Social positioning and the construction of a youth sports club

This article uses the concept of social positioning to explore the construction of a youth sports club by young people, their parents and coaches. The year-long ethnography of Forest Athletics Club (FAC) identified two athlete positions of Samplers and Beginning Specializers. Four parents’ positions were identified, those of Non-Attenders, Spectators, Helpers and Committed Members. One coach position was the Committed Volunteer. Each of these positions was interdependent. Particular expectations, practices and values were attached to these positions. It is argued that the club operates according to multiple agendas and that FAC is a complex and dynamic social phenomenon that is practised differently by the three groups of key players.

Analysis of proximal femur DXA scans in growing children: Comparisons of different protocols for cross-sectional 8-month and 7-year longitudinal data

Dual-energy X-ray absorptiometry (DXA) is a widely used method for measuring bone mineral in the growing skeleton. Because scan analysis in children offers a number of challenges, we compared DXA results using six analysis methods at the total proximal femur (PF) and five methods at the femoral neck (FN), In total we assessed 50 scans (25 boys, 25 girls) from two separate studies for cross-sectional differences in bone area, bone mineral content (BMC), and areal bone mineral density (aBMD) and for percentage change over the short term (8 months) and long term (7 years). At the proximal femur for the short-term longitudinal analysis, there was an approximate 3.5% greater change in bone area and BMC when the global region of interest (ROI) was allowed to increase in size between years as compared with when the global ROI was held constant. Trend analysis showed a significant (p < 0.05) difference between scan analysis methods for bone area and BMC across 7 years. At the femoral neck, cross-sectional analysis using a narrower (from default) ROI, without change in location, resulted in a 12.9 and 12.6% smaller bone area and BMC, respectively (both p < 0.001), Changes in FN area and BMC over 8 months were significantly greater (2.3 %, p < 0.05) using a narrower FN rather than the default ROI, Similarly, the 7-year longitudinal data revealed that differences between scan analysis methods were greatest when the narrower FN ROI was maintained across all years (p < 0.001), For aBMD there were no significant differences in group means between analysis methods at either the PF or FN, Our findings show the need to standardize the analysis of proximal femur DXA scans in growing children.

Calcium accretion in girls and boys during puberty: A longitudinal analysis

The primary purpose of this study was to estimate the magnitude and variability of peak calcium accretion rates in the skeletons of healthy white adolescents. Total-body bone mineral content (BMC) was measured annually on six occasions by dual-energy X-ray absorptiometry (DXA; Hologic 2000, array mode), a BMC velocity curve was generated for each child by a cubic spline fit, and peak accretion rates were determined. Anthropometric measures were collected every 6 months and a 24-h dietary recall was recorded two to three times per year. Of the 113 boys and 115 girls initially enrolled in the study, 60 boys and 53 girls who had peak height velocity (PHV) and peak BMC velocity values were used in this longitudinal analysis. When the individual BR IC velocity curves were aligned on the age of peak bone mineral velocity, the resulting mean peak bone mineral accrual rate was 407 g/year for boys (SD, 92 g/year; range, 226-651 g/year) and 322 g/year for girls (SD, 66 g/year; range, 194-520 g/year). Using 32.2% as the fraction of calcium in bone mineral, as determined by neutron activation analysis (Ellis et al., J Bone Miner Res 1996;11:843-848), these corresponded to peak calcium accretion rates of 359 mg/day for boys (81 mg/day; 199-574 mg/day) and 284 mg/day for girls (58 mg/day; 171-459 mg/day). These longitudinal results are 27-34% higher than our previous cross-sectional analysis in which we reported mean values of 282 mg/day for boys and 212 mg/day for girls (Martin et al., Am J Clin Nutr 1997;66:611-615). Mean age of peak calcium accretion was 14.0 years for the boys (1.0 years; 12.0-15.9 years), and 12.5 years for the girls (0.9 years; 10.5-14.6 years). Dietary calcium intake, determined as the mean of all assessments up to the age of peak accretion was 1140 mg/day (SD, 392 mg/day) for boys and 1113 mg/day (SD, 378 mg/day) for girls. We estimate that 26% of adult calcium is laid down during the 2 adolescent years of peak skeletal growth. This period of rapid growth requires high accretion rates of calcium, achieved in part by increased retention efficiency of dietary calcium.

The effect of moderate aerobic exercise and relaxation on secretory immunoglobulin A

A deficiency in secretory immunoglobulin A (sIgA) is associated with recurrent upper respiratory tract infections both in the general community and in elite athletes. The aim of this paper was to investigate the effect of aerobic exercise and relaxation on various indices of sIgA in 12 male and 8 female adults who varied in levels of recreational activity. Salivary samples were obtained before, immediately after and 30 minutes after an incremental cycle ergometer test to fatigue. after 30 minutes of cycling at 30% or 60 % of maximum heart rate, and after 30 minutes of relaxation with guided imagery. Each session was run on a separate day. When expressed in relation to changes in salivary flow rate, sIgA did not change after exercise. However, both the absolute concentration and secretion rate of sIgA increased during relaxation (167 +/- 179 mug ml(-1), p < 0.001: and 37 +/- 71 g(.)min(-1), p < 0.05 respectively). Nonspecific protein increased more than sIgA during incremental exercise to fatigue (decrease in the sIgA/protein ratio 92 +/- 181 g(.)mg protein(-1), p(0.05), but sIgA relative to protein did not change during relaxation. Our findings suggest that sIgA secretion rate is a more appropriate measure of sIgA than sIgA relative to protein, both for exercise and relaxation. These data suggest the possibility of using relaxation to counteract the negative effects of intense exercise on sIgA levels.