Long Arm Crunch
- Target muscle
- Rectus Abdominis
- Synergist muscles
- Obliques
- Equipment
- Body weight
- Body part
- Waist
- Type
- Strength
The Long Arm Crunch is an abdominal exercise that targets the rectus abdominis while engaging the obliques as synergists. By extending your arms overhead, you lengthen the lever arm, placing significantly greater demand on the core compared to a standard crunch. It is an effective bodyweight move for building core strength and improving abdominal definition without any equipment.
How to do the Long Arm Crunch
- 1Lie flat on your back on a mat with your knees bent and feet flat on the floor, hip-width apart.
- 2Extend both arms straight overhead, keeping them close to your ears and parallel to the floor — this is your starting position.
- 3Brace your core by drawing your navel gently toward your spine.
- 4Exhale and slowly curl your head, neck, and shoulder blades off the mat, reaching your extended arms forward and upward toward your knees.
- 5Continue the upward curl until your shoulder blades are fully lifted off the mat, pausing briefly at the top of the movement.
- 6Inhale and slowly lower yourself back to the starting position under control, keeping your arms extended throughout.
- 7Repeat for the desired number of repetitions without letting momentum take over between reps.
Form tips
- Keep your lower back pressed into the mat throughout the movement — if it arches, you are relying on hip flexors rather than your abs.
- Avoid pulling your chin toward your chest; instead, maintain a fist-width gap between your chin and chest and keep your gaze angled upward.
- To reduce neck tension, place your tongue on the roof of your mouth and focus on lifting through your sternum rather than your head.
- Move your arms as one unit with your torso — let them travel in the same arc as your upper body rather than swinging them independently.
- Control the lowering phase; a slow, deliberate descent under a 2–3 second count maximises time under tension and protects the spine.
Common mistakes
- Pulling on the neck: Straining the head forward with the arms or interlacing the fingers behind the head compresses the cervical spine and transfers the work away from the abs, increasing injury risk.
- Using momentum: Swinging the arms and jerking the torso up reduces abs activation and places sudden stress on the lower back; always perform the movement with slow, controlled intention.
- Partial range of motion: Barely lifting the head off the mat misses the full contraction of the rectus abdominis — aim to raise the entire shoulder blade complex off the floor.
- Arching the lower back: Allowing the lumbar spine to lift off the mat turns the crunch into a hip-flexor exercise and can strain the lower back; keep the spine neutral and the core braced.
- Holding the breath: Forgetting to breathe raises intra-abdominal pressure unnecessarily; exhale on the way up and inhale on the controlled descent to maintain proper core engagement.
Frequently asked questions
What muscles does the Long Arm Crunch work?
The Long Arm Crunch primarily works the rectus abdominis — the muscle responsible for the 'six-pack' appearance. The obliques (both internal and external) act as synergists, assisting with trunk flexion and stabilising the torso throughout the movement.
How is the Long Arm Crunch different from a regular crunch?
In a standard crunch, your arms rest across your chest or lightly behind your head, keeping your centre of mass close to your hips. The Long Arm Crunch extends your arms overhead, which lengthens the lever arm and shifts more weight further from the fulcrum. This increases the torque your abs must overcome, making the exercise mechanically harder without adding any external load.
How many sets and reps should I do for the Long Arm Crunch?
For general core strength and endurance, aim for 3 sets of 12–20 repetitions with a 60-second rest between sets. If you are a beginner, start with 2 sets of 10 reps and focus on form. More advanced trainees can increase reps, add a pause at the top, or slow the tempo to progress without needing weights.
Is the Long Arm Crunch safe for people with lower back pain?
For many people, crunches performed with proper form — lower back pressed into the mat, controlled movement, no momentum — are tolerable. However, if you have an existing lower back injury or disc issue, the spinal flexion involved may aggravate your condition. Consult a healthcare professional before including this exercise in your routine.
Can I replace the Long Arm Crunch with a sit-up?
They are related but not interchangeable. The Long Arm Crunch isolates the upper abs by keeping the lower back on the mat and only lifting the shoulder blades. A full sit-up involves greater range of motion and heavier hip-flexor recruitment. The crunch variation typically places less stress on the lumbar spine, making it preferable when targeting the abs in isolation.
