What's harness sphering like, and is it ok to do it if I get occasional back pains?

I've been invited to go harness sphering, and I'm not normally into adrenaline kind of activities. What's it like? My back is ok at the moment but I've had a dodgy back in the past and I'm worried if this kind of activity might throw me about a bit even though I'm strapped in. What do you reckon?