Exercise Guide
How to do frog crunch
Master the setup, range of motion, and tempo for safer, more effective reps.
Overview
By placing the soles of your feet together and letting your knees fall open, you shorten the hip flexors. This 'turns them off,' forcing your rectus abdominis (the six-pack muscles) to do the work of curling your torso. It is a highly effective way to target the midsection without the lower back strain that often comes with traditional sit-ups.
Why Use It
- Isolates the abdominal wall by removing hip flexor assistance.
- Reduces the risk of lower back arching during core work.
- Requires zero equipment and can be done anywhere.
When to Use It
Use this as a finisher at the end of your workout or as part of a core-focused circuit.
Stats
Instructions for Proper Form
Setup
- The Position: Lie on your back and pull your heels toward your groin. Press the soles of your feet together.
- The Knees: Let your knees fall open toward the floor like a butterfly stretch.
- The Hands: Place your hands lightly behind your head or cross them over your chest.
Execution
- The Crunch: Exhale and use your abs to lift your head and shoulder blades off the mat.
Pro Tip: Imagine you are trying to slide your ribs down into your hip bones.
- The Squeeze: Hold the top position for a second, blowing out the last bit of air to maximize the burn.
Coaching Cues
- Push your feet together hard
- Keep your chin off your chest
- Flatten your lower back into the mat
Common Mistakes
- Neck Yanking: Using the hands to pull the head forward instead of using the abs.
- Closing the Knees: Letting the knees drift upward, which brings the hip flexors back into the move.
- Rushing Reps: Using momentum to bounce up and down without control.
How to Fix It
- Neck Yanking: Keep your elbows wide and imagine holding an orange between your chin and chest.
- Closing the Knees: Actively push the outer edges of your feet into the floor to keep the knees open.
- Rushing Reps: Pause for a full second at the top and bottom of every single rep.
Mistakes by Level
Beginner
- Holding the breath.
- Lifting the lower back off the floor.
Intermediate
- Not reaching full contraction at the top.
Advanced
- Moving too fast through the lowering phase.
Mechanics
Use these setup and execution anchors to keep the rep organized, repeatable, and easier to progress.
Movement Pattern
Other
Body Position
Supine
Load Style
Bodyweight
Muscles Worked
Primary
- Rectus-abdominis
Secondary
- Obliques
Stabilizers
- Transverse-abdominis
Setup Requirements
- Lie flat on your back on a mat.
- Bring the soles of your feet together and let your knees drop out to the sides.
- Place your fingertips lightly behind your ears.
Form Checklist
- Are your knees staying wide?
- Are you pulling on your neck or lifting with your stomach?
- Is your lower back staying pressed into the floor?
Range of Motion
Lift your head and shoulder blades off the floor until you feel a maximum contraction in your abs. Lower back down until your shoulders just touch the floor.
Breathing Pattern
Exhale all your air as you crunch up to deepen the contraction; inhale as you lower.
Tempo Guidance
2 seconds up, 1 second squeeze, 2 seconds down.
Caution Notes
- Do not interlock your fingers behind your head; this often leads to neck strain.
Programming
Treat these guidelines as practical programming defaults, then scale load, volume, and frequency to match the rest of the training week.
Best For
- Abdominal isolation.
- Core control.
- Beginner core training.
Goal Tags
Rep Ranges
- 15-25 reps for endurance.
- 10-15 slow reps for strength.
Set Guidance
3 sets of 20 reps.
Rest Guidance
30-45 seconds.
Frequency
3-4 times per week.
Pairings
- Pair with planks.
- Superset with bird-dogs.
Audience Notes
- Perfect for those who feel traditional crunches mostly in their thighs or hips.
Substitution Targets
- Butterfly sit-up
- Standard crunch
Variations
Use progressions to increase difficulty when you master the movement, and regressions if you struggle with proper form or face mobility limitations.
Regressions
Standard Crunch
If the frog position is too intense for your hips, keep your feet flat.
Best for: Hip mobility issues.
Progressions
Weighted Frog Crunch
Holding a small weight plate on your chest increases the resistance.
Best for: Advanced core strength.
FAQ
Common Questions
Why do my inner thighs feel a stretch?
The frog position naturally stretches the adductors. If it's uncomfortable, move your feet further away from your body.
Alternatives
Start with the closest related options, then browse fallback alternatives that keep the same primary training focus.