A two-segment simulation model of long horse vaulting

Optimal technique for maximal forward rotating vaults in men's gymnastics

In vaulting a gymnast must generate sufficient linear and angular momentum during the approach and table contact to complete the rotational requirements in the post-flight phase. This study investigated the optimization of table touchdown conditions and table contact technique for the maximization of rotation potential for forwards rotating vaults. A planar seven-segment torque-driven computer simulation model of the contact phase in vaulting was evaluated by varying joint torque activation time histories to match three performances of a handspring double somersault vault by an elite gymnast. The closest matching simulation was used as a starting point to maximize post-flight rotation potential (the product of angular momentum and flight time) for a forwards rotating vault. It was found that the maximized rotation potential was sufficient to produce a handspring double piked somersault vault. The corresponding optimal touchdown configuration exhibited hip flexion in contrast to the hyperextended configuration required for maximal height. Increasing touchdown velocity and angular momentum lead to additional post-flight rotation potential. By increasing the horizontal velocity at table touchdown, within limits obtained from recorded performances, the handspring double somersault tucked with one and a half twists, and the handspring triple somersault tucked became theoretically possible.

The influence of touchdown conditions and contact phase technique on post-flight height in the straight handspring somersault vault

In vaulting the gymnast must generate sufficient linear and angular momentum during the approach and table contact in order to complete the rotational requirements in the post-flight phase. This study investigated the effects of touchdown conditions and contact technique on peak post-flight height of a straight handspring somersault vault. A planar seven-segment torque-driven computer simulation model of the contact phase in vaulting was evaluated by varying joint torque activation time histories to match three performances of a straight handspring somersault vault by an elite gymnast. The closest matching simulation was used as a starting point to optimise peak post-flight height of the mass centre for a straight handspring somersault. It was found that optimising either the touchdown conditions or the contact technique increased post-flight height by 0.1m whereas optimising both together increased post-flight height by 0.4m above that of a simulation matching the recorded performance. Thus touchdown technique and contact technique make similar contributions to post-flight height in the straight handspring somersault vault. Increasing touchdown velocity and angular momentum lead to additional post-flight height although there was a critical value of vertical touchdown velocity beyond which post-flight height decreased.

Modifying landing mat material properties may decrease peak contact forces but increase forefoot forces in gymnastics landings

This study investigated how changes in the material properties of a landing mat could minimise ground reaction forces (GRF) and internal loading on a gymnast during landing. A multi-layer model of a gymnastics competition landing mat and a subject-specific seven-link wobbling mass model of a gymnast were developed to address this aim. Landing mat properties (stiffness and damping) were optimised using a Simplex algorithm to minimise GRF and internal loading. The optimisation of the landing mat parameters was characterised by minimal changes to the mat's stiffness (<0.5%) but increased damping (272%) compared to the competition landing mat. Changes to the landing mat resulted in reduced peak vertical and horizontal GRF and reduced bone bending moments in the shank and thigh compared to a matching simulation. Peak bone bending moments within the thigh and shank were reduced by 6% from 321.5 Nm to 302.5Nm and GRF by 12% from 8626 N to 7552 N when compared to a matching simulation. The reduction in these forces may help to reduce the risk of bone fracture injury associated with a single landing and reduce the risk of a chronic injury such as a stress fracture.

Reducing ground reaction forces in gymnastics' landings may increase internal loading

The aim of this study was to use a subject-specific seven-link wobbling mass model of a gymnast, and a multi-layer model of a landing mat, to determine landing strategies that minimise ground reaction forces (GRF) and internal forces. Subject-specific strength parameters were determined that defined the maximum voluntary torque/angle/angular velocity relationship at each joint. These relationships were used to produce subject-specific 'lumped' linear muscle models for each joint. Muscle activation histories were optimised using a Simplex algorithm to minimise GRF or bone bending moments for forward and backward rotating vault landings. Optimising the landing strategy to minimise each of the GRF reduced the peak vertical and horizontal GRF by 9% for the backward rotating vault and by 8% and 48% for the forward rotating vault, compared to a matching simulation. However, most internal loading measures (bone bending moments, joint reaction forces and muscle forces) increased compared to the matching simulation. Optimising the landing strategy to minimise the peak bone bending moments resulted in reduced internal loading measures, and in most cases reduced GRF. Bone bending moments were reduced by 27% during the forward rotating vault and by 2% during the backward rotating vault landings when compared to the matching simulations. It is possible for a gymnast to modify their landing strategy in order to minimise internal forces and lower GRF. However, using a reduction in GRF, due to a change in landing strategy, as a basis for a reduction in injury potential in vaulting movements may not be appropriate since internal loading can increase.

The continuous measurement of the springboard reaction force in gymnastic vaulting

A new method was established for the continuous measurement of force applied from a springboard to a gymnast in vaulting (board reaction force). Male gymnasts performed a handspring vault using a springboard mounted on force platforms. A high-speed video camera sampled the springboard motion at 500 Hz. The springboard was initially partitioned into 29 segments. The force due to the accelerative motion of the springboard was determined by summing the forces of the individual segments. The board reaction force acting on the gymnast was calculated by subtracting the force due to the accelerative motion of the springboard and weight from the force recorded by the force platform. The new method succeeded in illustrating transient changes of the board reaction force. The horizontal and vertical components of the peak values of the board reaction force were three and two times greater respectively than the average values. A series of tests was conducted to determine whether the number of segments of the springboard model could be reduced without affecting accuracy. A model consisting of only four segments produced almost the same accuracy as the 29-segment model. The simplified model is recommended as a more efficient method to measure board reaction force.

Factors influencing performance in the Hecht vault and implications for modelling

This paper investigated the factors that influence Hecht vault performance and assessed the level of model complexity required to give an adequate representation of vaulting. A five-segment planar simulation model with a visco-elastic shoulder joint and a torque generator at the shoulder joint was used to simulate the contact phase in vaulting. The model was customized to an elite gymnast by determining subject-specific segmental inertia and joint torque parameters. The simulation model was matched to a performance of the Hecht vault by varying the visco-elastic characteristics of the shoulders and the arm-horse interface and the activation time history of the shoulder torque generator until the best match was found. Perturbing the matching simulation demonstrated that appropriate initial kinematics are necessary for a successful performance. Fixing the hip and knee angles at their initial values had a small effect with 3 degrees less rotation. Applying shoulder torque during the contact phase also had a small effect with only a 7 degrees range in landing angles. Excluding the hand segment from the model was found to have a moderate effect with 15 degrees less rotation and the time of contact reduced by 38%. Removing shoulder elasticity resulted in 50 degrees less rotation. The use of a five-segment simulation model confirmed that the use of shoulder torque plays a minor role in vaulting performance and that having appropriate initial kinematics at touchdown is essential. However, factors such as shoulder elasticity and the hands which have previously been ignored also have a substantial influence on performance.

A Predicted Optimal Performance of the Yurchenko Layout Vault in Women’s Artistic Gymnastics

The Yurchenko layout vault is the base vault from which more advanced forms of the Yurchenko family of vaults have evolved. The purpose of the study was to predict an individual’s optimal Yurchenko layout vault by modifying selected critical mechanical variables. The gymnast’s current performance characteristics were determined using the Peak-Motus video analysis system. Body segment parameters were determined using the elliptical zone mathematical modeling technique of Jensen (1978). A 5-segment computer simulation model was personalized for the gymnast comprising the hands, upper limbs, upper trunk, lower trunk, and lower limbs. Symmetry was assumed, as the motion was planar in nature. An objective function was identified which translated the subjective points-evaluation scheme of the Federation of International Gymnastics (FIG) Code of Points to an analytic expression that was mathematically tractable. The objective function was composed of performance variables that, if maximized, would result in minimal points being deducted and bonus points being allocated. A combined optimal control and optimal parameter selection approach was applied to the model to determine an optimum technique. The predicted optimal vault displayed greater postflight amplitude and angular momentum when compared with the gymnast’s best trial performance. Increased angular velocity, and consequently greater angular momentum at impact and greater shoulder flexion angle at impact with the horse, were related with this optimum technique. The impact phase therefore serves to increase the angular momentum during horse contact. Since the optimized parameters at impact with the horse were within the accepted physical capacity limits observed for the individual, the predicted vault is viable.

Gymnastics

The purpose of the study was to quantify the muscle torques required in the performance of an optimised Yurchenko layout vault based on a five-segment rigid link model and using input data from an elite female gymnast. At impact, the wrist torque trajectory indicated an extension-flexion action while the shoulder was characterised by extension. The approximate 100 Nm (wrist flexor) and 125 Nm (shoulder extensor) respective peak torque magnitudes indicated that the impact action is not passive in nature. The contribution of joint torques to the adjoining segments was apportioned to the relative components namely; centripetal, gravity and net joint torque components. Despite the presence of both large wrist and shoulder joint torques, the net turning effect on the upper limb and hand segments about their centre of mass (CM) was small. The principal role of the upper limb joint torques was therefore to effect the appropriate joint motions and to support the weight of the gymnast. The performance of the optimum vault was primarily the result of the interplay between the centripetal and the net joint torque components at the wrist, hip and shoulder joints. This has implications to the performer in that successful execution of the vault is principally concerned with the ability to create a high angular momentum for horse impact and to then apply an appropriate level of joint torques that will make optimal use of the initial kinetic condition.