I'm currently training a horse who was originally just broke to w/t/c, then was used on trails for the past 10 years. He is my eventer, but I recently took him to the fair for a week as my 4h project. He NEVER takes the left lead, which I have ideally thought was from sore hocks. I've been told several different things to try: twisting him so he has to throw the shoulder and the lead, putting him on a lunge line to see if he takes it (if he does, he doesn't have sore hocks, it's rider error) and using spurs. As far as I've heard, he was originally trained using spurs, but over the years of trail riding, has been un sensitised after being really iffy on the aids. Is it possible that using spurs could make him throw the lead? I don't understand how that would work any better than what I've been trying.