Ive gotten botox in neck (scm) for several years. also have been sedentary for 6ish years. trying to start running, but afterwards my neck muscles are shot. can i gain strength in neck muscles over time even with botox treatment? will it improve?

Are you able to stop the Botox injections? If so, the toxin does wear off usually after 3-4 months. You should see a physical therapist for neck exercises to strengthen your neck. Some good info can also be found on YouTube. Just be careful about the source.

Why are you getting Botox in your SCM? Try a lower dose if you must continue. SCM primarily does a rotation so the rest of your neck muscles should be fine but may be atrophied from non-use from the sedentary lifestyle. Strengthening the muscles with exercise/ PT should be helpful.