Gaze behavior of trampoline gymnasts during a back tuck somersault

Acute Effect of Video Feedback on Self-Regulation and Proprioceptive Control of Standing Back Tuck Somersault in the Absence of Vision

The purpose of this study was to assess the immediate effect of video feedback on the regulation and control of the standing back tuck somersault in the absence of vision. Two groups of male parkour athletes performed the standing back tuck somersault under both open and closed eyes conditions. The first group received video feedback, while the second group received verbal feedback. Concurrent analysis, including kinetic data from a force plate (Kistler Quattro-Jump) and kinematic data in two-dimensional by Kinovea freeware, was employed for motion and technical performance analysis. The results indicate that the loss of vision during the standing back tuck somersault affected only the take-off and ungrouping angle, as well as the vertical velocity and displacement. These effects were consistent regardless of the type of feedback provided (i.e., video feedback or verbal feedback). Furthermore, a significant Vision × Feedback interaction was observed at the level of technical performance. This suggests that the use of video feedback enabled the parkour athletes to maintain a high level of technical performance both with and without vision (i.e., 13.56 vs. 13.00 points, respectively, p > .05 and d = 2.233). However, the verbal feedback group technical performance declined significantly under the no-vision condition compared with the vision condition (13.14 vs. 10.25 points, respectively, with and without vision, p < .001 and d = 2.382). We concluded that when the movement is proprioceptively controlled (i.e., without vision), the video feedback enables the athletes to globally assess the technical deficiencies arising from the lack of vision and to correct them. These findings are discussed based on parkour athletes' ability to evaluate the kinematic parameters of the movement.

Does a visual reference help ballet dancers turn more successfully?

In dance, performing multiple rotations around the longitudinal axis is a complex task that can only be accomplished proficiently by highly skilled dancers. However, this extraordinary skill has been investigated sparsely. The few studies to date have focused on the biomechanical analysis of ballet rotations. However, none have investigated the influence of visual information on continuous rotations, such as Fouettés or à la Seconde turns. Therefore, the present study aims to examine the role of a visual reference on balance control and the dance-specific head coordination - spotting - during turning performance of highly skilled ballet dancers. To this end, 12 participants performed 12 Fouettés (females) or à la Seconde turns (males) with and without a visual reference. As dependent measures, we analysed balance control (i.e., supporting foot path length), spotting duration, head isolation, and orientation (i.e., deviation of pelvis from the front). A linear mixed model was performed to analyse the influence of the visual conditions overall and over the continued performance of 12 consecutive rotations. The results revealed that overall, path length was significantly smaller in the condition without a visual reference. Spotting duration and head isolation did not differ significantly between conditions. Moreover, dancers oriented themselves better towards the front in the condition with a visual reference. When looking closer into the progression of performance over each consecutive rotation, highly skilled ballet dancers significantly decreased the supporting foot path length, and improved orientation when turning with a visual reference. On the other hand, without a visual reference, the dancers increased the spotting duration over time. Additionally, dancers increased head isolation towards the end of the turns in both conditions. These findings suggest that a visual reference helps ballet dancers sustain performance of consecutive rotations, mainly in optimising balance control and orientation. Thus, the more rotations a ballet dancer must turn, the more relevant a visual reference becomes for sustaining successful performance.

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.

Three-Dimensional Foot Position Estimation Based on Footprint Shadow Image Processing and Deep Learning for Smart Trampoline Fitness System

In the wake of COVID-19, the digital fitness market combining health equipment and ICT technologies is experiencing unexpected high growth. A smart trampoline fitness system is a new representative home exercise equipment for muscle strengthening and rehabilitation exercises. Recognizing the motions of the user and evaluating user activity is critical for implementing its self-guided exercising system. This study aimed to estimate the three-dimensional positions of the user's foot using deep learning-based image processing algorithms for footprint shadow images acquired from the system. The proposed system comprises a jumping fitness trampoline; an upward-looking camera with a wide-angle and fish-eye lens; and an embedded board to process deep learning algorithms. Compared with our previous approach, which suffered from a geometric calibration process, a camera calibration method for highly distorted images, and algorithmic sensitivity to environmental changes such as illumination conditions, the proposed deep learning algorithm utilizes end-to-end learning without calibration. The network is configured with a modified Fast-RCNN based on ResNet-50, where the region proposal network is modified to process location regression different from box regression. To verify the effectiveness and accuracy of the proposed algorithm, a series of experiments are performed using a prototype system with a robotic manipulator to handle a foot mockup. The three root mean square errors corresponding to X, Y, and Z directions were revealed to be 8.32, 15.14, and 4.05 mm, respectively. Thus, the system can be utilized for motion recognition and performance evaluation of jumping exercises.

A Measurement of 'Walking-the-Wall' Dynamics: An Observational Study Using Accelerometry and Sensors to Quantify Risk Associated with Vertical Wall Impact Attenuation in Trampoline Parks

This study illustrates the application of a tri-axial accelerometer and gyroscope sensor device on a trampolinist performing the walking-the-wall manoeuvre on a high-performance trampoline to determine the performer dynamic conditions. This research found that rigid vertical walls would allow the trampolinist to obtain greater control and retain spatial awareness at greater levels than what is achievable on non-rigid vertical walls. With a non-rigid padded wall, the reaction force from the wall can be considered a variable force that is not constrained, and would not always provide the feedback that the trampolinist needs to maintain the balance with each climb up the wall and fall from height. This research postulates that unattenuated vertical walls are safer than attenuated vertical walls for walking-the-wall manoeuvres within trampoline park facilities. This is because non-rigid walls would provide higher g-force reaction feedback from the wall, which would reduce the trampolinist's control and stability. This was verified by measuring g-force on a horizontal rigid surface versus a non-rigid surface, where the g-force feedback was 27% higher for the non-rigid surface. Control and stability are both critical while performing the complex walking-the-wall manoeuvre. The trampolinist experienced a very high peak g-force, with a maximum g-force of approximately 11.5 g at the bottom of the jump cycle. It was concluded that applying impact attenuation padding to vertical walls used for walking-the-wall and similar activities would increase the likelihood of injury; therefore, padding of these vertical surfaces is not recommended.

How Task Constraints Influence the Gaze and Motor Behaviours of Elite-Level Gymnasts

Perception-action coupling is fundamental to effective motor behaviour in complex sports such as gymnastics. We examined the gaze and motor behaviours of 10 international level gymnasts when performing two skills on the mini-trampoline that matched the performance demands of elite competition. The presence and absence of a vaulting table in each skill served as a task-constraint factor, while we compared super-elite and elite groups. We measured visual search behaviours and kinematic variables during the approach run phase. The presence of a vaulting table influenced gaze behaviour only in the elite gymnasts, who showed significant differences in the time spent fixating on the mini-trampoline, when compared to super-elite gymnasts. Moreover, different approach run characteristics were apparent across the two different gymnastic tasks, irrespective of the level of expertise, and take-off velocity was influenced by the skill being executed across all gymnasts. Task constraints and complexity influence gaze behaviours differed across varying levels of expertise in gymnastics, even within a sample of international level athletes. It appears that the time spent fixating their gazes on the right areas of interest during the approach run is crucial to higher-level performance and therefore higher scores in competition, particularly on the mini-trampoline with vaulting table.

Long term measures of vestibulo-ocular reflex function in high level male gymnasts and its possible role during context specific rotational tasks

In a prior publication, we described a previously unknown eye movement phenomenon during the execution of actively performed multiaxial rotations in high level gymnasts. This phenomenon was consistently observed during the phase of fast free flight rotations and was marked by a prolonged and complete suppression of nystagmus and gaze stabilizing “environment referenced eye movements” (EREM; such as the vestibulo-ocular reflex, optokinetic reflex, smooth pursuit and others). Instead, these eye movements were coupled with intersegmental body movements. We have therefore called it “spinal motor-coupled eye movements” (SCEM) and have interpreted the phenomenon to likely be caused by anti-compensatory functions of more proprioceptive mediated reflexes and perhaps other mechanisms (e.g., top-down regulation as part of a motor plan) to effectively cope with a new-orientation in space, undisturbed by EREM functions. In the phase before landing, the phenomenon was replaced again by the known gaze-stabilizing EREM functions. The present study specifically evaluated long-term measures of vestibulo-ocular reflex functions (VOR) in high level gymnasts and controls during both passively driven monoaxial rotations and context-specific multiaxial somersault simulations in a vestibular lab. This approach provided further insights into the possible roles of adaptive or mental influences concerning the VOR function and how they are associated with the described phenomenon of SCEM. Results showed high inter-individual variability of VOR function in both gymnasts and controls, but no systematic adaptation of the VOR in gymnasts, neither compared to controls nor over a period of three years. This might generally support the hypothesis that the phenomenon of SCEM might indeed be driven more by proprioceptively mediated and situationally dominant eye movement functions than by adaptative processes of the VOR.

Gaze, head and eye movements during somersaults with full twists

Somersaults with or without twists are the most important elements in sports such as gymnastics or trampolining. Moreover, to perform elements with the highest possible difficulty gymnasts should show good form and execution during the flight phase. In order to ensure perfect body control and a safe landing, gaze behavior has been proven to be crucial for athletes to orientate in the air. As eye movement and head movement are closely coordinated, both must be examined while investigating gaze behavior. The aim of the current study is to analyze athletes' head motion and gaze behavior during somersaults with full twists. 15 skilled trampoline gymnasts performed back straight somersaults with a full twist (back full) on the trampoline. Eye movement and head movement were recorded using a portable eye-tracking device and a motion capture suit. The results indicate that gymnasts use the trampoline bed as a fixation point for orientation and control the back full, whereas the fixation onsets for athletes of a better performance class occur significantly later. A strong coordination between gymnasts' eye movement and head movement could be determined: stabilizing the gaze during the fixation period, the eyes move in combination with the head against the twisted somersault direction to counteract the whole body rotation. Although no significant differences could be found between the performance classes with regard to the maximum axial head rotations and maximum head extensions, there seems to be a trend that less skilled gymnasts need orientation as early as possible resulting in greater head rotation angles but a poorer execution.