⭕️HOW SHOULD YOU ARCH IN A BENCH?⭕️
Arching during a bench press is completely fine and SHOULD be done in order to create a very strong set up & prevent shoulders from rounding excessively during the eccentric portion of the lift (which can be a cause of shoulder injury).
How to do it?
By retracting and depressing the scapulas against the rib cage.
.."BuT DaS NoT aRcH1nG?"
Well, when you pull your scapulas down and back against the rib cage, your thorax extends slightly as a result. You can try that yourself.
And that's what you should be doing. Your shoulders are kept safe and stable and they're prevented from rounding excessively during the eccentric.
It's far from saying that you just need to arch "for the sake of it, without giving any context to the arch.
Now, yes, the "arch" it self will vary greatly depending on people's mobility and in some it won't even seem to be there but that doesn't matter. As long as you're keeping your shoulders safe (retraction + depression of the scapulas) through the set up, you're good to go.
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