Sex and standard levels differences in anthropometric and physical fitness characteristics in youth handball players

This study analyzed the relationships between throwing velocity and anthropometric and fitness parameters in young female and male handball players of different ages. A total of 159 players participated: females under-16 (FU16, n=44) and under-14 (FU14, n=21); males under-16 (MU16, n=54) and under-14 (MU14, n=40). The following was measured: body height, arm span, body mass, total finger span, hand length, maximal isometric handgrip force, handball throwing velocity, 20-m sprints, countermovement jump, and change of direction. Group MU16 showed significantly (p<.05) greater values of anthropometric characteristics than groups FU16 and MU14. No significant differences were observed between FU14 and MU14 in any of the anthropometric variables analyzed, or between the two female groups (FU16 vs. FU14). MU16 showed significantly (p<.05) better performance in all fitness parameters than FU16 and MU14. No significant differences were observed between FU14 and MU14 or between FU16 and FU14. Throwing performance correlated (p<.05) with almost all the anthropometric and fitness parameters evaluated within each group. Taken together, male handball players showed greater anthropometric and fitness characteristics in the U16 compared to the U14, whereas no substantial differences were observed in female handball players between the two groups. Handball throwing velocity is associated with body and hand dimensions and other physical performance parameters.

Coincidence avoidance principle in surface haptic interpretation

When multiple fingertips experience force sensations, how does the brain interpret the combined sensation? In particular, under what conditions are the sensations perceived as separate or, alternatively, as an integrated whole? In this work, we used a custom force-feedback device to display force signals to two fingertips (index finger and thumb) as they traveled along collinear paths. Each finger experienced a pattern of forces that, taken individually, produced illusory virtual bumps, and subjects reported whether they felt zero, one, or two bumps. We varied the spatial separation between these bump-like force-feedback regions, from being much greater than the finger span to nearly exactly the finger span. When the bump spacing was the same as the finger span, subjects tended to report only one bump. We found that the results are consistent with a quantitative model of perception in which the brain selects a structural interpretation of force signals that relies on minimizing coincidence stemming from accidental alignments between fingertips and inferred surface structures.

A Novel Length Display Device for Cognitive Experiments and Rehabilitation

The purpose of this study was to develop a finger display device that has a four-degree-of-freedom (4DOF) length. This device was designed for rehabilitation and cognitive experimentation. The device can change the finger span between the thumb and four fingers, and the distance between digits is controlled by four motors. The positions of each unit, including the motor, are self-adjusted. Adjustments are made after recording the motion of the individual’s hand and analyzing fingertip movement. Each finger is controlled independently, and rehabilitation is performed on each individual finger. The device can be used for not only rehabilitation but also basic tactile studies. In particular, this device provides a valid method to measure length.

Grasp Stiffness as a Function of Grasp Force and Finger Span

The purpose of this study was to determine whether direct measurements of grasp stiffness agreed with stiffness inferred from the slopes of isovolitional force-span characteristics derived from previous grasp-effort matching data. Grasp stiffness for three-finger pinch was measured as a function of initial force and finger span using step displacements applied in a do-not-intervene paradigm. Subjects pinched a free-floating, motorized manipulandum in each hand and squeezed both with equal effort; one of the hands was perturbed at random. Stiffness was calculated from the initial and final steady-state values of force and span. The effects of step amplitude, rise-time, and initial load stiffness were investigated; grasp stiffness decreased significantly for larger steps, increased slightly for longer rise-times, and was unaffected by load stiffness. Grasp stiffness then was measured as a function of initial force and span using a single set of step parameters. Stiffness increased significantly in proportion to force but was changed only slightly by span. It was concluded that the perturbation and effort-matching measures of stiffness are not equivalent and represent different components of motor behavior.