006. An electromyographic analysis of commercial and common abdominal exercises: implications for rehabilitation and training fourteen participants across nine abdominal exercises, with the crunch among the highest for upper and lower rectus abdominis and for both obliques, and with rectus femoris activity greatest in the bent-knee sit-up, which the authors say may be a problem for people with low back pathology
- Monfort-Pañego and colleagues, Journal of Manipulative and Physiological Therapeutics, 2009. Electromyographic studies in abdominal exercises: a literature synthesis a synthesis of eighty-seven EMG studies naming spine flexion without hip flexion, and inclined planes or added load to raise contraction intensity, among the main factors in choosing abdominal exercises; a synthesis, not a meta-analysis
- Parfrey and colleagues, Applied Physiology, Nutrition, and Metabolism, 2008. The effects of different sit- and curl-up positions on activation of abdominal and hip flexor musculature fourteen subjects holding sit-up and curl-up positions, where fixing the feet produced significantly lower activation at every abdominal site measured and higher rectus femoris activation; isometric holds on the floor, not reps on a decline