How shoulder muscles help lift your arm in different directions
Three-dimensional continuous muscle moment arm maps for the anatomical shoulder.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists used real human shoulders from donated bodies to see how different shoulder muscles help lift the arm depending on the direction. They found each muscle helps in specific ways depending on where your arm is.
Surprising Findings
The supraspinatus switches from pulling the arm backward and inward to pulling it forward and outward depending on arm position.
This biphasic function contradicts the common view that supraspinatus is simply an abductor or stabilizer — it actively changes roles mid-motion.
Practical Takeaways
Adjust your pressing or raising exercises slightly forward or backward to emphasize front or side deltoid activation.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists used real human shoulders from donated bodies to see how different shoulder muscles help lift the arm depending on the direction. They found each muscle helps in specific ways depending on where your arm is.
Surprising Findings
The supraspinatus switches from pulling the arm backward and inward to pulling it forward and outward depending on arm position.
This biphasic function contradicts the common view that supraspinatus is simply an abductor or stabilizer — it actively changes roles mid-motion.
Practical Takeaways
Adjust your pressing or raising exercises slightly forward or backward to emphasize front or side deltoid activation.
Publication
Journal
Journal of biomechanics
Year
2025
Authors
David Axford, Robert Potra, R. Appleyard, Janos Tomka, Antonio Arenas-Miquelez, David Hollo, S. Raniga, Louis M. Ferreira
Related Content
Claims (5)
The front part of your shoulder muscle is better at lifting your arm forward, while the side part works harder when you lift your arm backward — they’re specialized for different directions.
When you reach your arm forward, the back part of your shoulder muscle might actually work against lifting your arm up — helping instead to control rotation, not movement, at least in dead bodies studied in labs.
The shoulder muscle called supraspinatus switches jobs depending on how you move your arm — it pulls one way when you lift your arm forward and the opposite way when you lift it backward, like a muscle with two different gears.
In dead shoulders, two muscles help lift the arm but twist it in opposite ways—one turns it outward, the other inward—so they work together like a team that also pushes against each other to keep the shoulder steady.
When studying dead shoulders, most big shoulder muscles change what they do depending on how the arm is positioned — but one part, the bottom part of a muscle called subscapularis, always does the same job: helping the arm move inward and across the body, no matter the position.