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Exercise guide

Body Extension

  • Intermediate
  • Isolation
  • Timed hold
  • Lower legs
  • Upper legs
  • Waist

The Body Extension is a high-tension movement that builds core stability and eccentric quadriceps strength by lengthening the body's lever arm against gravity.

Reviewed by the Crucible team · Updated June 2026

Watch the Body Extension demonstrationGuided video and your full workout live in the Crucible app.

Muscles worked

Primary

  • Abs
  • Quadriceps

Secondary

  • Erector spinae
  • Glutes
  • Hamstrings

Equipment

  • Body weight

Setup

  1. Stand with your feet hip-width apart and your arms resting at your sides.
  2. Engage your core and tuck your pelvis slightly to maintain a neutral spine.
  3. Fix your gaze straight ahead to keep your neck in a neutral position.

How to do it

  1. Inhale and simultaneously reach your arms overhead while rising onto the balls of your feet.
  2. Lean your entire body forward in a straight line from your hands to your heels, extending as far as you can while maintaining balance.
  3. Exhale and forcefully contract your abdominals and quadriceps to pull your body back to the vertical starting position.
  4. Perform the movement with a controlled tempo, pausing for one second at the point of maximum extension.

Form checklist

  • Maintain a 'hollow body' position by keeping the ribs tucked and the core braced.
  • Ensure the movement occurs at the ankles; do not bend or 'break' at the hips.
  • Keep your glutes squeezed throughout the set to protect the lower back.
  • Avoid arching the lumbar spine as you reach forward.

Pro tips

  • To maximize quad activation, focus on pushing through the balls of your feet as you return to the start.
  • Think of your body as a solid plank; the further you lean, the more tension you create in the rectus abdominis.

Make it harder

  • Increase the duration of the isometric hold at the peak of the extension to 3-5 seconds.
  • Perform the movement with a slower eccentric (leaning) phase to increase time under tension.

Frequently asked

What muscles does the body extension work?
The body extension primarily targets the abs and quadriceps, and also works the erector spinae, glutes, and hamstrings as secondary muscles.
What equipment do you need for the body extension?
The body extension requires no equipment — just your body weight.
Is the body extension good for beginners?
The body extension is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.

Related exercises

  • 90 To 90Beginner · abs, glutes, obliques, and quadriceps
  • 90 To 90 SwitchIntermediate · abs, glutes, obliques, and quadriceps
  • Alternate Leg Lift TwistIntermediate · abs, obliques, and quadriceps
  • Alternating Hamstring Curl JackIntermediate · abs, glutes, hamstrings, and quadriceps

Train this with a plan, not guesswork

Crucible builds the body extension into a precise program around your body, equipment, location, and time.

Download on the App Store