Luisa Soares-Miranda

Compliance with physical activity guidelines in preschool children.

Abstract The aims of this study were (1) to document differences in physical activity (both total and moderate-to-vigorous physical activity) between the sexes on weekdays and weekend days in preschoolers, and (2) to assess compliance with recommendations for total physical activity (National Association for Sport and Physical Education guidelines) and moderate-to-vigorous physical activity on weekdays and weekend days in the same children. The sample comprised 245 preschoolers (105 girls, 140 boys) aged 3.5–6.0 years old. Physical activity was assessed using an Actigraph accelerometer. Data were analysed with specific software and activity was measured as counts per minute. An independent t-test and general linear model with repeated-measures were used to assess differences between the sexes and differences between days (weekdays and weekend days) within each sex, respectively. A chi-square test was used to determine differences between the sexes in the proportion of children complying with physical activity guidelines. In both sexes, sedentary behaviour accounted for the majority of the time on weekdays and weekend days (weekdays: 83%; weekend days: 83.9%). Boys engaged in significantly more (P < 0.05) total physical activity and moderate-to-vigorous physical activity than girls (weekdays: boys 155.4 min vs. girls 128.22 min; weekend days: boys 111.2 min vs. girls 90.5 min). On average, preschool children engaged in significantly more (P < 0.05) total physical activity and moderate-to-vigorous physical activity on weekdays than weekend days. Altogether, 74.3% and 93.5% of the children met the National Association for Sport and Physical Education guidelines and moderate-to-vigorous physical activity recommendations respectively on weekdays, whereas compliance with both recommendations was substantially less in both sexes on weekend days. The results of this study suggest that despite 83% of time during the day being spent in sedentary behaviour, most preschool children met the daily physical activity and moderate-to-vigorous physical activity recommendations on weekdays. Future research should consider the two constructs of physical activity and sedentary behaviour independently, as they might not necessarily counteract each other.

Physical Activity and Heart Rate Variability in Older Adults The Cardiovascular Health Study

Background— Cardiac mortality and electrophysiological dysfunction both increase with age. Heart rate variability (HRV) provides indices of autonomic function and electrophysiology that are associated with cardiac risk. How habitual physical activity among older adults prospectively relates to HRV, including nonlinear indices of erratic sinus patterns, is not established. We hypothesized that increasing the levels of both total leisure-time activity and walking would be prospectively associated with more favorable time-domain, frequency-domain, and nonlinear HRV measures in older adults. Methods and Results— We evaluated serial longitudinal measures of both physical activity and 24-hour Holter HRV over 5 years among 985 older US adults in the community-based Cardiovascular Health Study. After multivariable adjustment, greater total leisure-time activity, walking distance, and walking pace were each prospectively associated with specific, more favorable HRV indices, including higher 24-hour standard deviation of all normal-to-normal intervals (Ptrend=0.009, 0.02, 0.06, respectively) and ultralow-frequency power (Ptrend=0.02, 0.008, 0.16, respectively). Greater walking pace was also associated with a higher short-term fractal scaling exponent (Ptrend=0.003) and lower Poincaré ratio (Ptrend=0.02), markers of less erratic sinus patterns. Conclusions— Greater total leisure-time activity, and walking alone, as well, were prospectively associated with more favorable and specific indices of autonomic function in older adults, including several suggestive of more normal circadian fluctuations and less erratic sinoatrial firing. Our results suggest potential mechanisms that might contribute to lower cardiovascular mortality with habitual physical activity later in life.

Exercise and Risk of Major Cardiovascular Events in Adult Survivors of Childhood Hodgkin Lymphoma: A Report From the Childhood Cancer Survivor Study

PURPOSE Survivors of Hodgkin lymphoma (HL) are at increased risk of treatment-related cardiovascular (CV) events; whether exercise modifies this risk is unknown. METHODS Survivors of HL (n = 1,187; median age, 31.2 years) completed a questionnaire evaluating vigorous-intensity exercise behavior. CV events were collected in follow-up questionnaires and graded according to Common Terminology Criteria for Adverse Events (version 4.03). The primary end point was incidence of any major (grade 3 to 5) CV event. Poisson regression analyses were used to estimate the association between exercise exposure (metabolic equivalent [MET] hours/week(-1)) and risk of major CV events after adjustment for clinical covariates and cancer treatment. RESULTS Median follow-up was 11.9 years (range, 1.7 to 14.3 years). Cumulative incidence of any CV event was 12.2% at 10 years for survivors reporting 0 MET hours/week(-1) compared with 5.2% for those reporting ≥ 9 MET hours/week(-1). In multivariable analyses, the incidence of any CV event decreased across increasing MET categories (Ptrend = .002). Compared with survivors reporting 0 MET hours/week(-1), the adjusted rate ratio for any CV event was 0.87 (95% CI, 0.56 to 1.34) for 3 to 6 MET hours/week(-1), 0.45 (95% CI, 0.26 to 0.80) for 9 to 12 MET hours/week(-1), and 0.47 (95% CI, 0.23 to 0.95) for 15 to 21 MET hours/week(-1). Adherence to national vigorous intensity exercise guidelines (ie, ≥ 9 MET hours/week(-1)) was associated with a 51% reduction in the risk of any CV event in comparison with not meeting the guidelines (P = .002). CONCLUSION Vigorous exercise was associated with a lower risk of CV events in a dose-dependent manner independent of CV risk profile and treatment in survivors of HL.

Objectively Measured Physical Activity and Body Mass Index in Preschool Children

Aim. To examine the association between objectively measured physical activity (PA) and body mass index (BMI) in preschool children. Methods. The study comprised 281 children (55.9% boys) aged from 4 to 6 years. PA was measured by accelerometer. Children were categorized as non-overweight (NOW) and overweight/obese (OW) according to the sex-adjusted BMI z-score (<1 and ≥1, resp.). Results. Total and moderate intensity PA were not associated with BMI. We observed that a higher proportion of OW children were classified as low-vigorous PA compared to their NOW peers (43.9 versus 32.1%, resp., P > .05). Logistic regression analysis showed that children with low-vigorous PA had higher odds ratio (OR) to be classified as OW compared to those with high-vigorous PA (OR = 4.4; 95% CI: 1.4–13.4; P = .008) after adjusting for BMI at first and second years of life and other potential confounders. Conclusion. The data suggests that vigorous PA may play a key role in the obesity development already at pre-school age.

Metabolic syndrome, physical activity and cardiac autonomic function

Our primary aim was to investigate the associations that components of metabolic syndrome and physical activity have with cardiac autonomic nervous system activity as estimated by heart rate variability (HRV) in young adults free of metabolic abnormalities. We also aimed to identify predictors of 3‐year changes in HRV.

Physical Activity and Risk of Coronary Heart Disease and Stroke in Older Adults: The Cardiovascular Health Study

Background— Although guidelines suggest that older adults engage in regular physical activity (PA) to reduce cardiovascular disease (CVD), surprisingly few studies have evaluated this relationship, especially in those >75 years. In addition, with advancing age the ability to perform some types of PA might decrease, making light-moderate exercise such as walking especially important to meet recommendations. Methods and Results— Prospective cohort analysis among 4207 US men and women of a mean age of 73 years (standard deviation=6) who were free of CVD at baseline in the Cardiovascular Health Study were followed from 1989 to 1999. PA was assessed and cumulatively updated over time to minimize misclassification and assess the long-term effects of habitual activity. Walking (pace, blocks, combined walking score) was updated annually from baseline through 1999. Leisure-time activity and exercise intensity were updated at baseline, 1992, and 1996. Incident CVD (fatal or nonfatal myocardial infarction, coronary death, or stroke) was adjudicated using medical records. During 41 995 person-years of follow-up, 1182 CVD events occurred. After multivariable adjustment, greater PA was inversely associated with coronary heart disease, stroke (especially ischemic stroke), and total CVD, even in those ≥75 years. Walking pace, distance, and overall walking score, leisure-time activity, and exercise intensity were each associated with lower risk. For example, in comparison with a walking pace <2 mph, those that habitually walked at a pace >3 mph had a lower risk of coronary heart disease (0.50; confidence interval, 0.38–0.67), stroke (0.47; confidence interval, 033–0.66), and CVD (0.50; confidence interval, 0.40–0.62). Conclusions— These data provide empirical evidence supporting PA recommendations, in particular, walking, to reduce the incidence of CVD among older adults.

Sitting time and body mass index, in a Portuguese sample of men: results from the Azorean Physical Activity and Health Study (APAHS).

The aim of this study was to verify the relation between body mass index (BMI) and sitting time in a sample of 4,091 Azorean men. BMI was calculated from self-reported weight and height. Total physical activity (PA) time and total sitting time were assessed with the IPAQ (short version). Linear Regression analysis showed that total sitting time (hours/day) was positively associated with BMI (B = 0.078; p < 0.001) after adjustments for age, meal frequency, alcohol and tobacco consumptions, island of residence, education level and total PA time. Although the cross sectional design precludes us from establishing causality, our findings emphasize the importance of reducing sedentary behavior to decrease the risk of obesity.

Metabolic risk factors, physical activity and physical fitness in azorean adolescents: a cross-sectional study

BackgroundThe prevalence of metabolic syndrome has increased over the last few decades in adolescents and has become an important health challenge worldwide. This study analyzed the relationships between metabolic risk factors (MRF) and physical activity (PA) and physical fitness (PF) in a sample of Azorean adolescents.MethodsA cross-sectional school-based study was conducted on 417 adolescents (243 girls) aged 15-18 from the Azorean Islands, Portugal. Height, weight, waist circumference, fasting glucose, HDL-cholesterol, triglycerides, and blood pressure were measured. A sum of MRF was computed, and adolescents were classified into three groups: no MRF, one MRF and two or more MRF. PA was assessed by a sealed pedometer. PF was assessed using five tests from the Fitnessgram Test Battery. Dietary intake was obtained using a semi-quantitative food frequency questionnaire.ResultsMean daily steps for girls and boys were 7427 ± 2725 and 7916 ± 3936, respectively. Fifty-nine percent of the adolescents showed at least one MRF and 57.6% were under the healthy zone in the 20 m Shuttle Run Test. Ordinal logistic regression analysis showed that after adjusting for sex, body mass index, socio-economic status and adherence to a Mediterranean diet, adolescents who were in the highest quartile of the pedometer step/counts (≥9423 steps/day) and those who achieved the healthy zone in five tests were less likely to have one or more MRF (OR = 0.56;95%CI:0.33-0.95; OR = 0.55;95%CI:0.31-0.98, respectively).ConclusionsDaily step counts and PF levels were negatively associated with having one or more MRF among Azorean adolescents. Our findings emphasize the importance of promoting and increasing regular PA and PF to reduce the public health burden of chronic diseases associated with a sedentary lifestyle.

Comparison of different VO2max equations in the ability to discriminate the metabolic risk in Portuguese adolescents

There is increasing evidence that cardiorespiratory fitness (CRF) is an important health marker already in youth. This study aimed to determine the ability of five VO(2max) equations to discriminate between low/high Metabolic Risk in 450 Portuguese adolescents aged 10-18. We measured waist and hip circumferences, fasting glucose, total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, and blood pressure. For each of these variables, a Z-score was computed. The HDL-cholesterol was multiplied by -1. A metabolic risk score was constructed by summing the Z scores of all individual risk factors. High risk was considered when the individual had ≥1 SD of this score. Cardiorespiratory fitness (CRF) was measured with the 20-m shuttle run test. We estimated VO(2max) from the CRF tests using five equations. ROC analyses showed a significant discriminatory accuracy for the Matsuzaka and Barnett(a) equations in identifying the low/high metabolic risk in both genders (Matsuzaka girls: AUC=0.654, 95%CI: 0.591-0.713, p<0.001, VO(2max)=39.5 mL kg⁻¹min⁻¹; boys: AUC=0.648, 95%CI: 0.576-0.716, p<0.001, VO(2max)=41.8 mL kg⁻¹min⁻¹; Barnett(a) girls: AUC=0.620, 95%CI: 0.557-0.681, p<0.001, VO(2max)=46.4 mL kg⁻¹min⁻¹; boys: AUC=0.628, 95%CI: 0.555-0.697, p=0.04, VO(2max)=42.6 mL kg⁻¹min⁻¹), and the Ruiz equation in boys (AUC=0.638, 95%CI: 0.565-0.706, p<0.001, VO(2max)=47.1 mL kg⁻¹min⁻¹). The VO(2max) values found require further testing in other populations as well as in longitudinal studies; the identification of adolescents who have low CRF levels can help detect youth with an increased risk of metabolic disease.

Metabolic syndrome and physical fitness in a sample of Azorean adolescents

BACKGROUND Metabolic syndrome, a predecessor of cardiovascular disease and type 2 diabetes, has become prevalent in adolescents. This study aimed to estimate the prevalence of metabolic syndrome and its components and to analyze the relationship between metabolic syndrome and overall physical fitness levels in a sample of Azorean adolescents. METHODS A cross-sectional school-based study, the Azorean Physical Activity and Health Study II, was conducted on 517 adolescents (297 girls, 220 boys) aged 15-18 years old from the Azorean Islands. Body height, weight, waist circumference, and arterial blood pressure were measured according to standards. Fasting intravenous blood samples were analyzed (high-density lipoprotein cholesterol, triglycerides, and glucose). Physical fitness was assessed using five tests from Fitnessgram Test Battery 8.0: Curl-up, push-up, trunk lift, pacer, and sit-and-reach. Adolescents were then classified as being in the healthy zone or above or under the healthy zone. Metabolic syndrome was defined according to the 2007 International Diabetes Federation‘s guidelines for adolescents. RESULTS The prevalence of metabolic syndrome was 5% (4.7% in girls and 5.5% in boys, P > 0.05). Waist circumference was the most prevalent component (32.9%), and hypertriglyceridemia the least (4.4%). Logistic regression analysis showed that after adjusting for pubertal stage and socioeconomic status, unfit adolescents (healthy zone criteria in <or=2 tests) were more likely [odds ratio (OR) = 3.414; 95% confidence interval (CI), 1.150-10.129] to be classified as having metabolic syndrome. CONCLUSIONS The prevalence of metabolic syndrome is high in Azorean adolescents. Unfit adolescents were more likely to have metabolic syndrome than fit adolescents. Improving overall physical fitness levels and abdominal obesity reduction may be important strategies in overcoming this public health problem and its consequences.