Quite simply, you are going to have to build up your distance again!
Keep in a low gear and keep cycling steady, increase your mileage by say, 10% every two weeks. Several months down the line and you will wonder what the fuss was about and be covering a good distance.
I am of course assuming that your bike is adjusted for your height and you are not mega unfit.
Just to let you know, that many roadies who don’t ride during the winter have the same problem and can only build up, by doing Long steady distances (LSD or base training). When this is done correctly with a HRM you are actually riding fustratingly slow but it’s the only way to build endurance.
Hope this helps.
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Mr G is right on. the only way to get back into it, is to get back on the saddle and work at it. I would recomend a tune-up and re-fitting of your bike. assuming you aren’t a kid who has undergone any growth spurts over the last 3 years, that should be sufficient. if you have experienced significant growth (other than girth), get your bike fitted as best as possible, and start saving for a new ride..
M, you are doing what a lot of us do, you are trying to pick up where you left off three years ago. Not gonna happen. So, like anything else worth doing, you have to start the journey with baby steps. Call it Progressive Overloading. You should be in possession of three things, the bike with properly inflated tires, a properly fitted helmet, and a cyclometer/speedometer. … You must start out from within your current capacity to do the activity. Don’t think in terms of miles pedaled, but in minutes on the bike. So for now go for just fifteen minutes at an easy 10 mph at 60 rpm pedal speed, no lower. And you take your time to build up from there going three, then four times a week. Before you know it everything will be back to normal. It will help your effort if you can find someone to ride with regularly. … If you keep walking you have to pick up the pace. Obviously you are walking too slowly to get a real fitness effect on your heart and lungs.
… I like the biking çause I can coast, it makes a wind on my face, and I get to see more scenery.