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This paper illustrates how movement analysis could be performed using publicly available videos and freeware to generate meaningful information for sports practitioners and researchers. Using acrobatic sports as a case, we performed kinematic analysis on 206 YouTube videos of high-level competitions in diving and gymnastics using Kinovea. Results revealed good to excellent inter-rater reliability of variables analyzed. Significant differences in angular speed ( p < 0.001, η ² p = 0.213) and flight time ( p < 0.001, η ² p = 0.928) were found among eight different events. Divers had longer flight time ( p < 0.001, η ² p = 0.569) and were somersaulting faster than gymnasts ( p = 0.021, η ² p = 0.026). Angular speed was higher in tuck than pike somersaults ( p < 0.001, η ² p = 0.214). Shorter the flight time was significantly correlated with faster angular speed ( rho = −0.533, p < 0.001) in gymnastics events. Coaches and scientists can consider applying the proposed method to monitor the athletes’ performance and to identify errors (e.g., insufficient flight time). The kinematics measurements can also be used to guide the transition plan across different apparatus and categories (e.g., 10-m platform to 3-m springboard). In conclusion, the present study highlights the potential of using readily available information and open-source freeware to generate scientific data for sports applications. Such data analysis approach can accommodate a wide range of video qualities, is easily accessible, and not restricted by situations such as social distancing, quarantine, lockdown or other restrictive measures.
Forward and reverse springboard somersaulting dives use similar approaches with a hurdle step prior to the final board contact phase during which forward rotation is produced in forward takeoffs and backward rotation in reverse takeoffs. This study compared forward and reverse takeoffs for joint strength, activation complexity, technique kinematics, and rotation potential. A planar 8-segment torque-driven computer simulation model of springboard diving takeoff was used to determine isometric joint strength by matching performances of a forward 2½ somersault dive and a reverse 1½ somersault dive. Activation complexity for the reverse takeoff was increased to achieve a similar closeness of match as for the forward takeoff. Takeoff technique was optimised to maximise rotation potential of forward and reverse somersaulting dives. Kinematics at touchdown, lowest point and takeoff were compared for the optimised forward and reverse takeoff simulations. It was found that the optimised reverse somersaulting dive exhibited greater isometric strength for ankle plantarflexion and shoulder flexion, greater joint torque activation complexity for ankle plantarflexion and for knee flexion. There was also less forward motion during board depression, more hip extension and knee flexion during the later stages of board recoil, less capacity for rotation potential, and greater vertical velocity at takeoff.
Purpose: Trampoline parks are becoming popular in many countries, providing recreational facilities for children and adults. This study investigated the effects of trampoline training on knee muscles strength and balance in young adults. Methods: Twenty-six participants (14 males, 12 females) were randomized into trampoline training (TT) and resistance training (RT) groups to undergo a 6-week supervised intervention program (2 × 30 min per week). TT group performed basic trampoline exercises while the RT group performed resistance training targeting lower extremities muscles. Peak knee extension and flexion torque, postural sway characteristics, and Y balance test (YBT) performance were evaluated before and after the intervention. A mixed model analysis of variance (group × time) was applied. Results: After training there were significant improvements in knee extension torque (mean differencepost-pre [95% CI], TT: 0.27 [0.00, 0.54] N∙m/kg, RT: 0.31 [0.09,0.54] N∙m/kg, p = .001), knee flexion torque (TT: 0.25 [0.17,0.33] N∙m/kg, RT: 0.21 [0.08,0.34] N∙m/kg, p < .001), and dynamic balance (YBT composite scores, mean differencepost-pre [95% CI], TT: 4.9 [-0.3, 10.2]%, RT: 5.2 [2.4,8.0]%, p = .001). No difference between groups was found. Conclusion: Trampoline training can be as effective as resistance training for improving knee muscles strength and dynamic balance in young men and women.
Performance in the flight phase of springboard diving is limited by the amounts of linear and angular momentum generated during the takeoff phase. A planar 8-segment torque-driven simulation model combined with a springboard model was used to investigate optimum takeoff technique for maximising rotation in forward dives from the one metre springboard. Optimisations were run by varying the torque activation parameters to maximise forward rotation potential (angular momentum × flight time) while allowing for movement constraints, anatomical constraints, and execution variability. With a constraint to ensure realistic board clearance and anatomical constraints to prevent joint hyperextension, the optimised simulation produced 24% more rotation potential than a simulation matching a 2½ somersault piked dive. When 2 ms perturbations to the torque onset timings were included for the ankle, knee and hip torques within the optimisation process, the model was only able to produce 87% of the rotation potential achieved in the matching simulation. This implies that a pre-planned technique cannot produce a sufficiently good takeoff and that adjustments must be made during takeoff. When the initial onset timings of the torque generators were unperturbed and 10 ms perturbations were introduced into the torque onset timings in the board recoil phase, the optimisation produced 8% more rotation potential than the matching simulation. The optimised simulation had more hip flexion and less shoulder extension at takeoff than the matching simulation. This study illustrates the difficulty of including movement variability within performance optimisation when the movement duration is sufficiently long to allow feedback corrections.
This study examined if the centre of mass (CM) position of static balances in gymnastics textbooks were correctly illustrated. Out of 108 gymnastics textbooks screened for figures that illustrated CM positions in static balance postures, 33 images from four textbooks were retrieved for analysis. In each image, the actual CM was calculated using the segmentation method based on measured segmental lengths and body segmental inertial parameters. The offset distance between the illustrated and calculated CM was quantified to indicate the accuracy of the book illustration. To facilitate comparisons among images of different sizes, the offset distance was normalised to the leg length of the body as a percentage error. An error of less than 10% was considered small, 10 to 20% moderate, and greater than 20% large. Results showed that the average error was 12.8% (ranging from 0% to 39.0%). The error was small in 17 (52%) images, moderate in 11 (33%) images, and large in 5 (15%) images. Calculated CM were often (26 out of 33, or 78.8%) superior to the illustrated positions. One common misconception was that the illustrated CM tended to lie within the body in postures where the calculated CM was outside the body (e.g. half headstand, seated pike stretch). These incorrect CM illustrations and concepts in gymnastics textbooks may misguide the pedagogical practices for physical education teachers and coaches. To better reflect the true CM of gymnastics postures, future reference materials should incorporate anatomical and biomechanical expertise in the preparation of figures.
The traditional approach to evaluate gymnastics by subjective rating requires an experienced eye, posing challenges to teachers and coaches who may not have the necessarypersonal experience. This study presented a simple and objective method for analyzing a dynamic, asymmetrical and multi-planar gymnastics skill (cartwheel). Two studies were conducted to analyze videos of cartwheel performances by quantifying ankle, knee, hip, shoulder, and torso angles using an open source freeware. Study 1 tested whether the method could differentiate between highly trained gymnasts and novices, and assessed the reliability of the method. Study 2 evaluated whether the method could track the progression of novice learners: Performances of an experimental and a control groups were compared before and after a 20-minute intervention. Results showed excellent intra- and inter-rater reliability (intra-class correlation > 0.90, standard error of measurement < 5°). Highly trained gymnasts displayed better forms than novices at the ankle, knee, shoulder and torso (all p < 0.05).After brief practice, novel learners showed improvements at the knees (p = 0.007) and ankles (group × time p = 0.05) when performing a cartwheel. In conclusion, the proposed video analysis method demonstrated good potential for assessing the cartwheel in a simple and objective way.
This study used optimisation procedures in conjunction with an 8-segment torque-driven computer simulation model of the takeoff phase in springboard diving to determine appropriate subject-specific strength parameters for use in the simulation of forward dives. Kinematic data were obtained using high-speed video recordings of performances of a forward dive pike (101B) and a forward 2 1/2 somersault pike dive (105B) by an elite diver. Nine parameters for each torque generator were taken from dynamometer measurements on an elite gymnast. The isometric torque parameter for each torque generator was then varied together with torque activation timings until the root mean squared (RMS) percentage difference between simulation and performance in terms of joint angles, orientation, linear momentum, angular momentum, and duration of springboard contact was minimised for each of the two dives. The two sets of isometric torque parameters were combined into a single set by choosing the larger value from the two sets for each parameter. Simulations using the combined set of isometric torque parameters matched the two performances closely with RMS percentage differences of 2.6% for 101B and 3.7% for 105B. Maximising the height reached by the mass centre during the flight phase for 101B using the combined set of isometric parameters and by varying torque generator activation timings during takeoff resulted in a credible height increase of 38 mm compared to the matching simulation. It is concluded that the procedure is able to determine appropriate effective strength levels suitable for use in the optimisation of simulated forward rotating dive performances.
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.