Rear Delt Destroyer: The W-Fly Exercise
Summary
Jeff Cavalier (ATHLEAN-X) introduces a upgraded rear delt exercise that combines a traditional rear fly with external shoulder rotation. He argues that most lifters neglect external rotation, which not only limits rear delt development but also sets them up for shoulder injuries. The “W-Fly” is his solution to address both problems simultaneously.
Key Points
- Most lifters overdevelop internal rotators — chest pressing and lat work constantly rotate the shoulder inward, creating a muscular imbalance
- External rotation is required to fully activate the rear delt — simply performing a rear fly without rotating the shoulder outward leaves significant muscle activation on the table
- Demonstrating the concept: by rotating the shoulder externally from a neutral position, you can visibly and physically feel deeper muscle engagement in the posterior shoulder
- The “W-Fly” upgrades the standard rear delt fly by adding a thumbs-back rotation at the top of the movement, forming a “W” shape with the arms
- Performing the exercise on a stability ball adds an additional core stability challenge compared to using a flat or incline bench
- Neglecting external rotation is a dual problem — it both limits aesthetic shoulder development and increases the risk of shoulder injury over time
- As a physical therapist, Cavalier emphasizes that exercise selection should support long-term training longevity, not just short-term muscle gains
Exercise Details
The W-Fly (Rear Delt W-Raise)
Target Muscles
- Rear deltoid (posterior deltoid)
- External rotator muscles of the shoulder (infraspinatus, teres minor)
Setup
- Lie face-down on an incline bench or stability ball, holding a dumbbell in each hand
- Using a stability ball increases the core stability demand
Proper Form Cues
- Start with arms hanging down, thumbs pointing inward toward each other
- Raise the arms out and up into a “W” shape
- As you lift, rotate the thumbs backward (externally rotating the shoulder) so thumbs point behind you at the top
- Hold briefly at the top — this is the point of maximum rear delt contraction
- Lower slowly and repeat
The Key Distinction from a Standard Rear Fly
- A standard rear fly uses a neutral or pronated grip with no deliberate rotation
- The W-Fly combines abduction with external rotation, recruiting more of the posterior shoulder complex
Common Mistakes to Avoid
- Performing rear delt work without external rotation, which reduces muscle activation
- Neglecting the rear delt entirely in favor of front and lateral shoulder work
- Failing to control the movement on a stability ball (rolling to one side)
Sets/Reps
- No specific sets or reps were mentioned in the video