I recently was diagnosed with slight wear on two of my cervical vertebrae.
My only way to account for this damage has been 17 years of aikido, as I have not suffered any other traumatic insults to my neck.
Most of the time I have practiced aikido I have been technically obese (~33% body fat), putting me at about 246#. Coupled with my height, 6'1", I have to wonder if I was at particular risk for injury. None of my fellow aikidoka who have practiced as much have reported any issues. (Nota bene: none of them are obese.)
We have practiced on standard 2" blue mats, with no other shock absorbing elements.
And so I am bringing this issue to the table: Ought obese students be allowed to practice given the elevated risk of serious injury? I think this ought to be considered, especially in regards to break falls.
I am a big guy too. All I can say is I am careful with who my nage is....99% of my injuries over the years have been the result of sloppy/poorly executed technique...and yes size has allot to do with that...Most folks either try too hard (He's a big guy he can take it) or get a little intimidated and don't follow through properly. I no longer do break falls at too many seminars for this reason until I see the strange Nage in action.
My weight however is on me... If I don't get lean soon then my Aikido "career" WILL be cut short...That is just the laws of physics on the human body my friend.