Oblique Crunch
The oblique crunch is a floor ab exercise in which you curl up and turn your upper body so one elbow moves towards the opposite knee, alternating sides. It works the obliques along with the rectus abdominis.
Also called: Side Crunch, Lateral Crunch, Twisting Crunch, Cross Crunch · Equipment: bodyweight · Pattern: isolation
Step by step
- Lie on your back with your knees bent and your feet flat on the floor, hip-width apart.
- Rest your fingertips lightly behind your head or cross your arms over your chest.
- Breathe out and brace, keeping your low back on the floor.
- Curl your shoulders off the floor and turn your upper body so one elbow moves towards the opposite knee.
- Pause briefly at the top, then uncurl slowly to the floor.
- Repeat to the other side, alternating for the set, with your hips staying flat on the floor.
- Shoulder towards the opposite knee
- Curl up first, then turn
- Hands light behind your head
- Hips stay flat on the floor
- Slow on the way down
In VALDA, these cues are one tap away on the exercise while you train.
What it trains
| Muscle | Role | Evidence |
|---|---|---|
| Obliques (internal/external) | Prime mover | C |
| Rectus abdominis | Secondary | C |
| Hip flexors | Stabiliser | D |
Evidence grades: A = strong research base · B = good · C = limited · D = coaching consensus.
What goes wrong, and the fix
Pulling on the head
Fix: Keep your fingertips light and lift from your ribs, not your hands.
Swinging the elbow only
Fix: Turn your shoulder towards the knee so your whole upper body rotates.
Hips rolling to the side
Fix: Keep both feet flat and your hips square on the floor.
Rushing from side to side
Fix: Pause at the top of each rep and uncurl for about two seconds.
Sitting all the way up
Fix: Lift only until your shoulder blades clear the floor.
What the research says
General fitnessEndurance
- Muscle activity — EMG research shows the obliques are the main trunk muscles in twisting efforts, and a twisting bicycle crunch produced high oblique activity in a comparison of 13 ab exercises. The floor oblique crunch itself has not been measured, and EMG measures activity, not growth.
- Volume — Research links more weekly sets for a muscle to more growth, with diminishing returns.
- Reps — A common approach is higher-rep sets, alternating sides. Holding a light plate at the chest is a common next step.
Swap it mid-workout
With VALDA Pro, FLEX offers alternatives like these when you swap an exercise mid-workout.
Log the oblique crunch in VALDA, with these cues one tap away while you train and your history for it in one place.
General information about exercise technique, not medical advice. If you have an injury or a health condition, your healthcare provider is the right person to ask.