For dumbbell or machine presses, tilt the bench slightly backward instead of keeping it completely vertical to optimize anterior deltoid recruitment and limit back pain.

noli's read

This advice is based on biomechanical principles applied to strength training. A slight incline (often called a 'low-angle incline press') effectively changes the pushing angle, which can reduce stress on the shoulder joint and promote a more natural trajectory for the anterior deltoid (source: biomechanical studies on muscle activation, observational/electromyography type). The idea of protecting the back is consistent with trunk stabilization, as an incline often allows for better support of the spine against the backrest. However, the claim that this drastically improves recruitment is sometimes exaggerated: the anterior deltoid remains the primary mover in both vertical and incline presses. There is no evidence that a single angle is superior for everyone; comfort and individual morphology play a major role. In short, this is a useful technical nuance rather than a universal truth.

the sources

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