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 that targets the abdominal wall, especially the rectus abdominis, with contribution from the external and internal obliques. Bending the knees places the hips and knees in flexion while the arms remain straight overhead, increasing the lever arm and challenge to the anterior core. Hip flexors (iliopsoas and rectus femoris) assist to bring the torso up, but the movement should be initiated by spinal flexion rather than by pulling through the hips. Keeping the arms straight and near the ears discourages swinging and momentum, promoting controlled segmental flexion and extension through the spine. This variation is best performed with steady tempo and mindful breathing to maintain ribcage control and minimize excessive lumbar extension during the descent.
- Muscle Groups: Abs, Core, Waist
- Target Muscles: Rectus Abdominis
- Assisting Muscles: External Obliques, Internal Obliques
- 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: Vertical
- Muscle Position: Anterior
- Gender: Male
How To Do The Flexion Leg Sit Up (Straight Arm) Exercise
‘- Lie supine with knees bent, feet flat and hip-width apart. Arms straight overhead, elbows extended, hands in line with or slightly behind the shoulders.
– Lightly brace the abdominal wall. Bring ribs down, maintain a neutral head/neck with a small chin nod.
– Posteriorly tilt the pelvis to engage the abdominals, then curl the head and upper back off the floor first.
– Continue segmental trunk flexion to sit up tall over the sit bones. Keep arms straight beside the ears; avoid swinging them forward.
– Keep feet in contact with the floor and shoulders relaxed away from the ears.
– Lower with control by reversing the motion: unroll the spine back to the floor one segment at a time, arms still straight overhead.
– Breathe steadily—exhale as you rise, inhale as you lower.
– Avoid jerking, bouncing, or using momentum; do not tug the head or flare the ribs or arch the low back during the descent.
Flexion Leg Sit Up (Straight Arm) Tips
‘- Set up with knees bent, feet flat and hip-width apart, and arms straight overhead with hands in line with or slightly behind the shoulders.
– Lightly brace the abdominal wall and bring the ribs down before you start moving.
– Maintain a neutral head and neck with a small chin nod as you curl up.
– Posteriorly tilt the pelvis, then curl the head and upper back off the floor first to initiate spinal flexion.
– Continue segmental trunk flexion until you sit up tall over the sit bones, rather than pulling through the hips.
– Keep the arms straight beside the ears throughout and avoid swinging them forward for momentum.
– Keep the feet in contact with the floor and shoulders relaxed away from the ears.
– Lower with control by reversing the motion, unrolling the spine back to the floor one segment at a time with arms still straight overhead.
– Breathe steadily—exhale as you rise and inhale as you lower.
– Avoid jerking, bouncing, tugging the head, flaring the ribs, or arching the low back during the descent.
Flexion Leg Sit Up (Straight Arm) Beginner Introduction
The Flexion Leg Sit-Up (straight arm) is a bodyweight core exercise that centers on the abs and side abs while the hips and knees stay bent. The person lies on the back with the legs bent and the arms stretched long above the head, creating a long lever that places extra demand on the front of the torso. As the upper body rises, the spine curls gradually, segment by segment, so the movement comes from the midsection rather than from a forceful pull at the hips. Muscles at the front of the hips and thighs support the action but do not dominate it.
Throughout the motion, the arms remain extended close to the head, which limits swinging and reduces momentum, encouraging a smooth, controlled rise and return. A steady rhythm and coordinated breathing help with control of the ribcage and comfort through the lower back, especially on the way down. This sit-up style highlights thoughtful movement of the spine and careful positioning rather than speed, making it a more precise and challenging take on a traditional curl-up.