Hi, this put a smile on my face imagining it being used in place of 'ultimate'. Toxic Frisbee. :)

I guess the definition should be revised to "extreme behaviour, directly having an overbearing effect on another person's wellbeing".

Maybe there could also be a side definition for running competitively in a nuclear contamination zone though!

Now that I think about it, toxic endurance sports hits too close to home...

Toxic = excessive to the point of being harmful