Expertise Development in Volleyball: the Role of Early Sport Activities and Players’ Age and Height

The purpose of this study was to analyse the developmental pathway of skilled and less skilled volleyball players by focusing on the quantity and type of sporting activities, as well as their age and height in comparison to peers in those experiences. Retrospective interviews were conducted to provide a longitudinal and detailed account of sport involvement of 30 skilled and 30 less skilled volleyball players (15 male and 15 female players per group) throughout different developmental stages (stage 1: 8-12 years; stage 2: 13-16 years; stage 3: 17-20 years). Results indicated that the developmental pathway of these volleyball players (i.e. skilled and less skilled) was characterized by an early diversified sport involvement with a greater participation in sport activities during stages 1 and 2. However, skilled players specialized later in volleyball (between age 14 and 15) and performed more hours of volleyball at stage 3 (from 17 years of age onwards). Also, skilled players (male and female) were younger in both the diversified sport activities and volleyball at the later stages of development (i.e. stages 2 and 3), and skilled female players were taller than peers in those activities in the early stages of development (i.e. stages 1 and 2). The present findings suggest early diversification as a feasible pathway to reach expertise in volleyball and highlight the importance of practicing with older peers once specialization in the main sport has occurred. The findings highlight the need for coaches and sport programs to consider different stimuli existing within the training environment (i.e. characteristics of athletes, such as age and height) that influence the quality of practice and contribute to players’ expertise development.

MRI Registration for Human Hip Kinematics

Measurement of joint kinematics can provide knowledge to help improve joint prosthesis design, as well as identify joint motion patterns that may lead to joint degeneration or injury. More investigation into how the hip translates in live human subjects during high amplitude motions is needed. This work presents a design of a non-invasive method using the registration between images from conventional Magnetic Resonance Imaging (MRI) and open MRI to calculate three dimensional hip joint kinematics. The method was tested on a single healthy subject in three different poses. MRI protocols for the conventional gantry, high-resolution MRI and the open gantry, lowresolution MRI were developed. The scan time for the low-resolution protocol was just under 6 minutes. High-resolution meshes and low resolution contours were derived from segmentation of the high-resolution and low-resolution images, respectively. Low-resolution contours described the poses as scanned, whereas the meshes described the bones’ geometries. The meshes and contours were registered to each other, and joint kinematics were calculated. The segmentation and registration were performed for both cortical and sub-cortical bone surfaces. A repeatability study was performed by comparing the kinematic results derived from three users’ segmentations of the sub-cortical bone surfaces from a low-resolution scan. The root mean squared error of all registrations was below 1.92mm. The maximum range between segmenters in translation magnitude was 0.95mm, and the maximum deviation from the average of all orientations was 1.27◦. This work demonstrated that this method for non-invasive measurement of hip kinematics is promising for measuring high-range-of-motion hip motions in vivo.

Prevention of cement leakage into the hip joint by a standard cement plug during PFN-A cement augmentation: a technical note.

Medial penetration of the helical blade into the hip joint after fixation of trochanteric fractures using the proximal femur nail antirotation (PFN-A) is a potential failure mode. In low demand patients a blade exchange with cement augmentation may be an option if conversion to total hip arthroplasty is unfeasible to salvage the cut-through. This article describes a technique to avoid intraarticular cement leakage using a cement plug to close the defect in the femoral head caused by the cut-through.

Development of proposed height standards and tolerances for light-post traffic barriers. Interim report.

Federal Highway Administration, Office of Research, Development and Technology, Washington, D.C.

Field study of a variable-height highway-noise barrier. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Determination of motor vehicle eye height for highway design. Final report.

Federal Highway Administration, Office of Research and Development, Washington, D.C.

Tree height reduction for parallel processing of blocks of Fortran assignment statements.

Thesis (M.S.)--University of Illinois.

Determination of mooring load and transmitted wave height for a floating tire breakwater /

"September 1979."

Estimating nearshore significant wave height for irregular waves /

"October 1979."

Depth-limited significant wave height : a spectral approach /

"August 1982."

A model for the distribution function for significant wave height /

"January 1981."

Wave-height prediction for wave generators in shallow water /

"March 1964."