Características antropométricas, condición física y velocidad de lanzamiento en balonmano de élite y amateur

166 p.

Sun exposure and sun protection behaviours among young adult sport competitors

Objective: To explore the relationship between sun protection and physical activity in young adults (18-30 years) involved in four organised sports.

Methods: Participants (n=237) in field hockey, soccer, tennis and surf sports completed a self-administered survey on demographic and sun-protective behaviours while playing sport. Differences in sun-protective behaviour were explored by sport and by gender.

Results: Sunburn during the previous sporting season was high (69%). There were differences between sports for sunburn, sunscreen use and reapplication of sunscreen. Lifesaving had the highest rates compared with the other three sports. Hats and sunglasses worn by participants varied significantly by sports. A greater proportion of soccer and hockey players indicated they were not allowed to wear a hat or sunglasses during competition. For all sports, competition was played mainly in the open with no shade provision for competitors while they were playing. There were some gender differences within each of the sports. Female soccer and tennis players were more likely to wear sunscreen compared with males. Female hockey players were more likely to wear a hat compared with males.

Conclusions: Our findings highlight that there is still room for improvement in sun-protective behaviours among young adult sport competitors. There is a need for a systematic approach to sun protection in the sporting environments of young adults.

Implications: Health promotion efforts to increase physical activity need to be paired with sun protection messages.

Reduced ankle dorsiflexion range may increase the risk of patellar tendon injury among volleyball players

Patellar tendon injury, a chronic overuse injury characterised by pain during tendon loading, is common in volleyball players and may profoundly restrict their ability to compete. This cross-sectional study investigated the association between performance factors and the presence of patellar tendon injury. These performance factors (sit and reach flexibility, ankle dorsiflexion range, jump height, ankle plantarflexor strength, years of volleyball competition and activity level) were measured in 113 male and female volleyball players. Patellar tendon health was determined by measures of pain and ultrasound imaging. The association between these performance factors and patellar tendon health (normal tendon, abnormal imaging without pain, abnormal imaging with pain) was investigated using analysis of variance. Only reduced ankle dorsiflexion range was associated with patellar tendinopathy (p < 0.05). As coupling between ankle dorsiflexion and eccentric contraction of the calf muscle is important in absorbing lower limb force when landing from a jump, reduced ankle dorsiflexion range may increase the risk of patellar tendinopathy.

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.

Anthropometric risk factors for patellar tendon injury among volleyball players

Objective: Abnormal imaging in the patellar tendon reveals pathology that is often associated with knee pain. Anthropometric measures of body size and mass, such as height, weight and waist-to-hip ratio (WHR), have been individually associated with abnormal imaging. The aim of this study was to investigate the anthropometric factors that have the strongest relationship with abnormal imaging in volleyball players.

Methods: Height, weight, body mass index (BMI), waist girth, hip girth and WHR were measured in a cohort of 113 competitive volleyball players (73 men, 40 women). The univariate (ANOVA) and multivariable (discriminant function analysis) association between abnormal imaging and these anthropometric factors were investigated.

Results: No significant association was found in the female volleyball players. A significant univariate association was observed between abnormal imaging and heavier weight, greater BMI, larger waist and hip girth and larger WHR in the male volleyball players. Waist girth was the only factor that retained this association in a multivariable model (p<0.05).

Conclusions: Men with a waist girth greater than 83 cm seem to be at greater risk of developing patellar tendon pathology. There may be both mechanical and biochemical reasons for this increased risk.

Effects of long-term tennis playing on the muscle-bone relationship in the dominant and non-dominant forearms

The relationship between muscle strength and bone mineral density illustrates the positive effect of mechanical loading on bone. But local and systemic factors may affect both muscle and bone tissues. This study investigated the effects of long-term tennis playing on the relationship between lean tissue mass and bone mineral content in the forearms, taking the body dimensions into account. Fifty-two tennis players (age 24.2 +/- 5.8 yrs, 16.2 +/- 6.1 yrs of practice) were recruited. Lean tissue mass (LTM), bone area, bone mineral content (BMC), and bone mineral density were measured at the forearms from a DXA whole-body scan. Grip strength was assessed with a dynamometer. A marked side-to-side difference (p < 0.0001) was found in favor of the dominant forearm in all parameters. Bone area and BMC correlated with grip strength on both sides (r = 0.81 - 0.84, p < 0.0001). The correlations were still significant after adjusting for whole-body BMC body height, or forearm length. This result reinforced the putative role of the muscles in the mechanical loading on bones. In addition, forearm BMC adjusted to LTM or grip strength was higher on the dominant side, suggesting that tennis playing exerts a direct effect on bone.

Cortical and trabecular bone at the forearm show different adaptation patterns in response to tennis playing

Bone responds to impact-loading activity by increasing its size and/or density. The aim of this study was to compare the magnitude and modality of the bone response between cortical and trabecular bone in the forearms of tennis players. Bone area, bone mineral content (BMC), and bone mineral density (BMD) of the ulna and radius were measured by dual-energy X-ray absorptiometry (DXA) in 57 players (24.5 ± 5.7 yr old), at three sites: the ultradistal region (50% trabecular bone), the mid-distal regions, and third-distal (mainly cortical bone). At the ultradistal radius, the side-to-side difference in BMD was larger than in bone area (8.4 ± 5.2% and 4.9 ± 4.0%, respectively, p < 0.01). In the cortical sites, the asymmetry was lower (p < 0.01) in BMD than in bone area (mid-distal radius: 4.0 ± 4.3% vs 11.7 ± 6.8%; third-distal radius: 5.0 ± 4.8% vs 8.4 ± 6.2%). The asymmetry in bone area explained 33% of the variance of the asymmetry in BMC at the ultradistal radius, 66% at the mid-distal radius, and 53% at the third-distal radius. The ulna displayed similar results. Cortical and trabecular bone seem to respond differently to mechanical loading. The first one mainly increases its size, whereas the second one preferentially increases its density.

Short-term and long-term site-specific effects of tennis playing on trabecular and cortical bone at the distal radius

Mechanical loading during growth magnifies the normal increase in bone diameter occurring in long bone shafts, but the response to loading in long bone ends remains unclear. The aim of the study was to investigate the effects of tennis playing during growth at the distal radius, comparing the bone response at trabecular and cortical skeletal sites. The influence of training duration was examined by studying bone response in short-term (children) and long-term (young adults) perspectives. Bone area, bone mineral content (BMC), and bone mineral density (BMD) of the radius were measured by DXA in 28 young (11.6 ± 1.4 years old) and 47 adult tennis players (22.3 ± 2.7 years old), and 70 age-matched controls (12 children, 58 adults) at three sites: the ultradistal region (trabecular), the mid-distal region, and the third-distal region (cortical). At the ultradistal radius, young and adult tennis players displayed similar side-to-side differences, the asymmetry in BMC reaching 16.3% and 13.8%, respectively (P < 0.0001). At the mid- and third-distal radius, the asymmetry was much greater in adults than in children (P < 0.0001) for all the bone parameters (mid-distal radius, +6.6% versus +15.6%; third-distal radius, +6.9% versus +13.3%, for BMC). Epiphyseal bone enduring longitudinal growth showed a great capacity to respond to mechanical loading in children. Prolonging tennis playing into adulthood was associated with further increase in bone mineralization at diaphyseal skeletal sites. These findings illustrate the benefits of practicing impact-loading sports during growth and maintaining physical activity into adulthood to enhance bone mass accrual and prevent fractures later in life.

Importance of the contribution of Australians to the penetration of China by the China Inland Mission in the period 1888-1953, with particular reference to the work of Australian women missionaries

Australians, in the main, are unaware of the role which Australia played in the evangelization of China in the late nineteenth and the first half of the twentieth century. Most would never have heard of the China Inland Mission (CIM), the largest of the Protestant bodies which penetrated the Middle Kingdom, and few would know of the contribution that its Australian contingent, which consistently comprised about a tenth of the CIM's numbers, made towards the Christianization of that vast country. This thesis aims to raise the level of awareness in this area. Academic researchers have not totally neglected to examine the proselytization of China, and historians of the stature of Latourette have not let it escape their attention. However, most of the studies which have not merely fleetingly focused on the subject while viewing a larger canvas, have been North American, singling out the efforts of United States and Canadian bodies in introducing Christianity to the Chinese. Here, authors like Amerding, Bacon, Creighton, Gates, Hawkes, Ho, Ko, Mensendiek, Michell and Quale have left their mark. In the case of the present thesis, the outlook from which events played out in China are viewed is firmly based in Australia rather than North America. Earlier Australian research has been scarce, and is dominated by Loane and Dixon. Loane, evidently primarily working from Australasian Council minutes, mainly concentrates on the efforts of the CIM's Home Council, examining its endeavours decade by decade against a backdrop of contemporaneous events in China, and briefly referring to aspects of the lives of a cross-section of Australasian missionaries, without providing much idea about what they actually did in the field or what they achieved there. Because of its preoccupation with the Home Council, which never admitted women into its ranks, Loane's treatise is systemically biased towards men, though the more prominent of the women, like Mary Reed and Susie Garland, are given due recognition. The current thesis looks in detail at what Australians did in the field, the level of success they achieved, and at the particular contribution of Australian women towards the evangelization of China. Dixon took upon herself the formidable task of examining the endeavours of all missions in China which contained Australian missionaries. Because of the magnitude of her task, she could not focus to any great extent on particular missions, nor pursue in any detail the work of individual Australian missionaries. Like Loane, she was unable to explore what they actually did in the field or what they achieved there. Neither could she delve to any depth into the work of Australian women missionaries, though on the basis of the information she had accumulated, she drew the conclusion that Australian women had largely only brought about some unintended feminist consequences amongst Chinese women. This sweeping generalization failed to take into account the other very real social changes for Chinese women the Australian female missionaries quite purposely helped to bring about, and this thesis makes good that omission. This thesis studies aspects of the Australian missionary endeavour which both Loane and Dixon have neglected, thereby breaking new ground, and sets out to correct erroneous impressions which Dixon's dissertation has left on the historical record. One of these impressions concerned the longevity of the effect of the Australian effort in China. She had the View, writing in 1978, that the Chinese Church was moribund (a view shared by Varg and Lacy) , and that therefore the effects attributable to the endeavours of any nationality had proved fruitless, whereas the author is able to show, using modern-day sources, that the church has burgeoned in recent years thanks to earlier missionary endeavours and later neo-evangelistic efforts like Gospel radio, and now has a complement of perhaps 50 million adherents, making it second only to the United States in the size of its Protestant evangelical population. Another impression she left was that the Australian input into the evangelization of China can be largely dismissed because no totally Australian organization emerged, leaving the direction of Australia's effort in other hands. Contrary to that impression, the author shows that the Australian impact in China was significant and that Australians enjoyed more power than Dixon ever imagined. The author also shows that Australians were accepted as the equal of other nationalities in the CIM once they had acquired the necessary field expertise, a factor which doubtless also applied in respect of other missions with Australian components in China. Marchant has suggested that it is a fiction perpetuated by mission periodicals that Christianity spread and progressed in a determined manner in China. This thesis establishes that within the CIM's bailiwick, though there was some patchiness, Christianity progressed steadily and inexorably. One mission alone, the CIM, is concentrated upon, firstly in order to render the data manageable, secondly because it was the largest mission in China and had a sizeable Australian (including female) contingent, and thirdly because it exemplified many of the problems which would have been faced by missions in that country and their Australian components. The methodology employed is multifaceted. The written testimony of the missionaries themselves, contained in CIM periodicals, Field Bulletins, Monthly Notes, Annual Reports, autobiographies, personal files, diaries and letters is used to illustrate various aspects of the CIM's work in which Australians were engaged. This approach is augmented by other sources such as China and Australasian Home Council Minutes, missionary conference reports, Candidates' Books, biographies, and other selected material from archival holdings in Australia, Singapore, the United Kingdom, America and Canada. Statistics, especially ratio analyses and growth rate comparisons are used to demonstrate the relative success of different missions, missionaries and genders. Also employed are reminiscences of missionaries and descendants obtained by personal interview, and these are aggregated to provide some general conclusions. Data from these various sources have been synthesized to serve the central objective of demonstrating the importance of the contribution of Australians to the penetration of China by the CIM in the period 1888-1953 with particular reference to the work of Australian women missionaries.

The prevalence of mood and anxiety disorders in Australian women

Objective: We aimed to report the prevalence, age-of-onset and comorbidity of mood and anxiety disorders in an age-stratified representative sample of Australian women aged 20 years and over.

Method: Mood and anxiety disorders were diagnosed utilising a clinical interview (SCID-I/NP). The lifetime and current prevalence of these disorders was determined from the study population (n = 1095) and standardized to 2006 census data for Australia.

Results: Approximately one in three women (34.8%) reported a lifetime history of any mood and/or anxiety disorder, with mood disorders (30.0%) being more prevalent than anxiety disorders (13.5%). Of these, major depression (23.4%), panic disorder (5.5%) and specific phobia (3.5%) were the most common. The lifetime prevalence of other disorders was low (≤3%). A total of 14.4% of women were identified as having a current mood and/or anxiety disorder, with similar rates of mood (8.9%) and anxiety disorders (8.0%) observed. The median age-of-onset for mood disorders was 27.0 years and 18.5 years for anxiety disorders.

Conclusions: This study reports the lifetime and current prevalence of mood and anxiety disorders in the Australian female population. The findings emphasize the extent of the burden of these disorders in the community.

Prevalence of osteoporosis in Australian women : Geelong Osteoporosis Study

To evaluate the prevalence of osteoporosis at various sites among Australian women, cross-sectional bone mineral density (BMD) data for adult females was obtained from an age-stratified population-based sample (n = 1494; 20–94 yr) drawn at random from the Barwon Statistical Division, a population characteristic of Australia. Age- and weight- (and for three sites, height) matched reference ranges for BMD at the lumbar spine, proximal femur, forearm, and total body were developed using regression techniques. The cutoff BMD level for osteoporosis at the PA spine was 0.917 g/cm² and 0.713 g/cm² at the femoral neck according to the World Health Organization (WHO) guidelines. The upper cutoff level for osteopenia was 1.128 g/cm² at the PA spine and 0.913 g/cm² for the femoral neck. The proportion of Australian women categorized as having osteoporosis at the PA spine, femoral neck, or midforearm ranged from 0.9% among those aged 40–44 yr to 87.0% for those older than 79 yr. This study provides reference data representative of the Australian female population. A large proportion of elderly Australian women has osteoporosis according to the WHO guidelines.

Job satisfaction and 'welfare-to-work' : is any job a good job for Australian mothers?

This exploratory study sought to assess the job satisfaction of employed Australian single mothers who had mandatory employment participation requirements. In particular, we sought to identify the characteristics of the job and the individual that were closely associated with participant’s job satisfaction. Self‑report data on job satisfaction, employment characteristics and parenting stress were collected from 155 employed single mothers. Participant job satisfaction was compared to female Australian population norms and linear regression analyses determined the job‑related and individual predictors of single mothers’ job satisfaction. Findings from this exploratory study revealed that single mothers involved in a mandatory welfare‑to‑work program experienced significantly lower job satisfaction than the Australian female population. The individual variable, parental distress, negatively predicted each of the six job satisfaction domains while being employed on a casual basis was inversely associated with three domains (job security, work hours and overall job satisfaction). The Australian government purported that making the transition from welfare to work would improve wellbeing for program participants, under the assumption that ‘any job’s a good job’. However, the relatively low levels of job satisfaction experienced by single mothers in the current study provide little support for this assumption.

Quantification of tackling demands in professional Australian football using integrated wearable athlete tracking technology

Objectives
To describe and quantify the frequency, velocity and acceleration at impact during tackling in Australian football using a combination of video and athlete tracking technology.

Design
Quasi-experimental.

Methods
Data was collected from twenty professional Australian Football League players during four in-season matches. All tackles made by the player and those against the player were video-coded and time stamped at the point of contact and then subjectively categorised into low, medium and high intensity impact groups. Peak GPS and acceleration data were identified at the point of contact. Two-way analysis of variance was used to assess differences (p < 0.05) between tackle type (made and against) and tackle intensity.

Results
A total of 173 tackles made and 179 tackles against were recorded. Significant differences were found between all tackle intensity groups. Peak velocity was significantly greater in high (19.5 ± 6.1 km h−1) compared to medium (13.4 ± 5.8 km h−1) and low intensity (11.3 ± 5.0 km h−1) tackles. Peak Player Load™, a modified vector magnitude of tri-axial acceleration, was significantly greater in high (7.5 ± 1.7 a.u.) compared to medium (4.9 ± 1.5 a.u.) and low intensity (4.0 ± 1.3 a.u.) tackles.

Conclusions
High intensity tackles, although less frequent, are significantly greater in speed of movement immediately prior to contact and in the resultant impact acceleration compared to tackles of lower intensity. Differences in accelerometer data between tackles observed to be progressively greater in intensity suggest a level of ecological validity and provide preliminary support for the use of accelerometers to assess impact forces in contact invasion sports.

The design and implementation of a novel method for quantifying training loads in elite rowing: the T2minute method

Introduction: A systematic approach to managing the training of elite athletes is supported by accurate training load measurement. However, quantifying the training of elite Australian rowers is complex due to unique challenges: 1) the multi-centre, multi-state structure of the national program; 2) the variety of training undertaken, incorporating rowing-specific and non-specific modalities, with continuous and interval efforts that span the full intensity spectrum; and 3) the limitations of existing quantification methods for capturing total training loads undertaken from varied training. These challenges highlighted a need to create a consistent, location-independent framework for prescribing training in elite rowing, with a capacity to account for varied training. Methods: An in-house proprietary measure (the T2minute method) was developed at the National Rowing Centre of Excellence (NRCE), as a collaborative project between sport scientists and national squad coaches. The design phase was informed by assessments of the existing training measures, and built upon standardised intensity zones established at the Australian Institute of Sport. A common measurement unit was chosen: one T2minute equates to one minute of on-water single scull rowing at T2 intensity (∼60–72% VO2max). Each intensity zone was assigned a weighting factor according to the curvilinear relationship between power output, intensity, and blood lactate response. Each training mode was assigned a weighting factor based on whether coaches perceived it to be “harder” or “easier” than onwater rowing. With coaches’ feedback, the method was refined over a period of five months. The T2minute method was implemented as the core framework for prescribing training for elite Australian rowers throughout the 2009–2012 Olympic cycle. Results: The implementation of the T2minute method successfully established consistency with training prescription and monitoring practices within the NRCE high performance program. The national roll out this method has influenced rowing training methodology at elite and sub-elite levels in Australia. Since implementation, the method has undergone scientific validation. Further research is underway, utilising the method to explore complex relationships between rowers’ training and performance outcomes. Conclusion: The T2minute method is a novel approach that allows rowing coaches and sport scientists to utilise one consistent system to quantify load from varied training. Its implementation represents a considerable achievement in establishing a common framework for managing the training process within a complex organisational structure. This collaborative approach used to develop the T2minute method provides unique insight into the important considerations and practical challenges of applying training science to enhance elite sport performance.

Monitoring neuromuscular fatigue in team-sport athletes using a cycle-ergometer test

PURPOSE: To compare a novel sprint test on a cycle ergometer with a countermovement-jump (CMJ) test for monitoring neuromuscular fatigue after Australian rules football match play. METHODS: Twelve elite under-18 Australian rules football players (mean ± SD age 17.5 ± 0.6 y, stature 184.7 ± 8.8 cm, body mass 75.3 ± 7.8 kg) from an Australian Football League club's Academy program performed a short sprint test on a cycle ergometer along with a single CMJ test 1 h prematch and 1, 24, and 48 h postmatch. The cycle-ergometer sprint test involved a standardized warm-up, a maximal 6-s sprint, a 1-min active recovery, and a 2nd maximal 6-s sprint, with the highest power output of the 2 sprints recorded as peak power (PP). RESULTS: There were small to moderate differences between postmatch changes in cycle-ergometer PP and CMJ PP at 1 (ES = 0.49), 24 (ES = -0.85), and 48 h postmatch (ES = 0.44). There was a substantial reduction in cycle-ergometer PP at 24 h postmatch (ES = -0.40) compared with 1 h prematch. CONCLUSIONS: The cycle-ergometer sprint test described in this study offers a novel method of neuromuscular-fatigue monitoring in team-sport athletes and specifically quantifies the concentric component of the fatigue-induced decrement of force production in muscle, which may be overlooked by a CMJ test.