..having been there myself, the first couple of months after my concussion, I did nothing. In that time of doing nothing, I made a mental plan of how I was going to get back into shape and get my cycling form back.

I'm an amateur cyclist in CAT4. Last year, I had ridden many many hours on the bike to perform well and to keep in tip-top shape. (Daily two hour rides with longer rides in the weekend up to 7 hours. Lots of races too.)

I started by doing nothing but stretches and went into physical therapy since I also had a left leg issue (where I also got hit). Doing yoga-type stretches was the basic foundation in moving better. Get a someone to help you out to doing low impact exercises first. That should get your system going and retrain your brain to physical activity.

Once you've established a foundation and you feel like you're ready to some weights, do very limited weights. I would suggest starting at 5% of your max pre-injury, if not, lower than that. One thing you do not want to do is overtax your brain. What you WANT to do is retrain your brain to physical exertion at a steady, slow pace.

Then incrementally increase your activity/effort every two weeks.

It's taken me more than 4 months to back to a base for my cycling training. Now that I've done the ground work, I'm able to take it to the next level, but even that is uncertain because I'm not sure if I can reach 100% again.

The mentality you have to go by is that of an athlete that really knows your own body, your limitations, and how fast you think you can progress. Don't feed your ego by going too hard too fast. You will pay for it more if you do.

If you haven't already done so, you can "test" yourself by doing certain exercises at the pre-injury level and then gauge your efforts from there. I did a test ride a couple of times after my accident and while I was riding fast, I had no strength and no stamina. I had to rebuild everything.

This also means eating well - organic foods, gluten-free if possible, eat your veggies, plenty of protein and amino acids. I'm at a point where I'm transitioning to a vegan diet and I've been feeling much better because of it.

Hope this helps and ask me any questions you have.