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Refereed/Peer-reviewed Background: Few studies have investigated the optimal anthropometric index associated with potential cardio-metabolic risk.Using direct measures of standing height, body mass, and waist circumference, we sought to identify the optimal index fordetecting cardio-metabolic risk associated with diabetes and hypertension in a nationally representative sample of US adults Methods: Complete (non-missing) cross-sectional data from 8375 US adults aged 18–80+ years were obtained from the 2015–16and 2017–March 2020 (pre-pandemic) cycles of the National Health and Nutrition Examination Survey. The cardio-metabolic risk was identified using blood pressure and glycohemoglobin (A1c). Allometric models were used to identify the optimal anthropometric indices associated with cardio-metabolic risk. Receiver operating characteristics curves were used to verify the discriminatory ability of the identified index in comparison with other anthropometric measures. Results: The optimal anthropometric index associated with cardio-metabolic risk was waist circumference divided by body massto the power of 0.333 (WC/M0.333). The ability for this new index to discriminate those with diabetes (area under the ROC curve: 0.73[95%CI: 0.71–0.74]) and hypertension (area under the curve: 0.70 [95%CI: 0.69–0.72]) was superior to all other anthropometricmeasure/indices investigated in this study (body mass index, waist circumference, waist-to-height ratio, and waist/height0.5) Conclusions: We identified WC/M0.333 as the optimal anthropometric index for identifying US adults with hypertension anddiabetes. Instead of using body mass index (kg/m2), we recommend using WC/M0.333 in clinical and public health practice to better identify US adults at potential cardio-metabolic risk associated with hypertension and diabetes.

Objective To determine the association between social media use (SMU) and physical activity (PA) among Canadian adolescents. Methods We used data from 12,358 participants in grades 6 to 10 who responded to the Canadian component of the 2017/2018 Health Behaviour in School-aged Children (HBSC) survey. Social media intensity and problematic SMU were assessed using a 4-point mutually exclusive scale that contained three categories based on intensity (non-active, active, and intense SMU) and one category based on the presence of addiction-like symptoms irrespective of intensity (problematic SMU). PA was assessed for five domains (i.e., school curriculum, organized sport, exercise, outdoor play, and active transport) and dichotomized using the first quartile to represent high PA engagement in each domain. Meeting PA recommendation of 60 min per day of moderate-to-vigorous PA was calculated using the sum of the five domains. Logistic regression models were used to assess the association between SMU and PA, with active SMU used as the reference group for all models. Results Non-active SMU was associated with lower odds of meeting the daily PA recommendations and of high engagement in all five domains of PA when compared to active SMU. Intense SMU was associated with higher odds of meeting the daily PA recommendations. Problematic SMU was not associated with meeting daily PA recommendations, but it was significantly associated with lower odds of high PA engagement in the exercise domain. Conclusion The findings of this study suggest that non-active SMU was significantly associated with lower PA levels. Problematic SMU was only significantly associated with lower PA levels in the exercise domain. Intense SMU was associated with higher odds of meeting the PA recommendation.

Cardiorespiratory fitness (CRF), which reflects the overall aerobic capacity of the cardiovascular, respiratory, and muscular systems, is significantly related to health among youth. The aim of this systematic review was to identify health-related criterion-referenced cut-points for CRF among youth aged 5–17 years. A systematic search of two electronic databases (MEDLINE and SPORTDiscus) was conducted in September 2020. Only peer-reviewed studies that developed health-related criterion-referenced cut-points for CRF among youth were eligible provided they included (1) youth aged 5–17 years from the general population; (2) at least one quantitative assessment of CRF (e.g., peak oxygen uptake [ $${V}$$ O2peak]); (3) at least one quantitative assessment of health (e.g., cardiometabolic risk); (4) a criterion for health; and (5) a quantitative analysis (e.g., receiver operating characteristic [ROC] curve) of at least one health-related cut-point for CRF. A narrative synthesis was used to describe the results of the included studies. Collectively, 29 included studies developed health-related criterion-referenced cut-points for CRF among 193,311 youth from 23 countries. CRF cut-points, expressed as $${V}$$ O2peak, estimated using the 20-m shuttle run test, demonstrated high discriminatory ability (median area under the curve [AUC] ≥ 0.71) for both cardiometabolic and obesity risk. Cut-points derived from maximal cycle-ergometer tests demonstrated moderate discriminatory ability (median AUC 0.64–0.70) for cardiometabolic risk, and low discriminatory ability for early subclinical atherosclerosis (median AUC 0.56–0.63). Cut-points for CRF using submaximal treadmill exercise testing demonstrated high discriminatory ability for cardiometabolic risk, but only moderate discriminatory ability for obesity risk. CRF cut-points estimated using submaximal step testing demonstrated high discriminatory ability for cardiometabolic risk and moderate discriminatory ability for high blood pressure, while those for the 9-min walk/run test demonstrated moderate-to-high discriminatory ability for obesity risk. Collectively, CRF cut-points, expressed as $${V}$$ O2peak, demonstrated moderate-to-high discriminatory ability (median AUC ≥ 0.64) for cardiometabolic risk, obesity risk, and high blood pressure. Currently, there is too wide a range of health-related criterion-referenced cut-points for CRF among youth to suggest universal age- and sex-specific thresholds. To further inform the development of universal cut-points, there is a need for additional research, using standardized testing protocols and health-risk definitions, that examines health-related criterion-referenced cut-points for CRF that are age, sex, and culturally diverse. PROSPERO registration number: CRD42020207458.

Background: Musculoskeletal fitness is an excellent functional measure that is significantly related to health among youth. Objective: Our objective was to identify health-related criterion-referenced cut-points for musculoskeletal fitness (MSF) among youth. Methods: A systematic search of two electronic databases (MEDLINE and SPORTDiscus) was conducted in September 2020. Only peer-reviewed studies that developed health-related criterion-referenced cut-points for MSF among youth were eligible provided they included (1) youth aged 5–17 years from the general population, (2) at least one quantitative assessment of MSF (e.g., muscular strength), (3) at least one quantitative assessment of health (e.g., cardiometabolic risk), (4) a criterion for health, and (5) a quantitative analysis [e.g., receiver operating characteristic (ROC) curve] of at least one health-related cut-point for MSF. A narrative synthesis was used to describe the results of included studies. Results: Collectively, 13 studies that developed health-related criterion-referenced cut-points for MSF among 14,476 youth from 15 countries were included. Muscular strength demonstrated high discriminatory ability [median area under the curve (AUC) ≥ 0.71] for cardiometabolic risk/metabolic syndrome, sarcopenic obesity risk and bone health, and moderate discriminatory ability (median AUC 0.64–0.70) for asthma. Muscular power also demonstrated high discriminatory ability for bone health but only moderate discriminatory ability for cardiometabolic risk/metabolic syndrome and low discriminatory ability (median AUC 0.56–0.63) for cognition/academic performance. Both muscular endurance and flexibility demonstrated low discriminatory ability for musculoskeletal pain. Health-related cut-points for MSF that demonstrated significant discriminatory ability were generally higher for boys than for girls (for muscular strength and power) and generally increased with age for muscular strength and power but remained stable for flexibility. Conclusions: Data remain insufficient to establish universal health-related cut-points for MSF among youth. Despite variations in the health-related discriminatory ability of different MSF tests, handgrip strength and standing broad jump emerged as the two tests with the highest discriminatory ability. More research, using standardized testing protocols and health-risk definitions, is required to better triangulate universal health-related cut-points for MSF among youth. Refereed/Peer-reviewed

Background: The standing broad jump (SBJ) is an excellent functional measure of explosive lower-body strength that is significantly related to health among children and adolescents. Objectives: The aim of this study was to estimate national (country-level) and international (pooled global data) temporal trends in SBJ performance for children and adolescents, and to examine the relationships between national trends in SBJ performance and national trends in health-related and socioeconomic/demographic indicators. Methods: Data were obtained from a systematic search of studies reporting temporal trends in SBJ performance for 9- to 17-year-olds, and by examining national fitness datasets. Sample-weighted regression models estimated trends at the study/dataset-country-sex-age level, with national and international trends estimated by a post-stratified population-weighting procedure. Pearson’s correlations quantified relationships between national trends in SBJ performance and national trends in health-related and socioeconomic/demographic indicators. Results: Data from 34 studies/datasets were extracted to estimate trends for 10,940,801 children and adolescents from 24 high-, 4 upper-middle-, and 1 low-income countries between 1960 and 2017. Collectively, there was a negligible (per decade) improvement in SBJ performance of 1.73 cm (95% CI 1.71–1.75), 0.99% (95% CI 0.97–1.01) or a standardized effect size of 0.07 (0.07–0.07) over the entire period, with the rate of improvement steady from the 1960s to the 1980s, slowing in the 1990s, before declining. Sex- and age-related temporal differences were negligible. Trends differed between countries, with most countries experiencing declines. National trends in SBJ performance were not significantly related to national trends in health-related and socioeconomic/demographic indicators. Conclusions: SBJ performance of children and adolescents has declined since 2000 (at least among most of the countries in this analysis) and is suggestive of a modern decline in functional explosive lower-body strength. Growing recognition of the importance of muscular fitness as a marker of population health highlights the need for continued tracking of temporal trends in SBJ, especially among low- and lower-middle-income countries for which temporal data are lacking. Refereed/Peer-reviewed

Background: Handgrip strength (HGS) is an excellent marker of functional capability and health in adults, although little is known about temporal trends in adult HGS. Objectives: The aim of this study was to systematically analyze national (country-level) temporal trends in adult HGS, and to examine the relationships between national trends in adult HGS and national trends in health-related and socioeconomic/demographic indicators. Methods: Data were obtained from a systematic search of studies reporting temporal trends in HGS for adults (aged ≥ 20 years) and by examining national fitness datasets. Trends in mean HGS were estimated at the country–sex–age group level by best-fitting sample-weighted linear/polynomial regression models, with national and sub-regional (pooled data across geographically similar countries) trends estimated by a post-stratified population-weighting procedure. Pearson’s correlations quantified relationships between national trends in adult HGS and national trends in health-related and socioeconomic/demographic indicators. Results: Data from ten studies/datasets were extracted to estimate trends in mean HGS for 2,592,714 adults from 12 high- and 2 upper-middle-income countries (from Asia, Europe and North America) between 1960 and 2017. National trends were few, mixed and generally negligible pre-2000, whereas most countries (75% or 9/12) experienced negligible-to-small declines ranging from an effect size of 0.05 to 0.27, or 0.6 to 6.3%, per decade post-2000. Sex- and age-related temporal differences were negligible. National trends in adult HGS were not significantly related to national trends in health and socioeconomic/demographic indicators. Conclusions: While trends in adult HGS are currently limited to 14 high- and upper-middle-income countries from three continents, adult HGS appears to have declined since 2000 (at least among most of the countries in this analysis), which is suggestive of corresponding declines in functional capability and health Refereed/Peer-reviewed

Objective: To estimate national and international temporal trends in handgrip strength for children and adolescents, and to examine relationships between trends in handgrip strength and trends in health-related and sociodemographic indicators. Methods: Data were obtained through a systematic search of studies reporting temporal trends in the handgrip strength for apparently healthy 9–17-year-olds, and by examining large national fitness datasets. Temporal trends at the country–sex–age level were estimated by sample-weighted regression models relating the year of testing to mean handgrip strength.International and national trends were estimated by a post-stratifed population-weighting procedure. Pearson’s correlation squantifed relationships between national trends in handgrip strength and national trends in health-related/sociodemographic indicators. Results: 2,216,320 children and adolescents from 13 high-, 5 upper-middle-, and 1 low-income countries/special administrative regions between 1967 and 2017 collectively showed a moderate improvement of 19.4% (95% CI 18.4–20.4) or 3.8% perdecade (95% CI 3.6–4.0). The international rate of improvement progressively increased over time, with more recent values(post-2000) close to two times larger than those from the 1960s/1970s. Improvements were larger for children (9–12 years)compared to adolescents (13–17 years), and similar for boys and girls. Trends difered between countries, with relationships between national trends in handgrip strength and national trends in health-related/sociodemographic indicators negligible to-weak and not statistically signifcant. Conclusions: There has been a substantial improvement in absolute handgrip strength for children and adolescents since 1967. There is a need for improved international surveillance of handgrip strength, especially in low- and middle-income ountries, to more confdently determine true international trends. Refereed/Peer-reviewed