Lying 90 Degree Alternate Leg Extension

Muscles worked

Setup

1. Lie flat on your back on a mat with your arms by your sides, palms facing down.
2. Lift both legs into a 'tabletop' position, with knees bent at 90 degrees and shins parallel to the floor.
3. Press your lower back firmly into the floor to engage your core and eliminate any arching in the spine.

How to do it

1. Inhale and slowly extend one leg forward, straightening the knee until the leg is hovering just above the floor.
2. Exhale as you use your lower abdominals to pull the leg back to the 90-degree tabletop starting position.
3. Repeat the movement with the opposite leg, maintaining a controlled 2-second extension and 2-second return tempo.
4. Continue alternating legs while keeping the stationary leg perfectly still at a 90-degree angle.

Form checklist

• Keep the lower back glued to the floor at all times to protect the spine.
• Ensure the stationary knee stays directly over the hip, not drifting toward the chest.
• Move with control; do not use momentum to swing the legs back and forth.
• Keep your neck and shoulders relaxed on the mat throughout the set.

Pro tips

• Focus on 'zipping up' your abdominal wall toward your spine as the leg extends to maximize deep transverse abdominis engagement.
• Squeeze the quadriceps of the extending leg at the bottom of the movement to increase the intensity of the leg isolation.

Make it harder

• Lower the extending leg closer to the floor without letting your lower back lift off the mat.
• Perform the movement with your head and shoulders lifted off the mat in a 'hollow body' position to engage the upper abdominals.

Frequently asked

What muscles does the lying 90 degree alternate leg extension work?

The lying 90 degree alternate leg extension primarily targets the abs, and also works the hip flexors as secondary muscles.

What equipment do you need for the lying 90 degree alternate leg extension?

The lying 90 degree alternate leg extension requires no equipment — just your body weight.

Is the lying 90 degree alternate leg extension good for beginners?

The lying 90 degree alternate leg extension is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.

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