Physical activity trajectories from childhood to late adolescence and their implications for health in young adulthood.

Physical activity has been associated with physical and mental health across the life course, yet few studies have used group-based trajectory modeling to examine the effect of longitudinal patterns of physical activity during childhood and adolescence on adult health outcomes. The Raine Study data from Gen2 follow-ups at 8, 10, 14, 17, 20, and 22 years collected between 1998 and 2014 were used. Latent class analysis identified trajectories using parent-reported physical activity for ages 8 to 17. Associations between trajectories and physical and mental health outcomes at ages 20 and 22 were explored, adjusting for current physical activity and considering sex interactions. Analysis in 2019 identified three trajectories: low (13%), mid (65%) and high (22%) physical activity (n = 1628). Compared to the low-activity trajectory, those in the high-activity trajectory had lower adiposity, insulin, HOMA-IR and fewer diagnosed disorders, higher HDL-cholesterol, and faster cognitive processing. For example, those in the high-activity trajectory had lower percent body fat at age 20 compared to those in the mid-activity (-4.2%, 95%CI: -5.8, -2.7) and low-activity (-9.5%, 95%CI: -11.7, -7.2) trajectories. Physical activity trajectories showed different associations between sexes for self-reported physical and mental health, BMI, systolic blood pressure, and depression symptoms. Being in the high- or mid-activity trajectory was associated with a more favorable cardiometabolic and mental health profile in young adulthood. Strategies are needed to help less active children to increase physical activity throughout childhood and adolescence to improve young adult health outcomes.

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.

Osteogenic effects of a physical activity intervention in South African black children.

OBJECTIVES: To determine whether a weight-bearing physical activity intervention improves measures of bone density, size and strength in a pre- and early pubertal cohort of black South African children. METHODS: Twenty two school children (9.7±1.1 years) were cluster randomised into an exercise (EX; n=12) and control (CON; n=10) group. EX children performed a weight-bearing exercise program for 20 weeks. CON children continued their regular activities. Whole body DXA and tibial peripheral QCT scans were obtained. Urine was analysed for concentrations of cross-linked N-telopeptides of Type I collagen (NTX). RESULTS: Changes in 4% volumetric BMD, area and strength were greater in EX than CON. At the 38% site, change in bone area and density was greater in EX than CON. The greater change in periosteal circumference in the EX groups also resulted in a greater change in cortical thickness of the tibia compared to the CON group. NTX concentration was lower in the EX group than the CON group after the intervention. CONCLUSIONS: This study documents for the first time the beneficial response of trabecular and cortical bone of black children to a weight bearing exercise intervention.

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. METHODS: Children underwent two bone mass scans at ages nine and 10 years using dual X-Ray absorptiometry. PA levels and calcium intakes were assessed using questionnaires. Data were analyzed by regressing change in bone mineral content (BMC) and bone area (BA) from age nine to 10, against BA (for BMC), height and body weight. The residuals were saved and called residualized BMCGAIN and BAGAIN. Residualized values provide good indication of weight, height and BA-matched accumulation rates. RESULTS: White children had significantly higher PA levels and calcium intakes than black children. Most active white males had significantly higher residualized BMCGAIN and BAGAIN at the whole body, hip and spine but not at the radius, than those who were less active. Most active white females had significantly higher residualized BAGAIN at all sites except the radius than less-active girls. No such effects were seen in black children. There was no interactive effect on residualized BMCGAIN for calcium intake and PA (except at the spine in white girls). CONCLUSION: Bone mass and area gain is accentuated in pre- and early-pubertal children with highest levels of habitual physical activity. Limited evidence of an effect of dietary calcium intakes on BMC was found.

The relationship between socio-economic status and physical activity patterns in South African children.

AIM: To examine: (1) the associations between socio-economic status, physical activity, anthropometric and body composition variables in South African children; (2) the influence maternal characteristics have on children's physical activity levels; and (3) associations between television watching, activity level and body composition. METHODS: In 381 South African children, physical activity and socio-economic status were assessed via structured retrospective interview using validated questionnaires. An asset indicator score was calculated as a proxy measure of socio-economic status and used to divide children into quartiles. RESULTS: Children falling into the highest socio-economic status quartile had mothers with the highest educational levels, generally came from dual parent homes, were highly physically active, watched less television, weighed more and had greater lean tissue than children in lower quartiles. A greater percentage of children living in dual parent homes and with mothers of a higher educational status were highly active compared with children living in single parent homes and with mothers of a lower educational status. We found greater levels of lean mass with increased activity level after controlling for television watching time and fat mass. There were high levels of low activity and high television watching time among lower socio-economic status groups. There were significant racial differences in patterns of activity. White children were found to be more active than black children, more likely to participate in physical education classes at school and watched less television than black children. CONCLUSION: Physical activity levels and socio-economic variables are closely related in this population of South African children.

Associations between physical activity and bone mass in black and white South African children at age 9 yr.

We investigated differences in physical activity (PA) levels between black and white South African 9-yr-old children and their association with bone mineral content (BMC) and density (BMD) by using dual-energy X-ray absorptiometry. PA was analyzed in terms of a metabolic (METPA; weighted metabolic score of intensity, frequency, and duration) and a mechanical (MECHPA; sum of all ground reaction forces multiplied by duration) component. There were significant ethnic differences in patterns of activity. White children expended a significantly greater energy score (METPA of 21.7 +/- 2.9) than black children (METPA of 9.5 +/- 0.5) (P < 0.001). When children were divided into quartiles according to the amount and intensity of sport played, the most active white children (using METPA scores) had significantly higher whole body BMD and higher hip and spine BMC and BMD than less active children. White children in the highest MECHPA quartile also showed significantly higher whole body, hip, and spine BMC and BMD than those children in the lowest quartile. No association between exercise and bone mass of black children was found. In this population, PA has an osteogenic association with white children, but not black children, which may be explained by the lower levels of PA in the black children. Despite this, black children had significantly greater bone mass at the hip and spine (girls only) (P < 0.001) even after adjustment for body size. The role of exercise in increasing bone mass may become increasingly critical as a protective mechanism against osteoporosis in both ethnic groups, especially because the genetic benefit exhibited by black children to higher bone mass may be weakened with time, as environmental influences become stronger.

PTFE (Goretex) femoropopliteal reconstruction for limb salvage.

We present the results of the use of polytetrafluoroethylene (PTFE, Goretex) grafts for limb salvage in 20 cases of femoropopliteal or more distal arterial reconstruction. There appears to be no relationship between graft survival and 'run-off' or the overall disease state of the vessels. Cumulative graft patency was almost 50% at 6 months, which is in contrast with higher patency rates reported from other countries.