Hi everyone, this is my first post and i'd just like to say thank you for responses, regardless of whether or not they come.

I'll preface my question with saying that I've had two concussions, one as a result of an accident that occurred New Year's Day of this year, after which i was diagnosed with "concussion symptoms." The other concussion was prior to that, when i was in approximately 7th grade, and was skateboarding, hit my head on the pavement, retained consciousness and seemed to have been symptomatically fine afterwards.

I was wondering, if falling, at 1-2 mph, with no contact, could possibly induce a concussion, in addition to pondering as to whether or not getting hit in the head with a tennis ball, by my 14 year old sister, could cause one.

Thank you for your time,

aterzian