Twisting techniques used by competitive divers

Angular velocity around the longitudinal axis in combination with head movements of springboard divers during twisted somersaults

The ability of springboard divers to perform and control difficult elements with multiple twisted somersaults before entering the water is of great interest for coaches and researchers. In order to produce twists within somersaults, divers use both 'contact' and 'aerial' techniques. After completing body axes rotations, head movements seem to be important, as they enable visual information in the air. The current study aims at investigating angular velocities around the longitudinal axis in combination with head movements of 13 springboard divers during twisted somersaults. Divers performed forward and backward somersaults with different numbers of half twists. The results revealed maximum longitudinal axis angular velocities between 500°/s and 1300°/s. Moreover, results showed that the use of contact technique was greater in twisted somersaults with backward approaches, and thus higher angular velocities could be achieved. While finishing the twists, head movements in the opposite direction to the longitudinal axis rotation occurred, which allow divers to orient themselves. Twist speeds influenced athletes' head movements to have greater angles and greater rotational velocities. Therefore, it is concluded that fast head movements are necessary in difficult twisted dives to allow orientation in the short phase between finishing the twist and entering the water surface.

DYNAMIC MODELLING FOR THE SECOND FLIGHT PHASE OF THE YURCHENKO LAYOUT VAULT BASED ON MSC. ADAMS

Gymnasts attempt to increase the angles of rotation about transversal and longitudinal axes during the post-flight of vaulting, and these angles are related to different mechanical properties. The present study uses a 3D angle-driven computer simulation model of a gymnast who performs Yurchenko layout vault using ADAMS software. Simulation initial conditions are horizontal and vertical velocities of gymnast’s pelvis center and angular velocities about the transversal and longitudinal axes which can be easily measured. The initial linear and angular velocity conditions of the simulation model are each changed in certain increments from measurement data collected from an elite woman gymnast. Increasing initial horizontal velocity results in an increased horizontal flight distance, but has no connection with the duration of flight and angle of twists. The overall angle of twists is concerned with initial vertical velocity and angular velocities about the transversal and longitudinal axes. Also, increasing initial vertical velocity and angular velocity about transverse axis leads to increase in touchdown angle between ground’s horizontal axis and gymnast’s longitudinal axis.  

The limits of aerial and contact techniques for producing twist in reverse 1½ somersault dives

An angle-driven computer simulation model of aerial movement was used to determine the maximum amount of twist that can be produced in a reverse 1½ somersault dive from a three-metre springboard using various aerial and contact twisting techniques. The segmental inertia parameters of an elite springboard diver were used in the simulations and lower bounds were placed on the durations of arm and hip angle changes based on recorded performances of twisting somersaults. A limiting dive was identified as that producing the largest possible odd number of half twists. Simulations of the limiting dives were found using simulated annealing optimisation to produce the required amounts of somersault, tilt and twist after a flight time of 1.5 s. Additional optimisations were then run to seek solutions with the arms less adducted during the twisting phase. It was found that the upper limits ranged from 3½ to 5½ twists with arm abduction ranges lying between 8° and 23°. Similar results were obtained when the inertia parameters of two other springboard divers were used. It may be concluded that a reverse 1½ somersault dive using aerial asymmetrical arm and hip movements to produce 5½ twists is a realistic possibility. To accomplish this limiting dive the diver needs to be able to coordinate the timing of configurational changes with the progress of the twist with a precision of 10 ms or better.

The limits of aerial techniques for producing twist in forward 1½ somersault dives

An angle-driven computer simulation model of aerial movement was used to determine the maximum amount of twist that can be produced in a forward 1½ somersault dive from a three-metre springboard using various aerial twisting techniques. The segmental inertia parameters of an elite springboard diver were used in the simulations and lower bounds were placed on the durations of arm and hip angle changes based on recorded performances of twisting somersaults. A limiting dive was identified as that producing the largest possible whole number of twists. Simulations of the limiting dives were found using simulated annealing optimisation to produce the required amounts of somersault, tilt and twist after a flight time of 1.5 s. Additional optimisations were then run to seek solutions with the arms less adducted during the twisting phase. It was found that the upper limits ranged from two to five twists with arm abduction ranges lying between 6° and 17°. Similar results were obtained when the inertia parameters of two other springboard divers were used.

Hip extension during the come-out of multiple forward and inward pike somersaulting dives is controlled by eccentric contraction of the hip flexors

A modelling approach was used in the present study to investigate the role of the hip muscles during the come-out of forward and inward multiple somersaulting dives in a pike position. A planar two-segment model was used to simulate the somersault and come-out of three commonly performed dives from a 3-m springboard: forward two-and-one-half somersault pike dive (105B), forward three-and-one-half somersault pike dive (107B), and inward two-and-one-half somersault pike dive (405B). Three simulations were run for each dive: (1) hip angle was constrained to be constant, (2) hip torque was removed after 0.1 s, and (3) hip angle was constrained to a typical come-out time history used by elite divers. Simulation results indicated that hip flexion torque was required both to maintain a rigid pike position during somersault (range = 205.5-282.3 Nm) and to control the hip extension movement during the come-out (peak torque range = 355.8-548.1 Nm) in forward and inward multiple somersaulting dives. Coaches and divers should be aware that dry-land exercise drills producing hip extension movement by concentric actions of the hip extensor muscles do not replicate the neuromuscular control during the come-out of fast rotating dives.

Optimal Knee Extension Timing in Springboard and Platform Dives from the Reverse Group

Optimized computer simulation, using a mathematical model of a diver, was employed to gain insight into the primary mechanical factors responsible for producing height and rotation in dives from the reverse group. The performance variable optimized was the total angular displacement of the diver as measured from last contact to the point where the diver's mass center passed the level of the springboard or platform. The times of onset, and lengths of activation for the joint torque actuators, were used as the control variables for the optimization process. The results of the platform simulation indicated that the magnitude of the hip torque was approximately twice that generated by the knee joint during the early extension phase of the takeoff. Most of the knee extension for the simulation model coincided with the period of reduced hip torque during the later phase of takeoff, suggesting that the knee torque served mainly to stabilize the lower limbs so that the force from the powerful hip extension could be delivered through to the platform. Maintaining a forward tilt of the lower legs (~50° from the horizontal) during hip and knee extension appeared to be paramount for successful reverse somersaults. Although the movement pattern exhibited by the springboard model was limited by the torque activation strategy employed, the results provided insight into the timing of knee extension. Peak knee extension torque was generated just prior to maximum springboard depression, allowing the diver's muscular efforts to be exerted against a stiffer board. It was also apparent that the diver must maintain an anatomically strong knee position (~140°) at maximum depression to resist the large upward force being exerted by the springboard against the diver's feet. The optimization process suggested that, as the number of reverse somersaults increases, both the angle of the lower legs with respect to the springboard and the angle of knee extension at completion of takeoff should decrease.

The biomechanics of the human in flight

I used a computer simulation model of aerial movement to investigate the techniques for producing and controlling rotations of the human body during free flight. I found that the rotational motion can change from a twisting somersault to a nontwisting somersault by flexing at the hips at a suitable time. Twist may be produced in the aerial phase by means of asymmetrical movements of arms or hips, which result in a tilting of the longitudinal axis away from the plane perpendicular to the angular momentum vector. Asymmetrical movements may also remove the tilt and stop the twist. Elite performances of twisting somersaults are characterized by a large contribution from aerial twisting techniques. A progression of movements is presented for learning a double somersault with one and a half twists in the second somersault.