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Background: Targeting sedentary time post exacerbation may be more relevant than targeting structured exercise for individuals with chronic obstructive pulmonary disease. Focusing interventions on sitting less and moving more after an exacerbation may act as a stepping stone to increase uptake to pulmonary rehabilitation., Objective: The aim of this paper was to conduct a randomized trial examining trial feasibility and the acceptability of an education and self-monitoring intervention using wearable technology to reduce sedentary behavior for individuals with chronic obstructive pulmonary disease admitted to hospital for an acute exacerbation., Methods: Participants were recruited and randomized in hospital into 3 groups, with the intervention lasting 2 weeks post discharge. The Education group received verbal and written information about reducing their time in sedentary behavior, sitting face-to-face with a study researcher. The Education+Feedback group received the same education component along with real-time feedback on their sitting time, stand-ups, and steps at home through a waist-worn inclinometer linked to an app. Patients were shown how to use the technology by the same study researcher. The inclinometer also provided vibration prompts to encourage movement at patient-defined intervals of time. Patients and health care professionals involved in chronic obstructive pulmonary disease exacerbation care were interviewed to investigate trial feasibility and acceptability of trial design and methods. Main quantitative outcomes of trial feasibility were eligibility, uptake, and retention, and for acceptability, were behavioral responses to the vibration prompts., Results: In total, 111 patients were approached with 33 patients recruited (11 Control, 10 Education, and 12 Education+Feedback). Retention at 2-week follow-up was 52% (17/33; n=6 for Control, n=3 for Education, and n=8 for Education+Feedback). No study-related adverse events occurred. Collectively, patients responded to 106 out of 325 vibration prompts from the waist-worn inclinometer (32.62%). Within 5 min of the prompt, 41% of responses occurred, with patients standing for a mean 1.4 (SD 0.8) min and walking for 0.4 (SD 0.3) min (21, SD 11, steps). Interviews indicated that being unwell and overwhelmed after an exacerbation was the main reason for not engaging with the intervention. Health care staff considered reducing sedentary behavior potentially attractive for patients but suggested starting the intervention as an inpatient., Conclusions: Although the data support that it was feasible to conduct the trial, modifications are needed to improve participant retention. The intervention was acceptable to most patients and health care professionals., Trial Registration: International Standard Randomized Controlled Trial Number (ISRCTN) 13790881; http://www.isrctn.com/ISRCTN13790881 (Archived by WebCite at http://www.webcitation.org/6xmnRGjFf)., (©Mark W Orme, Amie E Weedon, Paula M Saukko, Dale W Esliger, Mike D Morgan, Michael C Steiner, John W Downey, Lauren B Sherar, Sally J Singh. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 11.04.2018.)

Introduction: Mass-media campaigns such as, "Change4Life' in the UK and "get active America" in the US, promote physical activity (PA) recommendations of at least 150 min/week of moderate-to-vigorous PA (MVPA). We investigated whether different messages used in MVPA campaigns were associated with intention to engage in more MVPA., Materials and Methods: Theory of planned behavior (TPB) constructs; subjective norms, affective attitudes, instrumental attitudes and perceived behavioral control (PBC) were applied to explain the associations between campaign messages and intentions to engage in more MVPA., Results: A total of 1412 UK adults completed an online survey on MVPA and TPB. The sample was 70% female and 93% white with 23% reporting meeting PA guidelines. Participants received one of three messages: A walking message either with or without the 150 min/week threshold (WalkT; WalkNT); a physiological description of MVPA with the 150 min/week threshold (PhysT). ANCOVA examined group differences in intention. Path analysis evaluated mediation by TPB variables. ANCOVA identified lower intentions to increase MVPA in group PhysT relative to WalkT and WalkNT (P < 0.001). PBC mediated this relationship in WalkT (β = 0.014, 95% confidence interval [CI] = 0.004-0.028) whereas affective attitudes mediated this relationship in WalkNT (β = 0.059, 95% CI = 0.006-0.113)., Conclusions: Campaigns promoting MVPA guidelines need to choose their messages carefully. Messages which exemplified MVPA through walking were associated with higher intentions to increase MVPA than messages using a physiological description. Further, PBC was enhanced when the 150 min/week threshold was promoted alongside the walking exemplar. Future exemplars should be investigated to inform adults how to meet MVPA guidelines.

Objective: Adequate nutrition is paramount for premature infants. Longitudinal information is scant on the effects of early nutrition and later growth. The purpose of this study was to determine the influence of early energy and protein provision in premature infants on adolescent body composition and blood pressure., Methods: In 2007-2008 we obtained data from 36 male (12.3±1.7 years) and 25 female (11.5±1.8 years) adolescents born preterm at <34 weeks gestation (range 23-34 weeks) between October 1st 1989 and December 31st 1995 (birth weight <1850 g). The adolescents were divided into groups depending on infant intake mode (enteral vs parenteral), energy provision (<70 kcal/kg/d and ≥70 kcal/kg/d) and protein provision (>2.5 g/kg/d for ≥5 days and >2.5 g/kg/d for <5 days) during the first 14 days of life., Results: After controlling for birth weight and biological maturity, adolescents who received ≥70 kcal/kg/d during infancy were significantly taller (163±11 cm vs. 156±11 cm) and heavier (58±16 kg vs. 49±16 kg) than adolescents who received <70 kcal/kg/d. There were no significant differences in systolic and diastolic BP and total percent body fat between the two groups., Conclusions: Our data suggests that higher infant energy provision appears to be related to adolescent size, it does not appear to contribute to adverse risk factors such as higher systolic BP or increased body fat.

Context: Sparse data exist on the combined associations between physical activity and sedentary time with cardiometabolic risk factors in healthy children., Objective: To examine the independent and combined associations between objectively measured time in moderate- to vigorous-intensity physical activity (MVPA) and sedentary time with cardiometabolic risk factors., Design, Setting, and Participants: Pooled data from 14 studies between 1998 and 2009 comprising 20 871 children (aged 4-18 years) from the International Children's Accelerometry Database. Time spent in MVPA and sedentary time were measured using accelerometry after reanalyzing raw data. The independent associations between time in MVPA and sedentary time, with outcomes, were examined using meta-analysis. Participants were stratified by tertiles of MVPA and sedentary time., Main Outcome Measures: Waist circumference, systolic blood pressure, fasting triglycerides, high-density lipoprotein cholesterol, and insulin., Results: Times (mean [SD] min/d) accumulated by children in MVPA and being sedentary were 30 (21) and 354 (96), respectively. Time in MVPA was significantly associated with all cardiometabolic outcomes independent of sex, age, monitor wear time, time spent sedentary, and waist circumference (when not the outcome). Sedentary time was not associated with any outcome independent of time in MVPA. In the combined analyses, higher levels of MVPA were associated with better cardiometabolic risk factors across tertiles of sedentary time. The differences in outcomes between higher and lower MVPA were greater with lower sedentary time. Mean differences in waist circumference between the bottom and top tertiles of MVPA were 5.6 cm (95% CI, 4.8-6.4 cm) for high sedentary time and 3.6 cm (95% CI, 2.8-4.3 cm) for low sedentary time. Mean differences in systolic blood pressure for high and low sedentary time were 0.7 mm Hg (95% CI, -0.07 to 1.6) and 2.5 mm Hg (95% CI, 1.7-3.3), and for high-density lipoprotein cholesterol, differences were -2.6 mg/dL (95% CI, -1.4 to -3.9) and -4.5 mg/dL (95% CI, -3.3 to -5.6), respectively. Geometric mean differences for insulin and triglycerides showed similar variation. Those in the top tertile of MVPA accumulated more than 35 minutes per day in this intensity level compared with fewer than 18 minutes per day for those in the bottom tertile. In prospective analyses (N = 6413 at 2.1 years' follow-up), MVPA and sedentary time were not associated with waist circumference at follow-up, but a higher waist circumference at baseline was associated with higher amounts of sedentary time at follow-up., Conclusion: Higher MVPA time by children and adolescents was associated with better cardiometabolic risk factors regardless of the amount of sedentary time.

Background: This study tested a mediated effects model of psychological and behavioral adaptation to puberty within the context of physical activity (PA)., Methods: Biological maturity status, physical self-concept, PA, and health-related quality of life (HRQoL) were assessed in 222 female British year 7 to 9 pupils (mean age = 12.7 years, SD = .8)., Results: Structural equation modeling using maximum likelihood estimation and bootstrapping procedures supported the hypothesized model. Maturation status was inversely related to perceptions of sport competence, body attractiveness, and physical condition; and indirectly and inversely related to physical self-worth, PA, and HRQoL. Examination of the bootstrap-generated bias-corrected confidence intervals representing the direct and indirect paths between suggested that physical self-concept partially mediated the relations between maturity status and PA, and maturity status and HRQoL., Conclusions: Evidence supports the contention that perceptions of the physical self partially mediate relations maturity, PA, and HRQoL in adolescent females.

Background: The importance of aerobic performance in youth soccer is well established. The aim of the present study was to evaluate the contributions of chronological age (CA), skeletal age (SA), body size, and training to the longitudinal development of aerobic performance in youth male soccer players aged 10 to 18 years., Material and Methods: Players (n=83) were annually followed up during 5 years, resulting in an average of 4.4 observations per player. Decimal CA was calculated, and SA, stature, body weight, and aerobic performance were measured once per year. Fat-free mass (FFM) was estimated from age- and gender-specific anthropometric formulas, and annual volume training was recorded. After testing for multicollinearity, multilevel regression modeling was used to analyze the longitudinal data aligned by CA and SA (Model 1 and 2, respectively) and to develop aerobic performance scores., Results: The following equations provide estimations of the aerobic performance for young soccer players: ŷ(Model 1 [deviance from the null model =388.50; P<0.01]) =57.75+9.06×centered CA-0.57×centered CA(2)+0.03×annual volume training and ŷ(Model 2 [deviance from the null model=327.98; P<0.01])=13.03+4.04×centered SA-0.12×centered SA(2)+0.99×FFM+0.03×annual volume training., Conclusions: The development of aerobic performance in young soccer players was found to be significantly related to CA, biological development, and volume of training.

To examine developmental trajectories of trunk fat mass (FM) growth of individuals categorized as either low or high for cardiometabolic risk at 26 years, a total of 55 males and 76 females from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-2007) were assessed from adolescence (11.5 ± 1.8 years) to young adulthood (26.2 ± 2.2 years) (median of 11 visits per individual) and had a measure of cardiometabolic risk in young adulthood. Participants were categorized as low or high for blood pressure and cardiometabolic risk as adults using a sex-specific median split of continuous standardized risk scores. Individual trunk FM trajectories of participants in each risk group were analyzed using multilevel random effects models. Males and females in the high blood pressure group had significantly steeper (accelerated) trajectories of trunk FM development (0.61 ± 0.14 and 0.52 ± 0.10 log g, respectively) than those in the low blood pressure group for females in the high cardiometabolic risk group trajectory of trunk FM was significantly steeper (0.52 ± 0.10 log g) than those females in the low cardiometabolic risk group. Dietary fat was positively related (0.01 ± 0.003 g/1,000 kcal) and physical activity negatively related (-0.16 ± 0.05 physical activity score) to trunk FM development in males. Young adults with high cardiometabolic risk, compared to low, have greater trunk FM as early as 8 years of age, which supports the need for early intervention.

Background: Over the past decade, accelerometers have increased in popularity as an objective measure of physical activity in free-living individuals. Evidence suggests that objective measures, rather than subjective tools such as questionnaires, are more likely to detect associations between physical activity and health in children. To date, a number of studies of children and adolescents across diverse cultures around the globe have collected accelerometer measures of physical activity accompanied by a broad range of predictor variables and associated health outcomes. The International Children's Accelerometry Database (ICAD) project pooled and reduced raw accelerometer data using standardized methods to create comparable outcome variables across studies. Such data pooling has the potential to improve our knowledge regarding the strength of relationships between physical activity and health. This manuscript describes the contributing studies, outlines the standardized methods used to process the accelerometer data and provides the initial questions which will be addressed using this novel data repository., Methods: Between September 2008 and May 2010 46,131 raw Actigraph data files and accompanying anthropometric, demographic and health data collected on children (aged 3-18 years) were obtained from 20 studies worldwide and data was reduced using standardized analytical methods., Results: When using ≥ 8, ≥ 10 and ≥ 12 hrs of wear per day as a criterion, 96%, 93.5% and 86.2% of the males, respectively, and 96.3%, 93.7% and 86% of the females, respectively, had at least one valid day of data., Conclusions: Pooling raw accelerometer data and accompanying phenotypic data from a number of studies has the potential to: a) increase statistical power due to a large sample size, b) create a more heterogeneous and potentially more representative sample, c) standardize and optimize the analytical methods used in the generation of outcome variables, and d) provide a means to study the causes of inter-study variability in physical activity. Methodological challenges include inflated variability in accelerometry measurements and the wide variation in tools and methods used to collect non-accelerometer data.

The current study examined the mediating role of physical self-concept on relations between biological maturity status and self-reported physical activity in adolescent British females. Biological maturity status, physical self-concept and physical activity were assessed in 407 female British year 7-9 pupils (M age = 13.2 years, SD = 1.0). Participants completed the Physical Activity Questionnaire for Adolescents (Kowalski, Crocker, & Donen, 2004) and the Children and Youth Physical Self-Perceptions Profile (Whitehead, 1995). Percentage of predicted adult height attained at measurement was used as an estimate of biological maturity status. Structural equation modelling using maximum likelihood estimation and bootstrapping procedures revealed that perceptions of sports competence, body attractiveness and physical self-worth mediated an inverse relation between maturity status and physical activity. The results provide partial support for Petersen and Taylor's (1980) Mediated Effects Model of Psychological and Behavioural Adaptation to Puberty within the context of physical activity., (Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.)

Unlabelled: Tracking of physical activity through childhood and adolescence tends to be low. Variation in the timing of biological maturation within youth of the same chronological age (CA) might affect participation in physical activity and may partially explain the low tracking., Purpose: To examine the stability of physical activity over time from childhood to late adolescence when aligned on CA and biological age (BA)., Methods: A total of 91 males and 96 females aged 8-15 yr from the Saskatchewan Pediatric Bone Mineral Accrual Study (PBMAS) were assessed annually for 8 yr. BA was calculated as years from age at peak height velocity. Physical activity was assessed using the Physical Activity Questionnaire for Children/Adolescents. Tracking was analyzed using intraclass correlations for both CA and BA (2-yr groupings). To be included in the analysis, an individual required a measure at both time points within an interval; however, not all individuals were present at all tracking intervals., Results: Physical activity tracking by CA 2-yr intervals were, in general, moderate in males (r=0.42-0.59) and females (r=0.43-0.44). However, the 9- to 11-yr CA interval was low and nonsignificant (r=0.23-0.30). Likewise, tracking of physical activity by BA 2-yr intervals was moderate to high in males (r=0.44-0.60) and females (r=0.39-0.62)., Conclusions: Accounting for differences in the timing of biological maturity had little effect on tracking physical activity. However, point estimates for tracking are higher in early adolescence in males and to a greater extent in females when aligned by BA versus CA. This suggests that maturity may be more important in physical activity participation in females than males., (© 2011 by the American College of Sports Medicine)

Purpose: To examine the potential confounding effect of biological maturation on the relations between chronological age and health-related quality of life in adolescent British females., Methods: Biological maturation, chronological age, and health-related quality of life were assessed in 366 British female students in years 7-10 (M = 13.0 years, SD = 0.8). The Kid-Screen 10 was used to assess health-related quality of life. Percentage of predicted adult height attained at measurement was used as an estimate of biological maturation., Results: Pearson product moment correlation demonstrated a statistically significant inverse relation between chronological age and health-related quality of life. This relation was, however, attenuated and non-significant once biological maturation was controlled for., Conclusions: Researchers studying health-related quality of life in youth should consider and/or control for the potential confounding effect of biological maturation.

The purpose of this study was to determine the influence of preterm low birth weight on bone mineral content in adolescence. In 2007 to 2008, data on adolescents were obtained for study, including 16 females and 25 males who were born preterm (≤37 weeks' gestation) between October 1, 1989, and December 31, 1995, with a birth weight of less than 1850 g. Preterm low-birth-weight individuals were age- and sex-matched to full-term (>37 weeks) normal-birth-weight (>2500 g) controls. Total body, hip, and spine bone mineral content (BMC) was assessed using dual energy X-ray absorptiometry. Male preterm individuals had less BMC at the proximal femur in adolescence compared with controls ( p < 0.05). However, once adjusted for age, maturity, height, weight, physical activity, and diet, there were no differences between groups ( p < 0.05) in any bone parameters. These findings suggest that preterm birth and low birth weight did not influence bone accrual in these individuals at adolescence., (© Thieme Medical Publishers.)

Sex differences in physical activity (PA) through pubertal maturation and the growth spurt are often attributed to changing interests. The contribution of sex differences in biological maturation to the adolescent decline has received limited attention. This study examined the contribution of somatic maturation to sex differences in objective assessments of sedentary behavior and PA in Portuguese adolescents (N = 302, aged 13-16 years). Maturation was estimated from the percentage of predicted mature stature and physically active and inactive behaviors assessed with Actigraph GT1M accelerometers. The influence of age, sex and their interaction on body size, maturation and physical behaviors were examined using factorial ANOVA and, subsequently, ANCOVA (controlling for maturation) tested the effect of sex. Males spent more time in MVPA and less time in sedentary behavior than females. However, sex differences were attenuated when maturation was controlled; thus suggesting that maturity may play an important role in adolescent behaviors.

The decline in physical activity (PA) across adolescence is well established but influence of biological maturity on the process has been largely overlooked. This paper reviews the limited number of studies which examine the relationship between timing of biological maturity and PA. Results are generally inconsistent among studies. Other health-related behaviors are also considered in an effort to highlight the complexity of relationships between biological maturation and behavior and to provide future research directions.

Unlabelled: Minimal research has examined whether the decline in physical activity (PA) among adolescent girls is associated with chronological age (CA) or biological age (BA)., Purpose: To describe the PA levels and perceived barriers to PA of adolescent girls grouped by school grade and maturity status (i.e., early or late maturing) within grades., Methods: Two hundred and twenty-one girls (aged 8-16 yr, grades 4-10) wore an Actical accelerometer for 7 d and then completed a semistructured, open-ended questionnaire on perceived barriers to PA over the 7-d period. Predicted age at peak height velocity and recalled age at menarche were used to assess maturity among the elementary and high school girls, respectively. Maturity and grade group differences in PA were assessed using a MANCOVA and independent sample t-test and barriers to PA using chi-squared statistics., Results: Daily minutes spent in moderate to vigorous PA decreased by 40% between grades 4 and 10. Within grade groupings, no differences in PA were found between early and late maturing girls (P > 0.05). Grades 4 to 6 participants cited more interpersonal (i.e., social) barriers. Grades 9 to 10 participants cited more institutional barriers to PA, primarily revolving around the institution of school. No differences were found in types of barriers reported between early and late maturing girls., Conclusion: Because PA and types of perceived barriers to PA were dependent on grade, future research should work to identify the most salient (i.e., frequent and limiting) barriers to PA by CA in youth. Once reliably was identified, multipronged intervention strategies must be tested for effectiveness to help youth cope with their salient barriers.

Unlabelled: Intensive training at a young age may adversely affect the growth and sexual maturation of female athletes, resulting in compromised adult stature., Purpose: To compare the somatic growth, sexual maturation, and final adult height of elite adolescent female athletes., Methods: Serial measures of height, sitting height, and breast and pubic hair development were taken on 81 gymnasts, 60 swimmers, and 81 tennis players between 8 and 19 yr of age. Menarcheal age, parental heights, maternal menarcheal age, and number of training hours were also recorded. Final adult heights were obtained from a subsample of the athletes (N = 110)., Results: Gymnasts were significantly shorter than tennis players and swimmers at all chronological ages during adolescence, and they attained menarche at an older age (P < 0.05). No significant differences were found in adult heights. During adolescence, no difference were found in standing height to sitting height ratios, leg length to standing height ratios, or sitting height to leg length ratios between sports (P > 0.05)., Conclusion: The results from this study suggest that regular training did not affect final adult stature and that, when aligned by biological age, the tempo of sexual maturation was similar in these young athletes.

The aim of this study was to examine the relationships among biological maturity, physical size, relative age (i.e. birth date), and selection into a male Canadian provincial age-banded ice hockey team. In 2003, 619 male ice hockey players aged 14-15 years attended Saskatchewan provincial team selection camps, 281 of whom participated in the present study. Data from 93 age-matched controls were obtained from the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-1997). During the initial selection camps, birth dates, heights, sitting heights, and body masses were recorded. Age at peak height velocity, an indicator of biological maturity, was determined in the controls and predicted in the ice hockey players. Data were analysed using one-way analysis of variance, logistic regression, and a Kolmogorov-Smirnov test. The ice hockey players selected for the final team were taller, heavier, and more mature (P < 0.05) than both the unselected players and the age-matched controls. Furthermore, age at peak height velocity predicted (P < 0.05) being selected at the first and second selection camps. The birth dates of those players selected for the team were positively skewed, with the majority of those selected being born in the months January to June. In conclusion, team selectors appear to preferentially select early maturing male ice hockey players who have birth dates early in the selection year.

Investigations in a variety of chronologically grouped team sports have reported that elite young athletes were more likely born in the early months of the selection year, a phenomenon known as the relative age effect. The present study investigated the birth dates and developmental paths of 238 (15 to 20 years old) Major Junior 'A' hockey players from the Ontario Hockey League to determine if a relative age effect still exists in elite junior hockey and if the path to elite sport was accelerated (i.e., fast tracked). The results identified a relative age effect in elite hockey although it is only apparent among individuals who fast track.

Purpose: To investigate whether observed gender differences in objectively measured physical activity (PA) in children (8-13 yr) are confounded by physical maturity differences., Methods: Four hundred and one children (194 boys and 207 girls) volunteered for this study. An Actigraph accelerometer was used to obtain seven consecutive days of minute-by-minute PA data for each participant. Minutes of moderate to vigorous PA per day (MVPA), continuous minutes of MVPA per day (CMVPA), and minutes of vigorous PA per day (VPA) were derived from the accelerometer data. Age at peak height velocity (APHV), an indicator of somatic maturity, was predicted in all individuals. Gender differences in the PA variables were analyzed using a two-way (gender x age) ANOVA., Results: Levels of PA decreased with increasing chronological age in both genders (P < 0.05). When aligned on chronological age, boys had a higher MVPA at 10-13 yr, a higher CMVPA at 9-12 yr, and a higher VPA at 9-13 yr (P < 0.05). When aligned on biological age, PA declined with increasing maturity (P < 0.05); however, gender differences between biological age groups disappeared., Conclusion: The observed age-related decline in adolescent boys and girls PA is antithetical to public health goals; as such, it is an important area of research. To fully understand gender disparities in PA, consideration must be given to the confounding effects of physical maturity.

Objective: To validate and demonstrate how adult height can be predicted by using reference values obtained from maturity and sex-specific cumulative height velocity curves., Study Design: Serial height measurements were taken on 224 boys and 120 girls. Individuals were classified as early, average, or late maturers, depending on their age of peak height velocity. Maturity and sex-specific cumulative height velocity curves were developed for early, average, and late maturers, and the area under these curves were used to develop reference values to predict adult height., Results: This method can predict adult height within +/-5.35 cm 95% of the time in boys and +/-6.81 cm 95% of the time in girls., Conclusions: The technique is a valid, nonintrusive, inexpensive, and simple method of predicting adult height in adolescent children, free of growth limiting diseases.