The effect of mechanical loading on the size and shape of bone in pre-, peri-, and postpubertal girls: a study in tennis players

Exercise during growth results in biologically important increases in bone mineral content (BMC). The aim of this study was to determine whether the effects of loading were site specific and depended on the maturational stage of the region. BMC and humeral dimensions were determined using DXA and magnetic resonance imaging (MRI) of the loaded and nonloaded arms in 47 competitive female tennis players aged 8-17 years. Periosteal (external) cross-sectional area (CSA), cortical area, medullary area, and the polar second moments of area (I_p, mm⁴) were calculated at the mid and distal sites in the loaded and nonloaded arms. BMC and I _p of the humerus were 11-14% greater in the loaded arm than in the nonloaded arm in prepubertal players and did not increase further in peri- or postpubertal players despite longer duration of loading (both, _p < 0.01). The higher BMC was the result of a 7-11% greater cortical area in the prepubertal players due to greater periosteal than medullary expansion at the midhumerus and a greater periosteal expansion alone at the distal humerus. Loading late in puberty resulted in medullary contraction. Growth and the effects of loading are region and surface specific, with periosteal apposition before puberty accounting for the increase in the bone's resistance to torsion and endocortical contraction contributing late in puberty conferring little increase in resistance to torsion. Increasing the bone's rt.osistance to torsion is achieved hy modifying bone shape and mass, not necessarily bone density.

MMP2 and MMP9 plasma levels as markers of bone remodeling : a study on young male tennis players

Introduction
Our goal is to study the effects of tennis practice in pre-pubescent boys on bone remodeling, by means of enzyme activity involved in balance of matrix remodeling (MMP2 and MMP9).
Results
Mineral bone density has been found higher in the dominant arm (P < 0.0001) as well as MMP2 and MMP9 levels in plasma (P < 0.05).
Conclusion
Tennis practice in children increases bone remodeling, which can be assessed by MMP dosage, in addition of densitometry technique.

Highlights from the tennis Australia heritage collections : mini-exhibition in the player cafe, Rod Laver Arena

Summary : This 'mini-exhibition' arose as an opportunity to showcase recent acquisitions as well as established holdings of significant items of tennis related heritage within the Tennis Australia Heritage Collections. In general, the Collections have two main strengths, and the mini-exhibition was designed to communicate these. The first strength is the ability to show the evolution of tennis technology and practices over time, from the beginnings of modern tennis in the 1860s, to today. This evolution is a result of tennis being influenced by changes in the wider world, such as the Industrial Revolution. The second strength of the Collections is in showing the impact and influence of tennis on society. Many items in the Collections are evidence of the immense and enduring popularity of the sport across the world. The Collections contain many beautiful, rare and fascinating items of decorative arts, fashion, literature and social history which feature tennis as a motif. These items show the reverse influence - the deep impression tennis has made outside of the sport itself.  This mini-exhibition focuses on these two themes. Some displays focus on the first theme. They demonstrate the evolution of tennis racquets, tennis balls, instructional publications and other tennis related equipment over the past century and a half. Other displays focus on the second theme. There are cases which examine tennis' influence upon global popular culture, in board games, fashion and decorative arts from around the world.  The mini-exhibition includes items from the U.s, U.K., Germany, France, Austria, Japan and Australia, demonstrating the global phenomenon that tennis quickly became, and showcasing the international scope of the Collections.  Each case contains text panels listing the objects and their specifications, and panels providing contextual information about the display. The miniexhibition is expected to be on display until November 2009. A case-bycase breakdown of objects, with images and a layout map follows.

Adolescence and abuse : trauma and the socio-sexual abject in John Duigans lawn dogs

The article analyzes the presentation of youth in the film "Lawn Dogs," directed by John Duigan. In the film, the child as victim is defined by socio-economic contexts. The author explores the discursive moves by which means the film witnesses or occludes the traumatic experiences suffered by the child and adolescent characters, and how far it articulates a satiric revision of social hierarchies that construct generational identities of gender and class.

Tennis Australia : a case study of financial management for sport development at the club level

There has been substantial work that examines financial management in professional sport which has assisted scholars and practitioners to better understand processes and policies to ensure teams and leagues are sustainable (Andreff & Staudohar, 2000; Howard & Crompton, 2004; Kraekel, 2007; Lewis, Sexton, & Lock, 2007; Li, Hofacre, & Mahony, 2001). However, there has been a paucity of scholarly research that examines financial management at the grass roots levels of sport, and how this integrates with national sport organisation strategic planning, with the exception of the recent work by Havaris and Danylchuk (2007). This study aims to add to this gap in knowledge by examining financial management at the club level of tennis in Australia.

Tennis playing initiated before puberty leads to greater skeletal benefits in peri-pubertal boys than girls when training is maintained

Introduction: The purpose of the study was to compare the exercise-induced changes in bone mass and geometry between boys and girls.

Methods: Eighty competitive tennis players (43 boys, 37 girls) aged 7–19 years participated. Pubertal status was self-assessed using Tanner stages (TS 1–5). The dominant and nondominant humeri were compared for DXA-derived bone mass (BMC) and MRI-derived bone geometry [total bone area (TA), medullary area (MA) and cortical bone area (CA)].

Results/Discussion: Exercise-induced side-to-side differences in BMC, TA and CA were significant from TS1 to 5 in boys and girls (p < 0.06). Pre-pubertal (TS1) girls and boys show similar side-to-side difference in BMC after adjustment for training volume (19% vs. 15%, ns). Similar findings were found forTA and CA. In contrast, during puberty (TS2-4) boys displayed greater side-to-side differences than girls for BMC (27% vs. 18%, p < 0.05), TA (13–15% vs. 8%, p < 0.05) and CA (32% vs. 20%, p < 0.01), even after adjustment for tennis history. Girls partly compensated for the lack of an exercise-induced increase in bone size by a reduction of the medullary cavity on the dominant side (−5.5 to −13%, p < 0.05). In post-puberty (TS 5 or postmenarche), the size of the medullary cavity remained smaller on the dominant side in girls (−5% to −9%, p = 0.1–0.05??) whereas no such reduction was observed in boys.

Conclusion: Regular exercise initiated before puberty and maintained throughout puberty leads to greater skeletal benefits in peri-pubertal boys than girls for bone mass and bone size, two of the major determinants of bone strength.