I use a martingale for jumping at all, but only because my exracer and I have only been jumping for the last six weeks out of the seven months I've been retraining him. He still gets a bit racehorsey and wants to gallop at fences like a giraffe and jump flat. The martingale stops me losing control when he giraffes his neck. He's doing this less and less as I've been getting lessons and practicing, but I'm not ready to jump without it yet.