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Biomedical subjects

J Dapena

Publications and source records attributed to J Dapena.

27 records · Page 2Linked to original sources
PubMed1983

Use of separate hand locations to calculate ground reaction force exerted on a vaulting pole.

A model was developed to permit calculation of the force exerted by the ground on a vaulting pole given the flexibility characteristics of the pole, the grip height of the upper hand, and the coordinates of each of the two hands relative to the base of the pole. The flexural rigidity of the pole was assumed constant throughout the length of the pole and not subject to hysteresis or dynamic loading effects. The model was based on the following rationale: knowing the initial angle of the base of the pole (beta 0) and the force vector (F1) exerted by the ground on the pole, it was possible to estimate the shape of the pole and the coordinates of the two hands following an iterative procedure. Conversely, it was possible to find a combination of beta 0 and F1 that made the pole fit two specified hand locations.

Biomechanical Phenomena↗
PubMed1982

Three-dimensional cinematography with control object of unknown shape.

A technique for reconstruction of three-dimensional (3D) motion which involves a simple filming procedure but allows the deduction of coordinates in large object volumes was developed. Internal camera parameters are calculated from measurements of the film images of two calibrated crosses while external camera parameters are calculated from the film images of points in a control object of unknown shape but at least one known length. The control object, which includes the volume in which the activity is to take place, is formed by a series of poles placed at unknown locations, each carrying two targets. From the internal and external camera parameters, and from locations of the images of point in the films of the two cameras, 3D coordinates of the point can be calculated. Root mean square errors of the three coordinates of points in a large object volume (5m x 5m x 1.5m) were 15 mm, 13 mm, 13 mm and 6 mm, and relative errors in lengths averaged 0.5%, 0.7% and 0.5%, respectively.

Mathematics↗
PubMed1980

Mechanics of translation in the fosbury-flop.

The mechanics of the translations involved in the Fosbury-flop technique of high jumping were examined in the light of appropriate experimental data, generated using a 3-dimensional cinematographical method. The curved run-up was found to cause the athletes to lean toward the center of the curve at the start of the take-off phage (TD). The center of gravity (c.g.) of all the jumpers had a negative vertical velocity at TI). The lateral deviation of the path of the c.g. during the take-off phage was small, implying small centripetal forces. The initial trajectory of the parabolic path of the c.g. after the take-off made an angle of between 40 degrees and 48 degrees with the horizontal plane. During the take-off phase the take-off leg was found to flex at least as much as previouslyreported for athletes using the straddle style. One of the subjects in the study was able to clear the bar although the peak height of the parabolic path followed by his c.g. was at the same level as the bar.

Biomechanical Phenomena↗
PubMed1980

Mechanics of rotation in the Fosbury-flop.

The mechanics of the rotations involved in the Fosbury-flop technique of high jumping were examined in the light of appropriate experimental data generated by use of a 3-dimensional cinematographical method. At the start of the take-off phage, the six subjects who used the Fosbury-flop had little angular momentum. Most of the angular momentum necessary for a proper bar clerance was not produced during the run-up, but during the take-off phase. A curved approach run appeared to favor the production of "somersaulting" angular momentum (the component of angular momentum which mainly contributes to lower the shoulders and lift the knees during the flight phase), as well as a greater vertical range of motion of the c.g. during the take-off phase. These conclusions give little support to the hypothesis that the main purpose of the curved run-up is to produce angular momentum during the run-up. On the other hand, they favor the hypothesis that the main purpose of the curved approach run is to make the athletes lean away from the bar. One athlete with particularly small "somersaluting" angular momentum made effective use of a hitch-kick motion to accomplish an effcicient bar clearance.

Biomechanical Phenomena↗