Alternate Frog Crunch

Muscles worked

Setup

1. Lie flat on your back on a mat with your legs extended.
2. Bring the soles of your feet together and let your knees fall outward into a diamond shape.
3. Place your fingertips lightly behind your ears with your elbows flared out wide.
4. Press your lower back firmly into the floor to engage your deep core.

How to do it

1. Exhale as you lift your head and shoulder blades off the floor, bringing one knee toward your chest while rotating the opposite elbow to meet it.
2. Squeeze your obliques at the top of the movement, ensuring your shoulder—not just your elbow—is moving toward the knee.
3. Inhale as you lower back to the starting position with a controlled 2-second tempo.
4. Repeat the movement on the opposite side, alternating for the duration of the set.

Form checklist

• Keep your lower back glued to the mat throughout the entire movement.
• Avoid pulling on your neck; use your abdominal strength to lift your torso.
• Maintain the 'frog' leg position by keeping your knees pointed outward.
• Focus on bringing the shoulder toward the opposite hip to maximize oblique activation.

Pro tips

• Visualize your ribs sliding down toward your opposite hip bone to create a deeper contraction.
• Hold the peak contraction for one second to increase the intensity on the upper abs and obliques.

Make it harder

• Keep your feet hovering 2 inches off the ground throughout the entire set to maintain constant tension.
• Perform the movement with a weighted plate held against your chest.

Frequently asked

What muscles does the alternate frog crunch work?

The alternate frog crunch primarily targets the abs and obliques, and also works the hip flexors as secondary muscles.

What equipment do you need for the alternate frog crunch?

The alternate frog crunch requires no equipment — just your body weight.

Is the alternate frog crunch good for beginners?

The alternate frog crunch is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.

Related exercises

• 3/4 Sit-UpBeginner · abs and obliques
• 45 Degree Bicycle Twisting CrunchIntermediate · abs and obliques
• 45 Degree Lean Back Alternate Knee RaiseBeginner · abs and obliques
• 45 Degrees Arms PlankIntermediate · abs, deltoids, obliques, and pectorals