reckonerGHD sit-up
A sit-up on the glute ham developer. Your hips sit on the pad and your feet are locked in, so you can lean back past where the floor would stop you. It works your abs and your hip flexors together1, and that long range makes it the hardest sit-up Reckoner knows, so build into it slowly.
Lean back to level, then sit up tall.
- Pattern
- Core flexion
- Trains
- Abs, hip flexors
- Kit
- Glute ham developer
- 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
- Technical
- Recovery cost
- Moderate
- Not prescribed if you have declared
- Lower back
Muscles worked
How to do it
Set the foot plate
Sit on the pad with your hips just past its edge and your feet locked under the rollers.
Lean back to level
Cross your arms on your chest and lean back with control until your body is level with the floor. That is the full range to start with.
Sit up tall
Press your feet into the rollers and sit back up until your chest is over your hips.
Add range only when it is easy
Once level feels easy for a few sessions, go a little past it. Keep the early sessions short.
What goes wrong
Doing too many too soon
It looks like a sit-up, so it is tempting to do as many as you would on the floor. The extra range makes every rep much harder. Keep the first sessions short and shallow.
Falling back
Dropping back fast gets you to the bottom quickly. Lowering with control is half the work, and it keeps the bottom where you meant it to be.
Hanging far past level on day one
The machine lets you reach back toward the floor, which feels like the point of using it. In a lab study of twelve ab exercises, short curl-ups gave the most ab work for the least spine load2. A bigger range is a cost, so earn it.
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 earned the extra rep before the lighter week. The lighter week was for recovery, not a test, so it waited for it to end, and now it lands. 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
What does the GHD sit-up work?
Your abs, with your hip flexors working hard beside them. In sit-up style exercises, the rectus femoris, a hip flexor on the front of the thigh, is among the most active muscles1.
How far back should I go?
To level with the floor at first. Go past it only once level feels easy, and a little at a time.
Will Reckoner put this in my plan?
It can, once you are past the beginner stage, when your gym has a glute ham developer. Reckoner reaches for every easier sit-up and crunch first. Lower back is recorded against it, so declaring it in setup takes it out of your plan.
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 adults, where the bent knee sit-up was among the exercises with the highest rectus femoris (hip flexor) activity
- Axler and McGill, Medicine and Science in Sports and Exercise, 1997. Low back loads over a variety of abdominal exercises: searching for the safest abdominal challenge nine adults across twelve abdominal exercises, where partial curl-ups gave the highest abdominal challenge for the spine compression they cost