I can't recall how you sustained your TBI. If your neck is stable, some activities you could consider include golf, yoga, Pilates, Tai Chi, archery, snow shoeing, cross country skiing, canoeing, stationary biking and race walking.

However, as Mark said, take it SLOWLY. Some TBI folks find that too much increase in the their heart rate causes headache. Others are too bothered by heat to engage in outdoor activities during the summer months.

I hope you find something you can enjoy.