MAJOR QUESTION: 
Rhythmic gymnastics (RG) is considered an aesthetic sport combining both sport and art through expressive dance steps, which is accentuated through the use of apparatus including rope, hoop, ball, clubs and ribbon. Rhythmic gymnastics is internationally governed via the Federation Internationale de Gymnastique (FIG) where each routine complies with the current 2013-2016 code of points (COP) (Federation Internationale De Gymnastique, 2013). Each gymnast completes a total of 4 routines of various apparatus each going for the duration of 1 minute and 30 seconds. The routine comprises of an array of technical body difficulties, which are considered elements in combination with apparatus handling. The gymnasts are assessed by a judging panel which comprises of difficulty, artistry and execution. The gymnasts are judged on the execution and technical competence of each of their body difficulties. This forms contrasts with various sports that are assessed on how many goals are kicked or how fast an athlete runs. “In rhythmic gymnastics execution quality depends directly on the level of technical expertise, as well as physical performance of the gymnast” (Mkanouer, B. 2012). Each routine must correspond with the Code of Points and comprise of body difficulties including balances, leaps and pivots.
For gymnasts
to execute a leap they must demonstrate “defined and fixed shape during the
flight” and “height sufficient to show the corresponding shape” (Federation
Internationale De Gymnastique, 2013). It
is required throughout a turning split leap for the gymnast to achieve a
minimum of 180-degree split through their legs whilst demonstrating a
curvilinear motion. Each turning split leap is worth 0.50 in value, therefore two being worth 1.0 and are assessed by the difficulty judges. A common technical fault associated with the jumps and
leaps section in the current Code of Points is the lack of amplitude in the
shape and heavy landing (Federation
Internationale De Gymnastique, 2013). However, gymnasts who are able to
demonstrate the correct shape but display minor body errors such lack of
amplitude, flexed feet and heavy landings can have the difficulty awarded by
the judges but receive deductions from the execution judging panel. Therefore
to execute the skill of a turning split leap, gymnasts must demonstrate
flexibility, strength and power. Consequently, the following blog with analyse
the biomechanical principles associated with the rhythmic gymnastics body difficulty
of a turning split leap.
VARIOUS PHASES
ASSOCIATED WITH THE TURNING SPLIT LEAP:
PHASE 1: CHASSE - TRANSFER OF
WEIGHT
PHASE 2: STEP STEP -
TWO LARGE STEPS WHERE THEIR BODY TURNS 180 DEGREES
PHASE 3: SPLIT LEAP
In rhythmic gymnastics, gymnasts’ will ‘chassé’ and
then ‘step step’ prior to completing the leap. Phase one can be described as a
chassé with their preferred leg forwards, which can also be recognised as a
gallop which is a transfer of body weight between legs. Phase two occurs when
the gymnast then takes a step on their preferred foot, following the chassé.
The gymnast then take two large steps where they turn 180 degrees, as they
throw their preferred leg forward into the air to complete the split shape. The
split leap shape should be a minimum of 180 degrees in splits (Federation
Internationale De Gymnastique, 2013). For the gymnast to remain airborne whist
in the split leap position, gymnasts require great strength. This allows the
gymnast to propel their body in an upwards position whilst maintaining kinetic
energy. This will then counteract the vertical momentum which is lost by the
gymnast raising their legs into the split leg position. The two large steps in
phase two, prior to the leap being performed enable the gymnasts’ mass to move
forward at a steady speed. This contributes to the aesthetics and flow of the
leap which are significant factors considered by the judges when assessing the
leap. Throughout the completion of the turning split leap, the gymnasts body
mass does not change, although, the acceleration from the legs during the leap
does which occurs when the gymnast propels upward with a vertical force up off
the ground. Arm movement is also an essential part of the split leap. During
the chasse, the arms extend outwards and whilst phase two occurs, the gymnast brings her arms closer to the body
which reduces the moment of inertia and increases rotational velocity
(Blazevich, 2012).
As seen in the video below, at the peak of the leap, the gymnasts arms should be extended,
and during this movement, the gymnast will need to ensure that they continue to
remain stable over their centre of gravity. This will create control through
the start and end of the movement. Once the gymnast has then landed on their
preferred leg, they will then complete another turn, which will indicate the
finishing of the skill and prevent injury from a static landing. The landing of
the leap must be sequential to avoid jarring of the body and possible injury.
This skill can additionally be completed consecutively with more than one
turning leap in a row. To achieve this phase two and three are completed the
chasse is eliminated.
NEWTON'S LAWS:
The initial pre-execution phase of the turning split leap can be applied to Newton’s Third Law of Motion. This law states “for every action, there is an equal and opposite reaction force” (Blazevich, A. 2012. P.45). This can be effectively analysed in the video below whereby the gymnast demonstrates the chasse, step step preparation phase and demonstrates a parabolic path as there is obvious maximum height reached in the middle of the turning split leap and gymnasts gain kinetic energy. The force that is exerted in the preparation phase is applied when the gymnast’s feet contact the ground demonstrating both horizontal and vertical components of projectile motion (University of Victoria, Unknown). The variables of interest in this skill include the flight distance, flight time and the maximum height achieved by the gymnast. Gravity acts upon the body to increase the height of the leap by working against gravity. Therefore when the gymnast’s feet get in contact with the mats, the force absorbed in the step, step phase will determine how far they can propel into the air to achieve the 180-degree split shape. Therefore the greatest influential factors of the biomechanical model for this skill are this preparation phase as the force produced by the lower limbs determines the height and flight time.
The correlation between Newton’s third law and the kinetic energy exerted by the gymnast can be recognised as the summation of forces (Oxford University Press, 2014). It is what maximises the flight distance and maximum height. The power of the leap is initiated via the vertical force generated from the chasse, step, step and contact with the ground to push off of their legs in combination with the use of their arms. When the gymnast lands after the completion of the leap, a vertical downward force is applied which is considered the ground reaction force. In this circumstance, it is the contact with the mat surface. This force then exerts enough energy to overcome inertia through the equal and opposite reaction forces of their landing leg and the ground. A gymnasts second foot leaves the ground with a certain amount of angular momentum, created by the ground reaction force.
It is therefore central for gymnasts to create a greater velocity by demonstrating well established leg strength displayed in the chasse, which facilitates the leap to propel higher into the air without losing too much energy. This phase is fundamental to the height and execution of the leap and can be applied to Newton’s first law, “An object will remain at rest of continue to move with constant velocity as long as the net force equals zero (Blazevich, A. 2012. P.44). This can be applied once the gymnast completes the take-off phase of chasse, step, step, as she is already leaping in the air and consequently, momentum can no longer be generated. This therefore coincides with the Law of Conservation of Momentum, which explores why the take-off phase is critical to the height and flight time of the leap.
Furthermore, as the gymnasts perform skills utilising their own body weight, their mass is not altered which complies with Newton’s second law of motion which states Newton’s 2nd law states that “...the acceleration of an object is proportional to the net force acting on it and inversely relative to the mass of an object” (Blazevich, A. 2012. P.45). Therefore mass and acceleration are directly proportional in regards to force. It is evident that throughout the skill of the turning split leap, a gymnast with a lighter body mass has a greater ability to accelerate at a faster pace in comparison to a heavier gymnast when the same amount of force is applied, as to maximise the height in which they are leaping, and they need to overcome inertia. Therefore the ideal aesthetics of a gymnast are one of the lightest possible mass, with well-established leg strength which enables a gymnast to leap higher and accelerate the gymnast forward when the force is large enough to overcome inertia. This therefore ensures that the gymnasts leaping performance can reach the desired height whilst minimizing energy cost (Blazevich, 2012).
PHYSICAL DEMANDS OF THE SPORT:
Such a sport “...requires support from enhanced
physiological requirements necessary...including cardiovascular fitness, muscle
flexibility, muscular strength/power”. (Malkogeorgos, A., Zaggelidou, E.,
Zaggelidis, G., & Christos, G. 2013). In order for gymnasts to successfully
achieve this, they are required to engage in an array of strength based
plyometric activities and flexibility exercises to ensure best possible
execution of the skill with split legs of 180+ degrees. “An improvement
in lower body muscular strength and power appears to have positive effects on
aspects of performance (Brown, Wells, Schade, Smith, & Fehling, 2007;
Koutedakis et al., 2007)”. Exercises include hip flexor and hamstring
stretches from a raised surface in combination with over splits, where gymnasts
perform splits off a raised surface enable split beyond 180 degrees in their
leaps. Moreover, plyometric training and lower body conditioning including jump
lunges, block jumps and jump squats are also critical as they increase an athlete’s
explosive power. Gymnasts may also perform kicks wearing ankle weights to
increase muscle strength, tone and explosive power. Additionally, gymnast’s
improvement in lower body muscular strength coincides with a gymnast's ability
to prevent injury (Malkogeorgos, A., Zaggelidou, E., Zaggelidis, G., &
Christos, G. 2013). In adopting an appropriate flexibility and strength regime,
it fosters the gymnast to practice the various phases of the movement with best
possible chance of execution from the judging panel.
BIOMECHANICAL PRINCIPLES ASSOCIATED WITH THE TURNING SPLIT LEAP:
Torque
is considered the “...magnitude of force causing the rotation of an object” (P.63).
Both torque and rotational inertia are principles of physics that can be seen
to significantly affect the execution of the turning split leap. These
principles determine the speed and balance of the turn and leap whilst in
flight. When the gymnast brings their arms in close to their body after phase
one, “the chasse” during the second phase step step, prior to phase three the
split leap the gymnast gains angular momentum. This allows them to execute
their leap at a faster pace. The step step phase fosters the gymnasts mass to
continue propelling forward at a consistent speed, therefore demonstrating flow
in the movement. This contributes to minimal deductions from the
judges and greater likeliness of the body difficulty being paid.
This
step step which completes a 180 degree turn is considered the pivot point that
the gymnast applies force too, as this phase assists to determine the height of
the leap. Whilst the arms are brought together, the rotational inertia is small
and the angular velocity is greater. Whilst the gymnast is completing the
third phase of the skill, the split leap, the gymnast applies a large force
into the ground, which can be considered the inertial force as the lower limbs
experience swing. Whilst the gymnast creates a swing and extends both her arms
and legs, the rotational inertia is greater and therefore the angular velocity
is smaller. The gymnasts centre of mass is moving forwards over the base of
support (their non-preferred leg which contacts the ground prior to the leap),
which causes rotation of the body and her lower limbs are brought closer to her centre of mass,
therefore the radius of gyration is decreased. This enables the gymnast to travel a greater distance which is
caused by the force of gravity, creating a forward acceleration (Blazevich,
2012). This ensures the skill is completed at the fastest pace possible with
the least amount of muscle force, resulting in movement efficiency (Blazevich,
2012). However, whilst in the split shape, the centre of mass should be
maintained in an upright position, whereby the gymnast engages her core to
ensure appropriate amplitude of the body in the leap. Additionally, whilst the
trajectory is always the same, gymnasts have the ability to create an illusion
as though they are floating, which is achieved through raising their arms and
legs and altering the position of their head.
As
this leap can be completed consecutively, by completing more than one turning
leap in a row the rotational inertia is altered. This can be seen through the
extension and retraction of the leg at the completion of the leap, prior to the
next leap. This can be analysed when the gymnasts leg retracts from one leap
and they then complete another ‘step step’ as they turn extremely quickly prior
to leaping again where the leg experiences extension, producing torque.
As a gymnast completes the leap, her velocity increases which causes an increase in momentum, as momentum equals mass time velocity (Wooten, W., Hodgin, J., 2000). As the gymnasts’ mass does not change while she is airborne and her velocity is increasing, it corresponds with the increase in momentum in the leap. As the leap commences and and a gymnasts foot has left the mat, her momentum is conserved. This therefore means she will continue to move through the air consuming the same force she initially left the floor with. Therefore, gymnasts have to maintain their momentum to continue to leap and stay airborne. Gymnasts’ often manipulate force to benefit their landing from a leap.
Momentum is linked to force by ‘impulse’, which simply put as impulse = force x time as one of these factors increases, the other decreases (Mero, A., 1988). As the gymnast completes the leap and bends her knees whist landing, she essentially increases the time it takes her to slow down, therefore decreasing the amount of force and pressure being placed on her knees and ankles. If the gymnast does not bend her knees she puts herself at risk of potential injury. This can be explored as the time that it would essentially then take her to slow down would decrease and the force, which is pushing back on her would essentially increase. As the force of the landing increases, so does the risk of injury. For example, if the gymnast experiences a heavy landing with straight legs, there is a risk that she would hyperextend her leg, as the force has nowhere else to go causing severe knee problems. Additionally, acute-severe ankle injuries can occur if the gymnast experiencing a heavy landing where she lands awkwardly on her ankle as the force will continue to push back, which could essentially cause a break or sprain. It is evident that 70% of injuries result from landing floor exercises in the sport of gymnastics (Pettrone, F. A., & Ricciardelli, E. 1987).
The Law of Conservation of Energy states that ‘the total energy of an isolated cannot change - it is said to be conserved over time. Energy can be neither created nor destroyed, but can change form’ (Knight, R. 2004). Therefore when a gymnast is at their highest flight point in the air, their kinetic energy is the lowest, however, their potential energy is higher. When a gymnast is in the final phase of the split leap and is about to spring into her leap, she is building up her potential energy. As she then begins to conclude her leap, that initial potential energy is then converted into kinetic energy (Knight, R. 2004). The faster the gymnast turns and springs into her leaps, the more kinetic energy she would gain from potential energy. This therefore means that phase 2, the chasse, can be recognised as potential energy and as the gymnast experiences flight in her leap, the kinetic energy is evident as the leap recieved motion from the chasse to accelerate the gymnasts body from rest to an increased velocity.
There are two types of kinetic chain movement patterns; push-like and throw like movement patterns (Joyce, 2003). According to Blazevich (2012), the throw-like movement occurs when the joints of the kinetic chain extend sequentially. The skill of a turning split leap would be considered a throw-like movement pattern as during phase three, the thighs are accelerated prior to the lower leg resulting in a greater velocity (Blazevich, 2012). The large muscles that surround the hip assist to accelerate the thigh and it can be noted that the hip plays a role of a lever, to ensure the greatest amount of force is accumulated during the leap (Blazevich, 2012). The knee bend preparation demonstrated in phase one and two ensures the split leap is achieved sequentially in combination with the chasse and step step which contributes to the aesthetics of leap.
THE ANSWER:
Throughout the research and analysis of the three phases of the split leap, it became evident that numerous biomechanical principles are necessary in order to establish a turning split leap that corresponds with various judging factors in the 2013-2016 Code of Points. During the first phase of the chasse, the gymnasts draws her arms away from her body to create a swing which effectively increases her rotational velocity (Blazevich, 2012). During the second phase and prior to phase three, the gymnast essentially gains angular momentum. This allows them to execute their leap at a faster pace. During the step step phase, when the gymnast takes those two large steps this enables their mass to move forward and stay at a steady speed. Furthermore, this essentially contributes to the aesthetics of the leap, which is a crucial judging factor in combination with the landing and amplitude of the leap.
For
the gymnast to remain airborne during the leap phase, the gymnast will be
required to maintain kinetic energy by propelling her body in an upward
position. The split leap effectively demonstrates Newton’s
Third Law of Motion as gymnasts complete all three phases of the split leap. Gymnasts
create velocity by demonstrating leg strength, which, is displayed in the
chasse and the leap, which facilitates the leap to propel height into the air
without losing too much energy. This phase is fundamental to the height and
execution of the leap and can be applied to Newton’s First Law. It is evident
that throughout the skill of the turning split leap, a gymnast with a lighter
body mass has a greater ability to accelerate at a faster pace in comparison to
a heavier gymnast when the same amount of force is applied, as to maximise the
height in which they are leaping, and they need to overcome inertia. Therefore it
is crucial for both gymnasts and coaches to adopt an appropriate strength and flexibility
regime, one that fosters the execution of the leap by involving plyometric
activities to increase leg power which facilitates a gymnast’s ability to
increase their explosive power. Additionally, gymnasts should complete an array of flexibility
based activities such as super splits and kicks to ensure they meet the
requirements of 180+ degree split line as seen in the image below, where she additionally alters her head position to look as if she is flying. In conclusion, there are an array of
biomechanical principles that assist in executing a turning split leap within
the context of rhythmic gymnastics that can be analysed by both coaches and athletes
to ensure optimal performance.
HOW CAN
THIS INFORMATION BE USED:
There are various ways in which the
underlying biomechanical principles of a turning split leap can be utilised to
enhance performance of the gymnast. This information can therefore be applied
to improve both leap height and flight time. Such information can additionally
be applicable to other leaping contexts within rhythmic gymnastics, for example
turning hops, turning stag leaps and turning double stag leaps. Additionally
these principles can be applied to other sports that utilise similar techniques
and involve comparable skills, for example dancers and ice skaters who perform
aesthetic body difficulties and are judged on the presentation and execution of
their skills. As such, a significant emphasis was placed on both mass and
acceleration being directly proportional regarding the force to overcome
inertia, it can be noted that these principles could foster the incorporation
of strength and flexibility exercises by coaches. It is fundamental for both
the athlete and the coach to explore the biomechanical principles associated
with the skills they perform as this enables them both to gain an understanding
on how to improve body difficulties and thereby increases the likelihood of the
athlete possessing greater skills in their desired sport. This includes plyometric
exercises such as jump lunges, super splits of a heightened surface, kicks with
therabands and leaping with ankle weights. This would then enable the athletes
to show power through their legs to ensure they comply with the requirements of
the skill, that being a split leap whereby the legs achieve a 180+ degree split
line. Moreover, if gymnasts have a lighter body mass and more defined leg
strength, it allows them to conserve energy and increases the chances of the
gymnast reaching the desired height whilst minimising their energy expenditure.
Increased leg strength can also translate to a greater velocity of the athlete, as the force exerted in
the chasse, will assist to propel the leap higher into the air without losing
too much energy. To conclude, if a gymnast is able to analyse the biomechanical principles associated with the turning split leap, she is more inclined to receive less deductions from the judges. This would enable a gymnast to alter their leaps to demonstrate a leap that excels the height required, demonstrates safe landing techniques and good amplitude to ensure they receive the 0.50 value for this skill with minimal deductions.
REFERENCE LIST:
Blazevich, A.
(2012). Sports biomechanics: the basics : optimising human performance (2nd
ed.). London: A. & C. Black.
Di
Cagno, A., Baldari, C., Battaglia, C., Brasili, P., Merni, F., Piazza, M., ...
& Guidetti, L. (2008). Leaping ability and body composition in rhythmic
gymnasts for talent identification. Journal of sports medicine and physical
fitness, 48(3), 341.
International Gymnastics
Federation. (2013). Rhythmic Gymnastics Code of Points 2013-2016.
Retrieved 8 June 2014, 2014, from https://http://www.fig-gymnastics.com/site/page/view?id=472
Joyce, D.
(2003). Sports Injury Prevention and Rehabilitation. Routledge.
Knight,
R. D. (2004). Physics for scientists and
engineers (Vol. 1). Pearson.
Mkaouer,
B., Amara, S., & Tabka, Z. (2012). Split leap with and without ball
performance factors in rhythmic gymnastics. Science of Gymnastics Journal,
4(2), 75-81.
Malkogeorgos,
A., Zaggelidou, E., Zaggelidis, G., & Christos, G. (2013). Physiological
Elements Required by Dancers. Sport Science Review, 22(5-6),
343-368.
Mero, A. (1988). Force-time characteristics and
running velocity of male sprinters during the acceleration phase of sprinting. Research Quarterly for Exercise and Sport, 59(2), 94-98.
Pettrone, F. A.,
& Ricciardelli, E. (1987). Gymnastic injuries: the Virginia experience
1982-1983. The American journal of sports medicine, 15(1), 59-62.
Oxford University Press. (2014).
Physical Education - Applying biomechanics to sport. Retrieved 17th
June 2014, 2014, from
https://http://www.oup.com.au/titles/secondary/health__and__physical_education/physical_education/queensland/9780195573862/03_RUS_QSPE_3pp.pdf
Wooten, W. L., & Hodgins, J. K. (2000).
Simulating leaping, tumbling, landing and balancing humans. In Robotics and Automation, 2000. Proceedings. ICRA'00. IEEE
International Conference on (Vol. 1,
pp. 656-662). IEEE.
Zetaruk,
M. N., Fors, M. V., Zurakowski, D., Mitchell Jr, W. A., & Micheli, L. J.
(2006). Injuries and training recommendations in elite rhythmic gymnastics. Apunts:
Medicina de l'esport, 41(151), 100-106.
