Exercise guide
Straight Leg Crossed Arms Sit Up
- Beginner
- Compound
- Rep-based
- Waist
This variation targets the rectus abdominis and hip flexors by increasing the lever length of the lower body, while the crossed-arm position prevents the use of momentum.
Reviewed by the Crucible Fit team · Updated June 2026
Muscles worked
Setup
- Lie flat on your back on a mat with your legs fully extended and feet together.
- Cross your arms over your chest, placing your hands on opposite shoulders.
- Engage your core and press your lower back firmly into the floor to eliminate any arch.
How to do it
- Exhale as you slowly peel your spine off the floor, leading with your chest while keeping your heels pinned to the ground.
- Continue the movement until your torso is vertical and your chest is upright.
- Inhale as you reverse the movement, lowering your torso back to the floor one vertebra at a time with a controlled 2-3 second tempo.
- Avoid resting completely at the bottom; immediately begin the next rep to maintain tension.
Form checklist
- Keep your heels glued to the floor throughout the entire range of motion.
- Maintain a neutral neck by looking slightly upward rather than tucking your chin to your chest.
- Avoid 'jerking' the torso up; use abdominal strength rather than momentum.
- Ensure your lower back makes contact with the floor before your shoulder blades during the descent.
Pro tips
- Focus on 'curling' your spine up and down like a carpet to maximize the contraction of the rectus abdominis.
- Squeeze your quadriceps and flex your toes toward your shins to help stabilize your lower body and prevent your legs from lifting.
Make it harder
- Hold a weight plate or dumbbell against your chest to increase resistance.
- Perform the exercise on a decline bench to increase the range of motion and time under tension.
Frequently asked
- What muscles does the straight leg crossed arms sit up work?
- The straight leg crossed arms sit up primarily targets the abs and obliques, and also works the serratus anterior as secondary muscles.
- What equipment do you need for the straight leg crossed arms sit up?
- The straight leg crossed arms sit up requires no equipment — just your body weight.
- Is the straight leg crossed arms sit up good for beginners?
- Yes. The straight leg crossed arms sit up is a beginner-friendly movement and a strong foundation to build on.