This got me back into doing a few pushups a day throughout the day, not part of a "workout," just to get my upper body back into decent shape. I've noticed it's helping on bike rides -- I can support my upper body more easily, less tiring, less neck cramping on chipseal and rough pavement.
Even when I was in top shape I could never do 73 year old Jack Palance one-arm pushups. He was a bad, bad man.
When I was in Navy boot camp we had a guy who could do
one-arm pullups -- no assist from the other arm. I've never seen anything like it before or since. I've seen many folks claim they can do one-arm pullups, but then they'll use their free hand to assist by grabbing the other wrist or forearm. Not this guy. He was a stealth badass. Looked like Matthew Modine in Full Metal Jacket, but hard as a rock. About halfway through boot camp he got bored, got a call from an ocean based oil rig company offering to hire him for a lot of money, so he claimed he lied about drugs on this entrance exam, claimed he'd done a buttload of LSD, etc. Frankly I thought he was one of the sanest, best adjusted young guys I'd met. Low key, low drama, the kind of guy you'd want on your side in a fight. Anyway, off he went back to the real world to make money.