Saturday, February 16, 2008

Bar Clearance in High Jumping

Editors Note: My new site is now at www.just-fly-sports.com Check it out for a wealth of information on jumping higher and running faster, all backed by research and practical experience!

I have decided that it is about time for me to get back to a technical article of some sort. Most of what I have written recently has been about training theory in general, and not so much about the great sport of high-jumping. In my "technical high jump manifesto" I conclude that in most cases, the body will automatically respond to the bar in order to clear it. In most cases this is true, at least after a certain amount of hours spent in practice. I have realized, however, that there are some people that really have a gift to contort their body over the bar, while others struggle to control their body in the air at all. I would consider myself a holistic coach. I don't mess around with a lot of drills (I will write more on this later) because I feel that actually high jumping with accurate cues and feedback is much better than the sum of its parts.

One drill that I do like to use, however, is the standing backover. I often see many mistakes in the performance of this drill, which lead to bad habits. Before I get to those, here is a video of a standing backover in high-jump.




Now this is a great standing high jump, and the bar clearance is excellent. Notice the timing of the arch through the hips and the drawing in off the feet towards the buttocks. There are times, however, when this drill can lead to bad habits. One variation of this drill that leads to bad habits is standing too close to the bar when it is performed. When this happens, the dynamic chain which leads to successful bar clearance is compromised. This happens because the parabolic curve which the bodies center of mass is much more straight up-and-down then a typical high jump where there is far more horizontal displacement. Standing too close when performing this drill will lead to improper timing in throwing the head back, and bringing the hips and knees up. Here is a video of a good jumper with tremendous leaping ability who stands just a little too close to the bar when performing this drill:




My recommendation for a standing back-over would be to have your feet a distance from the bar that is simliar to where you actually take off from in high jump. Athletes who take off from very far away can move this mark in a few inches or even a foot if they take off from over a meter away. I would also advise those athletes whose best standing jump is less than 1.60m to use a booster box (6-12 inches) when doing this drill. This will help create more similarity between the backover and the bar clearance encountered in the actual jump.

The second aspect I would like to cover when addressing bar clearance is that of rotation. Rotation over the bar is primarily determined by the forces at take-off but can also be influenced by the shortening of the bodies levers over the bar. Proper rotation can be determined by a simple analysis. When the jumper is at their apex over the bar, their total body alignment (if they were to straighten their body) would be around parallel to the ground. Many jumpers who jump with inadequate lean at takeoff, or long levers will be at an angle to the ground, here is a helpful illustration.

This jumper is demonstrating proper bar clearance, and is in a good setup for the hips to clear easiler. This position comes from proper rotation and not just throwing the head back and arching. The next picture demonstrates an improper bar clearance/rotation.


Now here is a very common clearance position for a lot of jumpers who either have not developed their curve and takeoff properly, or just don't have coaches who know better. In this jump, the hips have not reached the high point that the upper back has, because of a lack of rotation. Now rotation can be achieved in two ways. The first is to learn the proper way to run a curve, and not come out of it on the last two steps. It is a common fault to see a jumper come "straight up" on the last two steps of their curve. Once a jumper has effectively learned a curve, they must learn to have short and effective levers in the air. Here is a picture of a jumper who has very short and effective levers in bar clearance.


Linus Thornblad

Here is another picture of a jumper who demonstrates good rotation and bar clearance.



Blanca Vlasic


Notice how she is actually rotated past parallel when she is clearing the bar. I have noticed that in jumpers with longer limbs, sometimes, more rotation is necessary than those with shorter limbs. This makes is possible for jumpers with longer legs to clear the bar more effectively. In closing, here are some tips for helping you or your jumpers clear the bar more effectively.

1. Backovers are an effective drill, but do not focus the marjority of your practice on them
2. The transition from a standing backover to a full high jump can be made easier by doing "running" 2-footed high jumps following standing backover work.
3. Cues such as bringing the feet tighter to the buttocks, spreading the knees apart, throwing the head back, and getting the hips up can all be used in standing and running 2 foot backover drills.
4. A drill that I like is a short approach high jump off of one leg where the coach stands behind the pit and holds up 1-5 fingers with his/her hand. The jumper must then look backwards during the jump and tell the coach how many fingers they held up. This is an advanced variation of the standing drill with holding fingers up.
5. Standing and running high jumps are different motor skills, always keep that in mind. Just because someone can do standing backovers well, does not automatically mean they will be good at the full jump, and don't let a jumper focus on standing backovers just because they are good at them and their standing backover jump makes them feel good about themselves. Focus on their weaknesses.
6. Perfect form in a full-high jump will be clearing the bar by simliar amounts with the shoulders, back, and hips, keep this in mind when a jumper comments on how far their back was over the bar in a given jump.


Finally, on a closing note, realize that sometimes when a jumper rotates too fast, or is not used to their speed of rotation, they may start kicking the bar off with their feet. This happens more often in taller, longer jumpers who need to compensate for the increased rotation with a more powerful foot kick. Work on a good extension of the legs as well as the other factors with these jumpers.

Good luck,

Joel

Thursday, February 14, 2008

Rubber-Band Man Retraction

Well, I went and did it. I have thrown some ideas out in my last post that were not entirely correct. You see most of my last post was based off of research that I had looked at in a comprehensive review of around 50 scholarly-articles. A large amount of what I wrote was correct, but what is still up in the air, so to speak in the scholarly realm is if increasing tendon compliance is truly effective for increasing sport movement. Research by Keitaro Kubo shows that, yes, compliant tendons are more effective for stretch-shortening cycle movement, but, compliant tendons can also cause problems with force transmission from muscle to bone. After an email exchange with Dr. Kubo, he has concluded that it is still unknown if increased compliance or (increased stiffness) in tendon is truly useful for improving sport effectiveness. So basically, don't worry about specifics on improving your tendons. My advice is simply to put an emphasis on your primary sport movement, and the optimal tendon configuration should take care of itself.

I still do think my last article has some value in the relation of slow and fast twitch dominant athletes and sport performance. If nothing else, it is a valuable analytical tool. Finally, I would like to thank Roger "RJ" Nelson for his notes on my original article which led to this retraction. Sport science is something that is dynamic and evolving, and I try my best to stay on top of it. If anything is wrong, I will always let you know, and it is my utmost intention to keep everyone on the right track in the sport science world.

Joel