Why is the TRX Sit-Up harder than a regular sit-up?

With the legs straight and raised in the cradles, you cannot bend the knees or kick the legs to help, and the straps swing if you jerk, so the abs have to lift the torso smoothly on their own.

Why do I feel it in my hips more than my abs?

The hip flexors help lift the torso in any straight-leg sit-up. Curl the spine first, pull the ribs toward the hips, and slow the reps down, or bend the knees slightly to shift more of the work to the abs.

What should I do if the TRX Sit-Up is too hard?

Try the TRX Jack Knife or the Crunch, or bend the knees a little and place the hands on the chest to shorten the lever.

Is the TRX Sit-Up safe for a bad back?

It is not a good choice during a back pain flare-up, because the straight legs load the lumbar spine through the hip flexors. A trainer or clinician can suggest gentler options such as the Dead Bug.

TRX Sit-Up

What Is the TRX Sit-Up?

TRX Sit-Up is a compound exercise that primarily targets the core, and it also engages the hip flexors and the shoulders. It is an intermediate-level movement: you lie on your back with both feet in the suspension cradles, legs straight, and curl your torso up to a seated position while the straps hold your legs off the floor.

With the feet raised in the cradles and the legs straight, you cannot tuck the knees or kick the legs to help you up, so the trunk does the lifting on its own. That makes it harder than a floor Sit-Up or a Crunch, and the hip flexors work alongside the abs to bring the torso up. The rectus abdominis and obliques are the main movers when you round the spine and pull the ribs toward the pelvis, while the arms reaching forward add a small shoulder demand and a longer lever for the torso.

The exercise suits people who already hold a Plank comfortably and can do clean floor sit-ups or crunches with control. If it is too hard, build up with the TRX Jack Knife, the Crunch or the Dead Bug first. Bending the knees slightly or placing the hands on the chest instead of reaching forward shortens the lever and makes each rep easier.

It usually sits in the middle or at the end of a session as abdominal work, after the main lifts. Slow, controlled reps with a deliberate lowering phase give the most return, and a sensible target is 6 to 12 clean reps per set.

Muscles Worked

MuscleActivation

Rectus Abdominis: Primary
External Oblique: High
Rectus Femoris: High
Rectus Abdominis (Lower): Medium
Sartorius: Medium
Tensor Fasciae Latae: Medium
Deltoid: Low
Serratus Anterior: Low

Instructions

Anchor the suspension trainer overhead and lengthen the straps so the foot cradles hang a short distance above the floor.
Lie on your back with your feet toward the anchor point and place both feet in the cradles, legs straight and toes pointing up.
Raise both arms straight toward the ceiling and brace your abs so your lower back stays close to the floor.
Tuck your chin slightly, then curl your head, shoulders and upper back off the floor, rounding the spine as you pull your ribs toward your hips.
Keep your legs straight and the straps steady as you continue up to a seated position, lowering your arms to reach straight forward at the top.
Pause briefly with your torso upright and your abs tight, without leaning back.
Lower slowly, rolling down one section of the spine at a time, and bring your arms back overhead as you reach the floor.
Let your shoulders touch down lightly, then start the next rep without letting the straps swing.

Common Mistakes

Swinging up with momentum
Throwing the arms or kicking the straps to get up takes the work off the abs and makes the straps sway, so start each rep from a still position.
Hinging from the hips
Sitting up as one stiff piece lets the hip flexors do the lift and pulls on the lower back, so curl the spine and pull the ribs toward the hips first.
Arching the lower back
Letting the low back lift off the floor at the start puts the spine under load, so brace the abs and keep the ribs down before each rep.
Dropping on the way down
Falling back to the floor skips the lowering phase, which is where much of the abdominal work happens, so roll down slowly.
Pulling on the neck
Jerking the head forward strains the neck, so keep the chin slightly tucked and reach the arms forward instead.

Injuries

TRX Sit-Up is a medium risk exercise when performed with proper technique. The straight, suspended legs make the hip flexors pull strongly on the lumbar spine, so the main strain points are the lower back, the hip flexors and, if the hands pull on the head, the neck.

To keep the load on the abs, round the trunk and pull the ribs toward the pelvis instead of hinging up from the hips. Keep the straps still, move at a slow tempo and lower with control rather than dropping back. Reaching the arms forward, not behind the head, keeps the neck out of the movement.

If the lower back arches or the hips feel like they are doing all the work, bend the knees a little, shorten the range or switch to the TRX Jack Knife or the Dead Bug. Stop the set if you feel sharp or pinching pain in the back, or pain that travels into the hip or leg. People with a history of back pain or disc problems should check with a clinician before adding sit-ups of any kind.

Overview

Primary Focus: Core
Equipment: Suspension trainer and body weight
Modality: Strength
Difficulty: Intermediate

Alternative Exercises

Frequently Asked Questions

Q: Why is the TRX Sit-Up harder than a regular sit-up?: With the legs straight and raised in the cradles, you cannot bend the knees or kick the legs to help, and the straps swing if you jerk, so the abs have to lift the torso smoothly on their own.
Q: Why do I feel it in my hips more than my abs?: The hip flexors help lift the torso in any straight-leg sit-up. Curl the spine first, pull the ribs toward the hips, and slow the reps down, or bend the knees slightly to shift more of the work to the abs.
Q: What should I do if the TRX Sit-Up is too hard?: Try the TRX Jack Knife or the Crunch, or bend the knees a little and place the hands on the chest to shorten the lever.
Q: Is the TRX Sit-Up safe for a bad back?: It is not a good choice during a back pain flare-up, because the straight legs load the lumbar spine through the hip flexors. A trainer or clinician can suggest gentler options such as the Dead Bug.