Until the pandemic I commuted through London by bike for about 7 years - ranging from 5 to 12 miles a day. I fell off maybe a couple of times, never hitting my

Until the pandemic I commuted through London by bike for about 7 years - ranging from 5 to 12 miles a day. I fell off maybe a couple of times, never hitting my head. If the OP is sustaining multiple concussions from bike riding, they're either riding a lot (bike messenger?) or riding very recklessly (or perhaps both).