Joanne A. McVeigh

Bone mass accretion rates in pre- and early-pubertal South African black and white children in relation to habitual physical activity and dietary calcium intakes.

Aim: To examine bone mass changes in 321 black and white South African children in relation to habitual physical activity (PA) levels and calcium intakes.

A two-year history of high bone loading physical activity attenuates ethnic differences in bone strength and geometry in pre-/early pubertal children from a low-middle income country.

We examined the interplay between ethnicity and weight-bearing physical activity on the content and volumetric properties of bone in a pre- to early pubertal South African Black and White population. Sixty six children [Black boys, 10.4 (1.4)yrs, n=15; Black girls, 10.1 (1.2)yrs, n=27; White boys, 10.1 (1.1)yrs, n=7; White girls, 9.6 (1.3)yrs, n=17] reported on all their physical activities over the past two years in an interviewer administered physical activity questionnaire (PAQ). All participants underwent a whole body and site-specific DXA scan and we also assessed bone structure and estimated bone strength with pQCT. Children were classified as being either high or low bone loaders based on the cohorts median peak bone strain score estimated from the PAQ. In the low bone loading group, Black children had greater femoral neck bone mineral content (BMC) (2.9 (0.08)g) than White children (2.4 (0.11)g; p=0.05). There were no ethnic differences in the high bone loaders for femoral neck BMC. At the cortical site, the Black low bone loaders had a greater radius area (97.3 (1.3) vs 88.8 (2.6)mm(2); p=0.05) and a greater tibia total area (475.5 (8.7) vs. 397.3 (14.0)mm(2); p=0.001) and strength (1633.7 (60.1) vs. 1271.8 (98.6)mm(3); p=0.04) compared to the White low bone loaders. These measures were not different between the Black low and high bone loaders or between the Black and White high bone loaders. In conclusion, the present study shows that there may be ethnic and physical activity associations in the bone health of Black and White pre-pubertal children and further prospective studies are required to determine the possible ethnic specific response to mechanical loading.

Organized sport trajectories from childhood to adolescence and health associations

INTRODUCTION The purpose of this study was to identify unique organized sport trajectories from early childhood to late adolescence in an Australian pregnancy cohort, the Raine Study. METHODS Participation in organized sport was assessed at ages 5, 8, 10, 14, and 17 yr. Physical activity, body composition, and self-rated physical and mental health were assessed at the age of 20 yr. Latent class analysis was used to identify patterns of sport participation. To assess the internal validity of the trajectory classes, differences in health characteristics between trajectories were analyzed using generalized linear models. RESULTS For girls, three trajectory classes were identified: consistent sport participators (47.5%), sport dropouts (34.3%), and sport nonparticipators (18.1%). For boys, three trajectory classes were identified: consistent sport participators (55.2%), sport dropouts (36.9%), and sport joiners (8.1%). For girls, there were overall differences across trajectory classes in lean body mass (P = 0.003), lean mass index (P = 0.06), and physical health (P = 0.004). For boys, there were differences across classes in physical activity (P = 0.018), percent body fat (P = 0.002), lean body mass (P < 0.001), lean mass index (P < 0.001), physical health (P = 0.06), and depression scores (P = 0.27). CONCLUSION This study identified unique, sex-specific trajectories of organized sport participation. The differences in health outcomes between trajectory classes, such as participants with consistent sport participation having more preferable health outcomes at the age of 20 yr, support the internal validity of the trajectories. Strategies are needed to identify and encourage those in the dropout trajectory to maintain their participation and those in the nonparticipator or joiner trajectories to join sport earlier. Specifically, interventions to encourage early sport participation in girls and help nonparticipating boys to join sport during adolescence may help more children receive the benefits of sport participation.

Longitudinal Trajectories of Television Watching Across Childhood and Adolescence Predict Bone Mass at Age 20 Years in the Raine Study.

Sedentary behaviors such as watching television (TV) are associated with increased risk of cardiometabolic disease. The effects of TV watching during key developmental stages on skeletal health are uncertain. Hours of TV watching/week were recorded by parental or self‐report at 5, 8, 10, 14, 17, and 20 years of age in 1181 members (48% female) of a pregnancy cohort (the Raine Study). Participants were classified into one of three TV‐watching trajectories (using latent class analysis): low (consistently <14 h/week; 20.3%), high (consistently ≥14 h/week; 44.4%), or increasing (increased from <14 to ≥14 h/week during adolescence; 35.3%). General linear models tested associations between TV trajectory and bone mineral content (BMC) measured at age 20 years using dual‐energy X‐ray absorptiometry. After adjustment for height, body mass, physical activity, calcium intake, serum 25‐hydroxyvitamin D levels, alcohol, and smoking (all at age 20 years), males in the low TV‐watching trajectory had greater BMC for whole body (mean ± SEM, 3338 ± 59 g versus 3111 ± 31 g), legs (612 ± 12 g versus 569 ± 6 g), and arms (234 ± 5 g versus 214 ± 3 g) than those in the high TV‐watching trajectory. Differences between low and high TV‐watching trajectories were similar for females. BMC in the increasing TV‐watching trajectory also differed for both sexes, for example males in the increasing TV‐watching trajectory had greater whole‐body BMC (3252 ± 38 g) than males in the high TV‐watching trajectory (3111 ± 31 g) but less arm BMC (218 ± 3 g) than those in the low TV‐watching trajectory (234 ± 5 g). In this community‐based cohort, consistently high TV watching during childhood and adolescence independently predicted reduced peak bone mass at age 20 years. Because attainment of optimal peak bone mass is protective against osteoporosis in later life, reducing sedentary time in children may have long‐term skeletal benefits.

Changes in physical activity measured by accelerometry following initiation of DMARD therapy in rheumatoid arthritis

OBJECTIVE The aim of this study was to assess changes in habitual physical activity levels in response to DMARD therapy in RA patients. METHODS Eighteen drug-naive RA patients were prospectively assessed at baseline and following 3 months of DMARD therapy for habitual physical activity by accelerometry, disease activity using the clinical disease activity index (CDAI) and functional disability using the modified HAQ (mHAQ). Baseline physical activity was also compared with an equal number of healthy control participants matched for age, sex and BMI. RESULTS Following 3 months of DMARD therapy, in parallel with significant improvements in CDAI scores (P < 0.001) and HAQ scores (P < 0.001), accelerometry measures in the RA cohort showed that the average activity counts in sedentary thresholds decreased (P = 0.012), while average activity counts within higher-intensity thresholds increased (P = 0.039). Multiple regression analysis showed that the change in moderate activity was associated with a decrease in CRP (β = - 0.922, P = 0.026) while the decrease in sedentary activity and increase in moderate activity were associated with decreased morning stiffness of the joints (β = 0.694, P = 0.035 and β = -0.927, P = 0.024, respectively). At baseline, RA patients were less physically active than control participants in the morning (P = 0.048) and in the late afternoon (P = 0.016), but these diurnal differences were no longer significant after the DMARD intervention. CONCLUSION These findings suggest that accelerometry may potentially be a viable objective method of assessing changes in physical disability in response to various disease-modifying drugs.

Whole body vibration increases hip bone mineral density in road cyclists.

This study aimed to determine the effects of 10 weeks of whole body vibration training on the bone density of well-trained road cyclists. 15 road cyclists were assigned to either a vibrating group (n=8), who undertook 15 min of intermittent whole body vibration at 30 Hz, 3 times per week while continuing with their normal cycling training; or a control group (n=7), who continued with their normal cycling training for the 10-week period. Cyclists were age, body mass and height matched with 15 sedentary participants. At baseline, all participants underwent regional dual x-ray absorptiometry scans, where both cycling groups had lower pelvic (p<0.050) and higher head bone mineral density (p<0.050) than the sedentary participants with no other differences observed. After 10 weeks of training, vibrating cyclists showed a significantly greater increase in hip bone mineral density (0.020±0.010 g.cm - 2 (1.65%), p=0.024) while the control cyclists ( - 0.004±0.001 g.cm - 2 (0%)) showed no change (p>0.050). The control group had a significantly lower spine bone mineral density (1.027±0.140 g.cm - 2, p=0.020) compared to baseline (1.039±0.140 g.cm - 2). This loss was not observed in the vibrating group. 10 weeks of whole body vibration training increased hip and preserved spine bone mineral density in road cyclists.

Habitual Physical Activity, Sedentary Behaviour and Bone Health in Rheumatoid Arthritis

Associations between habitual physical activity levels and bone health in rheumatoid arthritis (RA) were assessed. Twenty nine female patients with RA were assessed for bone mineral density (BMD), and classified as having low or normal hip BMD. Habitual physical activity levels were assessed using accelerometry, and disease activity was assessed using the Clinical Disease Activity Index (CDAI). Twenty one patients had normal bone mass, while 8 had low bone mass. There was no difference in age in the normal bone mass group (51(8)) compared to the low bone mass group (57(12)), p=0.19. Patients with normal bone mass spent on average 2 h less per day in sedentary activity (65(4)% vs. 73(2)%, p<0.01), over 70 min more time in light activity (23(1)% vs. 18(2)%, p<0.01), and over 50 min more in moderate activity per day (12(3)% vs. 8(2)%, p<0.01) than did patients with low bone mass, independently of disease activity or duration. Patients with normal bone mass broke up their sedentary time more frequently per day (72(21) vs. 53(18) times per day, p=0.03). The results of this study indicate that higher habitual activity levels may be protective of bone health in patients with RA, and should be encouraged.

Trajectories of Television Watching from Childhood to Early Adulthood and Their Association with Body Composition and Mental Health Outcomes in Young Adults.

Introduction Prior studies examining longitudinal patterns of television (TV) watching have tended to use analytical approaches which do not allow for heterogeneity in the variation of TV watching over time. In the current study, we used latent class analysis (LCA) to examine the relationships between television watching (from childhood to early adulthood) and body fat percentage (%) and mental health. Methods Data were collected from 2411 participants (50% female) from the Raine Study, a prospective birth cohort study in Australia. Participants were followed up over 15 years and answered questions about hours of TV watching per week at six time-points (5, 8, 10, 14, 17 and 20yrs). Trajectories of television watching were estimated using LCA and appropriate regression models used to test the association of television watching class with percentage body fat (measured by DXA) and mental health (DASS-21) at age 20. Physical activity was used as a covariate. Results Three distinct trajectories of TV watching were identified. Class 1 (47.4%) had consistently high (>14 hrs/wk) levels of TV watching, Class 2 (37.9%) was characterised by an increase in TV watching over adolescence and Class 3 (14.7%) had consistently lower (<14 hrs/wk) TV watching over 15 years. Sex was used as an active covariate in the latent class model and was significantly associated with class membership (p<0.001), with females comprising 45%, 47% and 59% of Class 1, 2 and 3 respectively. In females, membership in Class 2 or 3 was associated with lower body fat % at age 20, compared to Class 1 (p<0.001). For males, membership in Class 2 was associated with lower body fat % compared with males in Class 1 (p = 0.026). Membership of TV watching class and mental health were not related (p>0.05). Conclusions TV watching from childhood to young adulthood appears to be a relatively stable behavior for around two thirds of participants, but not everyone tracks consistently. This study identified a subset of participants with low levels of TV watching in childhood and also that this group, despite an increase in TV watching over adolescence, maintained a lower level of body fat in young adulthood.

Radial bone size and strength indices in male road cyclists, mountain bikers and controls

Abstract Mountain biking (MB), unlike road cycling (RC) involves exposure to ground impact bone strain and requires upper-body muscle forces to maintain stability over uneven terrain and therefore may have differential effects on radial bone structure and strength. This study aimed to compare serum bone turnover marker concentration, 1-repetition maximum muscle strength and the radial proximal (diaphysis) and distal (metaphysis) bone structure [bone mineral content, total and cortical area (CoA), density and thickness, diameter and circumference], strength strain indices and muscle cross-sectional area (MCSA) using peripheral quantitative computed tomography (pQCT) between 30 male cyclists (18–34 years) MB (n = 10), RC (n = 10) and non-athletes controls (CON, n = 10). Differences were assessed by ANOVA and an ANCOVA (adjusting for body mass and height) where appropriate. MB radii were characterised by significantly stronger (14–16%), denser (9–27%) and larger (10%) metaphyses and stronger (22–23%) and larger (11–13%) diaphyses compared to RC and CON. RC had significantly 7% higher strength indices and 4% greater CoA and thickness than CON at the diaphysis, with no differences for other bone measurements. Serum C-terminal telopeptides of type-1 collagen concentration (bone resorption marker) was higher in RC than MB (p < 0.05) and above the age-reference range. MCSA and strength were greater in MB than RC (p < 0.05). Muscle forces generated during RC appear to produce an osteogenic stimulus to increase radial bone strength indices with minimal improvement in bone structure. However greater resorptive activity in RC suggests inadequate loading to support bone maintenance. In conclusion, bone loading, muscle size and strength of MB are superior to RC.

Pressure and cold pain threshold reference values in a large, young adult, pain-free population

Abstract Background and aims Currently there is a lack of large population studies that have investigated pain sensitivity distributions in healthy pain free people. The aims of this study were: (1) to provide sex-specific reference values of pressure and cold pain thresholds in young pain-free adults; (2) to examine the association of potential correlates of pain sensitivity with pain threshold values. Methods This study investigated sex specific pressure and cold pain threshold estimates for young pain free adults aged 21–24 years. A cross-sectional design was utilised using participants (n =617) from the Western Australian Pregnancy Cohort (Raine) Study at the 22-year follow-up. The association of site, sex, height, weight, smoking, health related quality oflife, psychological measures and activity with pain threshold values was examined. Pressure pain threshold (lumbar spine, tibialis anterior, neck and dorsal wrist) and cold pain threshold (dorsal wrist) were assessed using standardised quantitative sensory testing protocols. Results Reference values for pressure pain threshold (four body sites) stratified by sex and site, and cold pain threshold (dorsal wrist) stratified by sex are provided. Statistically significant, independent correlates of increased pressure pain sensitivity measures were site (neck, dorsal wrist), sex (female), higher waist-hip ratio and poorer mental health. Statistically significant, independent correlates of increased cold pain sensitivity measures were, sex (female), poorer mental health and smoking. Conclusions These data provide the most comprehensive and robust sex specific reference values for pressure pain threshold specific to four body sites and cold pain threshold at the dorsal wrist for young adults aged 21–24 years. Establishing normative values in this young age group is important given that the transition from adolescence to adulthood is a critical temporal period during which trajectories for persistent pain can be established. Implications These data will provide an important research resource to enable more accurate profiling and interpretation of pain sensitivity in clinical pain disorders in young adults. The robust and comprehensive data can assist interpretation of future clinical pain studies and provide further insight into the complex associations of pain sensitivity that can be used in future research.