My question had to do with the stepping issue. There is a mind jarring that can progress up to the head with each foot plant. That mild impact can be problematic for some. A rower or stationary bicycle does not have the impact.

Rowing at 18 to 20 strokes per minute would be a good start. Spinning puts a low stress on blood pressure.

The goal should be to sustain 90 bpm for an extended period.

Regarding foot impacts, If you put in some foam ear plugs, you can hear the impact that travels to your head from each step. Changing to a softer sole shoe or changing your step to land more on your toes could help.

The vast majority of concussions include a subtle neck injury. Aggravating that neck injury can trigger symptoms. The right side issue suggests neck involvement.