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Qualitative description of the ideal Yurchenko

layout vault technique

Valentin Uzunov

J.E.T.S Gymnastics, Rochester MN, USA ABSTRACT The Yurchenko vault was first pioneered in 1982 by Natialie Yurchenko and has since become the most widely used vault entry for women. Male gymnasts also perform the Yurchenko. The aim of this paper is to examine the available literature and provide a detailed description of the key biomechanics characteristics and their interrelationship characteristic of high scoring Yurchenko Layout vaults. Current scientific literature has identified several biomechanical characteristic that are shared among outstanding performances: a) a quick and close to vertical take-off from the springboard following the round-off; b) very fast rotation backward onto the table, with a high angle of attack between 30-40°; c) a very short table support phase with an increasing vertical velocity on take-off with minimal losses in horizontal velocity, are the best predictive variable for a successful vault being angular momentum on departure from the springboard. Coaches who wish to improve their gymnast’s performance can compare their gymnast’s technique to the available data and devise training protocols to address their gymnast’s short comings based on comparisons with the proposed ideal kinematics. Coaches should also concentrate on developing the gymnast’s ability to generate and maintain angular momentum throughout the Round-off, pre-flight phase and table impact as these are the most technically challenging phases of the vault and also associated with a successful execution of this vault. Key Words: Yurchenko vault, Yurchenko layout, vault, vault mechanics INTRODUCTION The Yurchenko vault was first pioneered by Natalie Yurchenko at the 1982 World Cup in Zagreb (Croatia). It is distinguished by the round-off entry onto the springboard followed by a back handspring with or without turns onto the table. Initially the vault was considered by many as being too dangerous because of the possibility of missing the vault. This changed in 2001 with the introduction of the new vaulting. Since then the Yurchenko has become increasingly popular among all levels of gymnasts. The Yurchenko vault is particularly popular with female gymnasts. At the 2009 World Championships vault event finals, all female gymnasts performed at least one Yurchenko vault with most performing two (one being a ½ onto the table). In comparison, only 2 male gymnasts performed a Yurchenko as one of their vaults, with the majority still preferring Tsukahara or Handspring group vaults. Despitethe increased use and performance of the Yurchenko vaulting over the past decades there have been relatively few studies on the Yurchenko vault compared to handspring entry vaults. The few studies available have consistently

focused on examining the Yurchenko layout and the Yurchenko full vaults providing at least an array of comparable data on this vault (2,314,15,16). Most recently Koh, Jennings, Elliott, & Lloyd (2003) presented a deterministic model of the Yurchenko layout vault that highlights the relationship between the kinematic variables and performance scores, which are particularly useful in determining ideal technique. A shortfall of the available research, however, is that the majority of data and performance variables are derived from computer optimizations using input performance and anthropometric data and statistical analysis of digitized film of elite and Olympic female gymnasts only (2,15). As a result, the available data has limited use for direct application to coaching at younger levels, or non elite/Olympic athletes. It does however present insight into ideal technique. The aim of this paper is to qualitatively describe the kinematic variables characteristic in high scoring Yurchenko Layout vaults and provide practical recommendations to coaches teaching this skill. In order to accomplish this the article is divided into two parts. The first part will examine available research and highlight the key concepts and ideas coaches need to understand the mechanics of high scoring

vaults. The second part will propose a pedagogical model for the training of the Yurchenko layout based on the amalgamated knowledge presented in this article and expert coaching opinion and training methods. DISCUSSION The Yurchenko vault like all other vault groups has 6 critical phases: Run-up/approach, hurdle/pre-element, pre-flight, repulsion, post-flight and finally landing. In order to be able to perform any vault with maximal amplitude and technical proficiency, each phase has to be performed without error/s. Errors in execution in one phase have a cascading effect, resulting in errors in the subsequent phase/s. It is imperative that coaches understand the specific cause and effect relationships between errors in order to understand how to fix them. The following discussion will focus on examining the key kinematic variable of each phase based on available literature and provide a description of the ideal technical executions from a qualitative kinematic perspective. The aim is to give coaches a deeper understanding of the relationship between each phase and impart a greater understanding at a fundamental level of the cause and effect relationship between the kinematics of each phase. Before coaches compare the kinematics described in the literature to the performance of their own athletes it is important to remember that kinematic data, although descriptive of the ideal technique, is also dependent on the strength, flexibility, and somatotype of each individual athlete (15). Consequently, coaches should consider each athlete on an individual basis. Precisely because each athlete is unique it is essential to have a good grasp of the cause and effect dynamics of a well-executed Yurchenko vault. Run-up/Approach Every vault begins with a run-up. The run-up sets the precedence for the overall dynamics of the vault. Essentially, the aim of this phase is to generate as much kinetic energy as possible that will then be translated into corresponding vertical, horizontal and rotational velocities during the

hurdle and round-off. The formula that describes the kinetic energy generated during this run is, k= ½mν2 (where ν is the horizontal velocity of the gymnast and m is the mass of gymnast) (11). What this formula tells us is that a 10% increase in the gymnast’s running velocity will results in a 20% increase in total kinetic energy generated (11). Based on this, it is generally accepted that the faster the run-up the greater the potential to perform a dynamic and explosive vault, as the gymnast has more kinetic energy to convert/transform. However, it by no means guarantees a good vault on its own. Research reporting run-up speeds for different vaults has consistently shown that the Yurchenko vaults are performed with slower run-up speeds compared to Handspring or Tsukahara entry vaults. The difference is much more evident for male gymnasts and only marginal in the case of female gymnasts. Sands (2000) reports the average Yurchenko vault run-up velocity as 6.93 m/s for juniors and 7.36 m/s for senior female regional athletes. Similar figures are reported by Naundorf, Brehmer, Knoll, Bronst and Rolf Wagner (2008). They measured the speeds of all vaulters at the 2007 World Championship in Stuttgard and reported an average run-up velocity of 7.33 m/s for female gymnasts and 7.36m/s for men. Even though this is only one set of data, collected at one competition it can be at least preliminarily assumed that at the Elite level there is not a significant difference between the run-up velocities of Yurchenko vaults performed by male or female gymnasts. This suggests that both men and women have at least in part similar pre-conditions for entry into the round-off. This means differences in actual vaulting ability by males and female are predominantly the result of technique during the subsequent phases and not the run-up. Cuk & Karacsony (2004) point out that given the complex springboard entry of the Yurchenko vault, control of the run-up is likely more important for successful performance compared to achieving maximal run-up speeds, which is also supported by Koh & Jennings (2007). By the time the gymnast performs this vault in competition, he/she should have an established optimal run-up approach in order to have consistency in performance. This makes it very hard to modify a gymnast run-up approach once it has been established, however coaches need to consider this as an

Figure 1 – Cinematographic view of the hurdle phase performed by Anna Pavlova at the 2008 European Championships. It is important to notice the long and low hurdle into the round-of. This image is only meant to illustrate the length of the hurdle and not necessarily the ideal hurdle or round-off technique

option for gymnast who lack dynamics. Aside from actual speeds generated, Rybecki (2008) recommends that gymnasts have good running mechanics and posture, as this will set the gymnast up for a good efficient entry into the hurdle phase. Hurdle/pre-element The last step of the run-up in all vaults is characteristically longer and marked by a drop in speed prior to the actual hurdle, particularly so for the Yurchenko (5). The hurdle phase of the Yurchenko can reach lengths of up to 2.5m for women and 3m for men, depending on run-up speeds and deceleration prior to hurdle (Figure 1) (5). There are various techniques used in the hurdle phase, unfortunately as it is there is no available literature comparing techniques. From a coaching perspective, it is generally agreed that the hurdle techniques used need to be suitable for the gymnast’s own physical abilities to allow the gymnast to smoothly transitions into the round-off (RO) with minimal deceleration (7,8,9,10). The Round-off has also received little examination from the scientific community. Hence, there is no empirical data to suggest optimal technique. This is unfortunate as Penitente, Merni, Fantozzi, Perretta (2007) suggest that “The effectiveness of the round-off onto the springboard outlines the uppermost limits of what the gymnast can attain during the successive phases”. Koh et al. (2003) also concluded that the round-off technique which allows the

athlete to translate horizontal linear momentum and reorientation of the gymnast’s facing direction may be a critical factor in the execution of the vault. Indeed expert coaches also place greatest emphasis on correct RO execution onto the springboard for successful mastery and execution of this vault (8,9,10,12,13). One key characteristic of a good round-off is a fast turnover from feet to handstand to feet. Coaches should spend considerable time on

developing their athlete’s Round-off onto the springboard. One area of interest to coaches that has received some attention and is related to the efficiency of the round-off is the springboard contact. Penitente at al. (2007) found that the angle of first impact (when the toes first touch the springboard) with the springboard is on average about 60° with the feet parallel and approximately 30cm from the edge of the springboard (1,5) (reported figures ranged between 58° and 67°. The body angle was defined as the angle

between the horizontal line and the line passing through the COM and the toes at the board (Figure 2)). Penitente at al. (2007) suggest that by impacting the board at a greater angle the gymnast reduces the downward compression of the springboard and is thus able to reduce loses in horizontal velocity of the centre of mass (CoM) while maximizing vertical velocity of CoM and angular momentum on take-off (1). These conclusions are supported by research conducted by Kwon, Fortney & Shin, (1990). Video examination, by the author, of high scoring Yurchenko vaults by male and female vaulters at the 2002 World Championships, 2008 European Champions, and the 2008 Beijing Olympics also showed a similar angle of impact (approximately 60°) (unpublished results). It is important to point out that this angle is dependent on many variables such as horizontal velocity, vertical velocity following the round-off, CoM on impact, body position etc. To say that 60° is the ideal angle of impact is far too simplistic. However, this figure does suggest the ideal board impact should be in relatively upright position, which further highlights the importance of Round-off execution. As the gymnast impacts the board the springs compress, during which time the gymnast continues to rotate very rapidly over the top of his/her feet. As the springs recoil and the gymnast thrusts of the board with his legs departing from the board (springboard take-off), the body angle is reported to be close to 90° (mean value from data was 84°). Springboard contact times are reported to be on average between 0.14 - 0,16 seconds, with CoM displacement from contact to take-off being on average 67cm (1). These figures tend to be in support of Penitente at al. (2007) and expert gymnastics coaches (8,9,10,12,13) belief that a high on entry onto the springboard with a short contact time is characteristic of efficient springboard contact to achieve optimal pre-flight conditions, however more research is clearly needed to understand the optimal springboard conditions for pre-flight. Pre-Flight The ideal pre-flight kinematics are characterized by a very quick backward rotation of the gymnast’s CoM onto the table, with the CoM rising (2,3). In order to achieve this on

take-off from the springboard, the gymnast must forcefully be reaching back and under for the table while still in contact with the springboard (3,7). In doing so he/she would hopefully

align his/her upper

Figure 2 - Diagram of how the body angle was measured and defined by Penitente at al. (2007).

Figure 3 - Body alignment on springboard take-ff

limbs with the trunk on take-off from the board to a straight bodyline (7) (Figure 3). It has been reported that correct body segment alignment at take-off is correlated to higher scoring vaults, for both Tsukahara and Yurchenko vaults (7). Pre-flight times (from springboard take-off to table contact) are reported to be between 0.12ms and 0.22ms (5). Variations in times reported are likely the result of take-off angles, angular velocities between observed performances in the different studies and differences between female and males, with males having slightly shorter pre-flight times (5). In any case the most critical factor for a short pre-flight time is a large horizontal velocity on take-off. The fast opening of the shoulder angle and reaching back allows the gymnast to contact the table quickly, without leaning back. At the same time short springboard contact times, correct body alignment, and a close to vertical take-off angle maximizes the vertical velocity of the CoM. This entails the CoM will have a parabolic pathway and continue to rise while the gymnast is rotating backward. The resultant angular velocity (rotation) of the CoM on take-off is not consistently reported in literature, and these seem to be slight but significant difference among figures reported in studies, which have suggested is due to improvements over time in springboard design and manufacture and the change from vault horse to the vault table. Nonetheless, the literature uniformly shows that angular momentum at table contact is the most critical variable for a good post-flight (1,7). The level of angular momentum is established predominantly by the kinematic and kinetics of the Round-off onto the springboard (16). Repulsion Once the gymnast impacts the table he/she repulses from the table and propels his/her body up into the air thereby initiating what is known as the post-flight phase. A large vertical velocity of the CoM at departure from the table is deemed to be the most important variable for achieving a high post-flight. However, it is by no means the only one (7). The successful execution of the repulsion phase is characterized by: A large vertical velocity at table take-off, short contact time with the table, suitable body angle of attack, correct body alignment and coordination of joint actions during the table contact and table departure. Coaches often talk about ‘blocking’ off the table during this phase, which is observed as a quick change in direction from linear horizontal motion to vertical lift. In order to achieve a good block coaches emphasize that the gymnast needs to hit the table with an open shoulder angle (a shoulder joint angle of 180° is consider open) and quickly push of the table through the shoulder girdle and wrists. Research partially supports the coaches’ instruction. Studies show that the shoulder angle (defined as the angle between the arm and the anterior aspect of the mid trunk, Figure 4) at first impact

is usually between 160-170° (2,3,7). In a study by Koh et al (2003), a comparison of the live performance of an Olympic athlete with a computer optimization of this athlete’s vault demonstrated that the athlete’s shoulder angle at impact was 164.3° whereas the computer optimization (which resulted in a considerably better vault) was at 169.0°. The difference between the two trials was predominantly a 10% increase in angular momentum (in the optimization) during pre-flight. Even though this shoulder angle value is specific to the gymnast in the study, the result suggests that, with

increasing angular

momentum the gymnasts may need to impact the table at a greater shoulder angle (2,3). Some literature however warns that impact of the table with a hyper flexed shoulder angle can have

potentially injurious effects to the shoulders and wrists (3). Coaches need to consider this and ensure the gymnast is conditioned sufficiently to handle the forces under such conditions as to avoid injury (3). Along with the shoulder angle, the body attack angle (AoA) needs to be considered during table contact for effective repulsion. The body attack angle is defined as the angle the CoM makes with the point of impact and the horizontal axis (Figure 4). Literature hints at a possible interrelationship between these two variables, which is regulated by the angular momentum during pre-flight (2,3,15). Again, it is hard to prescribe an ideal AoA as so much is dependent on the gymnast’s own vaulting kinematics. Having said that, studies suggest the gymnast should impact with an angle around 45° (2,16,17). A lower angle of attack (AoA) can lead to reduction in angular momentum during the support phase because the gymnast’s weight acts as a moment arm in the counter-rotation direction of the vault (17). A higher angle of attack on the other hand tends to “facilitates the generation of angular momentum during impact with the horse because the reaction force passes behind the whole body CM” (17). It is also associated with shorter contact times during table support (17). For the gymnast to optimally deflect (repulse) from the table following a favourable contact he/she needs to apply a vertical impulse to the table. The vertical impulse is a function of muscular force and time of force application governed largely by the force-velocity relationship of skeletal muscles. This is best described by the impulse momentum relationship (F.∆t = m.∆ν ) (11). What this

Figure 4 – Illustration showing shoulder angle and the body angle of attack as defined in the literature.

relationship shows is that for the gymnast to increase his vertical velocity on take-off (∆ν) from the table he/she can either apply a larger force over a longer period of time, which is usually achieved by bending the elbows or applying a smaller force over a shorter period of time. Studies show the ideal technique requires short contact times during table support (7, 14). Contact times range between 0.16ms and 0.23ms, with female average contact time being slightly longer then male contact time (5.7). The key to this contact time is speed of rotation over the hands during table support. The faster the gymnast is rotating over the top of the table the easier it is to deflect off the table. This is largely dependent on the gymnast’s angular momentum established during pre-flight (2,3,7), which supports previous discussions on optimal ranges of the shoulder angle and AoA at impact. The resulting impulse forces are generated largely by wrist extension combined with shoulder girdle elevation, (Figure 5) as well as shoulder joint extension during table impact (2). A further benefit of impacting the table with a maximally open shoulder angle during table support is that the gymnast can apply more torque while in contact with the table by trying to close the shoulder angle in order to align the torso and legs as s/he leaves the table, thereby achieving further increases in vertical horse takeoff velocity (2). Post-Flight & Landing The successful execution of the post-flight phase is judged based on: Height of post-flight, landing distance from table, completing the number of somersaults and twists with technical perfection. Post flight height for Yurchenko Layout vaults by men have been reported to be around 0.84s and 0.72s for women (5) However, for more difficult vaults post-flight times increase significantly. For instance, post-flight times can reach up to a full second for a Yurchenko double back pike (5). In order to increase this post-flight time, vertical velocity on departure from the table is the most critical variable (5). Vertical velocity on repulsion will dictate to a large degree the gymnast’s ability to achieve and maintain a layout position during the post-flight (2). Once the gymnast has left the table he/she can no longer alter his/her flight path or change his or her angular momentum. The gymnast’s ability to maintain a stretched body has already been determined. He or she can only speed up rotation by reducing his/herinertia by altering of the body position (piking or tucking) which is observed in many vaults prior to landing. In a good Yurchenko vault, the gymnast CoM should show a stair case effect (Figure 6),

where the center of mass is rising during the pre-flight followed by a second rise following the repulsion. The efficiency of both phases (pre-

flight and repulsion) combine to produce the overall post-flight phase flight path.

Landing distance, although a factor of both horizontal and vertical velocities, may be predominantly attributed the horizontal velocity at initial hand contact with the table, along with the resultant velocity at push off from the table (2). An error free landing is vital for a successful vault. In a good landing the body must be fully extended prior to touchdown and the knees should flex slightly to absorb the forces on landing (7). CONCLUSIONS The Yurchenko vault has been performed internationally since 1982 when it debuted by Natilie Yurchenko. Since then it has become the preferred style of vaulting in Women’s gymnastics and has also been adopted by the men. Despite the popularity of this vault in current gymnastics only a few studies of it have been published. The available literature has consistently focused on the Yurchenko layout vault and has reported similar results, consistently identifying the same kinematics associated with ideal execution. The majority of data and performance variables have been derived from computer simulations using input (performance and anthropometric) data of elite female gymnasts (2) in order to predict optimal performance of the

Figure 5- Cinematic illustration of the shoulder girdle depression and elevation, wrist flexion and extension during the block off the table.

Figure 6 Notice the rising of CoM during the pre-flight b-d and the repulsion d-e. This double rise illustrates the stair case effect which is characteristic of good vaulting performances.

Yurchenko layout vault. The results of the computer optimization studies have tended to confirm the conclusions of kinematic studies of live performances. From available biomechanical data logical conclusions have be drawn to summarise the key variables and describe the kinematics of the Yurchenko layout vault. The key factors impacting on the performance of a Yurchenko layout as described in the literature are: (a) a controlled run-up and sustain maximal horizontal velocity during the hurdle and pre-element phase; (b) a high on angle of the body at springboard contact with a short contact time; (c) on take-off from the springboard the gymnast must depart with maximal angular momentum, with the CoM rising on table impact; (d) an explosive block of the table which further increases the gymnast’s vertical velocity and angular rotation resulting in a stair case effect of the CoM pathway; (e) a high rising post-flight is the result of summation of all preceding phases; (f) post flight height and distance of landing and a stuck landing are positively correlated variables to high scoring vault.

Practical recommendations based on the examination of the currently available literature is that coaches need to pay attention to: a) changes in rhythm and deceleration of the gymnast when transitioning from the run-up to round-off; b) the gymnast should try to take-off from the springboard as close to upright as possible with minimal contact time; c) very fast rotation over the table, with minimal shoulder angle and an angle of attack around 40° being vital for a quick block off the table. Coaches need to concentrate on developing the gymnast’s turnover during the pre-flight as the angular momentum at table impact is the most critical variable for the successful execution of this vault. In the next article methodological approaches to developing these variables will be addressed. DISCLAIMER Every care has been taken to ensure the accuracy of the information published in this article. The views and opinions expressed in this article are those of the author/s. The Gym Press, Gym Coach, or the author have no responsibility for the consequences of actions based on the advice contained in the article.

ACKNOWLEDGEMENTS I would like to thanks Toshiyuki Fujihara for reviewing this article and helping me with the necessary research. Sara Gill and Gibran Campos for proof reading and giving me their coaching perspectives. Lyubomir Uzunov for editing and proof reading. Address for correspondence: Uzunov V., J.E.T.S Gymnastics, Rochester MN, USA. valentin.uzunov@gmail.com REFERENCES 1- Penitente G. Merni F. Fantozzi S. & Perretta N. (2007). Kinematics of the springboard phase in Yurchenko-style

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