Crunch (Straight Leg-Up)
Crunch (Straight Leg-Up) Exercise Description
Crunch (straight leg-up) is a bodyweight trunk-flexion exercise performed supine with the legs extended vertically above the hips. It primarily targets the rectus abdominis; the external and internal obliques and the transverse abdominis assist by bracing and controlling the pelvis, while the hip flexors hold the legs in position isometrically. Keeping the knees extended lengthens the lower-limb lever, increasing the demand on the abdominal wall to keep a slight posterior pelvic tilt and prevent lumbar arching. The active motion is a small, controlled curl of the upper torso—lifting the shoulder blades from the floor—while the legs remain quiet and stacked over the hips. A gentle chin tuck and eyes toward the ceiling help maintain neutral cervical alignment so the motion comes from thoracic flexion rather than neck pulling. Coordinated breathing—exhaling on the curl and inhaling on the return—supports rib cage depression and consistent trunk bracing without external equipment.
- Muscle Groups: Abs, Core, Waist
- Target Muscles: Rectus Abdominis
- Assisting Muscles: External Obliques, Internal Obliques
- Stabilizing Muscles: Iliacus, Psoas Major, Rectus Femoris, 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: Single-joint
- Muscle Location: Stomach
- Movement Direction: Other
- Muscle Position: Anterior
- Gender: Female
How To Do The Crunch (Straight Leg-Up) Exercise
‘- Lie supine. Extend both legs straight up so ankles stack over hips; knees long but not locked, feet neutral.
– Reach arms toward the ceiling (or lightly support the head with fingertips, elbows wide—no pulling).
– Set a slight posterior pelvic tilt to keep the low back in light contact with the floor. Ribs down; brace the abdominal wall.
– Inhale to prepare. Gently tuck the chin (neck long, gaze up).
– Exhale as you curl the trunk: draw the sternum toward the pelvis and lift the shoulder blades just off the floor. Arms reach without swinging; legs stay still and vertical.
– Pause briefly at the top while maintaining pelvic control and a quiet lower body.
– Inhale as you lower the torso with control until the shoulder blades touch down, keeping the ribs down and low back supported.
– Form checks: avoid arching the lumbar spine, flaring the ribs, leading with the neck, or rocking the legs. If the pelvis tips or the low back lifts, bend the knees slightly or lower the legs a few degrees to re-stack over the hips.
Crunch (Straight Leg-Up) Tips
‘- Stack your ankles directly over your hips with legs straight, knees long but not locked, and feet neutral.
– Set a slight posterior pelvic tilt so your low back stays in light contact with the floor.
– Keep your ribs down and brace your abdominal wall before you start curling.
– Gently tuck your chin, keep your neck long, and gaze up to avoid leading with the neck.
– Exhale as you curl the trunk, drawing the sternum toward the pelvis and lifting the shoulder blades just off the floor.
– Reach your arms without swinging them, whether they are pointed to the ceiling or lightly supporting your head.
– Keep your legs quiet and vertical throughout the movement, avoiding any rocking.
– Pause briefly at the top while maintaining pelvic control and a still lower body.
– Inhale as you lower with control until your shoulder blades touch down, keeping ribs down and low back supported.
– If your pelvis tips or low back lifts, slightly bend your knees or lower your legs a few degrees to re-stack them over your hips.
Crunch (Straight Leg-Up) Beginner Introduction
Crunch (straight leg-up) is a floor-based core move that uses only bodyweight and a slow, controlled lifting action. The person lies on the back with both legs stretched upward so they point toward the ceiling, creating a long lever that challenges the midsection. The main effort comes from the abs, with support from the side abs and deep core muscles to steady the pelvis and protect the lower back. The hip flexors work steadily to keep the legs raised without swinging.
During the exercise, the upper body gently curls forward just enough for the shoulder blades to rise from the floor, while the legs remain vertical and still. The neck stays long and relaxed, with the gaze generally oriented upward rather than pulling from the head. Arms can reach toward the ceiling or lightly support the head. Breathing is coordinated with the motion, with a strong breath out on the lift and a controlled breath in as the torso returns to the starting position.