Saw Monty Roberts on Saturday night at Towerlands and it was incredible, however, towards the end he said 'Single line lunging is the second most cruel thing you can do to a horse'. I've never heard this before, and he didn't expand on why it was particularly cruel. I've always found, as a rider, that lunging was really useful but I'll never do it again if I think for a moment it's causing distress or pain to the horse. Can anyone explain why it's cruel? I don't want to kick off a massive argument, I'm just curious!