The bent-knee raised leg crunch holds the knees above the hips at roughly ninety degrees while the shoulders curl off the floor. Lifting the legs takes the feet away from the ground, which is what stops the hip flexors from anchoring the movement and turning it into a sit-up. The lower back also settles flat against the mat in this position, so the lumbar spine stays out of the range. What remains is a short, controlled spinal flexion driven by the abdominals.
Muscles Targeted
- Primary: Rectus abdominis
- Secondary: Obliques, transverse abdominis
- Tertiary: Hip flexors, serratus anterior
Starting Position
Lie on your back and lift the legs until the knees sit directly above the hips, shins roughly parallel to the floor. Press the lower back into the mat and hold it there. Place the fingertips lightly behind the ears or cross the arms over the chest, keeping the elbows wide. Leave a gap between the chin and chest so the neck stays long throughout.
Execution Steps
- Raise the knees directly over the hips and press the lower back flat into the mat.
- Brace the trunk so the ribs pull down toward the pelvis before anything else moves.
- Exhale and curl the shoulder blades off the floor, aiming the ribs toward the hips.
- Squeeze at the top for a full moment with the abdominals completely shortened.
- Lower slowly until the shoulder blades touch down again without releasing the brace.
- Keep the legs fixed in place and repeat for the whole set without dropping the knees.
Form Cues
- Ribs toward hips: the cue that produces flexion, rather than lifting the head.
- Knees stay put: legs drifting toward the chest means the hip flexors have joined in.
- Rest the fingertips behind the ears instead of lacing them behind the head.
- Keep the lower back flat for every repetition of the set.
- Curl slowly enough that no part of the movement relies on a bounce.
Common Mistakes
- Yanking the head forward: hands laced behind the head pull the chin down and strain the neck rather than the abdominals.
- Letting the knees drift: swinging the legs toward the chest adds momentum and hides how hard the abdominals are working.
- Arching the lower back: losing the flat back position at the top hands load to the hip flexors.
- Crunching too high: lifting the whole torso off the mat turns spinal flexion into a hip hinge driven by the hip flexors.
- Rushing the tempo: fast repetitions bounce on elastic recoil rather than building muscular tension in the abdominals.
Variations
- Feet-elevated crunch: rest the heels on a bench for an easier version.
- Weighted raised leg crunch: hold a plate on the chest for added resistance.
- Bicycle crunch: alternate elbow to opposite knee for the obliques.
- Reverse crunch: curl the hips up instead of the shoulders.
- Stability ball crunch: adds range through a longer starting stretch.
Tips for Progression
- Hold the top position for two seconds before adding reps.
- Extend the legs slightly to lengthen the lever once the form holds.
- Add a plate on the chest only after twenty clean bodyweight reps.
- Slow the lowering phase to three seconds for more time under tension.
Training Notes
Run this at the end of a session rather than before heavy squats or deadlifts, where a fatigued trunk costs more than the abdominal work is worth. Two to four sets of twelve to twenty reps fit most programmes. Stop the set when the knees start drifting or the lower back lifts, since both mean the abdominals have handed the work over.