The minimal physical activity intensity that would confer health benefits among adolescents is unknown. The purpose of this study was to examine the associations of accelerometer-derived ...light-intensity (split into low and high) physical activity, and moderate- to vigorous-intensity physical activity with cardiometabolic biomarkers in a large population-based sample.
The study is based on 1,731 adolescents, aged 12-19 years from the 2003/04 and 2005/06 National Health and Nutrition Examination Survey. Low light-intensity activity (100-799 counts/min), high light-intensity activity (800 counts/min to <4 METs) and moderate- to vigorous-intensity activity (≥ 4 METs, Freedson age-specific equation) were accelerometer-derived. Cardiometabolic biomarkers, including waist circumference, systolic blood pressure, diastolic blood pressure, HDL-cholesterol, and C-reactive protein were measured. Triglycerides, LDL- cholesterol, insulin, glucose, and homeostatic model assessments of β-cell function (HOMA-%B) and insulin sensitivity (HOMA-%S) were also measured in a fasting sub-sample (n=807).
Adjusted for confounders, each additional hour/day of low light-intensity activity was associated with 0.59 (95% CI: 1.18-0.01) mmHG lower diastolic blood pressure. Each additional hour/day of high light-intensity activity was associated with 1.67 (2.94-0.39) mmHG lower diastolic blood pressure and 0.04 (0.001-0.07) mmol/L higher HDL-cholesterol. Each additional hour/day of moderate- to vigorous-intensity activity was associated with 3.54 (5.73-1.35) mmHG lower systolic blood pressure, 5.49 (1.11-9.77)% lower waist circumference, 25.87 (6.08-49.34)% lower insulin, and 16.18 (4.92-28.53)% higher HOMA-%S.
Time spent in low light-intensity physical activity and high light-intensity physical activity had some favorable associations with biomarkers. Consistent with current physical activity recommendations for adolescents, moderate- to vigorous-intensity activity had favorable associations with many cardiometabolic biomarkers. While increasing MVPA should still be a public health priority, further studies are needed to identify dose-response relationships for light-intensity activity thresholds to inform future recommendations and interventions for adolescents.
High amounts of time spent sitting can increase cardiovascular disease risk and are deleteriously associated cardio-metabolic risk biomarkers. Though evidence suggests that accruing sitting time in ...prolonged periods may convey additional risk, verification using high-quality measures is needed. We examined this issue in adults from the Australian Diabetes, Obesity and Lifestyle Study, using accurate measures of sitting accumulation.
In 2011/12, 739 adults aged 36 to 89 years (mean±SD 58±10 years) wore activPAL3™ monitors (which provide accurate objective measures of sitting); 678 provided ≥4 valid days of monitor data and complete cardio-metabolic biomarker and confounder data. Multivariable linear regression models examined associations of sitting time, sitting time accrued in ≥30 minute bouts (prolonged sitting time), and three measures of sitting accumulation patterns with cardio-metabolic risk markers: body mass index (BMI), waist circumference, blood pressure, high- and low- density lipoprotein (HDL and LDL) cholesterol, triglycerides, glycated haemoglobin (HbA1c), fasting plasma glucose (FPG) and 2-hour post-load glucose (PLG). Interactions tests examined whether associations of sitting time with biomarkers varied by usual sitting bout duration.
Adjusted for potential confounders, greater amounts of sitting time and prolonged sitting time were significantly (p<0.05) deleteriously associated with BMI, waist circumference, HDL cholesterol, and triglycerides. Total sitting time was also significantly associated with higher PLG. Sitting accumulation patterns of frequently interrupted sitting (compared to patterns with relatively more prolonged sitting) were significantly beneficially associated with BMI, waist circumference, HDL cholesterol, triglycerides, PLG, and with FPG. Effect sizes were typically larger for accumulation patterns than for sitting time. Significant interactions (p<0.05) showed that associations of sitting time with HDL, triglycerides and PLG became more deleterious the longer at a time sitting was usually accumulated.
Adding to previous evidence reliant on low-quality measures, our study showed that accumulating sitting in patterns where sitting was most frequently interrupted had significant beneficial associations with several cardio-metabolic biomarkers and that sitting for prolonged periods at a time may exacerbate some of the effects of sitting time. The findings support sedentary behavior guidelines that promote reducing and regularly interrupting sitting.
Ecologists studying bird foraging ecology have generally focused on food quantity over quality. Emerging work suggests that food quality, in terms of highly unsaturated omega‐3 fatty acids (HUFA), ...can have equally important effects on performance. HUFA, which are present in aquatic primary producers, are all but absent in vascular plants, and HUFA content is also correspondingly higher in aquatic insects. Here, we show that Tree Swallow (Tachycineta bicolor) chicks rapidly accumulate HUFA from food during the nestling period. Using data sampled over 24 years, we also show that Tree Swallow breeding success is positively associated with the availability of HUFA‐rich aquatic insects. Variation in aquatic insect biomass during chick development was a strong predictor of fledging success, whereas variation in terrestrial insects had little effect on fledging success. Our results highlight the potential for nutritional mismatches between insectivores and high‐quality prey to affect avian reproductive performance.
Abstract Objective To investigate the short-term efficacy of a multicomponent intervention to reduce office workers' sitting time. Methods Allocation for this non-randomized controlled trial (n = 43 ...participants; 56% women; 26–62 years; Melbourne, Australia) was by office floor, with data collected during July–September 2011. The 4-week intervention emphasized three key messages: “Stand Up, Sit Less, Move More” and comprised organizational, environmental, and individual elements. Changes in minutes/day at the workplace spent sitting (primary outcome), in prolonged sitting (sitting time accumulated in bouts ≥ 30 min), standing, and moving were objectively measured (activPAL3). Results Relative to the controls, the intervention group significantly reduced workplace sitting time (mean change 95%CI: − 125 − 161, − 89 min/8-h workday), with changes primarily driven by a reduction in prolonged sitting time (− 73 − 108, − 40 min/8-h workday). Workplace sitting was almost exclusively replaced by standing (+ 127 + 92, + 162 min/8-h workday) with non-significant changes to stepping time (− 2 − 7, + 4 min/8-h workday) and number of steps (− 70 − 350, 210). Conclusions This multicomponent workplace intervention demonstrated that substantial reductions in sitting time are achievable in an office setting. Larger studies with longer timeframes are needed to assess sustainability of these changes, as well as their potential longer-term impacts on health and work-related outcomes.
Prolonged sedentary time is ubiquitous in developed economies and is associated with an adverse cardio-metabolic risk profile and premature mortality. This study examined the associations of ...objectively assessed sedentary time and breaks (interruptions) in sedentary time with continuous cardio-metabolic and inflammatory risk biomarkers, and whether these associations varied by sex, age, and/or race/ethnicity.
Cross-sectional analyses with 4757 participants (≥ 20 years) from the 2003/04 and 2005/06 US National Health and Nutrition Examination Survey (NHANES). An Actigraph accelerometer was used to derive sedentary time < 100 counts per minute (cpm) and breaks in sedentary time. Independent of potential confounders, including moderate-to-vigorous exercise, detrimental linear associations (P for trends < 0.05) of sedentary time with waist circumference, HDL-cholesterol, C-reactive protein, triglycerides, insulin, HOMA-%B, and HOMA-%S were observed. Independent of potential confounders and sedentary time, breaks were beneficially associated with waist circumference and C-reactive protein (P for trends <0.05). There was limited evidence of meaningful differences in associations with biomarkers by age, sex, or race/ethnicity. Notable exceptions were sex-differences in the associations of sedentary time and breaks with HDL-cholesterol, and race/ethnicity differences in the association of sedentary time with waist circumference with associations detrimental in non-Hispanic whites, null in Mexican Americans, and beneficial in non-Hispanic blacks.
These are the first population-representative findings on the deleterious associations of prolonged sedentary time with cardio-metabolic and inflammatory biomarkers. The findings suggest that clinical communications and preventive health messages on reducing and breaking up sedentary time may be beneficial for cardiovascular disease risk.
While excessive sitting time is related adversely to cardio-metabolic health, it is unknown whether standing is a suitable replacement activity or whether ambulatory movement is required. Using ...isotemporal substitution analyses, we modelled cross-sectional associations with cardio-metabolic risk biomarkers of reallocating time (2 h/day) from sitting to standing or to stepping.
A subsample of participants from the 2011/12 Australian Diabetes, Obesity, and Lifestyle Study wore the posture-based activPAL3 monitor 36-80 years (mean 57.9, SD 9.9 years); 57% women; n = 698 with data. Associations of activPAL3-derived mean daily time sitting/lying (sitting), standing and stepping with body mass index (BMI), waist circumference, blood pressure, HbA1c, fasting glucose and lipids (high-density lipoprotein-, HDL, and low-density lipoprotein-cholesterol, total/HDL-cholesterol ratio, and triglycerides), and 2-h plasma glucose were examined. Adjusted for relevant confounders, sitting-to-standing reallocations were only significantly (P < 0.05) associated with approximately 2% lower fasting plasma glucose, 11% lower triglycerides, 6% lower total/HDL-cholesterol ratio, and 0.06 mmol/L higher HDL-cholesterol per 2 h/day. Sitting-to-stepping reallocations were only significantly associated with approximately 11% lower BMI, 7.5 cm lower waist circumference, 11% lower 2-h plasma glucose, 14% lower triglycerides, and 0.10 mmol/L higher HDL-cholesterol per 2 h/ day, while standing-to-stepping reallocations were only significantly associated with ∼10% lower BMI, 7 cm lower waist circumference, and 11% lower 2-h plasma glucose.
Findings suggested that sitting-reduction strategies targeting increased standing, stepping, or both, may benefit cardio-metabolic health. Standing is a simple alternative to sitting, and requires further examination in prospective and intervention studies.
Once-abundant aerial insectivores, such as the Tree Swallow (Tachycineta bicolor), have declined steadily in the past several decades, making it imperative to understand all aspects of their ecology. ...Aerial insectivores forage on a mixture of aquatic and terrestrial insects that differ in fatty acid composition, specifically long-chain omega-3 polyunsaturated fatty acid (LCPUFA) content. Aquatic insects contain high levels of both LCPUFA and their precursor omega-3 PUFA, alpha-linolenic acid (ALA), whereas terrestrial insects contain much lower levels of both. We manipulated both the quantity and quality of food for Tree Swallow chicks in a full factorial design. Diets were either high-LCPUFA or low in LCPUFA but high in ALA, allowing us to separate the effects of direct LCPUFA in diet from the ability of Tree Swallows to convert their precursor, ALA, into LCPUFA. We found that fatty acid composition was more important for Tree Swallow chick performance than food quantity. On high-LCPUFA diets, chicks grew faster, were in better condition, and had greater immunocompetence and lower basal metabolic rates compared with chicks on both low LCPUFA diets. Increasing the quantity of high-LCPUFA diets resulted in improvements to all metrics of performance while increasing the quantity of low-LCPUFA diets only resulted in greater immunocompetence and lower metabolic rates. Chicks preferentially retained LCPUFA in brain and muscle when both food quantity and LCPUFA were limited. Our work suggests that fatty acid composition is an important dimension of aerial insectivore nutritional ecology and reinforces the importance of high-quality aquatic habitat for these declining birds.
Research indicates that high levels of sedentary behavior（sitting or lying with low energy expenditure） are adversely associated with health. A key factor in improving our understanding of the impact ...of sedentary behavior（and patterns of sedentary time accumulation） on health is the use of objective measurement tools that collect date and time-stamped activity information. One such tool is the activP AL monitor. This thigh-worn device uses accelerometer-derived information about thigh position to determine the start and end of each period spent sitting/lying, standing, and stepping, as well as stepping speed, step counts, and postural transitions. The activP AL is increasingly being used within field-based research for its ability to measure sitting/lying via posture. We summarise key issues to consider when using the activP AL in physical activity and sedentary behavior field-based research with adult populations. It is intended that the findings and discussion points be informative for researchers who are currently using activP AL monitors or are intending to use them. Pre-data collection decisions, monitor preparation and distribution, data collection considerations, and manual and automated data processing possibilities are presented using examples from current literature and experiences from 2 research groups from the UK and Australia.
To describe changes in workplace physical activity, and health-, and work-related outcomes, in workers who transitioned from a conventional to an 'activity-permissive' workplace.
A natural pre-post ...experiment conducted in Vancouver, Canada in 2011. A convenience sample of office-based workers (n=24, 75% women, mean SD age = 34.5 8.1 years) were examined four months following relocation from a conventional workplace (pre) to a newly-constructed, purpose-built, movement-oriented physical environment (post). Workplace activity- (activPAL3-derived stepping, standing, and sitting time), health- (body composition and fasting cardio-metabolic blood profile), and work- (performance; job satisfaction) related outcomes were measured pre- and post-move and compared using paired t-tests.
Pre-move, on average (mean SD) the majority of the day was spent sitting (364 43.0 mins/8-hr workday), followed by standing (78.2 32.1 mins/8-hr workday) and stepping (37.7 15.6 mins/8-hr workday). The transition to the 'activity-permissive' workplace resulted in a significant increase in standing time (+18.5, 95% CI: 1.8, 35.2 mins/8-hr workday), likely driven by reduced sitting time (-19.7, 95% CI: -42.1, 2.8 mins/8-hr workday) rather than increased stepping time (+1.2, 95% CI: -6.2, 8.5 mins/8-hr workday). There were no statistically significant differences observed in health- or work-related outcomes.
This novel, opportunistic study demonstrated that the broader workplace physical environment can beneficially impact on standing time in office workers. The long-term health and work-related benefits, and the influence of individual, organizational, and social factors on this change, requires further evaluation.
BACKGROUNDAccording to cross-sectional and acute experimental evidence, reducing sitting time should improve cardio-metabolic health risk biomarkers. Furthermore, the improvements obtained may depend ...on whether sitting is replaced with standing or ambulatory activities. Based on data from the Stand Up Victoria multi-component workplace intervention, we examined this issue using compositional data analysis — a method that can examine and compare all activity changes simultaneously.
METHODSParticipants receiving the intervention (n=136 ≥0.6 full-time equivalent desk-based workers, 65% women, mean±SD age=44.6 ±9.1 years from seven worksites) were asked to improve whole-of-day activity by standing up, sitting less and moving more. Their changes in the composition of daily waking hours (activPAL-assessed sitting, standing, stepping) were quantified, then tested for associations with concurrent changes in cardio-metabolic risk (CMR) scores and 14 biomarkers concerning body composition, glucose, insulin and lipid metabolism. Analyses were by mixed models, accounting for clustering (3 months, n=105–120; 12 months, n=80–97).
RESULTSSitting reduction was significantly (p<0.05) associated only with lower systolic blood pressure at three months, and with CMR scores, weight, body fat, waist circumference, diastolic blood pressure, and fasting triglycerides, total/HDL cholesterol and insulin at 12 months. Significant differences between standing and stepping were only observed for systolic blood pressure and insulin; both favored stepping. However, replacing sitting with standing was significantly associated only with improvements in CMR scores, while replacing sitting with stepping was significantly associated with CMR scores and six biomarkers.
CONCLUSIONSImprovements in several cardio-metabolic health risk biomarkers were significantly associated with sitting reductions that occurred in a workplace intervention. The greatest degree and/or widest range of cardio-metabolic benefits appeared to occur with long-term changes, and when increasing ambulatory activities.
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