Starfish Crunch
Quick answer
Starfish crunches are a lying core exercise where you start spread out like a starfish, then lift one straight arm and the opposite straight leg so they meet diagonally across your body. They work the abs and obliques, with the shoulders helping the reach.
Written by the GymStreak coaching team · Updated
Muscles worked
How to do Starfish Crunch
- 1
Lay flat on your back on the floor with your legs extended (heels in contact with the floor) and your arms straight above your head (palms facing the ceiling). Your legs should be spread slightly, so that your feet are wider than shoulder width apart and your arms the same so that your hands are wider than shoulder width apart. Your body should form the rough shape of a starfish. This is the starting position.
- 2
Keeping your arm straight, raise your right shoulder away from the floor. As you do so, raise you left heel away from the floor towards the ceiling and diagonally across your body (by internally rotating at the left hip) to meet your right hand. Keep your leg as straight as your hamstring flexibility will allow.
- 3
When you make contact between your right hand and your left foot (around the ankle), lower back towards the starting position.
- 4
Repeat the movement outline above but with the opposite arm and leg.
- 5
The act of raising your right hand to meet your left leg, and your left hand to meet your right leg, is equal to one repetition. Repeat for as many reps as necessary.
Form cues
- Start the reach by curling your ribs toward the opposite hip.
- Keep the resting shoulder and hip in contact with the floor.
- Keep the lifting leg as straight as your hamstrings allow.
- Touch wherever you can reach, such as the shin, rather than straining for the ankle.
- Lower slowly back to the starfish before switching sides.
Breathing: Breathe out as your hand reaches toward the opposite ankle and breathe in as you lower back to the floor; don't hold your breath.
Common Starfish Crunch mistakes
Swinging the arm to throw the body up
Lift your shoulder blade by curling through your abs, and let the arm follow rather than lead with momentum.
Lower back arching as the leg lifts
Brace your abs before each rep so your lower back stays close to the floor while the leg rises.
Rolling fully onto one side
Rotate only enough to reach across, keeping the opposite shoulder and hip on the floor.
Dropping the arm and leg back down
Lower both over about two seconds and let them touch down lightly before the next rep.
Sets and reps by goal
| Goal | Sets | Reps | Rest |
|---|---|---|---|
| Beginnerseach side | 1–3 | 10–15 | 60–90 s |
| Muscular enduranceeach side | 2–3 | 12–20 | 30–60 s |
Starting ranges in line with the ACSM guidance on resistance training. Pick a load you can lift with good form for every rep, and add weight or reps gradually.
Starfish Crunch variations and alternatives
Variations
- Bent-knee starfish crunch
Bend the lifting knee to shorten the lever if tight hamstrings stop you reaching.
- Jackknife Sit-Up
A harder version that brings both hands and both feet together at once.
Alternatives
- Cross-Body Crunch
A bent-knee diagonal crunch that trains the same rotation and is easier to control.
- Dead Bug
Opposite arm-and-leg core work with the back kept flat, good for beginners.
- Oblique Crunches
Pick these for more focused oblique work.
Starfish Crunch FAQ
What muscles does the starfish crunch work?
The rectus abdominis curls your upper body off the floor, and the obliques rotate your torso so your hand can reach across to the opposite foot. The hip flexors lift the straight leg, and the shoulders keep the reaching arm raised and extended.
Is the starfish crunch good for beginners?
It suits most beginners, since it uses only bodyweight and you control the range. If reaching the ankle is too hard, touch your shin or knee instead, or bend the lifting leg. Keep the other shoulder and hip on the floor and move slowly rather than swinging.
What is the difference between a starfish crunch and a regular crunch?
A regular crunch curls straight forward and mainly works the rectus abdominis. The starfish crunch adds rotation and a straight-leg lift, so the obliques and hip flexors work harder and each rep takes more coordination. Many people include both in the same core routine.
How many starfish crunches should I do?
Start with 1–3 sets of 10–15 per side, resting about a minute between sets, and keep every rep slow and controlled. When 15 per side feels easy with good form, add a set, work toward 20 per side, or move on to a harder version such as the jackknife sit-up.
Sources
Related calculators
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