There to be a dispute among internet sources of which muscles a diamond pushup affects more deeply (triceps, chest/pecs, back), and whether it's "better" to do it with arms tight against the sides (like the yoga chaturanga) or wide.
If you watch this video, you can see that when I held my arms tight, I had a lot more stability, and was able to smoothly transition to the lowered position, as well as keep my shoulders in neutral position. When I tried to go wide-elbowed for the second set, I couldn't descend as far, and I will admit I was experiencing anterior shoulder impingement on my right arm that made me very unhappy post-video. That is NOT ahimsa (non-harming).
So, that being said, for an adaptive yoga practice, trying out new forms of pushups, I would say that if someone was going to try a "pushup" with hands close together, elbows close to the side, bending back toward the ribs is a far more supportive approach to keep the entire shoulder girdle, chest, and upper back musculature in concert to support the body weight.
For today's #22pushupchallenge for #activeheroes, we did our two sets of eleven to finish up day 18!
To donate to my challenge, click here: https://fundraise.activeheroes.org/fundraiser/2872670
To start your own challenge, click here: https://activeheroes.org/22pushups/