Archive for April 2009


April 21, 2009

Here is a spirited discussion that I have been having on vault technique at The Chalk Bucket Coaching Forum .

The discussion revolves around optimal vaulting technique during the pre-flight and initial table contact. The author of the post dislikes the USAG JO compulsory vaults because they emphasize too much of a hollow. I am in agreement that the term “hollow” is often misinterpreted and that “straight” is probably a better choice of wording. However, I disagree with his contention that gymnasts should be taught to come on with a tight arch. If you want to read the entire post, click on the link above or here .

Here are my comments…

Post #1

Go read this study by Takei et al.…omparative.pdf

Look at the diagrams between low-scoring Roche vaults (Hand double front) and high-scoring Roche vaults. The low-scoring has a big arch upon horse contact whereas the higher scoring vaults are considerably straighter.

I agree that some people over-do the idea of “straight-hollow” and end up teaching a curvilinear hollow. And, a lot of folks teach the head to be in when in fact it should be looking at the hands and slightly out on contact. The text even says that the gymnast’s eyes should be focused on the hands. So, yes, there should be an angle there.

But, to teach a big arch on contact and during the pre-flight is not optimal. The resultant vertical velocity will be better transmitted to the body with less segmentation and more rigidity. The key to a big post-flight is then trying to manipulate the angle of entry.

The reason that the Tsukahara and Yurchenko style vaults are more popular is because there is a mechanical advantage on the new table. The long table allows for the gymnast to make contact at a lower entry angle in those two vaulting styles. In contrast, it is much more difficult to contact at a low enough angle in the handspring front style of vaulting with the table as long as it is. You have to be very naturally powerful to pull this off. Most females are not that powerful and these other vaults offer better alternatives. It has little to do with training – women have different anthropometric profiles in general. Of course, there are always a few outliers like a Sacramone. But, those female athletes are few and far between.

The athlete in the picture that you have posted is actually a little high and that’s why he’s in a hard, tight arch because he’s trying to gain rotation by shortening the body. Unfortunately, he’s going to sacrifice height. If he focused on being a little straighter and trying to contact the table slightly lower, he’d have an even better post flight.

Post #2

Let me add one more clarification to my original post.

“Straight Hollow” is poorly worded by the JO Committee and I may bring this up. People naturally associate “hollow” with a curvilinear hollow. However, a straight hollow position is simply a straight position with the sternum pulled in slightly so that the thoracic spine is not in extension (i.e. arched). However, the thoracic spine should not be in extreme kyphosis (i.e. rounding) either.

So, better wording for the coaching community would be “straight.” And, that’s what I advocate. I want my athletes straight and tight with the eyes looking at the hands. So, yes, the head is out a bit.

At that point, I really emphasize board position and entry angle to achieve my desired post-flight. Do you have to arch in a handspring front? Yes, to an extent. But, I want the arch that occurs to happen through hip extension, not thoracic extension. Furthermore, I want this to occur immediately after the athlete has left the table because they will have maximized the vertical velocity due to the reaction force from the table. So, their flight path is now set and any changes in body position (arching, etc.) simply changes the inertial parameters and the resulting rotational (angular) velocity.

In coaching terms, they have now maximized their height after table contact and if they need to flip faster, this is the time to alter body position to achieve such. Furthermore, if the body is straighter coming off of the table, the rotational speed will be greater when they tuck or change position because there was greater resistance (inertia) from the initial body position. I know that I’m wording this poorly, but hopefully it makes some sense. Think of rotating and changing position in the middle of the air from a layout to a tuck versus a layout to a pike. Which is going to spin faster? Certainly, the layout to the tuck because tucking in tightly reduces the resistance to rotation to a greater extent than changing from a layout to a pike.

So, if I’m arched really hard coming onto the table, my body is already shortened and the speed of rotation when I tuck or change into whatever body position will be less than if I were straighter. Furthermore, due to the arch at contact, my center of mass is lower and therefore I will not attain as much height off of the table. My flight path will be a lower and flatter parabola.

Your continual argument of it being a tight arch versus a loose arch is irrelevant. Certainly being tighter will assist you relative to the transmission of the reaction force from the table. But, the arch alters the position of the center-of-mass regardless of whether you’re tight or loose. And, the position (angle) of the center-of-mass relative to the line of action of that reaction force is what plays an important role in flight path. The other variables of parabolic motion are take-off velocity (from the board and table) and the height of the center of mass from both the board and position on the table.

Post #3

I re-read my post a couple of times and have no idea where I explicitly stated that arching after leaving the table will generate rotation. You are correct that the flight path is set once the gymnast leaves the table. Arching after leaving the table changes the body position and could potentially increase the speed of rotation depending upon how “hard” the arch is because the body is being shortened. However, this would not be smart because of how the center-of-mass is re-positioned lower. A big, hard arch would spell disaster. To visualize this – I’m talking about an arch like in the high jump – the Fosbury Flop. The advantage to this high jump technique is that the center-of-mass actually goes beneath the bar because of the position of the body. So, it moves lower.

The big advantage to opening the hips (hip extension) is that it pre-stretches the hip flexors (eccentric action) just prior to snapping (concentric action of the hip flexors) into the desired shape (tuck, pike, etc.). This simply allows for a more forceful contraction into the desired position and this could be advantageous in terms of being able to contract into a tighter position. So, in the case of performing a handspring double front, the gymnast could get into a tighter tuck shape and possibly increase the angular velocity (rotational speed) enough to where he might have time to do more – like a half out or something more depending upon how high he got off of the table.

Post #4

I’ll add one more thing…

To those who are members of the United States Elite Coaches Association (USECA) for women’s gymnastics, Mark Young (Amy Chow’s coach) did a lecture on vaulting several years ago that was sent out on video by the USECA. It’s the lecture contained on the video titled as Vaulting #6.

In that video, he said that when he first taught Amy to do a hand front, he taught her to arch really hard and felt that it was a mistake. As he so eloquently put it (paraphrasing) – “I taught her to drive her heels hard and get her a$$ over her head.”

Later, he said that he saw the Korean men vaulting at an international competition and doing big handspring entry vaults and timers and observed their technique. They were coming on straighter and the hips would open as they left the vault (at this time, it was still the old horse). He termed this technique as the “Hollow-Hip Release” technique.

While Mark is not a biomechanist, his observation holds biomechanical validity as I’ve explained above. And, as he states in this lecture, he firmly believed that if he had taught Amy this technique, should would’ve medaled on vault at the 1996 Olympic Games because she would’ve been able to get a bigger vault. I have not watched the video for a LONG time, but I think that they were trying to get a handspring rudi.