My 17-year old gelding was doing great flexing left and right, nose to my boot, soft and willing. Then out of the blue...he started fighting me, and spinning and pulling and wouldn't flex, he'd finally do it, but for just a second, then toss his head.
Last night, we spent 2 glorious hour doing stricly ground work. I decided to work on flexing from the ground in only a halter instead of a bridle. He'd flex beautifully and lightly, but wouldn't hold it long, and when he brought his head back he'd stretch and toss his head.
My first thought is teeth, who knows when his last float was but I know it's been more than a year, so I'm scheduling that today. But besides that, are there any other reasons he could be doing this?