Wait until you feel your horses front feet leave the ground. You shouldn't be "jumping" so to say with your body...all you want to do is close your hip angle slightly and move your hands a bit...let your horses jump close your hip angle the rest of the way...also, are you posting all the way to the jump, or sitting (I am assuming this is for trot jumps)
First I think you should try and determine WHY you're jumping ahead.
1) Some people jump ahead because (as ahsisi mentioned) they are not waiting for their horse to jump, they are jumping for them. When I was growing my trainer taught us to sit back towards the jump, count 1, 2, 3, and then HURL ourselves forward into a "jumping" position. UGH! I have bad habits to this day from her! Instead, lighten yourseat towards the fence and think about having a relaxed hip. You are going to stay very still with your upper body and as your horse goes over think about keeping your upper body almost the same as your hips and knees will fold to stay with the horse. If you're just going over crossbars/2" jumps, you are barely going to move your upper body.
2) another problem with my trainer's method was that sitting back actually put you BEHIND the motion of the horse. And you had to throw yourself forward to catch up with your horse. When you approach the fence you should be in your 'light seat (or 'medium seat'). That's inbetween your full seat and jumping position.
3) Lots of people jump ahead because their foundation (aka leg) is not secure. If you're riding with a too long stirrup, there's a good chance this is a problem! If you have any issues with your position on the flat, you will have issues with your position over fences. A too long stirrup makes your lower leg unstable, which means your body is thrown forward over the jump. You must have an even distribution between your thigh, knee, and calf with your weight dropped into your heels, seat over the middle of your saddle. A VERY common reason for jumping ahead is pinching in with your knee. If you pinch in with your knee, it acts like a pivot and makes your lower leg swing back, which throws your upper body forward.
4) Make sure that your saddle is working with you and not against you! You need a saddle that puts you in the correct position, not every saddle does this!
Figure out what is causing you to jump ahead and go from there. Usually there is more then 1 issue! I applaud you for your desire to constantly improve yourself as a rider!
Upnover, your explanation was very helpful to me so I hope it was helpful to the OP. I love my trainer but after looking at a few shots of me riding, I noticed that I jump ahead. My trainer has said nothing to me about this so I was a little shocked to discover this. She also says we need to sit back and straight as we approach the fence and in my head I have always thought that this makes me feel behind the motion and is the reason I feel like to have to hurl myself to keep up with my horse over a fence. I have treid to shorten my stirrups a hole because I have been having issues with my heels on the flat that I have never had before. I think maybe the leather billet straps have stretched a little? Anyway, every time to shorten them she makes me unshorten them. But I think this might be contributing to my jumping ahead as well. Like I said, I love my trainer but sometimes I think she concentrates on us just getting over the fence instead of getting over it with the correct form as well.
Irish- Glad my post was helpful to you! I can go on all day about it since I was a PRO at jumping ahead (mainly because my trainer growing up NEVER ONCE mentioned it! UGH!). It's a habit that often wants to creep back into my life and I periodically have to work on again. And let's be honest, most people don't jump perfectly 100% of the time. I personally think jumping ahead is the most common jumping fault out there. The great thing about riding is that there's always something more to learn and always something else to work on!
I'm all about seeing people's posted videos! Post away!
Your jumping has improved TREMENDOUSLY!!!! You look like a different rider then I remember! I remember some video of you earlier where I was kind like, hm... Your hard work is definitely paying off! GOOD JOB!! Your leg is improving so much and over the top of your horse's bascule over the fence you are so much more in the middle of your saddle and balanced then you were!
You are still wanting to get a lilttle ahead on the take off though. If you look at 0:11 you are over the pommel of your saddle. I think :10 says a lot too. Remember, you don't want to let your body "start jumping" before your horse is, the jump doesn't begin until both of your horse's front feet are off the ground. In :10 you've started to throw your body forward. I'm going to guess that it's a bit of anticipation of the jump AND because you're supporting yourself with your horse's neck (not necessarily a bad thing, but timing is important). Here's something that might help. Some trainers will tell their beginning jumpers to grab mane in front of the jump, which is fine, because you don't want to hit your horse in the mouth. But once a student has gotten used to the motion of the jump I have my students grab mane as the horse lifts off, and not before. For several reasons actually. By throwing your hands down on the neck you've 1) made taking off harder for your horse because of the weight you've pushed on his neck and 2) it throws your body forward before the horse is ready to jump. And, 3) it can teach you to "abandon" your horse. While you're heading to the jump you have contact on your horse's mouth, you're riding, and basically you're saying "we're in this together horse", then second you throw your hands down on the mane (ESP when it's because it's going to be a funky distance) you've abandoned your horse. It's like saying "never mind, I lied, you're doing this on your own!" Some horse's after time will learn to stop if they've been taken to the fence and had their riders 'bail' on them, esp when it's going to be hard. I think you seem to do it most over the trot fences... interesting! So just keep thinking about supporting your horse and being there for him up until the base of the fence, and then jump. Your canter fences are much better. The canter jump at :29 I think is your best. You are definitely the most still with your body!
Another thing to think about is the landing. (I knwo this isn't about jumping ahead but I thought I"d throw it out there) You want to be careful not to land on your horse's back before he's finished jumping, which is the point when his back feet land. If you look at :31 and :50 your seat is already in the saddle even though his hind is in the air. This is actually something a lot of jumpers have trouble with. I know I did when I was learning to jump! My trainer had me stay in a 2 pt for an entire stride after the jump before I was allowed to sit again. That worked for me.
Anyways, just a few pointers I thought I'd throw out there! These are just my opinion, take them for what they are. But I AM very impressed by your improvement! You should be very proud of yourself!