Exercise guide
Side Lying External Rotation
- Beginner
- Isolation
- Rep-based
- Shoulders
- Upper arms
This isolation exercise targets the rotator cuff (infraspinatus and teres minor) and the posterior deltoid, which are essential for shoulder stability and postural health.
Reviewed by the Crucible team · Updated June 2026
Muscles worked
Primary
Equipment
Setup
- Lie on your side on a flat surface or mat with your legs stacked and knees slightly bent for stability.
- Rest your head on your bottom arm or a small pillow to keep your neck in a neutral position.
- Bend your top arm to a 90-degree angle at the elbow, resting your forearm across your midsection.
- Place a small rolled-up towel between your top elbow and your ribcage to ensure the elbow stays pinned to your side.
How to do it
- Keeping your elbow firmly pressed against the towel, exhale as you slowly rotate your forearm upward toward the ceiling.
- Rotate as far as your natural range of motion allows without letting your elbow leave your side or your torso roll backward.
- Pause for one second at the top of the movement to maximize the contraction in the back of the shoulder.
- Inhale as you slowly lower the forearm back to the starting position in a controlled 3-second tempo.
Form checklist
- Keep the working elbow tucked tightly against the ribs at all times.
- Ensure the torso remains perpendicular to the floor; do not lean back as you rotate.
- Maintain a consistent 90-degree bend in the elbow throughout the entire set.
- Keep the wrist straight and neutral, avoiding any flicking or curling of the hand.
Pro tips
- Focus on the 'mind-muscle connection' by visualizing the muscles on the back of your shoulder blade pulling the arm upward.
- Keep your shoulder blade retracted and depressed (down and back) to prevent the front of the shoulder from taking over.
Make it harder
- Slow down the eccentric phase to 5 seconds to increase time under tension for the rotator cuff.
- Perform a 3-second isometric hold at the peak of the rotation to improve end-range strength.
Frequently asked
- What muscles does the side lying external rotation work?
- The side lying external rotation primarily targets the rotator cuff.
- What equipment do you need for the side lying external rotation?
- The side lying external rotation requires no equipment — just your body weight.
- Is the side lying external rotation good for beginners?
- Yes. The side lying external rotation is a beginner-friendly movement and a strong foundation to build on.