When circulation is poor, the extremities take it the hardest. That includes hands, feet, ears and nose.
Improving my circulation has helped resolve a lot of the hand issues I once had. I have visibly healthier, stronger nails. My hands and feet don't readily get cold like they once did.
Etc.
If you have a "cup half full," it's the same areas that consistently get less oxygen, fewer nutrients, etc. Over time, that takes a very big toll.
I used to read medical records as part of my job. Diabetes, which is a blood issue, significantly impacts the feet. After many years of poor blood sugar control, feet issues become so serious that diabetics can end up needing to have a foot amputated.
I don't think it matters that much how much you move your arms per se. If you do aerobic exercise to strengthen your circulatory system, it eventually impacts the feet and hands significantly.
I was born with a serious medical condition that negatively impacts my circulation. After getting diagnosed, I began redressing a backlog of lifelong issues.
As circulation to my hands improved, I had pus appear under my cuticles. I spent weeks or months waking up with very painfully sensitive fingertips. My hands began to slough dead skin.
This stuff went on for a long time. I wasn't exercising my hands particularly. I was just improving my baseline health, including my circulation.
N=1 (sort of -- my son with the same condition also had a lot of hand drama as we got healthier)