Barriers and Facilitators to Participation in Vigorous Lifestyle Physical Activity in Adults Aged 55-75 Years: A Scoping Review

Despite the well-known benefits of physical activity, less than half of adults aged 55-75 years participate in sufficient physical activity. Short bouts of vigorous intermittent lifestyle physical activity (VILPA) accumulated throughout the day can contribute toward the recommended volume of physical activity. A rich characterization of the barriers and facilitators to participation in VILPA is needed to develop targeted interventions. This scoping review aimed to identify barriers and facilitators to participation in different components of VILPA in adults aged 55-75 years, and to map barriers and facilitators to the Theoretical Domains Framework. Within the 18 eligible studies, the most prevalent barriers were related to a person's skills, environmental context, and social influences. Most facilitators were related to a person's goals, social influences, and environmental context. Interventions to promote VILPA should test the effectiveness of behavioral change measures related to the unique barriers and facilitators in this age group.

Physical Activity Levels and Sedentary Behavior of People Living With Mild Cognitive Impairment: A Cross-Sectional Study Using Thigh-Worn Accelerometers

Community-dwelling people with Mild Cognitive Impairment self-reporting not to be meeting recommended physical activity levels participated in this study to (a) determine compliance of wearing (thigh-worn) accelerometers, (b) describe physical activity levels and sedentary behavior, and (c) determine the validity of the Physical Activity Scale for the Elderly (PASE) compared with activPAL accelerometers. A total of 79 people had valid accelerometer data (median [interquartile range]: age, 71 [54-75] years). Compliance was 86.81%. Participants were sedentary for 10.6 hr per day and engaged in a median of 9 min per day of moderate-intensity physical activity. Fair correlations were found between the PASE and total stepping time per day (r = .35, p < .01), total number of steps per day (r = .36, p < .01), and number of steps in stepping activities completed for ≤1 min (r = .42, p < .01). The PASE and Standing time (r = .04, p = .724) and PASE and Sitting time (r = .04, p = .699) had little to no relationship. The use of thigh-worn accelerometers for this population is achievable. People with Mild Cognitive Impairment have high levels of sedentary behavior and minimal engagement in moderate-intensity physical activity. The PASE has fair, positive criterion validity with activity-based outcomes measured by activPAL accelerometers but not with sedentary behavior, which is high for this population.

Relationships between physical behaviour phenotypes of mothers in pregnancy and their offspring with child body composition

AIM

The aim of this study was to identify physical behaviour phenotypes in mothers in the first trimester and in their offspring at 24 months of age. The secondary aim was to examine relationships between mother and child behaviours with child body composition at age 24 months.

METHODS

Longitudinal secondary analysis of the Glowing cohort collected between 1 February 2011 and 22 August 2017 in Little Rock, Arkansas. Behaviours were measured using ankle-worn accelerometers in mothers during the first trimester and offspring at 24 months of age, including total activity, sleep, sedentary time and a novel variable of daily variation, patternicity. Child body fat was measured using quantitative nuclear magnetic resonance.

RESULTS

Three phenotypes were identified for mothers and children (n = 159 complete dyads). There were no relationships between mother and child phenotypes, but higher maternal patternicity was associated with higher child patternicity (0.2, 95% CI 0.1, 0.3, p = 0.001). There were no associations between mother or child phenotypes with child body composition, however higher child activity was associated with lower body fat (-0.01, 95% CI: -0.02, -0.001, p = 0.031).

CONCLUSION

Limited associations were found between mothers' pregnancy physical behaviours with child behaviours or child body composition at 24 months of age. Factors such as child diet or current parental physical activity may be better predictors of early childhood outcomes.

Health behaviour profiles in young Australian adults in relation to physical and mental health: The Raine Study

ISSUES ADDRESSED

We aimed to identify latent health behaviour profiles of young adults and examine their associations with physical and mental health outcomes. We also characterised the profiles by socio-demographic characteristics.

METHODS

Data were collected between 2012 and 2014. Participants (N = 476) were young adults (M age [SD] = 22.1 [.57] years) from Generation 2 of the Raine Study longitudinal cohort. Health behaviours were measured via ActiGraph GT3X waist monitors (physical activity, sedentary behaviour) and questionnaires (diet quality, alcohol, smoking and sleep). Physical and mental health were measured using clinical health assessments, blood biomarkers, and questionnaires. Latent Profile Analysis using Mplus (8.2) was employed to identify profiles.

RESULTS

Four latent profiles were identified: 'heavy drinkers with moderately unhealthy eating habits' (high takeaway foods; n = 135), 'unhealthy food abstainers' (low takeaway foods; n = 138), 'moderately sedentary alcohol abstainers' (n = 139) and 'physically active drinkers with unhealthy eating habits' (high takeaway foods and sugary drinks; n = 64). 'Physically active drinkers with unhealthy eating habits' had the poorest (physical and mental) health outcomes, yet the lowest insulin resistance. 'Unhealthy food abstainers' had the most favourable health outcomes (adiposity, health perceptions, blood pressure). Sex differed among the profiles.

CONCLUSIONS

The profiles identified among young adults are different to profiles with general adult populations. A novel finding was that 'physically active drinkers with unhealthy eating habits' had low insulin resistance. The findings also suggest that future interventions may need to be sex specific.

SO WHAT

Our findings suggest that health behaviour interventions for young adults should be targeted to distinct profile characteristics.

Physical Activity, Sedentary and Sleep Phenotypes in Women During the First Trimester of Pregnancy

OBJECTIVES

Patterns of physical behaviors including physical activity, sedentary time, and sleep are unknown during pregnancy, but are likely to influence health outcomes. The purpose was to first identify "physical behavior phenotypes" from accelerometer-measured physical behaviors in pregnant women during the first trimester and secondly, to explore the associations between the identified phenotypes with demographic variables and body-mass-index (BMI).

METHODS

Data were from the Glowing Study (gov ID: NCT01131117), collected between 2011 and 2017 with accelerometer-measured physical behaviors of women in their 12th week of pregnancy. Latent class analysis was used to identify patterns of total physical activity, sleep time, sedentary time, and variation in physical activity. Maternal Body-Mass-Index (BMI). BMI and sociodemographic characteristics were compared between physical behavior phenotypes.

RESULTS

A total of 212 pregnant women were included in the study (mean age 30.2 years (range 22.1 to 42.4), mean days wear 4.3 (SD 0.7)). Three physical behavior phenotypes were identified from the four physical behavior constructs: low sedentary and stable activity (n = 136, 64%), variable activity (n = 39, 18%), high sedentary and low sleep (n = 37, 17%). BMI, race, and education were significantly different between the three phenotypes, with the low sedentary and stable activity phenotype having the lowest BMI and a higher percentage of white and college educated women.

CONCLUSIONS FOR PRACTICE

Total physical activity and physical behavior phenotypes during the first trimester were associated with early-pregnancy BMI, race, and education. Future research should examine whether these physical behavior phenotypes are associated with maternal and child health outcomes.

Associations of physical activity and quality of life in parapneumonic effusion patients

Introduction

Little is known about activity behaviours and quality of life (QoL) of patients with parapneumonic pleural effusions (PPE) after hospital discharge. This study is a secondary analysis of a randomised trial (dexamethasone versus placebo) for hospitalised patients with PPE. We: 1) described the patients' activity behaviour patterns and QoL measured at discharge and at 30 days post-discharge; and 2) examined the association between activity behaviours and QoL scores.

Methods

Activity behaviour (7-day accelerometry; Actigraph GT3X+) and QoL (Medical Outcomes Study Short-Form 36) were assessed. Repeated measures analysis of covariance controlling for baseline values and a series of linear regression models were undertaken.

Results

36 out of 53 eligible participants completed accelerometry assessments. Despite modest increases in light physical activity (+7.5%) and some domains of QoL (>2 points) from discharge to 30 days post-discharge, patients had persistently high levels of sedentary behaviour (>65% of waking wear time) and poor QoL (≤50 out of 100 points) irrespective of treatment group (p=0.135-0.903). Increasing moderate-to-vigorous physical activity was associated with higher scores on most QoL domains (p=0.006-0.037). Linear regression indicates that a clinically important difference of 5 points in physical composite QoL score can be achieved by reallocating 16.1 min·day-1 of sedentary time to moderate-to-vigorous physical activity.

Conclusion

Patients with PPE had low levels of physical activity and QoL at discharge and 30 days post-discharge irrespective of treatment. Moderate-to-vigorous physical activity participation was associated with higher QoL scores. Increasing moderate-to-vigorous physical activity following discharge from the hospital may be associated with improvements in QoL.

Childhood sleep health and epigenetic age acceleration in late adolescence: Cross-sectional and longitudinal analyses

AIM

Investigate if childhood measures of sleep health are associated with epigenetic age acceleration in late adolescence.

METHODS

Parent-reported sleep trajectories from age 5 to 17, self-reported sleep problems at age 17, and six measures of epigenetic age acceleration at age 17 were studied in 1192 young Australians from the Raine Study Gen2.

RESULTS

There was no evidence for a relationship between the parent-reported sleep trajectories and epigenetic age acceleration (p ≥ 0.17). There was a positive cross-sectional relationship between self-reported sleep problem score and intrinsic epigenetic age acceleration at age 17 (b = 0.14, p = 0.04), which was attenuated after controlling for depressive symptom score at the same age (b = 0.08, p = 0.34). Follow-up analyses suggested this finding may represent greater overtiredness and intrinsic epigenetic age acceleration in adolescents with higher depressive symptoms.

CONCLUSION

There was no evidence for a relationship between self- or parent-reported sleep health and epigenetic age acceleration in late adolescence after adjusting for depressive symptoms. Mental health should be considered as a potential confounding variable in future research on sleep and epigenetic age acceleration, particularly if subjective measures of sleep are used.

Sedentary Behaviour, Physical Activity, and Their Associations with Health Outcomes at the Time of Diagnosis in People with Inoperable Lung Cancer

This study aimed to examine sedentary behaviour (SB), physical activity (PA) and their associations with health-related measures at the time of diagnosis in people with inoperable lung cancer. People newly diagnosed with inoperable lung cancer were invited to participate in the study and asked to wear an accelerometer for seven consecutive days. Variables analysed included time spent in SB, light intensity PA (LIPA) and moderate-to-vigorous intensity PA (MVPA). Daily steps were also recorded. Data on symptoms, health-related quality of life (HRQoL), hand grip force, comorbidities and lung function were collected. Of the 120 patients referred to the study, 89 (74%) consented to participate, and SB/PA data were available for 79 (age 71 ± 11 years; 29 females). Participants spent 71% of their waking time in SB, 28% in LIPA and 1% in MVPA. Regression models demonstrated that increased SB was associated with more symptoms of fatigue and dyspnoea (p ≤ 0.02 for both), poorer HRQoL (general health and physical component score; p ≤ 0.02 for all) and lower hand grip force. For PA variables, higher daily step count was associated with better scores in all health-related measures (p < 0.05 for all). LIPA was associated with more health-related outcomes than MVPA. These findings may guide future interventions in this population.

Demographic and psychosocial correlates of measurement error and reactivity bias in a four-day image-based mobile food record among adults with overweight and obesity

Improving dietary reporting among people living with obesity is challenging as many factors influence reporting accuracy. Reactive reporting may occur in response to dietary recording but little is known about how image-based methods influence this process. Using a 4-day image-based mobile food record (mFRTM), this study aimed to identify demographic and psychosocial correlates of measurement error and reactivity bias, among adults with BMI 25-40kg/m2. Participants (n=155, aged 18-65y) completed psychosocial questionnaires, and kept a 4-day mFRTM. Energy expenditure (EE) was estimated using ≥4 days of hip-worn accelerometer data, and energy intake (EI) was measured using mFRTM. Energy intake: energy expenditure ratios were calculated, and participants in the highest tertile were considered to have Plausible Intakes. Negative changes in EI according to regression slopes indicated Reactive Reporting. Mean EI was 72% (SD=21) of estimated EE. Among participants with Plausible Intakes, mean EI was 96% (SD=13) of estimated EE. Higher BMI (OR 0.81, 95%CI 0.72-0.92) and greater need for social approval (OR 0.31, 95% CI 0.10-0.96), were associated with lower likelihood of Plausible Intakes. Estimated EI decreased by 3% per day of recording (IQR -14%,6%) among all participants. The EI of Reactive Reporters (n=52) decreased by 17%/day (IQR -23%,-13%). A history of weight loss (>10kg) (OR 3.4, 95% CI 1.5-7.8), and higher percentage of daily energy from protein (OR 1.1, 95%CI 1.0-1.2) were associated with greater odds of Reactive Reporting. Identification of reactivity to measurement, as well as Plausible Intakes, is recommended in community-dwelling studies to highlight and address sources of bias.

Balance on the Brain: a randomised controlled trial evaluating the effect of a multimodal exercise programme on physical performance, falls, quality of life and cognition for people with mild cognitive impairment-study protocol

INTRODUCTION

Exercise and physical activity have been shown to improve cognition for people living with mild cognitive impairment (MCI). There is strong evidence for the benefits of aerobic exercise and medium evidence for participating in regular strength training for people with MCI. However, people living with MCI fall two times as often as those without cognitive impairment and the evidence is currently unknown as to whether balance training for people with MCI is beneficial, as has been demonstrated for older people without cognitive impairment. The aim of this study is to determine whether a balance-focused multimodal exercise intervention improves balance and reduces falls for people with MCI, compared with a control group receiving usual care.

METHODS AND ANALYSIS

This single blind randomised controlled trial (Balance on the Brain) will be offered to 396 people with MCI living in the community. The multimodal exercise intervention consists of two balance programmes and a walking programme to be delivered by physiotherapists over a 6-month intervention period. All participants will be followed up over 12 months (for the intervention group, this involves 6-month intervention and 6-month maintenance). The primary outcomes are (1) balance performance and (2) rate of falls. Physical performance, levels of physical activity and sedentary behaviour, quality of life and cognition are secondary outcomes. A health economic analysis will be undertaken to evaluate the cost-effectiveness of the intervention compared with usual care.

ETHICS AND DISSEMINATION

Ethics approval has been received from the South Metropolitan Health Service Human Research Ethics Committee (HREC), Curtin University HREC and the Western Australia Department of Health HREC; and approval has been received to obtain data for health costings from Services Australia. The results will be disseminated through peer-review publications, conference presentations and online platforms.

TRIAL REGISTRATION NUMBER

ACTRN12620001037998; Australian New Zealand Clinical Trials Registry (ANZCTR).

Developmental trajectories of sleep during childhood and adolescence are related to health in young adulthood

AIM

Sleep behaviour is correlated and causally related to physical and mental health. Limited longitudinal data exist on the associations of poor sleep behaviour in childhood and adolescence with adult health. Parent-reported sleep behaviours from 1993 participants of the Raine Study (at ages 5, 8, 10, 14, 17) were used to determine sleep trajectories (using latent class growth analysis).

METHODS

Measures of physical and mental health were compared between sleep trajectories using generalised linear models (at age 20).

RESULTS

Three sleep trajectories were identified as follows: 43% of participants belonged to a trajectory with 'consistently minimal' sleep problems, 49% showed some 'declining' in reporting of sleep problems incidence and 8% had 'persistent' sleep problems. Participants in the 'consistently minimal' trajectory had better physical and mental health outcomes at age 20 compared to those in the 'declining' and 'persistent' trajectories. For example, 'consistently minimal' participants had significantly lower body fat percentage (mean difference: -3.89% (95% CI: -7.41 to -0.38)) and a higher (better) SF-12 mental component score (mean difference: 4.78 (95% CI: 2.35-7.21)) compared to participants in the 'persistent' trajectory.

CONCLUSION

Poor sleep behaviour across childhood and adolescent years is related to poorer physical and mental health in young adulthood.

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.

Cross-sectional and longitudinal comparisons of self-reported and device-assessed physical activity and sedentary behaviour

OBJECTIVES

To examine the longitudinal associations and differences between self-reported and device-assessed physical activity (PA) and sedentary behaviour (SB), using a multifaceted statistical approach.

DESIGN

Longitudinal measurement burst.

METHODS

In total, 52 university students (78% female) aged 18-38 years (mean=21.94±4.57 years) participated. The study consisted of three blocks of six days of measurement, during which participants wore an accelerometer on their wrist for the entire block, and self-reported their PA over the 6 days at the end of each block.

RESULTS

Meaningful latent differences between methods were observed for moderate PA and SB across all three assessment periods, such that participants underreported the time spent in each activity. Bland-Altman plots revealed a positive mean difference for vigorous PA, with over-reporting increasing as mean levels increased. Negative mean differences were observed for all other intensities. Underreporting of moderate PA increased as the mean level increased, whereas for light PA and SB, underreporting decreased at high levels. Repeated measures correlations revealed a meaningful association for vigorous PA only, suggesting that as self-reported minutes increase so too do device-measured minutes.

CONCLUSIONS

We found evidence of cross-sectional and longitudinal differences and weak associations between self-reported and device-assessed PA and SB. Future work is needed to enhance the quality of self-reported methods to assess PA and SB (e.g., face and content validity), and consider improvements to the processing of device-based data.

Improvements in Objectively Measured Activity Behaviors Do Not Correlate With Improvements in Patient-Reported Outcome Measures Following Total Knee Arthroplasty

BACKGROUND

Activity monitors have added a new dimension to our ability to objectively measure physical activity in patients undergoing total knee arthroplasty (TKA). The aim of the study is to assess whether changes in the time spent sitting, standing, and stepping were associated with changes in patient-reported outcome measures (PROMs) before and after TKA.

METHODS

Valid activPAL data (>3 days) and PROMs were obtained from 49 men and women (mean [SD] age, 62.8 [8.6] years; body mass index, 33.8 [7.1] kg/m²) who underwent primary TKA, before and at 6 weeks or 6 months after surgery. Patient-reported symptoms of pain, stiffness, and knee function were obtained using the Knee injury and Osteoarthritis Outcome Score and Oxford Knee Score questionnaires.

RESULTS

Mean (SD) Knee injury and Osteoarthritis Outcome Score (80.1 [16.3] to 41.6 [6.5], P < .001) and Oxford Knee Score (12.0 [9.8] to 17.7 [22.8], P < .001) scores improved 6 months after TKA. Walking time (mean [95% confidence interval]; min/d) increased from before (79 [67-91]) to 6 months after TKA (101 [88-114], P = .006). Standing time (318 [276-360] to 321 [291-352], P = .782) and sitting time (545 [491-599] to 509.0 [459.7-558.3], P = .285) did not change from before to 6 months after TKA. Participants took more steps (2559 [2128-2991] to 3515 [2983-4048] steps/day, P = .001) and accumulated more steps (31 [30-34] to 34 [33-35] steps/min, P < .001) after TKA compared to before. There were no associations between changes in activity behaviors and changes in PROMs (P > .05).

CONCLUSION

Despite improvements in self-reported knee pain and functional ability, these changes do not correlate with improvements in objectively measured light-intensity and sedentary activity behaviors.

A Review of Accelerometer-based Activity Monitoring in Cancer Survivorship Research

BACKGROUND

In the cancer survivorship context, physical activity and sedentary behavior have been measured using different methods.

PURPOSE

To conduct a narrative review of published research in cancer survivor populations to summarize the quality and identify gaps in reporting on accelerometer data collection, data processing, and outcome measures in cancer survivors.

METHODS

An initial PubMed® search of articles published in English was conducted in January 2017, and a final search was conducted in May 2017. Variables extracted included study characteristics, methods for accelerometry data collection (e.g., device used), data processing (e.g., cut points used), and data reporting (e.g., time spent in different activity intensities).

RESULTS

A total of 46 articles were eligible for inclusion in the review. The majority of studies (34 of 46) targeted a single cancer group and 18 of these 34 studies were in survivors of breast cancer. Half (54%) of the studies used an ActiGraph® accelerometer. Methods of accelerometer data processing varied across studies. Definitions of non-wear time, vectors used during processing, and filters applied during processing were reported by 51%, 60%, and 8% of studies, respectively. Most studies reported moderate and vigorous physical activity (78%), 50% reported sedentary time, and 43% reported light-intensity activity. Cut points to categorize these activities varied between studies.

CONCLUSIONS

This narrative review highlights inconsistency in the methods used to collect, process, and report accelerometry data across cancer survivor studies. Accelerometry has potential to add detailed knowledge of the levels and patterns of physical activities and sedentary behaviors across the cancer spectrum. Recommendations are made to improve data processing and reporting methods to maximize the scientific validity of future accelerometer research in this field.

Improving Nutrition and Activity Behaviors Using Digital Technology and Tailored Feedback: Protocol for the Tailored Diet and Activity (ToDAy) Randomized Controlled Trial

BACKGROUND

Excess weight is a major risk factor for chronic diseases. In Australia, over 60% of adults are overweight or obese. The overconsumption of energy-dense nutrient-poor (EDNP) foods and low physical activity (PA) levels are key factors contributing to population obesity. New cost-effective approaches to improve population diet and PA behaviors are needed.

OBJECTIVE

This 1-year randomized controlled trial (6-month intervention and 6-month follow-up) aims to investigate whether a tailored intervention using mobile technology can improve diet and PA behaviors leading to weight loss in adults (aged 18-65 years) who are overweight or obese and recruited through a social marketing campaign (LiveLighter).

METHODS

All eligible participants will provide data on demographics and lifestyle behaviors online at baseline, 6 months, and 12 months. Using two-stage randomization, participants will be allocated into one of three conditions (n=200 per group): tailored feedback delivered via email at seven time points, informed by objective dietary (mobile food record app) and activity (wearable activity monitor) assessment; active control receiving no tailored feedback, but undergoing the same objective assessments as tailored feedback; and online control receiving no tailored feedback or objective assessments. Primary outcome measures at 6 and 12 months are changes in body mass, EDNP food and beverage consumption, and daily moderate-to-vigorous PA (measured via accelerometry). Secondary outcomes include change in fruit and vegetable consumption, daily sedentary behaviors, and cost effectiveness.

RESULTS

Enrolment commenced in August 2017. Primary outcomes at 12 months will be available for analysis from September 2019.

CONCLUSIONS

Tailored email feedback provided to individuals may deliver a cost-effective strategy to overcome existing barriers to improving diet and PA. If found to be successful and cost effective, upscaling this intervention for inclusion in larger-scale interventions is highly feasible.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12617000554369; https://www.anzctr.org.au /Trial/Registration/TrialReview.aspx?id=371325&isReview=true.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/12782.

Organized Sport Participation From Childhood to Adolescence Is Associated With Bone Mass in Young Adults From the Raine Study

There is a critical need for longitudinal cohort studies to consider the association of the cumulative exposure of physical activity during childhood and adolescence and bone mass. The aim of this study was to investigate the relationship between organized sports trajectories (that capture distinct and potentially meaningful patterns over critical developmental periods) and bone mass at age 20 years. Participation in organized sport was recorded by parental report at ages 5, 8, 10, 14, and 17 years in 984 offspring (48% female) of a pregnancy cohort (Raine Study). Latent class analysis identified three trajectory classes in each sex. In females, these were "consistent sport participators" (48%), "dropouts" (34%), and "non-participators" (18%); in males, "consistent sport participators" (55%), "dropouts" (37%), and "sport joiners" (8%). Whole-body bone mineral content (BMC) at age 20 years was assessed by dual-energy X-ray absorptiometry (DXA). At age 20 years, after adjustment for covariates measured at age 20 years, including height, lean mass, physical activity, calcium intake, serum 25-hydroxyvitamin D, alcohol, and smoking, males who were "consistent sport participators" had significantly greater whole-body and leg BMC than those who dropped out of sport (p < 0.001), whereas males who joined sports had significantly greater leg BMC than those who dropped out of sport (p = 0.002). Females in the "consistent sport participator" trajectory had significantly greater leg BMC than those who dropped out (all p = 0.004). Participation in organized sport during childhood and adolescence is associated with bone mass at age 20 years. Because attainment of optimal peak bone mass in young adulthood is protective against osteoporosis in later life, this may have long-term skeletal benefits. © 2018 American Society for Bone and Mineral Research.

Early life factors are associated with trajectories of consistent organized sport participation over childhood and adolescence: Longitudinal analysis from the Raine Study

OBJECTIVES

The purpose of this study was to identify early life factors that were associated with childhood and adolescent organized sport participation trajectories.

DESIGN

Participants were in the Raine Study, a pregnancy cohort in Western Australia recruited from 1989 to 1991.

METHODS

Three organized sport trajectories over ages 5-17years were previously identified for girls (n=824: consistent participators, dropouts, and non-participators in sport) and boys (n=855: consistent participators, dropouts, joiners - those who joined sport in adolescence). Physical, psychological and social factors were measured from birth to age 5.

RESULTS

For girls and boys, children who were breastfed, were taller, did not have behavior problems, and attended childcare were more likely to consistently participate. Girls who had a previous injury (Relative risk ratio 1.55: 95% confidence interval 1.05, 2.29 vs never been injured) or who had parents who had worries about their child's health (1.56: 1.00, 2.42 vs no worries) were more likely to be in the dropout trajectory. Boys born preterm (2.00, 2.06, 3.76 vs full-term), did not have a previous injury (0.72, 0.53, 0.97 those with injury vs never been injured), had more difficult temperament (1.63, 1.02, 2.60 vs easy temperament), and higher family dysfunction (1.49, 1.06, 2.08) were more likely to be in the dropout trajectory.

CONCLUSIONS

Early life factors were associated with membership in sport trajectories. Physical, psychological, and social factors may serve as early warning signs for parents and practitioners that children may be at higher risk of dropping out of sports.

Does a Classroom Standing Desk Intervention Modify Standing and Sitting Behaviour and Musculoskeletal Symptoms during School Time and Physical Activity during Waking Time?

Children are increasingly spending more time sedentary at school and during leisure time. This study examined the effects of a standing desk intervention in a classroom on children's standing and sitting time at school, sedentary and physical activity levels throughout the day (waking hours), and musculoskeletal discomfort. A within-subjects crossover study design was used. Participants used either a standing desk or traditional seated desk for 21 days before swapping desks for another 21 days. Accelerometry and musculoskeletal discomfort data were collected during the last seven days of each 21-day period. Mixed models were used to analyse accelerometry data. Zero-inflated regression models and logistic regression models were used to analyse discomfort data. Forty-seven male students (aged 10⁻11 years) participated in the study. Standing time was 21 min/school day higher (p < 0.001) and sitting time was 24 min/school day lower (p = 0.003) when standing desks were used. No significant differences were found in sedentary and physical activity time during waking hours between the standing desk and seated desk conditions. Students were less likely to report musculoskeletal discomfort in the neck, shoulder, elbows and lower back when using standing desks (OR 0.52⁻0.74). Standing desks significantly increased classroom standing time and decreased musculoskeletal discomfort reports but had no overall effect on daily physical activity levels. Schools should consider moving towards classrooms enabling a variety of postures to potentially improve the long-term health of children.

Correlates of physical activity and sedentary time in young adults: the Western Australian Pregnancy Cohort (Raine) Study

Background

The socioecological model proposes a wide array of factors that influence behaviours. There is a need to understand salient correlates of these activity behaviours in a specific population. However, few studies identified socio-demographic, behavioural, physical, and psychological correlates of objectively-assessed physical activity and sedentary time in young adults.

Methods

This was a cross-sectional analysis of participants in the Raine Study (a pregnancy cohort started in 1989). Australian young adults (mean 22.1 years ± SD 0.6) wore Actigraph GT3X+ accelerometers on the hip 24 h/day for seven days to assess moderate-to-vigorous physical activity (MVPA) and sedentary time (n = 256 women, n = 219 men). Potential correlates were assessed via clinical assessment and questionnaire and included socio-demographic variables (ethnicity, relationship status, work/study status, education, mothers education), health behaviours (food intake, alcohol consumption, smoking status, sleep quality), and physical and psychological health aspects (anthropometrics, diagnosed disorders, mental health, cognitive performance). Backwards elimination (p < 0.2 for retention) with mixed model regressions were used and the gender-stratified analyses were adjusted for demographic variables, waking wear time and number of valid days.

Results

Increased time spent in MVPA was associated with: being single (IRR 1.44 vs in a relationship living together, 95%CI: 1.17, 1.77, p = .001) in women; and better sleep quality in men (lower scores better IRR 0.97, 95%CI: 0.93, 1.00). Less time spent sedentary was associated with: lower mother’s education (− 32.1 min/day, 95%CI -52.9, 11.3, p = 0.002 for having mother with no university degree vs at least a baccalaureate degree) and smoking (− 44.3 min/day, 95%CI: - 72.8, − 15.9, p = .0002) for women; lower education status (− 32.1 min/day, 95%CI: -59.5, − 4.8, p = 0.021 for having no university degree vs at least a baccalaureate degree) and lower depression scores in men (− 2.0, 95%CI: - 3.5, − 0.4, p = 0.014); more alcoholic drinks per week for women (− 1.9 min/day, 95%CI: -3.1, − 0.6, p = 0.003) and men (− 1.0, 95%CI: -1.8, − 0.3, p = 0.007).

Conclusions

Less desirable correlates were associated with positive levels of activity in young Australian adult women and men. Interventions to increase MVPA and decrease sedentary activity in young adults need to specifically consider the life stage of young adults.

Electronic supplementary material

The online version of this article (10.1186/s12889-018-5705-1) contains supplementary material, which is available to authorized users.

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.

The effect of loading and ethnicity on annual changes in cortical bone of the radius and tibia in pre-pubertal children

BACKGROUND

It is unclear what effect habitual physical activity or ethnicity has on annual changes in bone size and strength in pre-pubertal children.

AIM

To determine whether the annual relative change in bone size and strength differed between high and low bone loaders and also between black and white pre-pubertal children.

SUBJECTS AND METHODS

Peripheral quantitative computed tomography (pQCT) scans of the 65% radius and tibia were completed on 41 black and white children (15 boys, 26 girls) between the ages of 8-11 years, at baseline and 1 year later. Children were categorised into either a high or low bone loading group from a peak bone strain score obtained from a bone-specific physical activity questionnaire. Total area (ToA), cortical area (CoA), cortical density (CoD), strength-strain index (SSI), periosteal circumference (PC), endosteal circumference (EC) and cortical thickness (CT) were assessed.

RESULTS

There was no difference in annual relative change in radial or tibia bone size and strength between the low and high bone loaders. Black children had a greater annual relative change in CoD (p = 0.03) and SSI (p = 0.05) compared to the white children.

CONCLUSION

Children who performed high bone loading activities over a 1-year period had similar bone growth to children who did low bone loading activities over the same period. Rapid maturational growth over this period may have resulted in bone adapting to the strains of habitual physical activity placed on it. Black children may have greater tibial bone strength compared to white children due to a greater annual increase in cortical density.

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. © 2016 American Society for Bone and Mineral Research.

Validity of an automated algorithm to identify waking and in-bed wear time in hip-worn accelerometer data collected with a 24 h wear protocol in young adults

Researchers are increasingly using 24 h accelerometer wear protocols. No automated method has been published that accurately distinguishes 'waking' wear time from other data ('in-bed', non-wear, invalid days) in young adults. This study examined the validity of an automated algorithm developed to achieve this for hip-worn Actigraph GT3X  +  60 s epoch data. We compared the algorithm against a referent method ('into-bed' and 'out-of-bed' times visually identified by two independent raters) and benchmarked against two published algorithms. All methods used the same non-wear rules. The development sample (n  =  11) and validation sample (n  =  95) were Australian young adults from the Raine pregnancy cohort (54% female), all aged approximately 22 years. The agreement with Rater 1 in each minute's classification (yes/no) of waking wear time was examined as kappa (κ), limited to valid days (⩾10 h waking wear time per day) according to the algorithm and Rater 1. Bland-Altman methods assessed agreement in daily totals of waking wear and in-bed wear time. Excellent agreement (κ  >  0.75) was obtained between the raters for 80% of participants (median κ  =  0.94). The algorithm showed excellent agreement with Rater 1 (κ  >  0.75) for 89% of participants and poor agreement (κ  <  0.40) for 1%. In this sample, the algorithm (median κ  =  0.86) performed better than algorithms validated in children (median κ  =  0.77) and adolescents (median κ  =  0.66). The mean difference (95% limits of agreement) between Rater 1 and the algorithm was 7 (-220, 234) min d^-1 for waking wear time on valid days and  -41 (-309, 228) min d^-1 for in-bed wear time. In this population, the automated algorithm's validity for identifying waking wear time was mostly good, not worse than inter-rater agreement, and better than the evaluated published alternatives. However, the algorithm requires improvement to better identify in-bed wear time.

Radial and tibial bone indices in athletes participating in different endurance sports: a pQCT study

Low magnitude bone-loading sports may benefit bone structure and strength in the exercised limbs. This study compared peripheral quantitative computed tomography measures of radial and tibial diaphyseal strength (strength-strain index, SSI), structure (total area (ToA) and cortical area (CoA), density (CoD) and thickness (CT), and circumferences), muscle cross-sectional area (MCSA) and strength (one-repetition maximum, 1-RM) in male endurance athletes taking part in (i) non-weight-bearing and non-impact sports: swimmers (SWIM, n = 13) and road cyclists (RC, n = 10), (ii) non-weight-bearing, impact sport: mountain bikers (MB, n = 10), (iii) weight bearing and impact sport: runners (RUN, n = 9). All athlete groups were also compared to sedentary controls (CON, n = 10). Arm MCSA, 1-RM and radial bone size and strength tended to be greater in SWIM than CON and/or RC (ToA, %difference  ± 95%CI, SWIM-CON: 14.6% ± 12.7%; SWIM-RC: 12.9% ± 10.7%) but not different to MB and RUN. RUN had bigger tibial CoA than CON, SWIM and RC (CoA, RUN-CON: 12.1% ± 10.7%; RUN-SWIM: 10.9% ± 9.4%; RUN-RC: 15.8% ± 9.5%) without marked changes in tibial strength indices, lower-limb MCSA or 1-RM. Both MB and RC failed to display any difference in tibial indices, lower-limb MCSA and 1-RM compared to CON. In swimmers, the bone structure and strength of the primary exercised limbs, the arms, is greater than controls and road cyclists. Conversely, although runners experience impact and weight-bearing loading, tibial structure is greater without a substantial difference in tibial strength compared to controls and non-impact sports. Failure to observe a difference in tibial indices in MB and RC compared to controls is unexpected.

Rationale, design and protocol of a longitudinal study assessing the effect of total knee arthroplasty on habitual physical activity and sedentary behavior in adults with osteoarthritis

Background

Physical activity levels are decreased and sedentary behaviour levels are increased in patients with knee osteoarthritis (OA). However, previous studies have shown that following total knee arthroplasty (TKA), objectively measured physical activity levels do not change compared to before the surgery. Very few studies have objectively assessed sedentary behaviour following TKA. This study aims to assess patterns of objective habitual physical activity and sedentary behaviour in patients with knee OA and to determine whether these change following TKA.

Methods

Patients diagnosed with knee osteoarthritis and scheduled for unilateral primary total knee arthroplasty will be recruited from the Orthopaedic Division at the Charlotte Maxeke Johannesburg Academic Hospital. Eligible participants will have assessments completed one week before the scheduled arthroplasty, six weeks, and six months post-operatively. The primary outcomes are habitual physical activity and sedentary behaviour which will be measured using accelerometry (Actigraph GTX3+ and activPal monitors) at the specific time points. The secondary outcomes will be improvements in osteoarthritis-specific quality of life measures using the following questionnaires: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee injury and Osteoarthritis Outcome Score (KOOS), Oxford Knee Score (OKS), Knee Society Clinical Rating System (KSS), UCLA activity index; subjective pain scores, and self reported sleep quality.

Discussion

The present study will contribute to the field of musculoskeletal health by providing a rich detailed description of the patterns of accumulation of physical activity and sedentary behaviour in patients with knee OA. These data will contribute to existing knowledge using an objective measurement for the assessment of functional ability after total knee arthroplasty. Although studies have used accelerometry to measure physical activity in knee OA patients, the data provided thus far have not delved into the detailed patterns of how and when physical activity is accumulated before and after TKA. Accurate assessment of physical activity is important for physical activity interventions that target special populations.

Trial registration

NCT02675062 (4 February 2016).

In Patients with Established RA, Positive Effects of a Randomised Three Month WBV Therapy Intervention on Functional Ability, Bone Mineral Density and Fatigue Are Sustained for up to Six Months

Functional ability is often impaired for people with rheumatoid arthritis (RA), rendering these patients highly sedentary. Additionally, patients with RA often take medication known to negatively affect bone mass. Thus improving functional ability and bone health in this group of patients is important. The aim of this study was to investigate the effects of whole body vibration (WBV) therapy in patients with stable, established RA. Thirty one females with RA were randomly assigned to a control group (CON, n = 15) who continued with their normal activities or a WBV group (n = 16) who underwent a three month WBV therapy intervention, consisting of 15 minutes of intermittent vibration, performed twice per week. Patients were assessed at baseline, three months, and three months post intervention for functional ability using the modified Health Assessment Questionnaire; for RA disease activity using the Clinical Disease Activity Index, for quality of life using self-report fatigue and pain scores; for physical activity profiles using accelerometry, and for BMD and body composition using DXA. Patients in both groups were matched for all variables at baseline. After the intervention period, functional ability was significantly improved in the WBV group (1.22(0.19) to 0.92(0.19), p = 0.02). Hip BMD was significantly reduced in the CON group (0.97(0.05) to 0.84(0.05) g.cm(-2), p = 0.01), while no decreases were seen in the WBV group (1.01(0.05) to 0.94(0.05) g.cm(-2), p = 0.50). Despite no change in RA disease activity in either group at either follow up, fatigue levels were improved in the WBV group (4.4(0.63) to 1.1(0.65), yet remained unchanged in the CON group at both follow ups (p = 0.01). Ten minute bouts of light to moderate physical activity were significantly reduced in the CON group after the intervention (2.8(0.61) to 1.8(0.64) bouts per day, p = 0.01), and were preserved in the WBV group (3.1(0.59) to 3.0(0.61) bouts per day, p = 0.70). Intermittent WBV shows promise for sustained improvements in functional ability, for attenuating loss of bone mass at the hip, as well as for decreasing fatigue in patients with established RA.

TRIAL REGISTRATION

Pan African Clinical Trials Registry PACTR201405000823418.

Objectively measured patterns of sedentary time and physical activity in young adults of the Raine study cohort

Background

To provide a detailed description of young adults’ sedentary time and physical activity.

Methods

384 young women and 389 young men aged 22.1 ± 0.6 years, all participants in the 22 year old follow-up of the Raine Study pregnancy cohort, wore Actigraph GT3X+ monitors on the hip for 24 h/day over a one-week period for at least one ‘valid’ day (≥10 h of waking wear time). Each minute epoch was classified as sedentary, light, moderate or vigorous intensity using 100 count and Freedson cut-points. Mixed models assessed hourly and daily variation; t-tests assessed gender differences.

Results

The average (mean ± SD) waking wear time was 15.0 ± 1.6 h/day, of which 61.4 ± 10.1 % was spent sedentary, 34.6 ± 9.1 % in light-, 3.7 ± 5.3 % in moderate- and, 0.3 ± 0.6 % in vigorous-intensity activity. Average time spent in moderate to vigorous activity (MVPA) was 36.2 ± 27.5 min/day. Relative to men, women had higher sedentary time, but also higher vigorous activity time. The ‘usual’ bout duration of sedentary time was 11.8 ± 4.5 min in women and 11.7 ± 5.2 min in men. By contrast, other activities were accumulated in shorter bout durations. There was large variation by hour of the day and by day of the week in both sedentary time and MVPA. Evenings and Sundays through Wednesdays tended to be particularly sedentary and/or inactive.

Conclusion

For these young adults, much of the waking day was spent sedentary and many participants were physically inactive (low levels of MVPA). We provide novel evidence on the time for which activities were performed and on the time periods when young adults were more sedentary and/or less active. With high sedentary time and low MVPA, young adults may be at risk for the life-course sequelae of these behaviours.

Electronic supplementary material

The online version of this article (doi:10.1186/s12966-016-0363-0) contains supplementary material, which is available to authorized users.

Multiple components of fitness improved among overweight and obese adolescents following a community-based lifestyle intervention

Fitness is an important component of health, and obese adolescents regularly have poor fitness. Unfortunately, few have assessed the impact of community-based lifestyle interventions on multiple components of fitness. The purpose of this study was to assess the impact of participation in a community-based intervention involving adolescents and parents on multiple components of fitness of obese adolescents. In a within-subject, waitlist controlled clinical trial with 12 months follow-up in Western Australia, participants (n = 56) completed multiple fitness measures at baseline, immediately prior to beginning an 8-week intervention and at 3, 6 and 12 months during a maintenance period. Performance on the shuttle walk was improved immediately post-intervention (increase of 42.8 m, 95% CI: 7.5, 78.2) and at 12 months post-intervention (increase of 44.6 m, 95% CI: 1.3, 87.8) compared with pre-intervention. Muscle performance of quadriceps and deltoids were improved post-intervention (increase of 1.1 (95% CI: 0.1, 2.1) kg · F and 1.0 (0.02, 2.1) kg · F, respectively) and all muscle performance measures were improved at 12 months following the intervention. There were no changes in waist circumference. A community-based lifestyle programme such as Curtin University's Activity, Food and Attitudes Program (CAFAP) may be a viable strategy for improving fitness in overweight adolescents.

A three month controlled intervention of intermittent whole body vibration designed to improve functional ability and attenuate bone loss in patients with rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a chronic autoimmune condition that results in pain and disability. Patients with RA have a decreased functional ability and are forced into a sedentary lifestyle and as such, these patients often become predisposed to poor bone health. Patients with RA may also experience a decreased health related quality of life (HRQoL) due to their disease. Whole body vibration (WBV) is a form of exercise that stimulates bone loading through forced oscillation. WBV has also been shown to decrease pain and fatigue in other rheumatic diseases, as well as to increase muscle strength. This paper reports on the development of a semi randomised controlled clinical trial to assess the impact of a WBV intervention aiming to improve functional ability, attenuate bone loss, and improve habitual physical activity levels in patients with RA.

Methods/Design

This study is a semi randomised, controlled trial consisting of a cohort of patients with established RA assigned to either a WBV group or a CON (control) group. Patients in the WBV group will undergo three months of twice weekly intermittent WBV sessions, while the CON group will receive standard care and continue with normal daily activities. All patients will be assessed at baseline, following the three month intervention, and six months post intervention. Main outcomes will be an improvement in functional ability as assessed by the HAQ. Secondary outcomes are attenuation of loss of bone mineral density (BMD) at the hip and changes in RA disease activity, HRQoL, habitual physical activity levels and body composition.

Discussion

This study will provide important information regarding the effects of WBV on functional ability and BMD in patients with RA, as well as novel data regarding the potential changes in objective habitual physical activity patterns that may occur following the intervention. The sustainability of the intervention will also be assessed.

Trial registration

PACTR201405000823418 (19/05/2014).

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-403) contains supplementary material, which is available to authorized users.

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.

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 cohort's 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.

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.