I took up riding after a 10 year layoff from any sports- and Cycling was not one of them. First ride out was 28 milles and I enjoyed it. One of my friends suggested I go out with him to try some hills and all I can suggest to you is don't do hills till you have some fitness behind you- and a bike that has the gearing for them.
In the mean time get the butt adjusted by riding and enjoy.
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How long was I in the army? Five foot seven.
Spike Milligan