Straight Leg Sit-Up

The Straight Leg Sit-Up is a compound movement that trains the core with help from obliques, quadriceps and abductors. This guide covers the setup, the execution, the mistakes worth fixing early, and how to program it.

BodyweightIntermediateCompound

Updated 2026-10-20 · Written by the Metal Strength coaching team from the movement itself, and reviewed against the exercise library.

Straight Leg Sit-Up, performed through a full range of motion.

Curling the spine against resistance is what trains the core the way these muscles actually function — by shortening, not by being held still. Done with control and against real resistance, it is the most direct route to visible abdominal development.

Who it is for. Anyone building the midsection. Program it at the end of a session, and treat it like any other muscle by adding resistance over time.

Muscles worked

The prime mover here is the core, with obliques, quadriceps and abductors assisting — which is why this movement earns its place as more than a single-muscle exercise.

How to do it

Set up so your lower back is supported and your hips are fixed — the hips must not do the work.
Take your bodyweight if the movement is loaded, and set your hands where they will stay for the whole set.
Tuck your chin slightly and exhale to pull your ribs toward your hips before the first rep.
Curl your ribs toward your hips, rolling the spine up one segment at a time rather than hinging at the hip.
Squeeze the core hard at the top of the range and hold for a beat.
Uncurl slowly, resisting the way back down, and stop just short of fully relaxing.

Breathing. Breathe out forcefully as you curl up, in as you lower. The exhale is part of the contraction.

Form cues that matter

Curl the spine; do not hinge at the hip.
Breathe out hard at the top — it deepens the contraction.
Slow on the way back down.
Pulling on the head and neck with the hands
Hinging at the hips instead of curling the spine

Common mistakes

The mistake	Do this instead
Pulling on the head and neck with the hands	Rest the hands lightly, or cross them on your chest, and let the abs do the pulling.
Hinging at the hips instead of curling the spine	Shorten the range to just the part where your spine is actually flexing.
Doing endless bodyweight reps and never adding resistance	Hold a plate or use a cable and work in the 12 to 20 rep range instead.

What makes this variation different

The Straight Leg Sit-Up is a specific version of this movement, and the details in its name change how it should be performed.

Using only your bodyweight means you can train anywhere, and it keeps the whole body involved in stabilising the movement. Progress comes from leverage, range and reps rather than from adding plates.
Keeping the legs nearly straight lengthens the hamstrings through the movement, which makes this a stretch-focused variation. Stop the descent the moment your lower back begins to round.

Sets, reps and rest

Goal	Sets	Reps	Rest
Strength	3-5	8-12	45-75 s
Muscle growth	3-4	12-20	45-75 s
Endurance	2-3	20-30	45-75 s

6-16Weekly sets
2-1-2Tempo
45-75 sRest

How to progress

Add reps before you add weight. Stay at the same load until you reach the top of your rep range on every set, then increase the resistance and drop back to the bottom of the range. The Straight Leg Sit-Up responds better to accumulated quality reps than to heavy jumps.

Variations and alternatives

If you do not have the equipment, or you simply want to rotate the stimulus, these 8 movements train the core in a similar way.

Crunch Floor — Bodyweight
Cable Standing Crunch — Cable
3 4 Sit-Up — Bodyweight
Band Decline Sit-Up — Resistance band
Band Jack Knife Sit-Up — Resistance band
Band Kneeling Crunch — Resistance band
Band Standing Crunch — Resistance band
Bottoms Up — Bodyweight

Safety

Key takeaways

Curl the spine; do not hinge at the hip.
Breathe out hard at the top — it deepens the contraction.
Work in the 12-20 rep range for muscle growth, leaving a rep or two in reserve on most sets.
Full range of motion on the Straight Leg Sit-Up matters more than the weight on it.
Progress gradually and keep technique identical as the load goes up.

Go deeper

FAQ

What muscles does the Straight Leg Sit-Up work?

It works the core as the prime mover, with obliques, quadriceps and abductors assisting. The midsection also works throughout to keep you stable.

How many sets and reps should I do on the Straight Leg Sit-Up?

Three to four working sets of 12-20 reps suits most people training for muscle growth, leaving one or two reps in reserve. Across all the exercises that train this muscle, 6-16 hard sets a week is a productive range.

Is the Straight Leg Sit-Up good for beginners?

Yes, provided you start light enough to own the technique. Spend the first few weeks on the movement itself with a load you could do several more reps with, and add weight only once the pattern is automatic.

What can I do instead of the Straight Leg Sit-Up?

Crunch Floor, Cable Standing Crunch and 3 4 Sit-Up all train the core in a similar way, so any of them works as a substitute when the equipment is taken or you want to rotate the stimulus.

What equipment do I need for the Straight Leg Sit-Up?

This version uses your bodyweight. The pattern matters more than the tool, though — the alternatives above cover the same movement with whatever you have available.

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