Phase angle predicts physical function in older adults.

BACKGROUND: Phase angle (PhA) is recognized as an indicator of cellular health and may be a useful marker of physical functions in geriatric populations. AIMS: We aim to analyse the ability of the Phase angle (PhA) to predict the physical function in older adults. METHOD: 113 healthy older adults (67 female and 46 male) performed physical tests using the Fullerton Battery - Senior Fitness Test, to assess their physical fitness. Bioelectrical impedance spectroscopy was used to determine PhA at 50KHz and dual-energy x-ray absorptiometry to assess body composition. RESULTS: PhA was positively associated with functional fitness composite, chair stand, arm curl and 6 min walk test and negatively related with chair sit-and-reach and 8-foot and go (p < 0.05). Even after adjusting for potential confounding variables such as age, sex and appendicular lean soft tissue, PhA showed an association with arm curl (ß = 0.23,p = 0.038), and 8-foot and go (ß=-0.214,p = 0.042). CONCLUSIONS: Higher values of PhA are related with a better physical function. Regardless of sex, age, and skeletal muscle, PhA predicts body strength, agility and dynamic balance in healthy older adults.

Effects of pre- or post-exercise whey protein supplementation on body fat and metabolic and inflammatory profile in pre-conditioned older women: A randomized, double-blind, placebo-controlled trial.

BACKGROUND AND AIM: Protein supplementation and resistance training (RT) are interventions that may counteract decline in muscle mass and increase in fat mass, thus reducing the risk of developing chronic diseases during the aging process. The objective of this study was to investigate the effect of whey protein (WP) pre- or post-RT on metabolic and inflammatory profile in pre-conditioned older women. METHODS AND RESULTS: Seventy older women participated in this investigation and were randomly assigned to one of three groups: WP pre-RT and placebo post-RT (WP-PLA, n = 24), placebo pre-RT and WP post-RT (PLA-WP, n = 23) and placebo pre and post-RT (PLA-PLA, n = 23). Each group ingested 35 g of PLA or WP pre- and post-RT. RT was carried out over 12 weeks (three times/week; 3 x 8-12 repetition maximum). Body composition, blood pressure, blood samples and dietary intake were assessed pre- and post-intervention. After the intervention, WP groups showed greater improvements in appendicular lean soft tissue (ALST: WP-PLA, 3.1%; PLA-WP, 3.9%; PLA-PLA, 1.8%) and total cholesterol/high density lipoprotein cholesterol ratio (TC/HDL-C: WP-PLA, -12.11%; PLA-WP, -13.2%; PLA-PLA, -0.7) when compared with PLA-PLA. WP post-RT also showed improvements (P < 0.05) in ALST/appendicular fat mass ratio (PLA-WP, 5.8%; PLA-PLA, 1.3%), total body fat (PLA-WP, -3.8%; PLA-PLA: -0.1) and trunk fat mass (PLA-WP, -3.1%; PLA-PLA, -0.3%) when compared with PLA-PLA. CONCLUSION: WP pre- or post- RT promotes improvements in ALST and TC/HDL-C ratio in pre-conditioned older women. WP administered after RT was more effective in improving metabolic health Z-score and in reducing body fat compared to placebo group.

Correlations between resistance training-induced changes on phase angle and biochemical markers in older women.

The main purpose of this study was to investigate the effects of 12 weeks of resistance training (RT) on phase angle (PhA), inflammatory and oxidative stress biomarkers, and to evaluate whether these RT-induced adaptations are related to PhA changes. Fifty-one older women (70.6 ± 5.1 years; 26.9 ± 4.2 kg/m2 ) were randomly allocated into a training group (TG) that performed 12-week RT or a nonexercising control group (CG). The PhA (Xitron), body composition (DXA), and blood sample measurements (after a 12 hours fast) were performed before and after the intervention. The TG showed a significant (P < .05) increase in PhA (TG: +7.4±5.9% vs CG: -3.6 ± 8.8%), and interleukin-10 (IL-10; TG: +51.8 ± 71.1% vs CG: -46.6 ± 38.0%), and a decrease in tumor necrosis factor alpha (TNF-α; TG: -15.2 ± 11.1% vs CG: +6.9±17.7%), interleukin-6 (IL-6; TG: -17.9 ± 17.8% vs CG: +6.1 ± 24.8%), and C-reactive protein (CRP; TG: -24.1 ± 19.9% vs CG: +43.8 ± 31.1%). Moreover, TG upregulated catalase (TG: +11.4 ± 15.0% vs CG: -6.7 ± 10.2%). Changes in TNF-α (r = -.71), CRP (r = -.65), lower advanced oxidation protein products (r = -.55), and catalase (r = +.73) after RT were correlated with changes in PhA (P < .05). These results suggest that RT improves PhA, inflammatory and oxidative stress biomarkers, and the changes in inflammatory and oxidative damage markers are correlated with changes in PhA.

Does adiposity mediate the relationship between physical activity and biological risk factors in youth?: a cross-sectional study from the International Children's Accelerometry Database (ICAD).

BACKGROUND/OBJECTIVES: To model the association between accumulating 60 daily minutes of moderate-to-vigorous physical activity and a composite score of biological risk factors into a direct and an indirect effect, using abdominal obesity as the mediator. SUBJECTS/METHODS: Cross-sectional data from the International Children's Accelerometry Database (ICAD) including 6-18-year-old children and adolescents (N=3412) from 4 countries providing at least 3 days of accelerometry-assessed physical activity. A standardized composite risk score was calculated from systolic blood pressure and fasting blood samples of insulin, glucose, triacylglycerol and inverse HDL-cholesterol. Abdominal obesity was assessed by the waist-circumference:height ratio. Two-stage regression analysis, allowing for exposure-mediator interaction, was used for the effect decomposition. RESULTS: Participants achieving 60 daily minutes of moderate-to-vigorous physical activity had a 0.31 (95% CI: -0.39, -0.23) standard deviations lower composite risk score than those achieving less than 60 min. Modelling the associations suggested that 0.24 standard deviations (95% CI: -0.32, -0.16) was attributed to the direct effect and -0.07 (95% CI: -0.11, -0.02) to the indirect effect indicating that 22% of the total effect was mediated by central adiposity. Modelling 30 and 90 min of moderate-to-vigorous physical activity per day resulted in changes in the direct but not the indirect effect. CONCLUSIONS: One hour of daily moderate-to-vigorous physical activity was associated with clinically relevant differences in metabolic control compared to engagement in less than this minimally recommended amount. The majority of the difference was explained by the direct effect of physical activity.International Journal of Obesity advance online publication, 31 October 2017; doi:10.1038/ijo.2017.241.

Usefulness of motion sensors to estimate energy expenditure in children and adults: a narrative review of studies using DLW.

This corrects the article DOI: 10.1038/ejcn.2017.2.

Birth weight, biological maturation and obesity in adolescents: a mediation analysis.

This study was aimed to investigate associations between birth weight and multiple adiposity indicators in youth, and to examine potential mediating effects by biological maturation. This was a school-based study involving 981 Brazilian adolescents aged between 10 and 17 years. Birth weight was reported retrospectively by mothers. Maturation was estimated by age of peak height velocity. Adiposity indicators included body mass index (BMI), waist circumference and percent body fat estimated from triceps and subscapular skinfolds. Multilevel mediation analyses were performed using the Sobel test, adjusted for chronological age, gestational age, cardiorespiratory fitness and socio-economic status. Except for body fat in girls, biological maturation partly or fully mediated (P<0.05) positive relationships between birth weight with all other obesity indicators in both sexes with their respective values of indirect effects with 95% confidence intervals: BMI [boys: 0.44 (0.06-0.82); girls: 0.38 (0.13-0.64)], waist circumference [boys: 1.14 (0.22-2.05); girls: 0.87 (0.26-1.48)] and body fat [boys: 0.60 (0.13-1.07)]. To conclude, birth weight is associated with elevated obesity risk in adolescence and biological maturation seems to at least partly mediate this relationship.

Usefulness of motion sensors to estimate energy expenditure in children and adults: a narrative review of studies using DLW.

It is well documented that meeting moderate-to-vigorous physical activity guidelines of 150 min per week is protective against chronic disease, and this is likely explained by higher energy expenditure (EE). In opposition, sedentary behavior (low EE) seems to impair health outcomes. There are gold standard methods to measure EE such as the doubly labeled water (DLW) or calorimetry. These methods are highly expensive and rely on complex techniques. Motion sensors present a good alternative to estimate EE and have been validated against these reference methods. This review summarizes findings from previous reviews and the most recently published studies on the validity of different motion sensors to estimate physical activity energy expenditure (PAEE) and total energy expenditure (TEE) against DLW, and whether adding other indicators may improve these estimations in children and adults. Regardless of the recognized validity of motion sensors to estimate PAEE and TEE at the group level, individual bias is very high even when combining biometric or physiological indicators. In children, accelerometers explained 13% of DLW's PAEE variance and 31% of TEE variance. In adults, DLW's explained variance was higher, 29 and 44% for PAEE and TEE, respectively. There is no ideal device, but identifying postures seems to be relevant for both children and adults' PAEE estimates. The variance associated with the number of methodological choices that these devices require invite investigators to work with the raw data in order to standardize all these procedures and potentiate the accelerometer signal-derived information. Models that consider biometric covariates seem only to improve TEE estimations, but adding heart rate enhances PAEE estimations in both children and adults.

Waist-to-height ratio is independently related to whole and central body fat, regardless of the waist circumference measurement protocol, in non-alcoholic fatty liver disease patients.

BACKGROUND: Waist-to-height ratio (WHtR) has been reported as a preferable risk related body fat (BF) marker, although no standardised waist circumference measurement protocol (WCmp) has been proposed. The present study aimed to investigate whether the use of a different WCmp affects the strength of relationship between WHtR and both whole and central BF in non-alcoholic fatty liver disease (NAFLD) patients. METHODS: BF was assessed with dual energy X-ray absorptiometry (DXA) in 28 NAFLD patients [19 males, mean (SD) 51 (13) years and nine females, 47 (13) years]. All subjects also underwent anthropometric evaluation including height and waist circumference (WC) measurement using four different WCmp (WC1, minimal waist; WC2, iliac crest; WC3, mid-distance between iliac crest and lowest rib; WC4, at the umbilicus) and WHtR was calculated using each WC measurements (WHtR1, WHtR2, WHtR3 and WHtR4, respectively). Partial correlations were conducted to assess the relation of WHtR and DXA assessed BF. RESULTS: All WHtR were particularly correlated with central BF, including abdominal BF (r = 0.80, r = 0.84, r = 0.84 and r = 0.78, respectively, for WHtR1, WHtR2, WHtR3 and WHtR4) and central abdominal BF (r = 0.72, r = 0.77, r = 0.76 and r = 0.71, respectively, for WHtR1, WHtR2, WHtR3 and WHtR4), after controlling for age, sex and body mass index. There were no differences between the correlation coefficients obtained between all studied WHtR and each whole and central BF variable. CONCLUSIONS: Waist-to-height ratio was found a suitable BF marker in the present sample of NAFLD patients and the strength of the relationship between WHtR and both whole and central BF was not altered by using different WCmp in the present sample of NAFLD patients.

Muscular fitness and metabolic and inflammatory biomarkers in adolescents: Results from LabMed Physical Activity Study.

This study aimed to evaluate the associations between muscular fitness and inflammatory biomarkers and to investigate the relationship between muscular fitness and selected clustered inflammatory biomarkers in adolescents. This is a cross-sectional analysis with 529 adolescents (267 girls) aged 12-18 years. Handgrip strength and standing long jump tests assessed MF. Continuous scores of clustered inflammatory biomarkers (sum of Z-scores of C-reactive protein [CRP], C3, C4, fibrinogen, and leptin); metabolic risk factor (MRF) score (sum of Z-scores of SBP, triglycerides, ratio total cholesterol [TC]/HDL, HOMA-IR, and waist circumference [WC]) were computed. Regression analyses showed an inverse association between muscular fitness score (ß=-.204; P<.021) and clustered score of inflammatory biomarkers, adjusted for age, sex, pubertal stage, socioeconomic status, adherence to the Mediterranean diet, cardiorespiratory fitness (CRF), MRF score, and body fat. Analysis of covariance showed that adolescents with an adverse inflammatory profile with low levels of muscular fitness exhibit the poorest MRF score (F3,525 =6.461; P<.001), adjusted for age, sex, pubertal stage, socioeconomic status, adherence to the Mediterranean diet, CRF, and body fatness. The inflammatory state seems to explain a significant part of the highest MRF score and in adolescents with high inflammatory status and low muscular strength.

Effect of resistance training on phase angle in older women: A randomized controlled trial.

Phase angle (PhA) is an angular-derived bioelectrical impedance parameter based on resistance and reactance that has been widely used in different populations as an objective indicator of cellular health. The purpose of this study was to analyze the effect of resistance training (RT) on PhA in older women. Forty-one older women (67.2 ± 4.5 years, 64.0 ± 12.3 kg, 154.7 ± 5.2 cm, and 26.6 ± 4.8 kg/m2 ) were randomly assigned to one of two groups: a training group (TG, n = 19) that underwent progressive RT for 12 weeks (eight exercises, three sets of 10-15 repetitions maximum, three times per week) or a control group (CG, n = 22) that did not perform any type of exercise during the intervention period. Resistance, reactance, PhA, total body water (TBW), intracellular (ICW) and extracellular (ECW) water were assessed by spectral bioelectrical impedance. There was a significant group by time interaction (P < 0.05) for PhA, TBW, and ICW in which only the TG increased their scores after the intervention period (PhA = +6.5%, TBW = +2.8%, and ICW = +5.1%). The results suggest that progressive RT promotes an increase in PhA in older women. Therefore, the PhA seems to be a good parameter to assess changes in cellular health during RT intervention.

Hypertrophy-type Resistance Training Improves Phase Angle in Young Adult Men and Women.

The main purpose of the present study was to investigate the effect of a hypertrophy-type resistance training protocol on phase angle, an indicator of cellular integrity, in young adult men and women. 28 men (22.2±4.3 years, 67.8±9.0 kg and 174.2±6.8 cm) and 31 women (23.2±4.1 years, 58.7±12.1 kg and 162.7±6.4 cm) underwent a progressive RT for 16 weeks (2 phases, 8 weeks each), 3 times per week, consisting of 10 to 12 whole body exercises with 3 sets of 8-12 repetitions maximum. Phase angle, resistance, reactance and total body water (intra and extracellular water compartments) were assessed by bioimpedance spectroscopy (Xitron 4200 Bioimpedance Spectrum Analyzer). Total body water, intracellular water and phase angle increased significantly (P<0.05) in men (7.8, 8.3, and 4.3%, respectively) and women (7.6, 11.7, and 5.8% respectively), with no significant difference between sexes (P>0.05). Bioimpedance resistance decreased (P<0.05) similarly in both sex (men=-4.8%, women=-3.8%). The results suggest that regardless of sex, progressive RT induces an increase in phase angle and a rise in cellular hydration.

Changes in phase angle and body composition induced by resistance training in older women.

BACKGROUND: Resistance training (RT) has selective effects on body composition that may counteract the deleterious effects of aging. Changes in phase angle (PhA) may serve to monitor the influence of RT in older people. OBJECTIVES: To describe the effect of RT in training, detraining and retraining on body composition, including PhA in older women. SUBJECTS/METHODS: Thirty-three older women (⩾60 years old) participated. The RT program was carried out over 12 weeks for each stage (training, detraining and retraining). Whole-body fat-free mass and fat mass (FM) and appendicular lean soft tissue (ALST) measurements were carried out using a dual energy X-ray absorptiometry. Bioimpedance spectroscopy was used to estimate total body water (TBW), intra (ICF) and extracellular (ECF) fluids, whole-body resistance (R) and reactance (Xc) and PhA. Upper and lower body muscle strength were also assessed. RESULTS: From baseline to after training muscle strength, ALST and PhA significantly (P<0.05) increased. In detraining, significant (P<0.05) reductions in muscle strength, TBW, ECF, ICF and PhA along with significant (P<0.05) increases in R were observed, with the greatest magnitude observed for PhA (Δ=-7.6%). From detraining to retraining a significant reduction in FM along with increases in Xc, PhA and muscle strength were observed. Although an increase was observed from detraining to retraining in PhA, the values were still lower than baseline PhA. CONCLUSIONS: In untrained older women, a RT is associated with increases in PhA, whereas detraining results in a marked decrease in PhA, and more time may be required in retraining to counteract the negative influence of absence of exercise stimulus.

Peak Vertical Jump Power as a Marker of Bone Health in Children.

The objective of this investigation was to evaluate the accuracy of peak vertical jump power (VJP) to identify children with bone mineral density (BMD) below average, defined as BMD measured by DXA and adjusted for body height at the whole body less head≤- 1.0 standard deviation (SD). The sample included 114 boys and girls aged 8.5±0.4 years old. VJP was estimated from a countermovement jump performed on a contact mat using the measured flight time to calculate the height of rise of the center of gravity. Logistic regression analysis revealed that the odds ratio of having BMD≤1.0 SD decreased 1.2% per watt of power and the probability of BMD below average was 75.6% higher in boys than in girls with the same peak power jump. Receiver operating characteristic analysis showed that the best trade-off between sensitivity and specificity to identify children with BMD<- 1.0 SD was 635 watts in boys (sensitivity=63.3%; specificity=69.2%; AUC=0.816, 95% CI: 0.681-0.95; p<0.001) and 515 watts in girls (sensitivity=75.0%; specificity=77.0%; AUC=0.849, 95% CI: 0.698-0.999; p=0.002). These cut-off values correspond to a vertical jump of 19.9 cm and 20.5 cm in 8-year-old boys and girls, respectively. The VJP showed a reasonable sensitivity and specificity as well good discriminant ability to identify children with BMD below average.

Single and combined effects of body composition phenotypes on carotid intima-media thickness.

BACKGROUND: Central fatness might be a more sensitive predictor of atherosclerotic changes in children than are total body fat measures. However, it is unclear whether a total body fat measure coupled with an estimate of a more central pattern of fat accumulation predicts increased carotid intima-media-thickness (cIMT) better than either measure alone. OBJECTIVE: The objective of the study is to identify the ability of a combination of simple anthropometric screening tools or a combination of objective measures of body composition to predict cIMT. METHODS: cIMT was assessed on the common carotid artery in 349 children aged 11-12 years old (183 girls). Body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) were dichotomized according to established criteria and indices of total body (TBFI) and abdominal (ABFMI) fat were assessed by dual-energy X-ray absorptiometry and categorized (increased risk ≥85%). Single and combined associations among anthropometric and laboratorial measures with the risk of having increased cIMT (≥85%) and discriminatory performance were tested with logistic regression analysis and Receiver Operator Curve analysis. RESULTS: Children with higher total fatness (BMI and TBFI) or higher central pattern of fat accumulation (WC, WHtR and BFMI) were in higher risk for increased cIMT [odds ratio (OR): 2.08-3.24). The risk for increased cIMT was not higher among children who coupled high total and high central fatness (OR: 2.27-3.10). CONCLUSIONS: Combination of total and central measures of fat does not improve the prediction of increased cIMT in children. Simple surrogate measures of fatness can be used to predict increased cIMT urging special attention to those children who exhibit increased abdominal fat.

Cross-sectional and prospective associations between moderate to vigorous physical activity and sedentary time with adiposity in children.

BACKGROUND: Physical activity (PA) and sedentary time (SED) have both been suggested as potential risk factors for adiposity in children. However, there is paucity of data examining the temporal associations between these variables. OBJECTIVE: This study aimed to analyze the cross-sectional and prospective associations between PA, SED and body composition in children. METHODS: A total of 510 children (age at baseline 10.1±0.8, age at follow-up 11.8±0.9) from six Portuguese schools from the Oeiras Municipality participated in this study. PA and SED were measured by accelerometry and trunk fat mass (TFM) and body fat mass (BFM) were measured by dual energy X-ray absorptiometry. Fat mass index (FMI) was calculated as BFM divided by height squared. Several regression models adjusted for age, sex, maturity status, follow-up duration, baseline levels of the outcome variable and SED or moderate to vigorous PA (MVPA) were performed. RESULTS: MVPA (min per day) was cross-sectionally inversely associated with adiposity indexes (FMI, TFM and BFM). Adiposity indexes were inversely associated with time in MVPA. In prospective analyses, MVPA was associated with a lower levels of FMI (ß=-0.37, 95% confidence interval (CI): -0.49 to -0.26, P<0.001), TFM (ß=-0.20, 95% CI: -0.29 to -0.10, P<0.001) and BFM (ß=-0.37, 95% CI: -0.49 to -0.26, P<0.001). When the model was adjusted for age, sex, maturity status and for baseline levels of the outcome variables MVPA remained a significant predictor of lower adiposity indexes (FMI: ß=-0.09, 95% CI: -0.16 to -0.01, P<0.05; TFM: ß=-0.08, 95% CI: -0.15 to -0.01, P<0.05; BFM: ß=-0.07, 95% CI: -0.15 to 0.00, P<0.05). Adiposity was not associated with MVPA when modeled as the exposure in prospective analyses. SED was not related with adiposity indexes, except for the relationship with FMI. CONCLUSIONS: In cross-sectional and prospective analyses, MVPA is associated with lower adiposity independent of covariates and SED. Results suggest that promoting MVPA is important for preventing gain in adiposity in healthy children.

Sedentary Bout Durations Are Associated with Abdominal Obesity in Older Adults.

OBJECTIVES: In older adults, sedentary behavior has been positively associated with obesity and impaired metabolic health, additional to low moderate-to-vigorous physical activity (MVPA). Further to the total time spent in sedentary behavior, the manner in which it is accumulated - number of continuous sedentary bouts of different extends - may also be relevant. The association for objectively measured uninterrupted sedentary bouts and respective patterns with abdominal obesity in older adults was examined. DESIGN: Cross-sectional. SETTING: Community-based older people were recruited in each region of Portugal. Data collection was performed between September, 2007 and May, 2009. PARTICIPANTS: 351 older adults (230 women) mean age of 75-years. MEASUREMENTS: Sedentary time was measured by an accelerometer (counts/minute <100), worn during waking hours for four consecutive days. Continuous sedentary bouts of 560 length were treated (counts/minute <100). Abdominal obesity was defined by waist circumference (men>102 cm; women>88 cm). RESULTS: There were positive and escalating linear associations for the continuum of sedentary bouts' lengths with waist circumference. Logistic regression showed that for each additional sedentary bout of 10< min<20 the odds of being abdominally obese increased by 6.8% (OR=1.07, 95% CI: 1.02 - 1.13) up to 48% (OR=1.48, 95% CI: 1.07 - 2.03) for each 1-hour sedentary bout increment, after controlling for age, gender, total sedentary time, MVPA time, total wear time, movement counts within the sedentary bouts, socio-demographic and other behavioral attributes, and medical history. CONCLUSION: These findings indicate positive graded associations for continuous sedentary bouts with abdominal obesity. Public health recommendations regarding breaking up sedentary time more often, potentially avoiding very prolonged bouts of sedentary time, are expected to be relevant for older adults.

Independent Association of Muscular Strength and Carotid Intima-Media Thickness in Children.

The aim of this cross-sectional study was to examine the influence of muscular strength on carotid intima-media thickness (cIMT) in children, controlling for the effect of cardiorespiratory fitness (CRF) and central adiposity and to examine if differences among muscular strength tertiles translate to physiological differences. We assessed cIMT of the common carotid artery in 366 children between 11-12 years of age (191 girls). Measures included cIMT assessed with high-resolution ultrasonography, a maximal handgrip strength test, body fat mass and lean mass from DXA and CRF determined using a maximal cycle ergometer test. Association between muscular strength and cIMT adjusted for CRF and central adiposity, as measured by trunk fat, was tested with multiple linear regression analysis. Differences in risk factors among muscular strength groups were tested with ANOVA. The Muscular Strength Index (MSI) was inversely associated with cIMT independently of CRF and central adiposity (p<0.05). The low MSI group had the highest values of cIMT, waist circumference and systolic blood pressure and the lowest CRF (p<0.05). There was an inverse and independent association between muscular strength and cIMT. Low muscular strength was associated with higher levels of cardiovascular disease risk factors in children.

Accuracy of a combined heart rate and motion sensor for assessing energy expenditure in free-living adults during a double-blind crossover caffeine trial using doubly labeled water as the reference method.

BACKGROUND/OBJECTIVES: A combined heart rate (HR) and motion sensor (Actiheart) has been proposed as an accurate method for assessing total energy expenditure (TEE) and physical activity energy expenditure (PAEE). However, the extent to which factors such as caffeine may affect the accuracy by which the estimated HR-related PAEE contribution will affect TEE and PAEE estimates is unknown. Therefore, we examined the validity of Actiheart in estimating TEE and PAEE in free-living adults under a caffeine trial compared with doubly labeled water (DLW) as reference criterion. SUBJECTS/METHODS: Using a double-blind crossover trial (Clinicaltrials.gov ID: #NCT01477294) with two conditions (4-day each with a 3-day-washout period), randomly ordered as caffeine (5 mg/kg per day) and placebo (malt-dextrine) intake, TEE was measured by DLW in 17 physically active men (20-38 years) who were non-caffeine users. In each condition, resting energy expenditure (REE) was assessed by indirect calorimetry and PAEE was calculated as (TEE-(REE+0.1 TEE)). Simultaneously, PAEE and TEE were estimated by Actiheart using an individual calibration (ACC+HRstep). RESULTS: Under caffeine, ACC+HRstep explained 76 and 64% of TEE and PAEE from DLW, respectively; corresponding results for the placebo condition were 82 and 66%. No mean bias was found between ACC+HRstep and DLW for TEE (caffeine:-468 kJ per day; placebo:-407 kJ per day), although PAEE was slightly underestimated (caffeine:-856 kJ per day; placebo:-1147 kJ per day). Similar limits of agreement were observed in both conditions ranging from -2066 to 3002 and from -3488 to 1776 kJ per day for TEE and PAEE, respectively. CONCLUSIONS: Regardless of caffeine intake, the combined HR and motion sensor is valid for estimating free-living energy expenditure in a group of healthy men but is less accurate for an individual assessment.

Effect of a school-based intervention on physical activity and quality of life through serial mediation of social support and exercise motivation: the PESSOA program.

The aim of this study was to explore the effects of social support and behavioral regulation of exercise on physical activity (PA) and quality of life (QoL), in a Portuguese school-based intervention. We hypothesized that serial mediation effects would be present leading to greater levels of PA and QoL. The sample comprised 1042 students (549 boys), aged 10-16 years, BMI = 19.31 ± 3.51, allocated to two groups of schools: control (n = 207) and intervention (n = 835). This study will report the 24 months results of the program, which aimed to develop healthy lifestyles. Questionnaires were used to measure PA, QoL, motivation to exercise and social support. There was no direct impact of the intervention on QoL or PA. Serial mediation analyses were conducted. Social support (P < 0.019) and intrinsic motivation (P = 0.085) increased more on intervention group. Indirect effects were observed in all serial mediation models. The positive indirect effects on PA and QoL were explained by the increase on peer/parent support in serial with the increase in intrinsic motivation (P < 0.01). Parental support led to an increase on external motivation (P < 0.05), which buffered the effects of the intervention. This school-based intervention promoted the development of social support and motivational mechanisms that explained higher levels of PA and QoL.