Browsing by Subject "PHYSICAL-ACTIVITY"

Now showing 1 - 4 of 4
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    Extreme events reveal an alimentary limit on sustained maximal human energy expenditure.
    (Science advances, 2019-06-05) Thurber, Caitlin; Dugas, Lara R; Ocobock, Cara; Carlson, Bryce; Speakman, John R; Pontzer, Herman
    The limits on maximum sustained energy expenditure are unclear but are of interest because they constrain reproduction, thermoregulation, and physical activity. Here, we show that sustained expenditure in humans, measured as maximum sustained metabolic scope (SusMS), is a function of event duration. We compiled measurements of total energy expenditure (TEE) and basal metabolic rate (BMR) from human endurance events and added new data from adults running ~250 km/week for 20 weeks in a transcontinental race. For events lasting 0.5 to 250+ days, SusMS decreases curvilinearly with event duration, plateauing below 3× BMR. This relationship differs from that of shorter events (e.g., marathons). Incorporating data from overfeeding studies, we find evidence for an alimentary energy supply limit in humans of ~2.5× BMR; greater expenditure requires drawing down the body's energy stores. Transcontinental race data suggest that humans can partially reduce TEE during long events to extend endurance.
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    Lessons learned when innovations go awry: a baseline description of a behavioral trial-the Enhancing Fitness in Older Overweight Veterans with Impaired Fasting Glucose study.
    (Translational behavioral medicine, 2011-11) Hall, KS; Pieper, CF; Edelman, DE; Yancy Jr, WS; Green, JB; Lum, H; Peterson, MJ; Sloane, R; Cowper, PA; Bosworth, HB; Huffman, KM; Cavanaugh, JT; Chapman, JG; Pearson, MP; Howard, TA; Ekelund, CC; McCraw, BL; Burrell, JB; Taylor, GA; Morey, MC
    Individuals diagnosed with impaired glucose tolerance (i.e., prediabetes) are at increased risk for developing diabetes. We proposed a clinical trial with a novel adaptive randomization designed to examine the impact of a home-based physical activity (PA) counseling intervention on metabolic risk in prediabetic elders. This manuscript details the lessons learned relative to recruitment, study design, and implementation of a 12-month randomized controlled PA counseling trial. A detailed discussion on how we responded to unforeseen challenges is provided. A total of 302 older patients with prediabetes were randomly assigned to either PA counseling or usual care. A novel adaptive design that reallocated counseling intensity based on self-report of adherence to PA was initiated but revised when rates of non-response were lower than projected. This study presents baseline participant characteristics and discusses unwelcome adaptations to a highly innovative study design to increase PA and enhance glucose metabolism when the best-laid plans went awry.
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    Persistent Depressive Symptoms are Independent Predictors of Low-Grade Inflammation Onset Among Healthy Individuals.
    (Arquivos brasileiros de cardiologia, 2017-06) Franco, Fábio Gazelato de Mello; Laurinavicius, Antonio Gabriele; Lotufo, Paulo A; Conceição, Raquel D; Morita, Fernando; Katz, Marcelo; Wajngarten, Maurício; Carvalho, José Antonio Maluf; Bosworth, Hayden B; Santos, Raul Dias

    Background

    Depressive symptoms are independently associated with an increased risk of cardiovascular disease (CVD) among individuals with non-diagnosed CVD. The mechanisms underlying this association, however, remain unclear. Inflammation has been indicated as a possible mechanistic link between depression and CVD.

    Objectives

    This study evaluated the association between persistent depressive symptoms and the onset of low-grade inflammation.

    Methods

    From a database of 1,508 young (mean age: 41 years) individuals with no CVD diagnosis who underwent at least two routine health evaluations, 134 had persistent depressive symptoms (Beck Depression Inventory - BDI ≥ 10, BDI+) and 1,374 had negative symptoms at both time points (BDI-). All participants had been submitted to repeated clinical and laboratory evaluations at a regular follow-up with an average of 26 months from baseline. Low-grade inflammation was defined as plasma high-sensitivity C-Reactive Protein (CRP) concentrations > 3 mg/L. The outcome was the incidence of low-grade inflammation evaluated by the time of the second clinical evaluation.

    Results

    The incidence of low-grade inflammation was more frequently observed in the BDI+ group compared to the BDI- group (20.9% vs. 11.4%; p = 0.001). After adjusting for sex, age, waist circumference, body mass index, levels of physical activity, smoking, and prevalence of metabolic syndrome, persistent depressive symptoms remained an independent predictor of low-grade inflammation onset (OR = 1.76; 95% CI: 1.03-3.02; p = 0.04).

    Conclusions

    Persistent depressive symptoms were independently associated with low-grade inflammation onset among healthy individuals.
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    Water turnover among human populations: Effects of environment and lifestyle.
    (American journal of human biology : the official journal of the Human Biology Council, 2020-01) Swanson, Zane S; Pontzer, Herman
    OBJECTIVES:To discuss the environmental and lifestyle determinants of water balance in humans and identify the gaps in current research regarding water use across populations. METHODS:We investigated intraspecific variation in water turnover by comparing data derived from a large number of human populations measured using either dietary survey or isotope tracking. We also used published data from a broad sample of mammalian species to identify the interspecific relationship between body mass and water turnover. RESULTS:Water facilitates nearly all physiological tasks and water turnover is strongly related to body size among mammals (r2=0.90). Within humans, however, the effect of body size is small. Instead, water intake and turnover vary with lifestyle and environmental conditions. Notably, despite living physically active lives in conditions that should increase water demands, the available measures of water intake and turnover among small-scale farming and pastoralist communities are broadly similar to those in less active, industrialized populations. CONCLUSIONS:More work is required to better understand the environmental, behavioral, and cultural determinants of water turnover in humans living across a variety of ecosystems and lifestyles. The results of such work are made more vital by the climate crisis, which threatens the water security of millions around the globe.