Comment by CRConrad

Bikes (at least used to) come in different frame sizes. If ordinary commuter bikes don't any more, at least mountain bikes still tend to, as I understand it. And those have the top tube of the frame lower anyway, and with that usually also the top end of the saddle tube (that the saddle post slides in).

At 5'10" -- which is about my height (am I 5'9½"?) -- I'm fairly sure there exist bicycles that let you put the saddle low enough that you can reach the ground with your feet. [1] Sure, pedalling isn't super-comfortable at that height; it's a bit more effort than if you have your legs almost straight at the lower end of the stroke (but then you can't reach the ground while on the saddle). But it's not all that bad, and it certainly doesn't wholly prohibit the use of the bike.

Once you've used it for a while and got your sense of balance, you may not need the option of foot-on-the-ground-from-the-saddle any more, so you'll be able to raise the saddle to the "correct" (=more comfortable for pedalling) height. Or if not, the little bit of inefficiency will mean a more efficient workout! :-)

And hey, if you're really nervous about finding your balance, do what everyone recommends for little kids and remove the pedals, and use it as a "balance bike" to begin with. Anyway, I'm convinced you should be able to find a used mountain or "ladies" (=step-through) bike to try this stuff out on. Talk to the folks at a bike shop, they're often (not always, of course) knowledgeable and enthusiastic, and therefore helpful. Good luck!

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[1]: Dunno how tall the guy in the video is, but this sure looks like it should fit you: https://www.youtube.com/watch?v=QV88C5ZK0x0 . Not that I think you need that super-heavy brute, specifically, but the frame looks like quite a lot of mountain bikes you see around. So here's a cheaper alternative that also looks OK(ish, for its price). : https://www.youtube.com/watch?v=vLPpTFLgEb4 .