Flexion Leg Sit-Up (Straight Arm)

Flexion Leg Sit-Up (Straight Arm) Exercise Description

The Flexion Leg Sit-up (straight arm) is a bodyweight trunk-flexion exercise performed supine with legs extended and arms held straight overhead. It emphasizes the rectus abdominis via controlled spinal flexion, with the external and internal obliques assisting; because the torso rises relative to the legs, the hip flexors contribute as you complete the sit-up. Keeping the arms straight overhead lengthens the lever, increasing the challenge—so avoid swinging the arms for momentum. Use a smooth, segmental curl on the way up and a controlled descent to keep the abdominal wall, not inertia, driving the movement. Maintain a neutral neck and steady lumbopelvic control throughout to avoid excessive arching at the bottom. ([exrx.net](https://exrx.net/WeightExercises/RectusAbdominis/BWSitUp?utm_source=openai))

Muscle Groups: Abs, Core, Waist
Target Muscles: Rectus Abdominis
Assisting Muscles: External Obliques, Iliacus, Internal Obliques, Psoas Major
Stabilizing Muscles: Multifidus, Transversus Abdominis
Body Area: Upper Body
Body Parts: Core, Torso
Body Surface: Front
Body Symmetry: Other
Equipment: Bodyweight
Exercise Patterns: Other
Exercise Type: Strength
Functional Grouping: Trunk Flexors
Joint Involvement: Multi-joint
Muscle Location: Stomach
Movement Direction: Other
Muscle Position: Anterior
Gender: Female

How To Do The Flexion Leg Sit-Up (Straight Arm) Exercise

‘- Lie supine with legs straight together, heels lightly on the floor; reach arms straight overhead in line with your ears, palms facing each other.
– Brace your abdomen, set ribs “down,” and keep your neck neutral with a light chin tuck.
– Initiate by curling your head, shoulders, and upper back off the floor; continue flexing through the trunk as you sit up, keeping arms straight and in place—do not swing.
– Finish tall when your torso is upright, reaching through the fingertips while keeping legs quiet and heels grounded.
– Lower with control: reverse the motion, placing your spine down segment by segment until shoulder blades contact the floor.
– Keep breathing—exhale as you rise, inhale as you lower—while maintaining smooth, controlled tempo.
– If you cannot keep arms straight without swinging, reduce range slightly and focus on crisp trunk flexion and steady bracing.

Flexion Leg Sit-Up (Straight Arm) Tips

‘- Lie with legs straight together and heels lightly touching the floor to keep the lower body quiet.
– Reach arms straight overhead in line with your ears, palms facing each other, and maintain this position.
– Brace your abdomen and set your ribs “down” before you start moving.
– Keep your neck neutral with a light chin tuck as you curl up and down.
– Initiate the sit-up by segmentally curling your head, shoulders, and upper back off the floor rather than lifting all at once.
– Keep your arms straight and do not swing them; let the trunk do the work.
– Sit up until your torso is upright and “tall,” reaching through your fingertips while keeping heels grounded.
– Lower with control by reversing the motion and placing your spine down segment by segment until your shoulder blades touch the floor.
– Maintain a smooth, controlled tempo, exhaling as you rise and inhaling as you lower.
– If you start to swing your arms or bend them, reduce the range of motion and focus on crisp trunk flexion with steady bracing.

Flexion Leg Sit-Up (Straight Arm) Beginner Introduction

The Flexion Leg Sit-up (straight arm) trains the mid-section using only bodyweight, combining a long-leg position with arms extended behind the head. From a lying start on the back, the upper body steadily curls away from the floor until an upright sitting posture is reached, then returns in a slow, deliberate arc. The main effort centers on the abs, with the side abs and hip flexors joining in as the torso rises in relation to the legs. Because the arms stay straight and reach far from the center of the body, the load on the trunk increases and momentum from arm swinging is minimized.

Emphasis in this sit-up variation falls on smooth control rather than speed. The spine rolls through the movement in a flowing sequence, while the lower back and hips stay stable against the pull of the legs. Neck alignment stays relaxed and in line with the rest of the body, and breathing usually follows the rhythm of curling up and lowering down. This makes the exercise a focused way to challenge core strength, body awareness, and coordination in a simple floor-based setup.