Once you have had any kind of significant head injury you cannot really think of yourself as the same person that you were. The things that normal people can do, and the kinds of things that are good for normal people may not be a good idea for you. My first head injury was in May of 2000. I have just re-injured myself, but even before that I found that I was ultra-sensitive to any sort of shock. Before my first injury I used to run on a semi-regular basis. It was my main form of cardiovascular exercise. I have yet to be able to run for more than 20 to 30 seconds at a time. If I try I experience unbearable migraine headaches and worse than normal memory difficulties and mental fog. And this is even years after the initial injury. I have been skeptical of my own conclusions and have tried lots of times to run, but the result is always the same. It's not the exercise. It's the shock. Just like I can't jump or even spin around too quickly. It is also difficult for me to go on boat rides.

My theory is that the damaged-but-somewhat-recovered brain is a fragile group of connections of fine spiderweb-like filaments stuck in a blob of jello or silly putty. It doesn't take much to break the sensitive electrical connections. Destroying even that flimsy chance of a semi-normal existence. I walk or ride a stationary bike for cardio. Anything else, even a stationary rowing machine or a step machine for instance seems way too risky to me. And something like tennis? OMG. Or really any team sport like soccer or baseball or (god forbid) football. That's a re-injury just waiting to happen. I can pretty much guarantee that it will happen. It's not a matter of if, but of when. Hopefullly most of you already know that the more head injuries that you accumulate, the more likely the next one becomes.

In addition to avoiding shock I have also (mostly) stopped drinking alcohol, even in very small amounts. Although that I am far less sure about as far as being effective or necessary. When someone asks me why I don't drink, I have to launch into my head injury story. Sometimes I tell them that my doctor recommended that I never drink alcohol again, but that isn't true. I just read about it somewhere on the internet (although I cannot find the reference now) and the proposed mechanism seemed plausible to me.

Having said all this, I do realize that some people seem to recover 100% of their pre-injury abilities within the first year post-injury. In that case maybe the new connections are not so fragile and maybe it is okay to jump up and down all you want, even to jump rope or to sprint. But I would wait until I no longer had any symptoms of PCS before even thinking about testing such limits. Just my .02. As always, YMMV.