Over the last three decades, the combination of a sedentary lifestyle and excessive food intake has led to a significant increase in the prevalence of obesity. The latter favors a chronic low-grade inflammatory state and an over-activation of the innate immune system, which contribute to insulin resistance and type 2 diabetes. Physical exercise is a powerful preventive tool and treatment for several diseases as it induces metabolic and immune effects that provide health benefits. Exercise is known to reduce inflammation; however, the underlying mechanisms responsible are not fully elucidated. One proposed mechanism is a reduced expression and/or activation of pro-inflammatory toll-like receptors (TLRs) on innate immune cells after exercise, which could contribute to the protective effect of exercise against insulin resistance and the prevention of the development of metabolic diseases. The aim of the present study is therefore to review the current evidence about the anti-inflammatory effects of exercise and toll-like receptors regulation on immune cells in humans. Key PointsObesity leads to a low-grade chronic inflammatory state and an over-activation of the innate immune system that is directly involved in the develop metabolic syndrome.The anti-inflammatory effect of exercise has been previously suggested through the reduction of the expression and/or activation of pro-inflammatory toll-like receptors (TLRs) in innate immune cells, which represent one of the main inflammatory responses triggered by obesityThe underlying mechanisms in which toll-like receptors expression modulate the reduction of chronic inflammation are not fully elucidated.

BACKGROUND:This study was designed to test the hypothesis that antioxidant Vitamin C prevents the impairment of endothelial function during prolonged sitting.

MATERIAL AND METHODS:Eleven men (24.2± 4.4 yrs) participated in 2 randomized 3-h sitting trials. In the sitting without vitamin C (SIT) and the sitting with vitamin C (VIT) trial, participants were seated for 3 h without moving their legs. Additionally, in the VIT trial, participants ingested 2 vitamin C tablets (1 g and 500 mg) at 30min and 1 h 30 min, respectively. Superficial femoral artery (SFA) flow-mediated dilation (FMD) was measured hourly for 3 h.

RESULTS:By a 1-way ANOVA, there was a significant decline in FMD during 3 h of SIT (p<0.001). Simultaneously, there was a significant decline in antegrade (p=0.04) and mean (0.037) shear rates. For the SIT and VIT trials by a 2-way (trial x time) repeated measures ANOVA, there was a significant interaction (p=0.001). Pairwise testing revealed significant between-SFA FMD in the SIT and VIT trial at each hour after baseline, showing that VIT prevented the decline in FMD 1 h (p=0.009), 2 h (p=0.016), and 3 h (p=0.004). There was no difference in the shear rates between SIT and VIT trials (p>0.05).

CONCLUSIONS:Three hours of sitting resulted in impaired SFA FMD. Antioxidant Vitamin C prevented the decline in SFA FMD, suggesting that oxidative stress may contribute to the impairment in endothelial function during sitting.

Interruptions to time spent sitting can ameliorate detrimental metabolic-health consequences of high volumes of sedentary time, but their potential mental health benefits have not been examined. We used the Swedish Health Profile Assessment database, a general health assessment offered to all employees working for companies or organisations connected to occupational and health services. Cross-sectional analyses examined data from 40,550 employees (60% male, mean age = 42 years), collected in 2017-2019. Participants reported the proportion of time (almost always; 75% of the time; 50% of the time; 25% of the time; and almost never) usually spent in leisure-time sedentary behaviours; and, separately, the frequency (never; rarely; sometimes; often; and very often) of interruptions (every 30 min) to sedentary time. Logistic regression models assessed associations of sedentary time, and the frequency of interruptions to sedentary time, with depression/anxiety symptoms. Fully adjusted models included physical exercise. Compared to those in the lowest sedentary time category, those in the medium and high categories had 1.52 (95% confidence interval (CI) = 1.40-1.66) and 3.11 (95% CI = 2.82-3.42) higher odds of frequent depression/anxiety symptoms, respectively. Compared to those who never/rarely interrupted their sedentary time, those who reported interruptions sometimes, often and very often had 0.72 (95% CI = 0.65-0.80), 0.59 (95% CI = 0.53-0.65), and 0.53 (95% CI = 0.46-0.59) lower odds of depression/anxiety symptoms, respectively. In stratified analyses, more frequent interruptions to sedentary time were associated withlower odds of depression/anxiety symptoms, except among those in the lowest interruptions categories (never/25% of the time). More regularly interrupting sitting during leisure-time may reduce the odds of experiencing symptoms of depression and anxiety.

ObjectivesTo investigate the associations between objectively measured sedentary behavior (SB), light-intensity physical activity (LIPA) and moderate-to-vigorous physical activity (MVPA) and cardiometabolic and endocrine biomarkers, and to estimate the associations of reallocating time from one behavior to another with cardiometabolic and endocrine biomarkers.MethodsBaseline data from participants diagnosed with prediabetes or type 2 diabetes, n=175, 58% men, mean (SD) age=64.4 (7.7), recruited to a physical activity intervention was used. Time spent in SB, LIPA and MVPA was measured by accelerometer and transformed into isometric log-ratio coordinates. The associations between time spent in SB, LIPA and MVPA and biomarkers were examined by linear regression models. The change in each outcome of reallocating time between the three behaviors was estimated.ResultsThe findings show strong positive associations of time spent in MVPA and negative associations of time spent in SB relative to time spent in the other behaviors with sagittal abdominal diameter (SAD) and homeostasis model assessment for insulin resistance (HOMA-IR) and negative associations of time spent in SB with high-density lipoprotein (HDL) cholesterol. Theoretically, reallocation of 19 minutes MVPA to SB or to LIPA was associated with a 17% and 17% larger SAD, 39% and 36% larger HOMA-IR values and 3.3% and 2.3% lower levels of HDL, respectively.ConclusionIn conclusion, our analysis from a time-use perspective supports the current evidence that sedentary time is devastating for the cardiometabolic health. While LIPA probably requires more time, maintaining or increasing time in MVPA are the most important features of the time use behaviors when promoting a favorable cardiometabolic risk profile in adults with prediabetes and type 2 diabetes.

Platelet activation, including the formation of monocyte platelet aggregates (MPAs), contributes to atherosclerosis, thrombus formation and acute coronary syndromes. Regular participation in exercise can lower cardiovascular risk, but little is known regarding the impact of exercise training on platelet function. We investigated the effect of 6 months of walking exercise on platelet function in sedentary older adults without significant cardiovascular disease. Twenty-seven participants were randomly allocated to 6 months of either: no-exercise (n=13) or 3 x 50 mins/wk of supervised centre-based walking (n=14). Circulating and agonist induced MPAs were assessed using flow cytometry before (month 0 0M) and after (month 6 6M) the intervention. Circulating MPAs increased from 0M (3.7 {plus minus} 1.0%) to 6M (4.7 {plus minus} 1.6%) in the no-exercise group (P = 0.009), whereas a non-significant decrease was observed in the walking group (0M 4.3 {plus minus} 1.7% vs 6M 3.7 {plus minus} 1.2, P = 0.052). The change in MPAs between groups was significant (P = 0.001). There were no differences between groups in platelet responses to agonists across the interventions (all P>0.05). Collectively, these data suggest that the absence of regular exercise may increase MPAs, which are cellular mediators involved in atherosclerosis, whilst regular walking inhibits such increases. The thrombotic function of platelets appear to be relatively unaltered by exercise training. This study provides novel data related to the cardio-protective effects associated with participation in exercise.

Trial registration: ClinicalTrials.gov NCT02909894.

BACKGROUND:High amounts of sedentary behaviour have been associated with increased risks of several chronic conditions and mortality. However, it is unclear whether physical activity attenuates or even eliminates the detrimental effects of prolonged sitting. We examined the associations of sedentary behaviour and physical activity with all-cause mortality.

METHODS:We did a systematic review, searching six databases (PubMed, PsycINFO, Embase, Web of Science, Sport Discus, and Scopus) from database inception until October, 2015, for prospective cohort studies that had individual level exposure and outcome data, provided data on both daily sitting or TV-viewing time and physical activity, and reported effect estimates for all-cause mortality, cardiovascular disease mortality, or breast, colon, and colorectal cancer mortality. We included data from 16 studies, of which 14 were identified through a systematic review and two were additional unpublished studies where pertinent data were available. All study data were analysed according to a harmonised protocol, which categorised reported daily sitting time and TV-viewing time into four standardised groups each, and physical activity into quartiles (in metabolic equivalent of task [MET]-hours per week). We then combined data across all studies to analyse the association of daily sitting time and physical activity with all-cause mortality, and estimated summary hazard ratios using Cox regression. We repeated these analyses using TV-viewing time instead of daily sitting time.

FINDINGS:Of the 16 studies included in the meta-analysis, 13 studies provided data on sitting time and all-cause mortality. These studies included 1 005 791 individuals who were followed up for 2-18·1 years, during which 84 609 (8·4%) died. Compared with the referent group (ie, those sitting<4 h/day and in the most active quartile [>35·5 MET-h per week]), mortality rates during follow-up were 12-59% higher in the two lowest quartiles of physical activity (from HR=1·12, 95% CI 1·08-1·16, for the second lowest quartile of physical activity [<16 MET-h per week] and sitting<4 h/day; to HR=1·59, 1·52-1·66, for the lowest quartile of physical activity [<2·5 MET-h per week] and sitting>8 h/day). Daily sitting time was not associated with increased all-cause mortality in those in the most active quartile of physical activity. Compared with the referent (<4 h of sitting per day and highest quartile of physical activity [>35·5 MET-h per week]), there was no increased risk of mortality during follow-up in those who sat for more than 8 h/day but who also reported>35·5 MET-h per week of activity (HR=1·04; 95% CI 0·99-1·10). By contrast, those who sat the least (<4 h/day) and were in the lowest activity quartile (<2·5 MET-h per week) had a significantly increased risk of dying during follow-up (HR=1·27, 95% CI 1·22-1·31). Six studies had data on TV-viewing time (N=465 450; 43 740 deaths). Watching TV for 3 h or more per day was associated with increased mortality regardless of physical activity, exceptin the most active quartile, where mortality was significantly increased only in people who watched TV for 5 h/day or more (HR=1·16, 1·05-1·28).

INTERPRETATION:High levels of moderate intensity physical activity (ie, about 60-75 min per day) seem to eliminate the increased risk of death associated with high sitting time. However, this high activity level attenuates, but does not eliminate the increased risk associated with high TV-viewing time. These results provide further evidence on the benefits of physical activity, particularly in societies where increasing numbers of people have to sit for long hours for work and may also inform future public health recommendations.

FUNDING:None.

This work aimed to study the effect of swimming exercise on serum vitamin D level and tissue vitamin D receptors in experimentally induced type 2 Diabetes Mellitus. Sixty adult male rats were divided into control and diabetic groups. Each was further subdivided into sedentary and exercised subgroups. Diabetes Mellitus was induced by a single intraperitoneal dose of streptozotocin (50 mg/kg) dissolved in cold 0.01 M citrate buffer (pH 4.5). The exercised subgroups underwent swimming for 60 min, 5 times a week for 4 weeks. Serum glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), lipids, vitamin D and tissue Vitamin D receptors (VDR) were evaluated. Significant increase in serum glucose, insulin, HOMA-IR, cholesterol, triglycerides, and low density lipoprotein (LDL) levels in sedentary diabetic rats was detected. On the other hand, high density lipoprotein (HDL), free fatty acids, serum vitamin D and pancreatic, adipose, and muscular VDR showed a significant decrease in the same group. It is evident that all these parameters were reversed by swimming exercise indicating its beneficial role in type 2 Diabetes. In diabetic groups; serum vitamin D was found to be correlated negatively with serum glucose, insulin, HOMA, cholesterol, triglycerides, and LDL and positively correlated with HDL and tissue VDR. In conclusion, Disturbed vitamin D is associated with metabolic impairments in sedentary diabetic rats. Moderate swimming exercise is beneficial in improving these consequences through modulation of vitamin D status. Future studies could be designed to investigate the effect of the combination of vitamin D intake with exercise in diabetic patients.

BACKGROUND:Physical activity (PA) can be neuroprotective and reduce the risk for Alzheimer's disease (AD). In assessing physical activity, caloric expenditure is a proxy marker reflecting the sum total of multiple physical activity types conducted by an individual.

OBJECTIVE:To assess caloric expenditure, as a proxy marker of PA, as a predictive measure of gray matter (GM) volumes in the normal and cognitively impaired elderly persons.

METHODS:All subjects in this study were recruited from the Institutional Review Board approved Cardiovascular Health Study (CHS), a multisite population-based longitudinal study in persons aged 65 and older. We analyzed a sub-sample of CHS participants 876 subjects (mean age 78.3, 57.5% F, 42.5% M) who had i) energy output assessed as kilocalories (kcal) per week using the standardized Minnesota Leisure-Time Activities questionnaire, ii) cognitive assessments for clinical classification of normal cognition, mild cognitive impairment (MCI), and AD, and iii) volumetric MR imaging of the brain. Voxel-based morphometry modeled the relationship between kcal/week and GM volumes while accounting for standard covariates including head size, age, sex, white matter hyperintensity lesions, MCI or AD status, and site. Multiple comparisons were controlled using a False Discovery Rate of 5 percent.

RESULTS:Higher energy output, from a variety of physical activity types, was associated with larger GM volumes in frontal, temporal, and parietal lobes, as well as hippocampus, thalamus, and basal ganglia. High levels of caloric expenditure moderated neurodegeneration-associated volume loss in the precuneus, posterior cingulate, and cerebellar vermis.

CONCLUSION:Increasing energy output from a variety of physical activities is related to larger gray matter volumes in the elderly, regardless of cognitive status.

BACKGROUND:Sedentary behavior (SB) is associated with poor cognitive performance. However, the contribution of sedentary time to risk of mild cognitive impairment (MCI) remains unclear. This study assessed the association of SB with MCI in six low- and middle-income countries.

METHODS:The Study on Global Ageing and Adult Health (SAGE) survey included 34,129 adults aged≥50 years [mean (SD) age 62.1 (15.6) years; 51.7% females]. SB was self-reported and expressed as a categorical variable [<8 or≥8 h per day (high SB)]. The definition of MCI was based on the recommendations of the National Institute on Ageing-Alzheimer's Association. Multivariable logistic regression analysis was conducted to assess the association between SB and MCI.

RESULTS:The overall prevalence (95%CI) of MCI and high SB (i.e.,≥8 h/day) were 15.3% (14.4%-16.3%) and 10.1% (9.0%-11.3%), respectively. After adjustment for potential confounders, being sedentary for ≥8 h/day was associated with a 1.56 (95%CI = 1.27-1.91) times higher odds for MCI. A one-hour increase in SB was associated with a 1.08 (95%CI = 1.05-1.11) times higher odds for MCI.

CONCLUSION:Our study results highlight the need to further explore a sedentary lifestyle as a potential risk factor for MCI or subsequent dementia. Longitudinal and intervention studies are warranted to confirm/refute the current findings.

Physical activity has been positively associated with gray-matter integrity. In contrast, pro-inflammatory cytokines seem to have negative effects on the aging brain and have been related to dementia. It was investigated whether an inactive lifestyle and high levels of inflammation resulted in smaller gray-matter volumes and predicted cognitive decline across 6 years in a population-based study of older adults (n = 414). Self-reported physical activity (fitness-enhancing, health-enhancing, inadequate) was linked to gray-matter volume, such that individuals with inadequate physical activity had the least gray matter. There were no overall associations between different pro-and anti-inflammatory markers (IL-1β, IL-6, IL-10, IL-12p40, IL-12p70, G-CSF, and TNF-α) and gray-matter integrity. However, persons with inadequate activity and high levels of the pro-inflammatory marker IL-12p40 had smaller volumes of lateral prefrontal cortex and hippocampus and declined more on the Mini-Mental-State Examination test over 6 years compared with physically inactive individuals with low levels of IL-12p40 and to more physically active persons, irrespective of their levels of IL-12p40. These patterns of data suggested that inflammation was particularly detrimental in inactive older adults and may exacerbate the negative effects of physical inactivity on brain and cognition in old age. Hum Brain Mapp, 2016. © 2016 Wiley Periodicals, Inc.

BACKGROUND:Physical activity is associated with reduced cardiovascular disease risk, mainly through effects on atherosclerosis. Aortic stiffness may be an alternative mechanism. We examined whether patterns of physical activity and sedentary behavior are associated with rate of aortic stiffening.

METHODS AND RESULTS:Carotid-femoral pulse wave velocity (PWV) was measured twice using applanation tonometry at mean ages 65 (in 2008/2009) and 70 (in 2012/2013) years in the Whitehall-II study (N=5196). Physical activity was self-reported at PWV baseline (2008/2009) and twice before (in 1997/1999 and 2002/2003). Sedentary time was defined as sitting time watching television or at work/commute. Linear mixed models adjusted for metabolic and lifestyle risk factors were used to analyze PWV change. Mean (SD) PWV (m/s) was 8.4 (2.4) at baseline and 9.2 (2.7) at follow-up, representing a 5-year increase of 0.76 m/s (95% CI 0.69, 0.83). A smaller 5-year increase in PWV was observed for each additional hour/week spent in sports activity (-0.02 m/s [95% CI -0.03, -0.001]) or cycling (-0.02 m/s [-0.03, -0.008]). Walking, housework, gardening, or do-it-yourself activities were not significantly associated with aortic stiffening. Each additional hour/week spent sitting was associated with faster PWV progression in models adjusted for physical activity (0.007 m/s [95% CI 0.001, 0.013]). Increasing physical activity over time was associated with a smaller subsequent increase in PWV (-0.16 m/s [-0.32, -0.002]) compared with not changing activity levels.

CONCLUSIONS:Higher levels of moderate-to-vigorous physical activity and avoidance of sedentary behavior were each associated with a slower age-related progression of aortic stiffness independent of conventional vascular risk factors.

BACKGROUND:The association between physical activity (PA), sedentary behavior, and incident diabetes has been assessed in whites but is less well investigated in multiethnic populations.

OBJECTIVE:To assess the association between PA, sedentary behavior, and incident diabetes in the Multi-Ethnic Study of Atherosclerosis.

RESEARCH DESIGN AND METHODS:Incident diabetes was assessed among adults without prevalent baseline diabetes (2000-2002) at 5 in-person examinations between 2002 and 2012. Baseline PA (moderate, vigorous, and exercise-specific; metabolic equivalents of task-hours/week) and sedentary behaviors (television watching, reading; hours/day) were assessed by questionnaire. HRs were estimated using Cox proportional hazard models.

RESULTS:Among 5829 adults (mean age 61.8 years, 54% female, 42% white, 12% Chinese-American, 26% African-American, 21% Hispanic-American), there were 655 incident diabetes cases (median follow-up 11.1 years). After adjustment, diabetes risk was lower in those with brisk or striding compared with none or casual walking pace (HR 0.67; 95% CI 0.54 to 0.84), higher levels of exercise PA (HR for highest vs lowest quartile 0.79; 95% CI 0.63 to 0.98), and any compared with no vigorous PA (HR 0.79; 95% CI 0.66 to 0.95). Race/ethnicity influenced the association of walking pace, exercise PA, and any vigorous PA on diabetes risk, which was only significant among whites. Total leisure sedentary behaviors (HR for highest vs lowest quartile 1.65; 95% CI 1.26 to 2.14) and television watching (HR for highest vs lowest quartile 2.68; 95% CI 1.38 to 5.21) were significantly associated with diabetes risk in multiethnic analyses and were influenced by race/ethnicity.

CONCLUSIONS:These results confirm the importance of PA and sedentary behavior on diabetes risk in a multiethnic population and demonstrate potential variations across race/ethnic groups.

Genetics and lifestyle independently determine dementia risk, but the interaction is unclear. We assessed the interactive relationship of apolipoprotein E (APOE) genotype and physical exercise on dementia risk over a 5-year period in 1,646 older adults from the Canadian Study of Health and Aging who were dementia-free at baseline. Physical exercise moderated the relationship between genotype and dementia (p < 0.01). Specifically, for APOE ɛ4 non-carriers, the odds of developing dementia were higher in non-exercisers than exercisers (OR = 1.98, 95% CI = 1.44, 2.71, p < 0.001), whereas, for APOE ɛ4 carriers, the odds of developing dementia were not significantly different between non-exercisers and exercisers (OR = 0.71, 95% CI = 0.46, 1.31, p = 0.34). Given that most individuals are not at genetic risk, physical exercise may be an effective strategy for preventing dementia.

BACKGROUND:Leg swelling is a modern-day affliction of sedentary working women. The aim of this study was to evaluate the effectiveness of the intake of grape seed extract (GSE) on leg swelling in healthy Japanese women while sitting.

RESULTS:Single intake trials and 14 day intake trials were held in a double-blind, placebo-controlled, crossover clinical study. A prolonged sedentary position was maintained for 6 h after GSE or placebo administration. Leg volume distension, increase in body extracellular fluid, and leg water were significantly suppressed in the GSE groups.

CONCLUSION:The intake of GSE is a contributing factor in the inhibition of leg swelling in healthy women during prolonged sitting.

OBJECTIVE:This study investigated the association between sedentary behavior (SB) and anxiety, and explored factors that influence this relationship in six low- and middle-income countries.

METHOD:Cross-sectional data were analyzed from the World Health Organization's Study on Global Ageing and Adult Health. Multivariable linear and logistic regression analyses were conducted to assess the association between anxiety and self-reported SB. Potentially influential factors were examined with mediation analysis.

RESULTS:The sample consisted of 42,469 adults aged≥18years (50.1% female; mean age 43.8years). After adjusting for sociodemographics and country, people with anxiety engaged in 24 (95%CI=7-41) more minutes per day of SB than non-anxious individuals; the corresponding figure for the elderly (≥65years) was much higher (55min; 95% CI=29-81). Anxiety was associated with a 2.0 (95%CI=1.5-2.7) times higher odds for high SB (i.e., ≥8h/day). Overall, the largest proportion of the high SB-anxiety relationship was explained by mobility limitations (46.8%), followed by impairments in sleep/energy (44.9%), pain/discomfort (31.7%), disability (27.0%), cognition (13.3%), and physical activity levels (6.3%).

CONCLUSIONS:Anxiety was significantly associated with high SB, particularly among older adults. Future longitudinal studies are warranted to disentangle the potentially complex interplay of factors that may influence the anxiety-SB relationship.

Cognitive decline leading to dementia represents a global health burden. In the absence of targeted pharmacotherapy, lifestyle approaches remain the best option for slowing the onset of dementia. However, older adults spend very little time doing moderate to vigorous exercise and spend a majority of time in sedentary behavior. Sedentary behavior has been linked to poor glycemic control and increased risk of all-cause mortality. Here, we explore a potential link between sedentary behavior and brain health. We highlight the role of glycemic control in maintaining brain function and suggest that reducing and replacing sedentary behavior with intermittent light-intensity physical activity may protect against cognitive decline by reducing glycemic variability. Given that older adults find it difficult to achieve current exercise recommendations, this may be an additional practical strategy. However, more research is needed to understand the impact of poor glycemic control on brain function and whether practical interventions aimed at reducing and replacing sedentary behavior with intermittent light intensity physical activity can help slow cognitive decline.

Background: Emerging work is starting to investigate the cumulative effects of moderate-to-vigorous physical activity (MVPA), sedentary behavior and cardiorespiratory fitness on health. The objective of this study was to examine the cumulative and independent associations of MVPA, sedentary behavior and cardiorespiratory fitness on leukocyte telomere length (LTL).

Methods: Data from the 1999-2002 National Health and Nutrition Examination Survey (NHANES) were used (N = 1868 adults 20+ years); analyzed in 2016. Sedentary behavior and MVPA were subjectively assessed with cardiorespiratory fitness determined from a submaximal treadmill-based test; participants were classified as above or below the median values for each of these three parameters. A blood sample was obtained from each participant to assess LTL via quantitative polymerase chain reaction, with participants grouped into LTL tertiles.

Results: Participants who engaged in higher MVPA, sat less and had higher cardiorespiratory fitness had an increased odds (ranging from 85% to 105%) of being in LTL tertile 3 (vs. 1). In an extended adjusted multinomial logistic regression model, only MVPA was positively associated with LTL (odds ration [OR] = 1.37; 95% CI: 0.99-1.90; P = 0.05).

Conclusion: All three behavior characteristics, but particularly MVPA, may be important in preserving LTLs.

OBJECTIVES:Lack of physical activity (PA) and prolonged sitting time (ST) are associated with increased risk of mortality and chronic illnesses, including depression. While there have been claims that the two risks are 'independent', their joint and stratified effects are unclear. The aim of this study was to explore the combined effects of physical activity and sitting time on the 12year risk of depressive symptoms (DS) in young women.

DESIGN:Cohort-9061 young participants in the Australian Longitudinal Study on Women's Health completed triennial surveys from 2000 (age 22-27), to 2012.

METHODS:Generalised Estimating Equation models were used to calculate the joint effects of PA and ST on DS, with<4h/day of ST and the highest PA quartile as the reference categories. Relationships between PA and DS, and between ST and DS, were also examined after stratification by ST and PA respectively.

RESULTS:In the adjusted joint effects model, compared with the reference category (low sitting, high PA), odds for DS were significantly higher in women who sat for>4, 6 and 8h/day and reported doing no PA. In every physical activity category, women who sat for≥10h/day were at highest risk of DS (OR for lowest physical activity quartile, 1.72 [95% CI=1.38-2.14]; OR for highest physical activity quartile, 1.49 [95% CI=1.16-1.91]). After stratification by ST, odds of DS were reduced in women who reported any physical activity (compared with none), exceptwhen ST was>10h/day. After stratification by physical activity, the increased risk of sitting 8-10h/day was attenuated by any physical activity, but there was no reduction in risk of depressive symptoms with increasing PA levels in women who sat for≥10h per day.

CONCLUSIONS:These data suggest that there are both joint and stratified effects of too little activity and too much sitting on the risk of depressive symptoms in young women. High levels of PA are protective against the hazards of high ST at this life stage, except in women with very high levels of sitting.

BACKGROUND:Apply a more novel approach to systematically examine (1) associations of clustered cardio-metabolic risk and cardio-metabolic risk factors, and (2) theoretical substitution of sedentary time with either sleep, light physical activity (LPA) or moderate-and-vigorous physical activity (MVPA) and substituting LPA with MVPA.

METHODS:Physical activity and sleep were objectively measured in 410 Flemish adults (55.5[±9.6] years, 64% men) with a SenseWear Pro 3 Armband. Cardio-metabolic risk factors (obesity, hyperglycemia, dyslipidemia, and hypertension,), cardiorespiratory fitness were objectively measured. Isotemporal substitution analyses were performed to assess the associations between substituting time from a potentially negative behavior into another, potentially positive, behavior.

RESULTS:Theoretical substitution of sedentary time with MVPA was associated with decreased clustered cardio-metabolic risk (b = -0.06 [-0.08;-0.04]) and substituting LPA with MVPA was associated with a decrease in clustered cardio-metabolic risk (b = -0.08 [-0.11;-0.04]). Substituting sedentary time with LPA or sleep improved HDL-cholesterol, systolic and diastolic blood pressures, and waist circumference.

CONCLUSION:Theoretical replacement of sedentary time with either sleep, LPA or MVPA was positively associated with improved cardio-metabolic risk factor status. Interventions for increasing cardio-metabolic health can focus on replacing sedentary time with either sleep, LPA or MVPA depending on the risk parameters that need to be targeted.