Although it is no longer debatable that sedentary behaviors are an actual cause of many metabolic diseases, the physiology of physical inactivity has been poorly investigated for this purpose. Along ...with microgravity, the physiological adaptations to spaceflights require metabolic adaptations to physical inactivity, and that is exceedingly well-simulated during the ground-based microgravity bed-rest analogs. Bed rest thus represents a unique model to investigate the mechanisms by which physical inactivity leads to the development of current societal chronic diseases. For decades, however, clinicians and physiologists working in space research have worked separately without taking full awareness of potential strong mutual questioning. This review summarizes the data collected over the last 60 years on metabolic adaptations to bed rest in healthy subjects. Our aim is to provide evidence that supports the hypothesis that physical inactivity per se is one of the primary causes in the development of metabolic inflexibility. This evidence will focus on four main tenants of metabolic inflexiblity: 1) insulin resistance, 2) impaired lipid trafficking and hyperlipidemia, 3) a shift in substrate use toward glucose, and 4) a shift in muscle fiber type and ectopic fat storage. Altogether, this hypothesis places sedentary behaviors upstream on the list of factors involved in metabolic inflexibility, which is considered to be a primary impairment in several metabolic disorders such as obesity, insulin resistance, and type 2 diabetes mellitus.
Participation in regular physical activity is associated with a multitude of health benefits across the life course. However, many people fail to meet PA recommendations. Despite a plethora of ...studies, the evidence regarding the environmental (physical) determinants of physical activity remains inconclusive.
To identify the physical environmental determinants that influence PA across the life course.
An online systematic literature search was conducted using MEDLINE, ISI Web of Science, Scopus and SPORTDiscus. The search was limited to studies published in English (January 2004 to April 2016). Only systematic literature reviews (SLRs) and meta-analyses (MAs) of observational studies, that investigated the association between physical determinants and physical activity outcomes, were eligible for inclusion. The extracted data were assessed on the importance of determinants, strength of evidence and methodological quality.
The literature search identified 28 SLRs and 3 MAs on 67 physical environmental characteristics potentially related to physical activity that were eligible for inclusion. Among preschool children, a positive association was reported between availability of backyard space and outdoor toys/equipment in the home and overall physical activity. The availability of physical activity programs and equipment within schools, and neighbourhood features such as pedestrian and cyclist safety structure were positively associated with physical activity in children and adolescents. Negative street characteristics, for example, lack of sidewalks and streetlights, were negatively associated with physical activity in adults. Inconsistent associations were reported for the majority of reviewed determinants in adults.
This umbrella SLR provided a comprehensive overview of the physical environment determinants of physical activity across the life course and has highlighted, particularly amongst youth, a number of key determinants that may be associated with overall physical activity. Given the limited evidence drawn mostly from cross-sectional studies, longitudinal studies are needed to further explore these associations.
PROSPERO CRD42015010616.
Recent research shows that sedentary behaviour is associated with adverse cardio-metabolic consequences even among those considered sufficiently physically active. In order to successfully develop ...interventions to address this unhealthy behaviour, factors that influence sedentariness need to be identified and fully understood. The aim of this review is to identify individual, social, environmental, and policy-related determinants or correlates of sedentary behaviours among adults aged 18-65 years.
PubMed, Embase, CINAHL, PsycINFO and Web of Science were searched for articles published between January 2000 and September 2015. The search strategy was based on four key elements and their synonyms: (a) sedentary behaviour (b) correlates (c) types of sedentary behaviours (d) types of correlates. Articles were included if information relating to sedentary behaviour in adults (18-65 years) was reported. Studies on samples selected by disease were excluded. The full protocol is available from PROSPERO (PROSPERO 2014:CRD42014009823).
74 original studies were identified out of 4041: 71 observational, two qualitative and one experimental study. Sedentary behaviour was primarily measured as self-reported screen leisure time and total sitting time. In 15 studies, objectively measured total sedentary time was reported: accelerometry (n = 14) and heart rate (n = 1). Individual level factors such as age, physical activity levels, body mass index, socio-economic status and mood were all significantly correlated with sedentariness. A trend towards increased amounts of leisure screen time was identified in those married or cohabiting while having children resulted in less total sitting time. Several environmental correlates were identified including proximity of green space, neighbourhood walkability and safety and weather.
Results provide further evidence relating to several already recognised individual level factors and preliminary evidence relating to social and environmental factors that should be further investigated. Most studies relied upon cross-sectional design limiting causal inference and the heterogeneity of the sedentary measures prevented direct comparison of findings. Future research necessitates longitudinal study designs, exploration of policy-related factors, further exploration of environmental factors, analysis of inter-relationships between identified factors and better classification of sedentary behaviour domains.
To date, the scientific literature on socioeconomic correlates and determinants of physical activity behaviours has been dispersed throughout a number of systematic reviews, often focusing on one ...factor (e.g. education or parental income) in one specific age group (e.g. pre-school children or adults). The aim of this umbrella review is to provide a comprehensive and systematic overview of the scientific literature from previously conducted research by summarising and synthesising the importance and strength of the evidence related to socioeconomic correlates and determinants of PA behaviours across the life course.
Medline, Embase, ISI Web of Science, Scopus and SPORTDiscus were searched for systematic literature reviews and meta-analyses of observational studies investigating the association between socioeconomic determinants of PA and PA itself (from January 2004 to September 2017). Data extraction evaluated the importance of determinants, strength of evidence, and methodological quality of the selected papers. The full protocol is available from PROSPERO (PROSPERO2014:CRD42015010616).
Nineteen reviews were included. Moderate methodological quality emerged. For adults, convincing evidence supports a relationship between PA and socioeconomic status (SES), especially in relation to leisure time (positive relationship) and occupational PA (negative relationship). Conversely, no association between PA and SES or parental SES was found for pre-school, school-aged children and adolescents.
Available evidence on the socioeconomic determinants of PA behaviour across the life course is probable (shows fairly consistent associations) at best. While some evidence is available for adults, less was available for youth. This is mainly due to a limited quantity of primary studies, weak research designs and lack of accuracy in the PA and SES assessment methods employed. Further PA domain specific studies using longitudinal design and clear measures of SES and PA assessment are required.
A body mass loss has been consistently observed in astronauts. This loss is of medical concern since energy deficit can exacerbate some of the deleterious physiological changes observed during space ...flight including cardiovascular deconditioning, bone density, muscle mass and strength losses, impaired exercise capacity, and immune deficiency among others. These may jeopardize crew health and performance, a healthy return to Earth and mission's overall success. In the context of planning for planetary exploration, achieving energy balance during long-term space flights becomes a research and operational priority. The regulation of energy balance and its components in current longer duration missions in space must be re-examined and fully understood. The purpose of this review is to summarize current understanding of how energy intake, energy expenditure, and hence energy balance are regulated in space compared to Earth. Data obtained in both actual and simulated microgravity thus far suggest that the obligatory exercise countermeasures program, rather than the microgravity
, may be partly responsible for the chronic weight loss in space. Little is known of the energy intake, expenditure, and balance during the intense extravehicular activities which will become increasingly more frequent and difficult. The study of the impact of exercise on energy balance in space also provides further insights on lifestyle modalities such as intensity and frequency of exercise, metabolism, and the regulation of body weight on Earth, which is currently a topic of animated debate in the field of energy and obesity research. While not dismissing the significance of exercise as a countermeasure during space flight, data now challenge the current exercise countermeasure program promoted and adopted for many years by all the International Space Agencies. An alternative exercise approach that has a minimum impact on total energy expenditure in space, while preventing muscle mass loss and other physiological changes, is needed in order to better understand the in-flight regulation of energy balance and estimate daily energy requirements. A large body of data generated on Earth suggests that alternate approaches, such as high intensity interval training (HIIT), in combination or not with sessions of resistive exercise, might fulfill such needs.
Despite an increasing number of studies highlighting the health benefits of community gardening, the literature is limited by cross-sectional designs. The "JArDinS" quasi-experimental study aimed to ...assess the impact of community garden participation on the adoption of more sustainable lifestyles among French adults.
Individuals entering a community garden in Montpellier (France) in 2018 (n = 66) were compared with pairwise matched individuals with no experience in community gardening (n = 66). Nutritional quality, environmental impact and cost of monthly household food supplies, level of physical activity measured by accelerometers, as well as mental and social well-being, sensitivity to food waste, and connection with nature were evaluated at baseline (t0) and 12 months later (t1) to explore sustainability of lifestyles in social/health, environmental and economic dimensions. Linear mixed models were used to determine the independent effect of community gardening on investigated lifestyles components. In-depth interviews were conducted at t1 with 15 gardeners to better understand changes that may have occurred in gardeners' lives during the first year of gardening.
At t0, gardeners had lower education level, lower BMI and their household reported lower percentage of meals consumed outside of the home compared to non-gardeners (p < 0.05). Participating in the community garden had no significant impact, in spite of sufficient statistical power, on fruit and vegetables supplies (main outcome), nor on physical activity parameters, nor on others of the social/health, environmental and economic lifestyles components investigated. Qualitative interviews suggested the existence of pre-established health and environmental consciousness in some gardeners and revealed several barriers to the participation such as lack of time, lack of gardening knowledge, physical difficulty of gardening, health problems and conflicts with other gardeners.
The health benefits of community gardening previously reported by cross-sectional studies might be confounded by selection bias. The JArDinS study highlights the need to identify solutions to overcome barriers related to community garden participation when designing relevant public health interventions for the promotion of sustainable lifestyles.
The study was registered at clinicaltrials.gov as NCT03694782 . Date of registration: 3rd October 2018, retrospectively registered.
ABSTRACT
Long‐term spaceflight induces hypokinesia and hypodynamia, which, along microgravity per se, result in a number of significant physiological alterations, such as muscle atrophy, force ...reduction, insulin resistance, substrate use shift from fats to carbohydrates, and bone loss. Each of these adaptations could turn to serious health deterioration during the long‐term spaceflight needed for planetary exploration. We hypothesized that resveratrol (RES), a natural polyphenol, could be used as a nutritional countermeasure to prevent muscle metabolic and bone adaptations to 15 d of rat hindlimb unloading. RES treatment maintained a net protein balance, soleus muscle mass, and soleus muscle maximal force contraction. RES also fully maintained soleus mitochondrial capacity to oxidize palmitoyl‐carnitine and reversed the decrease of the glutathione vs. glutathione disulfide ratio, a biomarker of oxidative stress. At the molecular level, the protein content of Sirt‐1 and COXIV in soleus muscle was also preserved. RES further protected whole‐body insulin sensitivity and lipid trafficking and oxidation, and this was likely associated with the maintained expression of FAT/CD36, CPT‐1, and peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PGC‐1α) in muscle. Finally, chronic RES supplementation maintained the bone mineral density and strength of the femur. For the first time, we report a simple countermeasure that prevents the deleterious adaptations of the major physiological functions affected by mechanical unloading. RES could thus be envisaged as a nutritional counter‐measure for spaceflight but remains to be tested in humans.—Momken, I., Stevens, L., Bergouignan, A., Desplanches, D., Rudwill, F., Chery, I., Zahariev, A., Zahn, S., Stein, T. P., Sebedio, J. L., Pujos‐Guillot, E., Falempin, M., Simon, C., Coxam, V., Andrianjafiniony, T., Gauquelin‐Koch, G., Picquet, F., Blanc, S. Resveratrol prevents the wasting disorders of mechanical unloading by acting as a physical exercise mimetic in the rat. FASEB J. 25, 3646–3660 (2011). www.fasebj.org
Since low body weight is an important determinant of success in many sports such as gymnastics, martial arts and figure skating, athletes can benefit from effective weight loss strategies that ...preserve muscle mass and athletic performance. The present study investigates the effects of increased protein intake and exogenous ketosis on body composition, energy expenditure, exercise capacity, and perceptions of appetite and well-being during a hypocaloric diet in females.
Thirty-two female recreational athletes (age: 22.2 ± .5 years; body weight: 58.3 ± .8 kg; BMI: 20.8 ± .2 kg·m
) underwent 4 weeks of 30% caloric restriction and were randomized to receive either an increased daily amount of dietary protein (PROT, ∼2.0-2.2 g protein·kg
·day
), 3 × 20 g·day
of a ketone ester (KE), or an isocaloric placebo (PLA). Body composition was measured by DXA, resting energy expenditure (REE) by indirect calorimetry, exercise capacity during a VO
max test, appetite hormones were measured in serum, and perceptions of general well-being were evaluated
questionnaires.
The hypocaloric diet reduced body weight by 3.8 ± .3 kg in PLA, 3.2 ± .3 kg in KE and 2.4 ± .2 kg in PROT (P
<.0001). The drop in fat mass was similar between treatments (average: 2.6 ± .1 kg, P
<.0001), while muscle mass was only reduced in PLA and KE (average: .8 ± .2 kg, P
<.05), and remained preserved in PROT (P
<.01). REE adjusted for lean mass was reduced after caloric restriction in PLA (pre: 32.7 ± .5, post: 28.5 ± .6 kcal·day
·kg
) and PROT (pre: 32.9 ± 1.0, post: 28.4 ± 1.0 kcal·day
·kg
), but not in KE (pre: 31.8 ± .9, post: 30.4 ± .8 kcal·day
·kg
) (P
<.005). Furthermore, time to exhaustion during the VO
max test decreased in PLA (by 2.5 ± .7%,
< .05) but not in KE and PROT (P
<.05). Lastly, the perception of overall stress increased in PLA and PROT (
< .05), but not in KE (P
<.05).
Increased protein intake effectively prevented muscle wasting and maintained exercise capacity during a period of caloric restriction in female recreational athletes. Furthermore, exogenous ketosis did not affect body composition, but showed its potential in weight management by preserving a drop in exercise capacity and REE and by improving overall stress parameters during a period of caloric restriction.
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