Which arm position makes chest muscles work differently?
Force direction and arm position affect contribution of clavicular and sternal parts of pectoralis major muscle during muscle strength testing
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Maximal force decreases significantly with more shoulder external rotation, even though this position is often used to 'activate' the upper chest.
Many trainers recommend flared or externally rotated arm positions for upper chest development, but this study shows those positions reduce overall strength output.
Practical Takeaways
Use a +30° upward push direction with 45° shoulder external rotation when testing or training chest strength to maximize differentiation between upper and lower chest activation.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Maximal force decreases significantly with more shoulder external rotation, even though this position is often used to 'activate' the upper chest.
Many trainers recommend flared or externally rotated arm positions for upper chest development, but this study shows those positions reduce overall strength output.
Practical Takeaways
Use a +30° upward push direction with 45° shoulder external rotation when testing or training chest strength to maximize differentiation between upper and lower chest activation.
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Related Content
Claims (4)
If a guy does a chest muscle squeeze at a specific arm angle and twist, one part of his chest muscle lights up more than another — this might be the best way to test or train that specific chest area.
When men twist their arms outward, they get weaker when trying to pull them across their body — even if they're trying just as hard.
You can't fully work just the upper or lower part of your chest muscle when pushing as hard as you can — no matter how you position your arms, both parts end up working together.
The upper part of your chest muscle doesn't help much when you push something overhead out to the side, because it's in a bad position to pull. But it works a lot better when you push something overhead in front of you, because then it's in a good position to help.