To determine strategies for initiating rotation in armstand back and reverse triple somersaults tuck dives from the 10-m platform, videotaped records of 17 elite male divers performing in competitions between 1995 and 1999 were analyzed. Linear and angular momenta at last contact were similar for both dives. Although the lower extremity actions were comparable, they occurred significantly earlier (p < .05) in reverse triple takeoffs, allowing divers to enter the tuck more quickly. As divers lean, the moment arm of the vertical platform reaction force increases with respect to the CG. The vertical platform reaction force moment promotes back and opposes reverse somersaulting angular momentum. Meanwhile, the horizontal platform reaction force moment promotes reverse and opposes back somersaulting angular momentum. Consequently, divers performing reverse triples maintained a more vertical trunk position during the early part of the takeoff, while those executing back triples leaned further before initiating lower and upper extremity actions to exert force against the platform. Since the strategy for reverse rotation may result in the head passing close to the platform and there is very little to gain in degree of difficulty, it is recommended that competitors execute back rather than reverse somersaulting armstand dives.
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Karen Murtaugh and Doris I. Miller
Toshiaki Soga, Taspol Keerasomboon, Kei Akiyama, and Norikazu Hirose
has a BPA of approximately 50°, 14 it would be difficult to achieve a quasi-isometric movement of the hamstring at a knee flexion angle of <30°, where hamstring injuries usually occur. In this regard, the application of the NHE on a sloped platform has been recently devised as a method to generate an
Luca Correale, Vittoria Carnevale Pellino, Luca Marin, Massimiliano Febbi, and Matteo Vandoni
systems are placed on the shoe less invasively than other systems, are affordable, and permit naturally reproduction of walking. Despite the use of such accurate, portable, less expensive, and comfortable instruments in clinical analysis, a new generation of baropodometric platform could add load
K. Andrew R. Richards, Chad M. Killian, Christopher J. Kinder, Kaizeen Badshah, and Casey Cushing
exist, as social media can be used to promote custodial views and practices ( Tinning, 2004 ), and quality control is limited ( Erwin, 2016 ), the potential of platforms such as Twitter for teachers’ continuing professional development (CPD) and student learning in physical education (PE) is also
Maury L. Hull and Hiroko K. Gonzalez
Using a five-bar linkage model of the leg/bicycle system in conjunction with experimental kinematic and pedal force data, the inverse dynamics problem is solved to yield the intersegmental moments. Among the input data that affect the problem solution is the height of the pedal platform. This variable is isolated and its effects on the total joint moments are studied as it assumes values over a ±4-cm range. Platform height variation affects the total joint moment peak values by up to 13%. Relying on a cost function derived from the hip and knee moments, it is found that the platform height that minimizes the cost function is +2 cm. The sensitivity of the cost function to the platform height variable is low; over the variable range the cost function increases 2% above the minimum. These results hold for a pedaling rate of 90 rpm. As pedaling rate is varied above and below 90 rpm, the sensitivity of the cost function increases. The platform heights that minimize the cost function are the lower and upper limits for 60 and 120 rpm, respectively. Thus the platform height variable interacts with pedaling rate, requiring a compromise in platform height adjustment. The compromise height depends on the individual’s preferred pedaling rate range.
Matthew Brodie, Alan Walmsley, and Wyatt Page
A fusion integration algorithm is used to estimate the one-dimensional center of mass (COM) trajectory from force platform data. The resulting COM trajectory combines the best attributes of several established algorithms used to estimate the COM trajectory, and it appears to have the advantage of being robust, accurate, continuous in its higher derivatives, and fast to obtain. In current research projects, variations of the fusion integration algorithm have been adapted by the authors for the analysis of postural balance and the sensing of limb orientations with inertial measurement units.
Sonia Julià-Sánchez, Jesús Álvarez-Herms, Hannes Gatterer, Martin Burtscher, Teresa Pagès, and Ginés Viscor
Contradictory results are still reported on the influence of dental occlusion on the balance control. We attempted to determine whether there are differences in balance between opposed dental occlusion (Intercuspal position (ICP)/“Cotton rolls” mandibular position [CR]) for two extreme levels of stability (stable/unstable). Twenty-five subjects were monitored under both dental occlusion and level of stability conditions using an unstable platform Balance System SD. The resulting stability index suggests that body balance is significantly better when dental occlusion is set in CR (p < .001) in unstable but not in stable conditions. Occlusal traits significantly influencing postural control were Angle Class (p < .001), crowding (p = .006), midline deviation (p < .001), crossbite (p < .001), anterior open bite (p = .05), and overjet (p = .01). It could be concluded that the sensory information linked to the dental occlusion for the balance control comes strongly into effect in unstable conditions.
Kennon Francis, Scott Hopkins, and Ronald Feinstein
This study was conducted to determine if VO2, of stepping in children is affected by altering the step platform height based on leg length. The effect of leg length on VO2 and heart rate (HR) during stepping was examined in 19 children, ages 8–17, who stepped onto 5 different bench heights that corresponded to hip angles of 65°, 73°, 82°, 90°, or 98°. VO2 and HR response to a work load of 8 m · min−1 assumed a U-shaped curve with 82° assuming the lowest point of the curve. Efficiency of stepping was significantly higher at 82° when compared to the other hip angles. It was concluded that VO2 and HR in children is influenced by leg length during stepping, and there is an optimum step height for stepping that can be determined from the ratio of leg length to stature.
Ewa Szczerbik, Malgorzata Kalinowska, and Malgorzata Syczewska
platforms was investigated ( Kiss, 2011 ; Schmid et al., 2011 ). Another kind of instability can be reached using the balance mode of Biodex Balance System (BBS). While the subject is standing on the platform, the ball hinge stiffness changes to create conditions testing 2D balance control ( Biodex Medical
Joseph Hamill, Mark D. Ricard, and Dennis M. Golden
A study was undertaken to investigate the changes in total body angular momentum about a transverse axis through the center of mass that occurred as the rotational requirement in the four categories of nontwisting platform dives was increased. Three skilled subjects were filmed performing dives in the pike position, with increases in rotation in each of the four categories. Angular momentum was calculated from the initiation of the dive until the diver reached the peak of his trajectory after takeoff. In all categories of dives, the constant, flight phase total body angular momentum increased as a function of rotational requirement. Increases in the angular momentum at takeoff due to increases in the rotational requirement ranged from a factor of 3.61 times in the forward category of dives to 1.52 times in the inward category. It was found that the remote contribution of angular momentum contributed from 81 to 89% of the total body angular momentum. The trunk accounted for 80 to 90% of the local contribution. In all categories of dives except the forward 1/2 pike somersault, the remote percent contribution of the arms was the largest of all segments, ranging from 38 to 74% of the total angular momentum.
