I suggest you stay away from running unless you can learn a very soft gait that does not pound in your head. The way to tell is to take a walk or light run with foam ear plugs in. You can hear the pounding from your foot plants.

Bicycling, stationary or on the road is a decent exercise.

If your efforts cause head pressure, that is a sign to lighten up. The Buffalo Protocol says to keep your pulse 20% below your symptom threshold.

Even though everybody is different, the one issue that hold true is to no do activities that cause symptoms to manifest or get worse. The rest of the body responds to stress and injury by increasing blood flow and other healing mechanisms to the injured and strained muscle or other tissue. The brain does not have this response. It shuts down under stress. Coma is the brain shutting down due to extreme stress. medially induced comas are used to treat severe brain injuries so the brain can rest cognitively and put its efforts on healing or trying to find a balance.

Those of you who thrive on working out may have developed a dependency on adrenaline and the dopamine response. Adrenaline is counter to brain recovery.

PorscheTarbo - as Mark said, breaking down muscle puts extra byproducts in your blood to sort out. One of the things that makes concussion so "interesting" is the flood of biochemicals that get released which are normally not there. Glucose, potassium, etc.... Google "concussion neurometabolic waste" to learn more.

If your symptoms are cognitive, could be that the extra load in your bloodstream is burdening your brain. I'm no doctor, but based on my own experience, this could be a factor.

I started doing intense intervals regularly for about a year, several years after my last TBI, and that was fine for me. Interestingly, after taking some off from the daily exercise, when I went back to it, some of my symptoms returned -- especially the headaches. So, I changed up my routine, and that's been helping.

Generally, it can be a good idea to change up your workouts, anyway. It can keep you from plateauing and keep things interesting.

Good luck. Stay safe.