Physical activity intensity and subclinical atherosclerosis in Danish adolescents: The European Youth Heart Study

Effect of nationwide school policy on device-measured physical activity in Danish children and adolescents: a natural experiment

Background

A new Danish school policy with a requirement for 45 min physical activity daily during school hours was introduced in 2014. The objective of this natural experiment was to evaluate the effect of this nationwide school policy on physical activity in Danish children and adolescents.

Methods

Four historical studies completed between 2009 and 2012 comprised the pre-policy study population. Post-policy data were collected in 2017/18. All post-policy schools were represented in the four pre-policy studies. Age-groups and seasons were matched. In total, 4816 children and adolescents aged 6-17 were included in the analyses (2346 pre-policy and 2470 post-policy). Children and adolescents were eligible if they had accelerometer measurements and did not have any physical disabilities preventing activity. Physical activity was measured by accelerometry. Main outcome was any bodily movement. Secondary outcomes were moderate to vigorous physical activity and overall movement volume (mean counts per minute).

Findings

The school policy interrupted a linear decreasing pre-policy trend in physical activity during school hours. All activity outcomes increased post-policy during a standardized school day (8:10 am-1 pm). Increases were more pronounced in the youngest children. Specifically, we observed a daily increase during a standardized school day in 2017/2018 of 14.2 min of movement (95% CI: 11.4-17.0, p < 0.001), 6.5 min of moderate to vigorous physical activity (95% CI: 4.7-8.3, P < 0.001), and 141.8 counts per minute (95% CI: 108.5-175.2, P < 0.001).

Interpretation

A national school policy may be an important strategy to increase physical activity during school hours among children and adolescents.

Funding

The Danish Foundation TrygFonden has funded the PHASAR project (ID 115606).

A Systematic Review of the Associations of Adiposity and Cardiorespiratory Fitness With Arterial Structure and Function in Nonclinical Children and Adolescents

PURPOSE

To summarize the evidence on associations of adiposity and cardiorespiratory fitness (CRF) with arterial structure and function in nonclinical children and adolescents.

METHODS

Two researchers conducted a search in 5 electronic databases in April 2022 to find studies in nonclinical youth (age 5-17.9 y) reporting multivariable associations. Studies were eligible if adiposity and/or CRF were used as the predictor and arterial structure and/or function was the outcome. The Quality Assessment Tool for Quantitative Studies was used to assess methodological quality for experimental studies, and a modified version was used for observational studies.

RESULTS

Ninety-nine studies (72.7% cross-sectional) were included. Ninety-four assessed associations between adiposity and arterial outcomes, most using overall body proportion (n = 71), abdominal (n = 52), or whole-body adiposity (n = 40). Most evidence was inconsistent or nonsignificant, but 59 studies suggested higher abdominal adiposity and worse body proportion were associated with adverse arterial outcomes. Twenty-one assessed associations between CRF and arterial outcomes, with findings inconsistent. Most evidence was rated weak in quality.

CONCLUSION

While high adiposity may contribute to poor arterial outcomes, evidence is limited regarding CRF. Future studies should disentangle these associations by studying youth with healthy adiposity but poor CRF, or vice versa, using longitudinal or experimental study designs.

Cardiorespiratory Fitness and Carotid Intima-Media Thickness in Physically Active Young Adults: CHIEF Atherosclerosis Study

Background: The relationship of cardiorespiratory fitness (CRF) with subclinical atherosclerosis affected by the body adiposity has been observed in children, whereas this relationship remains unclear in young adults. Methods and Results: A total of 1520 military recruits, aged 18−40 years, were included in Taiwan in 2018−2020. All subjects underwent detailed physical and blood laboratory examinations. CRF was evaluated by time for a 3000 m run, and subclinical atherosclerosis was evaluated by intima−media thickness of the bulb of the left common carotid artery (cIMT) utilizing high-resolution ultrasonography. Multivariable linear regression analysis with adjustments for age, sex, cigarette smoking, alcohol intake, systolic and diastolic blood pressure, high- and low-density lipoprotein cholesterols, fasting glucose, waist circumference, serum uric acid and serum triglycerides were utilized to determine the correlation between CRF and cIMT. CRF was independently correlated with cIMT (standardized β: 0.11, p < 0.001). Of the cardiometabolic risk markers, serum triglycerides were the only independent risk marker of cIMT (standardized β: 0.063, p = 0.03). In addition, the association of CRF with cIMT did not differ between those with a body mass index (BMI) ≥ 25 kg/m2 and those with BMI < 25 kg/m2 (standardized β: 0.103 and 0.117; p = 0.01 and 0.005, respectively). Conclusions: In physically active young men and women, there was an inverse association of cIMT with CRF, which was observed in both overweight/mild obesity and normal-weight individuals, highlighting the importance of endurance capacity on reducing risk of early atherosclerosis and implying that the moderation effect of body adiposity might not be present in this population.

Physical activity and carotid atherosclerosis risk reduction in population with high risk for cardiovascular diseases: a cross-sectional study

Background

Decreased physical activity had been reported to be a common causal and modifiable risk factor for major vascular events. However, the relationship of physical activity and sedentary leisure time with carotid atherosclerosis in population with high risk for cardiovascular diseases (CVDs) is still inconclusive. We aimed to evaluate the association of physical activity and sedentary leisure time with the risk of carotid atherosclerosis, and investigate any possible effect modifiers in population with high risk for CVDs.

Methods

The study population was drawn from the China Patient-Centered Evaluative Assessment of Cardiac Events (PEACE) Million Persons Project-Jiangsu project, which is a population-based screening project that included permanent residents aged 35-75 years from 6 surveillance cities in Jiangsu Province. Linear regression models were used to evaluate the association of physical activity and sedentary leisure time with carotid intima-media thickness (CIMT). The risks of abnormal carotid artery and carotid plaque (CP) were estimated by odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression.

Results

Overall, a total of 10,920 participants were enrolled in the final analysis. There was a significant inverse association of physical activity level with CIMT (per SD increase: β=-0.0103; 95%CI: -0.0154, -0.0053). The risk of abnormal carotid artery and CP decreased significantly with the increase of physical activity level (per SD increase: OR=0.908, 95%CI: 0.869-0.948; OR=0.900, 95%CI: 0.857-0.945, respectively). When physical activity level was categorized as quartiles, a significantly lower risk of abnormal carotid artery and CP was found in quartiles 2-4 with quartile 1 as reference (P<0.05 for all). Furthermore, the inverse association were stronger in participants with age ≥60 years (vs. <60 years, P_interaction<0.001 for both). However, there were no significant association of sedentary leisure time with CIMT, abnormal carotid artery and CP.

Conclusions

In population with high risk for CVDs, physical activity was inversely associated with CIMT, abnormal carotid artery and CP, particularly among the elders. Sedentary leisure time was not associated with them. These results suggested that physical activity is important for carotid vascular health, and perhaps especially in elder population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-12582-6.

Exercise Training Duration and Intensity Are Associated With Thicker Carotid Intima-Media Thickness but Improved Arterial Elasticity in Active Children and Adolescents

Even though exercise generally has a positive effect on health, intensive exercise can have adverse effects on the vascular system of adults. This study aimed to investigate the association between training duration and intensity and vascular structure and function in 427 physically active children and adolescents (14.0 ± 1.94 years). In this study, we examined carotid intima-media thickness (cIMT), carotid diameter, and cIMT:diameter-ratio as parameters of carotid arterial structure and arterial compliance (AC), stiffness index β (β), elastic modulus (Ep), and carotid pulse wave velocity (PWVβ) as parameters of carotid arterial function with high-resolution ultrasound. We collected central systolic blood pressure (cSBP) and aortic pulse wave velocity (aPWV) as parameters of central arterial stiffness with an oscillometric device. We used the MoMo Physical Activity Questionnaire to record training duration and intensity. Training duration (p = 0.022) and intensity (p = 0.024) were associated with higher cIMT. Further, training duration was associated with lower central arterial stiffness (cSBP: p = 0.001; aPWV: p = 0.033) and improved AC (p < 0.001). Higher training intensity was related to improved AC (p < 0.001) and larger carotid diameter (p = 0.040). Boys presented thicker cIMT (p = 0.010), improved AC (p = 0.006), and lower central arterial stiffness (cSBP: p < 0.001; aPWV: p = 0.016) associated with higher training duration. Girls presented improved AC (p = 0.023) and lower Ep (p = 0.038) but higher β (p = 0.036) associated with higher training duration. Only boys demonstrated thicker cIMT (p = 0.016) and improved AC (p = 0.002) associated with higher training intensity. A quintile analyses of the training duration revealed thicker cIMT of children and adolescents in Q1 and Q5 than that in Q4 and Q5. Besides, Q1 showed lower cSBP compared to Q4 and Q5. Regarding training intensity, Q5 had thicker cIMT than Q2 and Q3. Although a higher training load is associated with thicker cIMT, the common carotid artery is also more elastic. This suggests that a higher training load leads to a functional adaptation of the carotid artery in youth.

Higher Total Physical Activity is Associated with Lower Arterial Stiffness in Swedish, Young Adults: The Cross-Sectional Lifestyle, Biomarkers, and Atherosclerosis Study

Purpose

Arterial stiffness describes the rigidity of the arterial walls and is associated with risk factors for cardiovascular disease (CVD). Arterial stiffness predicts future events and mortality, and the predictive value is stronger in younger versus older subjects. The aims of the present study were, firstly, to present data on physical activity (PA) and time spent sedentary, in the population of Swedish, young adults. Secondly, to explore the association between PA and arterial stiffness.

Material and Methods

Self-reported healthy, non-smoking, Swedish, young adults, 18–25 years old, participated in the cross-sectional Lifestyle, Biomarkers and Atherosclerosis (LBA) study. The daily PA was objectively measured with an accelerometer for 1 week. Of the 834 participants, 658 individuals had valid registrations. The arterial stiffness measures, pulse wave velocity (PWV) and augmentation index (AIx) were measured with applanation tonometry.

Results

Women were on overall more physically active than men, they spent 214 min/day in light PA (LPA) compared to men who spent 202 min/day. Women took significantly more steps per day than men, 7796 vs 7336 steps/day, and spent less time sedentary, 523 min/day, compared to men who spent 547 min/day sedentary. In total, 76% of the individuals spent on average at least 30 minutes per day in the recommended moderate and vigorous PA (MVPA). Lower arterial stiffness was associated with more MVPA and total PA in the total population.

Conclusion

We conclude that in this age group of young, self-reported healthy adults 18–25 years, it is important to highlight the health-enhancing possibilities of time spent in physical activity on the vascular function, measured as PWV and AIx. It is of high relevance in a public health perspective to expand preventive efforts beyond the high-risk groups and encourage young adults to be physically active.

Longitudinal associations of physical activity, sedentary time, and cardiorespiratory fitness with arterial health in children - the PANIC study

We investigated the longitudinal associations of physical activity (PA), sedentary time (ST), and cardiorespiratory fitness (CRF) with arterial health among children. In our primary analyses, we investigated 245 children (girls 51.8%) aged 6-9 years participating in the baseline examinations who had data on arterial health at 2-year follow-up. We also utilized a subsample of 90 children who had a complete arterial health data at baseline and 2-year follow-up. ST (≤1.5 METs), light PA (>1.5-4 METs), moderate PA (>4-7 METs), vigorous PA (>7METs), and moderate-to-vigorous PA (MVPA, >4 METs) were assessed by combined movement and heart rate monitoring and CRF by maximal exercise testing on a cycle ergometer at baseline and 2-year follow-up. Stiffness index (SI) as a measure of arterial stiffness and change in reflection index during exercise test (DRI) as a measure of arterial dilation capacity were assessed by pulse contour analysis. Two-year change in vigorous PA was associated with DRI in boys but not in girls (p=0.021 for interaction). In a subsample analyses, 2-year changes in MPA, VPA, and MVPA were inversely associated with 2-year change in SI. In conclusion, promoting PA at higher intensities may confer larger benefits on arterial health than reducing ST and increasing LPA.

Effect of Sex, Body Mass Index and Physical Activity Level on Peak Oxygen Uptake Among 14-19 Years Old Adolescents

The aim was to describe longitudinal trends in peak oxygen uptake (VO_2peak) among 14- to 19-year-old adolescents in Norway, and to examine effects of sex, body mass index (BMI), and physical activity (PA) level on VO_2peak during adolescence. Of 124 invited students from two lower secondary schools in Norway, 116 eighth-grade students (61 boys and 55 girls; 14 years old at baseline) volunteered to participate. The study has a longitudinal design with 6 yearly repeated measures of body height and mass, VO_2peak and PA level. VO_2peak allometrically scaled to body mass raised to the power of 0.67 was measured using a walking or running incremental test on a treadmill, whereas PA level was self-reported. Among 696 possible observations, 555 (79.7%) were valid. Multiple linear regression and linear mixed model analyses were used to examine the associations between age, sex, BMI, PA level and VO_2peak. VO_2peak showed a non-linear pattern from age 14 to 19, with a distinct increase for boys peaking at age 17, while the results provide a flatter and more stable curve for girls. Sex, BMI and PA level together explained 43–71% of the variance in VO_2peak at the different age levels. Sex and PA level contributed independently to explain a significant proportion of the variance in VO_2peak at all measurement occasions, while BMI did not. Adjusted sex differences in VO_2peak increased over time, from 26.5 ml·kg^−0.67·min⁻¹ at age 14 to 55.5 ml·kg^−0.67·min⁻¹ at age 19. The independent contribution from PA level to the variance in VO_2peak increased from age 14 to 16 and then decreased. While PA level explained 32.5% of the total variance in VO_2peak for 16-year-olds, this number was 14% in 19-year-olds. In conclusion, aerobic power showed a non-linear pattern during adolescence, peaking at age 17. Sex and PA level explained a large proportion of the variance in VO_2peak, each of them being an independent contributor to VO_2peak. Aerobic power is linked to improved health and seems to depend largely on sex and PA level in adolescents, emphasizing the importance of maintaining a sufficient PA level during adolescence.

Association Between Physical Activity Intensity Levels and Arterial Stiffness in Healthy Children

BACKGROUND

Physical activity (PA) has a substantial impact on arterial stiffness in adults; however, evidence regarding children is scarce. The aim of this study was to examine the association between objectively measured PA with different intensities and surrogate measures of arterial stiffness in healthy children.

METHODS

Altogether, 80 children (41 girls and 39 boys, ranging from 8-11 y) participated in this prospective, cross-sectional study. Sedentary time and PA of light, moderate, and vigorous intensity levels were measured over a period of 7 days by accelerometry. Arterial stiffness parameters, including pulse wave velocity and central systolic blood pressure (cSBP), were noninvasively assessed by the oscillometric Mobil-O-Graph. Associations were tested using multiple linear regressions with adjustments for potential confounders (α ≤ .05).

RESULTS

PA of moderate intensity was negatively associated with cSBP (β = -0.266, P = .017). PA of vigorous intensity was inversely related to pulse wave velocity (β = -0.225, P = .045) and cSBP (β = -0.286, P = .010), respectively.

CONCLUSION

Higher time spent in PA of moderate and vigorous intensity is associated with reduced pulse wave velocity and lower cSBP values in children. It suggests that PA is a favorable determinant of arterial health.

The Association of Physical Activity With Carotid Intima Media Thickening in a Healthy Older Population: Cooper Center Longitudinal Study

The purpose of this study was to examine the association between self-reported physical activity (PA) and mean common carotid artery intima-media thickness (CCA IMT) among older adults. The data are from 1,811 Cooper Center Longitudinal Study participants, who were aged ≥60 years, with no history of cardiovascular disease. A medical history questionnaire was used to assess PA. Carotid ultrasound was performed to measure CCA IMT and the presence of plaque and stenosis. Logistic regression models were constructed to estimate the association between PA and CCA IMT after adjustment for covariates. The participants were aged 69.2 ± 5.9 years, and the majority were male (73.3%) and White (96.7%). The odds ratio of abnormal thickening of CCA IMT was 0.72 (95% confidence interval [0.54, 0.96]) in physically active participants (≥500 metabolic equivalent·min/week) after adjustment for covariates. In the current study, meeting PA guidelines in older adulthood was associated with lower odds of abnormal thickening of CCA IMT.

Vascular Structure and Function in Children and Adolescents: What Impact Do Physical Activity, Health-Related Physical Fitness, and Exercise Have?

A physically active lifestyle can prevent cardiovascular disease. Exercise intervention studies in children and adolescents that aim to increase physical activity have resulted in reduced vascular wall thickening and improve cardiovascular function. Here we review the literature that explores the correlations between physical activity, health-related physical fitness, and exercise interventions with various measures of vascular structure and function in children and adolescents. While several of these studies identified improvements in vascular structure in response to physical activity, these associations were limited to studies that relied on questionnaires. Of concern, these findings were not replicated in studies featuring quantitative assessment of physical activity with accelerometers. Half of the studies reviewed reported improved vascular function with increased physical activity, with the type of vascular measurement and the way physical activity was assessed having an influence on the reported relationships. Similary, most of the studies identified in the literature report a beneficial association of health-related physical fitness with vascular structure and function. Overall, it was difficult to compare the results of these studies to one another as different methodologies were used to measure both, health-related physical fitness and vascular function. Likewise, exercise interventions may reduce both arterial wall thickness and increased vascular stiffness in pediatric populations at risk, but the impact clearly depends on the duration of the intervention and varies depending on the target groups. We identified only one study that examined vascular structure and function in young athletes, a group of particular interest with respect to understanding of cardiovascular adaptation to exercise. In conclusion, future studies will be needed that address the use of wall:diameter or wall:lumen-ratio as part of the evaluation of arterial wall thickness. Furthermore, it will be critical to introduce specific and quantitative measurements of physical activity, as intensity and duration of participation likely influence the effectiveness of exercise interventions.

Exercise-associated prevention of adult cardiovascular disease in children and adolescents: monocytes, molecular mechanisms, and a call for discovery

Atherosclerosis originates in childhood and adolescence. The goal of this review is to highlight how exercise and physical activity during childhood and adolescence, critical periods of growth and development, can prevent adult cardiovascular disease (CVD), particularly through molecular mechanisms of monocytes, a key cell of the innate immune system. Monocytes are heterogeneous and pluripotential cells that can, paradoxically, play a role in both the instigation and prevention of atherosclerosis. Recent discoveries in young adults reveal that brief exercise affects monocyte gene pathways promoting a cell phenotype that patrols the vascular system and repairs injuries. Concurrently, exercise inhibits pro-inflammatory monocytes, cells that contribute to vascular damage and plaque formation. Because CVD is typically asymptomatic in youth, minimally invasive techniques must be honed to study the subtle anatomic and physiologic evidence of vascular dysfunction. Exercise gas exchange and heart rate measures can be combined with ultrasound assessments of vascular anatomy and reactivity, and near-infrared spectroscopy to quantify impaired O2 transport that is often hidden at rest. Combined with functional, transcriptomic, and epigenetic monocyte expression and measures of monocyte-endothelium interaction, molecular mechanisms of early CVD can be formulated, and then translated into effective physical activity-based strategies in youth to prevent adult-onset CVD.

Impact of sedentary behavior on large artery structure and function in children and adolescents: a systematic review

Sedentary behavior contributes to increased atherosclerotic risk in adults. Whether or not this can be extended to pediatric populations is unclear. This systematic review assessed associations of sedentary behavior with large artery structure and function in pediatric populations. MEDLINE, EMBASE, CENTRAL, and Web of Science were searched from the earliest available date to 31st of December 2018. Analyses of associations of sedentary behavior with large artery structure or function in a pediatric (sub-)population were included, adhering to the PRISMA guidelines. The protocol was published in advance on PROSPERO (CRD42018112996). Study quality and quality of evidence were analyzed using NHLBI Study Quality assessment tools and GRADE. Six observational studies found no association of exposure and outcome variables, and one had contradicting results. One intervention found reduced flow-mediated dilation after 3 h of uninterrupted sitting. Exposure and outcome measures were highly heterogeneous. Study quality was low to moderate. Quality of evidence was very low or low in the observational studies and high in the intervention.Conclusion: In pediatric populations, current evidence is limited and of low quality about how acute effects of sedentary behavior translate into early vascular aging and the long-term development of vascular dysfunction and atherosclerotic risk. Future studies should emphasize a careful choice of the adequate type and measurement site of a biomarker for large artery structure and function as well as conduct a detailed assessment of sedentary behavior patterns.Trial registration: PROSPERO Registration Number: CRD42018112996What is known: • An independent association of sedentary behavior and biomarkers of large artery structure and function has been demonstrated in adults. • In children, sedentary behavior is directly associated with classical cardiovascular risk factors like elevated blood glucose levels, insulin resistance, high blood pressure, obesity, and elevated blood lipids.What is new: • Currently, only few studies of low quality in children and adolescents provide limited evidence about how acute effects of sedentary behavior translate into early vascular aging and the long-term development of atherosclerosis. • The type and measurement site of vascular biomarker need to be chosen carefully, and a detailed assessment of sedentary behavior patterns is important to minimize the methodological bias.

Influence of Vigorous Physical Activity on Structure and Function of the Cardiovascular System in Young Athletes-The MuCAYA-Study

Objective: Moderate physical activity (PA) is associated with a reduced risk to develop cardiovascular disease. However, junior athletes exercise between 10 and 20 h a week with intensities exceeding moderate levels by far. In this regard, the cardiovascular system has to increase its work five to six times compared to moderate intensities. This may result in potentially pathological adaptations of the cardiovascular system. The underlying process of vascular adaptations to exercise is yet not fully understood and hardly investigated in junior athletes. An increased blood pressure and pulse wave velocity, ventricular hypertrophy, arrhythmia, and even sudden cardiac death (SCD) has been reported in adult athletes. Studies, examining the cardiovascular system in children, its association to intensity and type of exercise, are rare. Therefore, we present the study protocol of a prospective cross-sectional study that investigates the influence of PA on the cardiovascular system in young athletes.

Methods and Design: Children and adolescents, 7–18 years, presenting for their annual pre-participation screening at the Institute of Preventive Pediatrics, Faculty of Sports and Health Sciences, Technical University of Munich (TUM), are examined in this prospective cross-sectional study. Vascular parameters measured by ultrasound are carotid intima-media thickness (cIMT), vascular stiffness (AC, Ep, β, PWV β), and the vascular diameter (D) to calculate the IMT:Diameter-Ratio (IDR). Cardiac function is evaluated by a 12-lead ECG, and echocardiographic parameters (end-diastolic left ventricular diameter, left ventricular diastolic posterior wall thickness, diastolic septal thickness, left ventricular mass and relative wall thickness, ejection fraction, and shortening fraction). A cardiopulmonary exercise test is performed on a bicycle ergometer, muscular strength is assessed with the handgrip test, and physical activity with the MoMo questionnaire.

Discussion: It is essential to follow young athletes over the course of their career in order to detect pathophysiological changes in the myocardium as soon as possible. If these changes are preceded or followed by changes in vascular structure and function is not known yet. Therefore, we present the study protocol of the Munich Cardiovascular adaptations in young athletes study (MuCAYA-Study) which investigates the association between vascular and cardiac adaptation to intensive exercise in junior athletes.

Oxidative Stress and Inflammation, Key Targets of Atherosclerotic Plaque Progression and Vulnerability: Potential Impact of Physical Activity

Atherosclerosis, a complex cardiovascular disease, is a leading cause of mortality and morbidity worldwide. Oxidative stress and inflammation are both involved in the development of atherosclerotic plaque as they increase the biological processes associated with this pathology, such as endothelial dysfunction and macrophage recruitment and adhesion. Atherosclerotic plaque rupture leading to major ischemic events is the result of vulnerable plaque progression, which is a result of the detrimental effect of oxidative stress and inflammation on risk factors for atherosclerotic plaque rupture, such as intraplaque hemorrhage, neovascularization, and fibrous cap thickness. Thus, both are key targets for primary and secondary interventions. It is well recognized that chronic physical activity attenuates oxidative stress in healthy subjects via the improvement of antioxidant enzyme capacities and inflammation via the enhancement of anti-inflammatory molecules. Moreover, it was recently shown that chronic physical activity could decrease oxidative stress and inflammation in atherosclerotic patients. The aim of this review is to summarize the role of oxidative stress and inflammation in atherosclerosis and the results of therapeutic interventions targeting them in both preclinical and clinical studies. The effects of chronic physical activity on these two key processes are then reviewed in vulnerable atherosclerotic plaques in both coronary and carotid arteries.

A cross-sectional and prospective analyse of reallocating sedentary time to physical activity on children's cardiorespiratory fitness

Cardiorespiratory fitness (CRF) is associated with health benefits in children, improving cardiac morphology, cardiovascular disease risk factors, and biological outcomes. This study aimed to examine the substitution effects of displaying a fixed duration of sedentary time with a fixed duration of physical activity (PA) at different intensities on children's CRF. A total of 315 children (136 boys) were assessed (age: 10.6 ± 0.6 years old). Outcomes at baseline and follow-up (16-months) were CRF determined using a maximal cycle test and sedentary time and PA measured with accelerometers. Data were analysed by isotemporal substitution analyses estimating the effect of reallocating 30 min/day of sedentary time by light (LPA), moderate (MPA) and vigorous physical activity (VPA) on CRF. VPA was positively and significantly associated with CRF cross-sectional (β = 0.026, p < 0.001) and prospectively (β = 0.010, p < 0.001). Reallocating 30 min/day of sedentary time into VPA was positively cross-sectionally (β = 0.780, p < 0.001) and prospectively (β = 0.303, p < 0.05) associated with CRF. Conversely, relocating 30-minutes of sedentary time into 30 minutes of LPA and MPA was not associated with CRF. These results suggest that reallocating an equal amount of time from sedentary into VPA is cross-sectional and prospectively associated with a favourable CRF.

Associations of Objectively Measured Physical Activity and Sedentary Time With Arterial Stiffness in Pre-Pubertal Children

PURPOSE

To investigate the relationships of objectively measured physical activity (PA) and sedentary time (ST) to arterial stiffness in prepubertal children.

METHOD

Altogether 136 children (57 boys, 79 girls) aged 6-8-years participated in the study. Stiffness index (SI) was assessed by pulse contour analysis based on photoplethysmography. ST, light PA, moderate PA, and vigorous PA were assessed using combined acceleration and heart rate monitoring. We investigated the associations of ST (<1.5METs) and time spent in intensity level of PA above 2-7METs in min/d with SI using linear regression analysis. We studied the optimal duration and intensity of PA to identify children being in the highest quarter of SI using Receiver Operating Characteristics curves.

RESULTS

Moderate PA, vigorous PA, and cumulative time spent in PA above 3 (β=-0.279, p = .002), 4 (β =-0.341, P<0.001), 5 (β =-0.349, P<0.001), 6 (β =-0.312, P<0.001), and 7 (β =-0.254, p = .005) METs were inversely associated with SI after adjustment for age, sex, and monitor wear time. The cutoffs for identifying children being in the highest quarter of SI <68 min/d for PA exceeding 5 METs and <26 min/d for PA exceeding 6 METs.

CONCLUSION

Lower levels of PA exceeding 3-6 METs were related to higher arterial stiffness in children.

Systematic review of the relationships between objectively measured physical activity and health indicators in school-aged children and youth

Moderate-to-vigorous physical activity (MVPA) is essential for disease prevention and health promotion. Emerging evidence suggests other intensities of physical activity (PA), including light-intensity activity (LPA), may also be important, but there has been no rigorous evaluation of the evidence. The purpose of this systematic review was to examine the relationships between objectively measured PA (total and all intensities) and health indicators in school-aged children and youth. Online databases were searched for peer-reviewed studies that met the a priori inclusion criteria: population (apparently healthy, aged 5-17 years), intervention/exposure/comparator (volumes, durations, frequencies, intensities, and patterns of objectively measured PA), and outcome (body composition, cardiometabolic biomarkers, physical fitness, behavioural conduct/pro-social behaviour, cognition/academic achievement, quality of life/well-being, harms, bone health, motor skill development, psychological distress, self-esteem). Heterogeneity among studies precluded meta-analyses; narrative synthesis was conducted. A total of 162 studies were included (204 171 participants from 31 countries). Overall, total PA was favourably associated with physical, psychological/social, and cognitive health indicators. Relationships were more consistent and robust for higher (e.g., MVPA) versus lower (e.g., LPA) intensity PA. All patterns of activity (sporadic, bouts, continuous) provided benefit. LPA was favourably associated with cardiometabolic biomarkers; data were scarce for other outcomes. These findings continue to support the importance of at least 60 min/day of MVPA for disease prevention and health promotion in children and youth, but also highlight the potential benefits of LPA and total PA. All intensities of PA should be considered in future work aimed at better elucidating the health benefits of PA in children and youth.

Reduced arterial stiffness in very fit boys and girls

Low cardiorespiratory fitness is associated with higher cardiovascular risk, whereas high levels of cardiorespiratory fitness protect the cardiovascular system. Carotid intima-media thickness and arterial distensibility are well-established parameters to identify subclinical cardiovascular disease. Therefore, this study investigated the influence of cardiorespiratory fitness and muscular strength on carotid intima-media thickness and arterial distensibility in 697 children and adolescents (376 girls), aged 7-17 years. Cardiorespiratory fitness and strength were measured with the test battery FITNESSGRAM; carotid intima-media thickness, arterial compliance, elastic modulus, stiffness index β, and pulse wave velocity β were assessed by B- and M-mode ultrasound at the common carotid artery. In bivariate correlation, cardiorespiratory fitness was significantly associated with all cardiovascular parameters and was an independent predictor in multivariate regression analysis. No significant associations were obtained for muscular strength. In a one-way variance analysis, very fit boys and girls (58 boys and 74 girls>80th percentile for cardiorespiratory fitness) had significantly decreased stiffness parameters (expressed in standard deviation scores) compared with low fit subjects (71 boys and 77 girls<20th percentile for cardiorespiratory fitness): elastic modulus -0.16±1.02 versus 0.19±1.17, p=0.009; stiffness index β -0.15±1.08 versus 0.16±1.1, p=0.03; and pulse wave velocity β -0.19±1.02 versus 0.19±1.14, p=0.005. Cardiorespiratory fitness was associated with healthier arteries in children and adolescents. Comparison of very fit with unfit subjects revealed better distensibility parameters in very fit boys and girls.

New relative intensity ambulatory accelerometer thresholds for elderly men and women: the Generation 100 study

Background

Public health initiatives world-wide recommend increasing physical activity (PA) to improve health. However, the dose and the intensity of PA producing the most benefit are still debated. Accurate assessment of PA is necessary in order to 1) investigate the dose–response relationship between PA and health, 2) shape the most beneficial public health initiatives and 3) test the effectiveness of such initiatives. Actigraph accelerometer is widely used to objectively assess PA, and the raw data is given in counts per unit time. Count-thresholds for low, moderate and vigorous PA are mostly based on absolute intensity. This leads to largely inadequate PA intensity assessment in a large proportion of the elderly, who due to their declining maximal oxygen uptake (VO_2max) cannot reach the moderate/vigorous intensity as defined in absolute terms. To resolve this issue, here we report relative Actigraph intensity-thresholds for the elderly.

Methods

Submaximal-oxygen-uptake, VO_2max and maximal heart rate (HR_max) were measured in 111 70–77 year olds, while wearing an Actigraph-GT3X+. Relationship between VO_2max percentage (%), counts-per-minute (CPM) and gender (for both the vertical-axis (VA) and vector-magnitude (VM)) and VO_2max% and HR_max% was established using a mixed-regression-model. VM-and VA-models were tested against each other to see which model predicts intensity of PA better.

Results

VO_2max and gender significantly affected number of CPM at different PA intensities (p < 0.05). Therefore, intensity-thresholds were created for both men and women of ranging VO_2max values (low, medium, high). VM-model was found to be a better predictor of PA-intensity than VA-model (p < 0.05). Established thresholds for moderate intensity (46−63 % of VO_2max) ranged from 669–3367 and 834–4048 CPM and vigorous intensity (64−90 % of VO_2max) from 1625–4868 and 2012-5423CPM, for women and men, respectively. Lastly, we used this evidence to derive a formula that predicts customized relative intensity of PA (either VO_2max% or HR_max%) using counts-per-minute values as input.

Conclusion

Intensity-thresholds depend on VO_2max, gender and Actigraph-axis. PA intensity-thresholds that take all these factors into account allow for more accurate relative intensity PA assessment in the elderly and will be useful in future PA research.

Trial registration

(ClinicalTrials.gov Identifier: NCT02017847, registered 17. December 2013)

Associations of cardiorespiratory fitness, physical activity, and adiposity with arterial stiffness in children

Associations of cardiorespiratory fitness (CRF), physical activity (PA), sedentary behavior, and body fat percentage (BF%) with arterial stiffness and dilation capacity were investigated in 160 prepubertal children (83 girls) 6-8 years of age. We assessed CRF (watts/lean mass) by maximal cycle ergometer exercise test, total PA, structured exercise, unstructured PA, commuting to and from school, recess PA and total and screen-based sedentary behavior by questionnaire, BF% using dual-energy X-ray absorptiometry, and arterial stiffness and dilation capacity using pulse contour analysis. Data were adjusted for sex and age. Poorer CRF (standardized regression coefficient β = -0.297, P < 0.001), lower unstructured PA (β = -0.162, P = 0.042), and higher BF% (β = 0.176, P = 0.044) were related to higher arterial stiffness. When CRF, unstructured PA, and BF% were in the same model, only CRF was associated with arterial stiffness (β = -0.246, P = 0.006). Poorer CRF was also related to lower arterial dilation capacity (β = 0.316, P < 0.001). Children with low CRF (< median) and high BF% (≥ median; P = 0.002), low CRF and low unstructured PA (< median; P = 0.006) or children with low unstructured PA and high BF% (P = 0.005) had higher arterial stiffness than children in the opposite halves of these variables. Poor CRF was independently associated with increased arterial stiffness and impaired arterial dilation capacity among children.

Linking cardiorespiratory fitness classification criteria to early subclinical atherosclerosis in children

It is unclear if cardiorespiratory fitness (CRF) can be used as a screening tool for premature changes in carotid intima-media thickness (cIMT) in paediatric populations. The purpose of this cross-sectional study was 3-fold: (i) to determine if CRF can be used to screen increased cIMT; (ii) to determine an optimal CRF cut-off to predict increased cIMT; and (iii) to evaluate its ability to predict increased cIMT among children in comparison with existent CRF cut-offs. cIMT was assessed with high-resolution ultrasonography and CRF was determined using a maximal cycle test. Receiver operating characteristic analyses were conducted in boys (n = 211) and girls (n = 202) aged 11-12 years to define the optimal sex-specific CRF cut-off to classify increased cIMT (≥75th percentile). Logistic regression was used to examine the association between the CRF cut-offs with the risk of having an increased cIMT. The optimal CRF cut-offs to predict increased cIMT were 45.81 and 34.46 mL·kg(-1)·min(-1) for boys and girls, respectively. The odds-ratios for having increased cIMT among children who were unfit was up to 2.8 times the odds among those who were fit (95% confidence interval: 1.40-5.53). Considering current CRF cut-offs, only those suggested by Adegboye et al. 2011. (Br. J. Sports Med. 45(9): 722-728) and Boddy et al. 2012 (PLoS One, 7(9): e45755) were significant in predicting increased cIMT. In conclusion, CRF cut-offs (boys: ≤ 45.8; girls: ≤ 34.5 mL·kg(-1)·min(-1)) are associated with thickening of the arterial wall in 11- to 12-year-old children. Low CRF is an important cardiovascular risk factor in children and our data highlight the importance of obtaining an adequate CRF.

Associations between bicycling and carotid arterial stiffness in adolescents: The European Youth Hearts Study

The aim of the study was to investigate the associations between bicycling and carotid arterial stiffness, independent of objectively measured moderate-and-vigorous physical activity. This cross-sectional study included 375 adolescents (age 15.7 ± 0.4 years) from the Danish site of the European Youth Heart Study. Total frequency of bicycle usage was assessed by self-report, and carotid arterial stiffness was assessed using B-mode ultrasound. After adjusting for pubertal status, body height, and objectively measured physical activity and other personal lifestyle and demographic factors, boys using their bicycle every day of the week displayed a higher carotid arterial compliance {standard beta 0.47 [95% confidence interval (CI) 0.07-0.87]} and distension [standard beta 0.38 (95% CI -0.04 to 0.81)]. Boys using their bicycle every day of the week furthermore displayed a lower Young's elastic modulus [standard beta -0.48 (95% CI -0.91 to -0.06)]. Similar trends were observed when investigating the association between commuter bicycling and carotid arterial stiffness. These associations were not observed in girls. Our observations suggest that increasing bicycling in adolescence may be beneficial to carotid arterial health among boys.

Fitness, fatness, and academic performance in seventh-grade elementary school students

BACKGROUND

In addition to the benefits on physical and mental health, cardiorespiratory fitness has shown to have positive effects on cognition. This study aimed to investigate the relationship between cardiorespiratory fitness and body weight status on academic performance among seventh-grade students.

METHODS

Participants included 1531 grade 7 students (787 male, 744 female), ranging in age from 12 to 14 years (Mage = 12.3 ± 0.60), from 3 different cohorts. Academic performance was measured using the marks students had, at the end of their academic year, in mathematics, language (Portuguese), foreign language (English), and sciences. To assess cardiorespiratory fitness the Progressive Aerobic Cardiovascular Endurance Run, from Fitnessgram, was used as the test battery. The relationship between academic achievement and the independent and combined association of cardiorespiratory fitness/weight status was analysed, using multinomial logistic regression.

RESULTS

Cardiorespiratory fitness and weight status were independently related with academic achievement. Fit students, compared with unfit students had significantly higher odds for having high academic achievement (OR = 2.29, 95% CI: 1.48-3.55, p < 0.001). Likewise, having a normal weight status was also related with high academic achievement (OR = 3.65, 95% CI: 1.82-7.34, p < 0.001).

CONCLUSIONS

Cardiorespiratory fitness and weight status were independently and combined related to academic achievement in seventh-grade students independent of the different cohorts, providing further support that aerobically fit and normal weight students are more likely to have better performance at school regardless of the year that they were born.