Main thing is to get out and try a cycle. Any cycle- Make certain it fits roughly and see how you get on. Then you will find out that the bike you have is OK- Doesn't fit- too highly geared- got the wrong tyres on- Is the wrong colour. That can happen if you go out and spend a lot of money on a new bike too- So Just get out and ride.
An ex runner here that used to run Competitively as an amateur but injuries starting to come in made me realise when to stop. 10 year break from excessive training and I started riding. You can get the same high- Once the body gets bike fit- The butt gets attuned and you are on about your 3rd bike. Took that long for me to take the plunge and get a respectable bike. Different muscles to build up- Different attitude to take on board and different training regime if you want to cycle without getting bored. But on top of all that- As a way of retaining the fitness you still have without injuring yourself- Can't think of a better way.
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How long was I in the army? Five foot seven.
Spike Milligan