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. Core & Abs
  6. /
  7. Dumbbell Side Plank With Rear Fly

Exercise guide

Dumbbell Side Plank With Rear Fly

  • Intermediate
  • Compound
  • Timed hold
  • Core

This compound movement combines isometric lateral core stability with dynamic posterior deltoid and upper back engagement, making it highly effective for shoulder health and oblique strength.

Reviewed by the Crucible Fit team · Updated June 2026

Watch the Dumbbell Side Plank With Rear Fly demonstrationVideo and instructions for every movement are in the Crucible Fit app.

Muscles worked

Primary

  • Abs
  • Deltoids
  • Lats
  • Obliques

Secondary

  • Glutes

Equipment

  • Dumbbell

Setup

  1. Lie on your side with your bottom forearm flat on the floor, elbow directly under your shoulder.
  2. Stack your feet or stagger them (top foot in front) for a more stable base.
  3. Hold a light dumbbell in your top hand with a neutral grip, arm extended toward the floor in front of your chest.
  4. Engage your core and lift your hips until your body forms a straight line from head to heels.

How to do it

  1. Exhale as you lift the dumbbell in a wide arc toward the ceiling, keeping a slight bend in the elbow.
  2. Continue the movement until the arm is vertical, squeezing the shoulder blade toward your spine at the top.
  3. Inhale as you slowly lower the dumbbell back to the starting position under control.
  4. Maintain a steady 2-1-2 tempo, ensuring the hips remain elevated and stationary throughout the set.

Form checklist

  • Keep the supporting shoulder pushed away from your ear to engage the serratus anterior.
  • Do not allow the hips to sag or the torso to rotate forward as the weight moves.
  • Keep your neck neutral and gaze forward or slightly toward the moving weight.
  • Ensure the movement occurs only at the shoulder joint, not by twisting the spine.

Pro tips

  • Focus on the 'mind-muscle connection' by initiating the fly with the rear deltoid rather than swinging the weight.
  • Press the edges of your feet firmly into the floor to create total-body tension and improve balance.

Make it harder

  • Perform the exercise from a high plank position (on the palm of the hand) to increase the stability demand on the supporting shoulder.
  • Lift the top leg into a 'star' position to further challenge the glutes and lateral core.

Frequently asked

What muscles does the dumbbell side plank with rear fly work?
The dumbbell side plank with rear fly primarily targets the abs, deltoids, lats, and obliques, and also works the glutes as secondary muscles.
What equipment do you need for the dumbbell side plank with rear fly?
The dumbbell side plank with rear fly uses dumbbell.
Is the dumbbell side plank with rear fly good for beginners?
The dumbbell side plank with rear fly is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.

Related exercises

  • Dumbbell Side Plank RaiseIntermediate · abs, deltoids, and obliques
  • Dumbbell Side Plank RowIntermediate · abs, glutes, lats, obliques, and trapezius
  • Medicine Ball SlamBeginner · abs, calves, lats, and obliques
  • Spell CasterIntermediate · abs, deltoids, 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