Skip to content
Crucible Fit
  • The Crucible
  • The Week
  • Programs
  • Train Your Way
  • Pricing
Get Crucible
  • The Crucible
  • The Week
  • Programs
  • Train Your Way
  • Apple Watch
  • Pricing
  • FAQ
  • Training Guides
Get Crucible
Crucible Fit

A daily functional fitness test for iPhone, Apple Watch and Android. Stations, reps and the Crux, sized to your readiness and your kit.

Download on the App StoreGet it on Google Play

Crucible Fit

  • The Crucible
  • The Week
  • Programs
  • Train Your Way
  • Apple Watch
  • Pricing

Explore

  • Training Guides
  • Exercise Library
  • FAQ
  • Press
  • Support

Legal

  • Terms and Conditions
  • Privacy Policy
  • Consumer Health Data Notice

CRUCIBLE FIT™ and Crux by Crucible Fit are trademarks of Crucible Fit, LLC.

© 2026 Crucible Fit, LLC. All rights reserved. Apple, the Apple logo, iPhone and Apple Watch are trademarks of Apple Inc., registered in the U.S. and other countries. App Store is a service mark of Apple Inc. Google Play and the Google Play logo are trademarks of Google LLC.

  1. Home
  2. /
  3. Exercises
  4. /
  5. Shoulders
  6. /
  7. Plank From Knees

Exercise guide

Plank From Knees

  • Beginner
  • Compound
  • Timed hold
  • Lower legs
  • Shoulders
  • Upper legs
  • Waist

This beginner-friendly core stability exercise builds foundational strength in the abdominals and glutes while reducing the load on the lower back. It is an essential movement for developing the pelvic control and spinal alignment necessary for more advanced plank variations.

Reviewed by the Crucible Fit team · Updated June 2026

Watch the Plank From Knees demonstrationVideo and instructions for every movement are in the Crucible Fit app.

Muscles worked

Primary

  • Abs
  • Obliques

Secondary

  • Erector spinae
  • Glutes
  • Quadriceps

Equipment

  • Body weight

Setup

  1. Kneel on a soft surface or exercise mat and place your forearms flat on the floor.
  2. Position your elbows directly underneath your shoulders with your forearms parallel to each other.
  3. Walk your knees back until your body forms a straight line from your head to your knees, crossing your ankles if comfortable.

How to do it

  1. Engage your core by pulling your belly button toward your spine and squeezing your glutes to lock your pelvis in place.
  2. Maintain a neutral neck by looking at the floor approximately 6 inches in front of your hands.
  3. Hold this isometric position for the desired duration, breathing deeply and steadily through your nose and out through your mouth.

Form checklist

  • Keep your hips in a straight line with your shoulders and knees; do not let your lower back arch.
  • Push actively through your elbows to prevent your shoulder blades from collapsing together.
  • Ensure your elbows remain directly under your shoulders to avoid unnecessary joint strain.
  • Keep your chin tucked slightly to maintain a neutral cervical spine.

Pro tips

  • Create 'internal tension' by trying to pull your elbows toward your knees without actually moving them to maximize abdominal recruitment.
  • Focus on a posterior pelvic tilt—tucking your tailbone—to ensure the abs are doing the work rather than the hip flexors.

Make it harder

  • Lift one knee off the ground slightly while keeping your hips perfectly level to challenge your obliques.
  • Transition to a full plank by extending one leg at a time until you are balancing on your toes.

Frequently asked

What muscles does the plank from knees work?
The plank from knees primarily targets the abs and obliques, and also works the erector spinae, glutes, and quadriceps as secondary muscles.
What equipment do you need for the plank from knees?
The plank from knees requires no equipment — just your body weight.
Is the plank from knees good for beginners?
Yes. The plank from knees is a beginner-friendly movement and a strong foundation to build on.

Related exercises

  • 45 Degrees Arms PlankIntermediate · abs, deltoids, obliques, and pectorals
  • Air BikeIntermediate · abs and obliques
  • Alternate Leg Lift TwistIntermediate · abs, obliques, and quadriceps
  • Alternate Single Leg Raise PlankIntermediate · abs, deltoids, hamstrings, and obliques

Train it with Crucible Fit.

Every movement in this library is in the app with video and instructions, ready for your own sessions on the days between Crucibles. Your first Crucible is on us.

Download on the App StoreGet it on Google Play

See how a Crucible works