Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...
I'd have a hard time believing tennis and running clubs rank that high. Especially compared to work place affairs, which is very common. Also, another source seems to be family and friends/neighbors.
But I'd be curious how they interpret affairs. I'm guessing pretty narrowly as in PA. if you threw all EAs in there too, I would suspect online to be #1. And many of those become PAs as well.
I don't "get devastated" anymore. I had several love affairs, very intense and lasting one, before I was married and knew how awful they could be; the pain you allow yourself to feel lessens with experience. I found the best way is to dump 'em if you don't think you can ever be normal again. With my wife I found I could be almost perfectly normal as I thought about the reasons she did these things ... I'm not so perfect myself, you see.