I'm 56, w/m, 6-0, 200#. Have played rec hockey and riding bikes most of adult life. I had lumbar decompression for stenosis of the ligamentum flavum in L3-L4 back on 7/8/2014. This was probably the most minor of spine surgeries. I've had low back pain for ~6 years of varying degrees and issues and I finally went to a surgeon who confirmed using MRI & CT myelography that I have stenosis and it had become a surgical condition. So I sailed thru surgery and did my initial recovery without a hitch. I'm now ~8 weeks post op and I've been bending (mildly, no loading) and riding my MTB around the 'hood for the past 3 weeks or so for ~3-4 miles (staying away from bumps, etc.) The pain I had before surgery is almost gone but I'm still a little stiff and lacking strength, which I haven't really tested since I'm still on restrictions. Probably shouldn't be riding outdoors, but I feel really good on the bike.
Cycling was the only thing I could do without pain for the year leading up to surgery so I'm hoping I'll be able to resume hard road and MTB'ing when Dr. gives the release. My only concern is will the vibration and bumps transmit thru the spine and irritate the surgery site thereby causing scar build-up and possibly eventual return of stenotic junk? That's probably one for my Dr. to answer!
One bit of advice I can give is to get diagnosed early and then if the condition gets to the point where you think you might need surgery, don't wait until you have bad pain and nerve damage to finally go under the knife. My BIL told me he shouldn't have waited and now he as a drop foot caused by nerve damage cuz he waited too long to get it fixed.