It's my 4 weeks and 1 day after l5 s1 discectomy, i want to ride a bike as a part of my exercise do you think i can?

Ask YOUR doctor: It should be fine. But, you're asking the wrong source. I wasn't there at your surgery to know if something looked abnormal. I would almost guarantee that if you just call, you doc would get an answer to you quickly. My patients i allow back once pain allows and not taking meds. Avoid bend/twist/lift for 2-3 months as much as reasonable.

Avoid bending: Since bending at the waist forces the lower lumbar disc nuclei backwards, and since you have a fresh discectomy where there is a defect in the fibrous rings of the disc called the annulus, and bending (including sitting) is cautioned. This includes bike riding. I advise my patients to avoid such sitting positions for 6 weeks (except the toilet). Allowable is sitting in a recliner partially bent