Straight Leg Sit-Ups (How To, Benefits & Alternatives)

Straight Leg Sit-Ups are a core exercise that targets the entire abdominal wall, especially the rectus abdominis, by taking your abs through a full range of motion. With your legs extended flat on the ground, this variation increases the challenge on your core and reduces momentum from the lower body.

It’s a solid bodyweight move for building ab strength and control.

Primary Muscles Worked: Rectus Abdominis
Secondary Muscles Worked: Obliques, Hip Flexors
Equipment Needed: None

How To Do Straight Leg Sit-Ups

Step-by-Step Instructions

Set-Up:
- Lie flat on your back with your legs extended straight and arms crossed over your chest or reaching overhead.
- Keep your heels on the ground and engage your core before starting the movement.
Execution:
- Using your core, lift your upper body off the ground in a smooth, controlled motion.
- Sit all the way up until your chest is over your hips.
- Slowly lower yourself back down to the floor with control—don’t flop down.
Tips for Proper Form:
- Keep your feet grounded and avoid lifting your heels off the floor.
- Don’t use your arms to swing—focus on using your core to lift.
- Exhale as you sit up, and inhale on the way down.

Key Benefits

Trains the abs through a full range of motion.
Builds core strength and muscular endurance.
Requires no equipment—perfect for home or travel workouts.

Modifications and Variations

Easier Option: Bend your knees or anchor your feet under something stable for support.
Harder Option: Hold a plate or dumbbell at your chest or overhead for added resistance.

Common Mistakes

Using Momentum: Avoid throwing your arms or jerking upward—keep it slow and controlled.
Lifting the Heels: Press your legs into the floor to stay grounded.
Not Controlling the Descent: Lower slowly to stay engaged and protect your lower back.

Reps and Sets Recommendations

For Beginners: 3 sets of 8–10 reps focusing on control.
For Core Strength: 3–4 sets of 10–12 reps with full range and steady tempo.
For Added Resistance: 3 sets of 8–10 reps holding a light to moderate weight.

Straight Leg Sit-Up Alternatives

If you’re unable to do Straight Leg Sit-ups, here are a few alternatives that you may be able to use as a substitution.

Crunches

The simplest alternative to Sit-ups is to switch them out for Crunches. If you’re struggling with Sit-ups, Crunches is the first thing I would suggest as a replacement until you’re ready to progress back to Sit-ups.

Start laying on your back as well, knees bent at 90 and feet off the floor. Instead of sitting all the way up, simply crunch up and squeeze the abs.

Sky Crunches

Sky Crunches are probably the best beginner-friendly progression to get you prepared to do Straight Leg Situps. You start in basically the exact same position – laying on your back with legs straight.

However, instead of sitting all the way up, you simply crunch up towards the sky (hence ‘sky crunches’).