Just out of curiosity...the lip was up and showing teeth ...was he shaking his head at the same time? That to me would show aggression.
He definitely didn't shake his head and he didn't bare his teeth like an angry horse does. It was like he was lifting his lips and I was getting glimpses of his teeth. If he was just tacked up and standing around, it would have looked like he was smelling something bad. But with lunging I just couldn't read what his expression meant.
It was obvious he didn't want to lunge. I just couldn't tell if he was angry or being bratty.
I was definitely scared for a moment there! I won't lie! But normally I'm very comfortable with this particular horse. That's why I started leasing him. But my fear did die down quickly when I took him to the other side of the ring and just tried again.
My first reaction is to do what you describe Joe and just lay into him. But I want to be sure that was the best way to handle a normally calm horse who seems like he's blowing up or "getting bigger" if that makes sense.
My trainer said that he's harder to work on his right side. She said that all horses have a side just like people are either left or right handed. She said that he works easier to his left and will sometimes resist his right. I assume this is correct information, isn't it? He doesn't seem to be in any pain. But it's certainly possible that he's sore on that side.
I should clarify, I definitely didn't coo him. It was more of a "It's alright" calm voice but I think I was telling myself that more than I was telling him!
I wasn't expecting his reaction like that. But we did work at least another 15 minutes after that. Then I called it quits. I wanted to end on a high note.
If I had to guess, I think this horse is used to a person being heavy handed and hard on him. He belonged to a man before he came to the barn and the guys I know who do roping aren't exactly soft on their horses. And I think I need to ramp up my commands on him. It's certainly possible I'm being too soft with him and he's realizing that.