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Growing attention to phytoplankton mixotrophy as a trophic strategy has led to significant revisions of traditional pelagic food web models and ecosystem functioning. Although some empirical estimates of mixotrophy do exist, a much broader set of in situ measurements are required to (i) identify which organisms are acting as mixotrophs in real time and to (ii) assess the contribution of their heterotrophy to biogeochemical cycling. Estimates are needed through time and across space to evaluate which environmental conditions or habitats favour mixotrophy: conditions still largely unknown. We review methodologies currently available to plankton ecologists to undertake estimates of plankton mixotrophy, in particular nanophytoplankton phago-mixotrophy. Methods are based largely on fluorescent or isotopic tracers, but also take advantage of genomics to identify phylotypes and function. We also suggest novel methods on the cusp of use for phago-mixotrophy assessment, including single-cell measurements improving our capacity to estimate mixotrophic activity and rates in wild plankton communities down to the single-cell level. Future methods will benefit from advances in nanotechnology, micromanipulation and microscopy combined with stable isotope and genomic methodologies. Improved estimates of mixotrophy will enable more reliable models to predict changes in food web structure and biogeochemical flows in a rapidly changing world.
Objective: To critically review developments over the first fifty years of research (1967-2017) on (a) how people feel when they participate in exercise and physical activity, and (b) the implications of these responses for their willingness to become and remain active. Design: Non-systematic narrative review. Method: Representative sources were selected through a combination of computer searches and cross-referencing. Results: For over three decades, exercise psychology exhibited a fixation on the idea that exercise and physical activity make people feel better. This notion, however, seemed to contrast with evidence that most adults in industrialized countries exhibit low levels of activity. In the last two decades, a critical examination and overhaul of the methodological platform resulted in the delineation of a dose-response pattern that encompasses positive as well as negative affective responses, and revealed marked interindividual differences. An emerging literature is aimed at refining and testing integrative dual-process models that can offer specific predictions about the behaviors that may result from the interaction of automatic processes (theorized to be heavily influenced by past affective experiences) and deliberative processes (such as cognitive appraisals). Conclusions: Affective responses to exercise and physical activity are more complex than the long-popularized "feel-better" effect, encompassing both pleasant and unpleasant experiences and exhibiting marked inter individual variation. The potential of affective experiences to influence subsequent behavior offers an opportunity for an expanded theoretical perspective in exercise psychology.
There is an increasing need for an assessment of the impacts of land use and land use change (LUCC). In this context, simulation models are valuable tools for investigating the impacts of stakeholder actions or policy decisions. Agricultural landscape generators (ALGs), which systematically and automatically generate realistic but simplified representations of land cover in agricultural landscapes, can provide the input for LUCC models. We reviewed existing ALGs in terms of their objectives, design and scope. We found eight ALGs that met our definition. They were based either on generic mathematical algorithms (pattern-based) or on representations of ecological or land use processes (process-based). Most ALGs integrate only a few landscape metrics, which limits the design of the landscape pattern and thus the range of applications. For example, only a few specific farming systems have been implemented. We conclude that existing ALGs contain useful approaches that can be used for specific purposes, but ideally generic modular ALGs are developed that can be used for a wide range of scenarios, regions and model types. We have compiled features of such generic ALGs and propose a possible software architecture. Considerable joint efforts are required to develop such generic ALGs, but the benefits in terms of a better understanding and development of more efficient agricultural policies would be high.
Alcohol in the aging brain
(2019)
As our society grows older new challenges for medicine and healthcare emerge. Age-related changes of the body have been observed in essential body functions, particularly in the loco-motor system, in the cardiovascular system and in cognitive functions concerning both brain plasticity and changes in behavior. Nutrition and lifestyle, such as nicotine intake and chronic alcohol consumption, also contribute to biological changes in the brain. This review addresses the effect of alcohol consumption on cognitive decline, changes in brain plasticity in the aging brain and on cardiovascular health in aging. Thus, studies on the interplay of chronic alcohol intake and either cognitive decline or cognitive preservation are outlined. Because of the inconsistency in the literature of whether alcohol consumption preserves cognitive functions in the aging brain or whether it accelerates cognitive decline, it is crucial to consider individual contributing factors such as culture, health and lifestyle in future studies.
In this volume, Egeberg and Trondal put forward an ‘organizational approach to public governance’ (p. 1) that, in their view, complements existing explanations for organizational change and behaviour in governance processes (‘Understanding’) and produces relevant advice for practitioners, specifically anyone involved in reorganizing public administration (‘Design’). Following the authors’ introduction of the theoretical reasoning behind their approach (chapter 1), they present supporting findings that are based on new material (chapters 2 and 9), but mainly draw on six previously published research articles (chapters 3–8). Egeberg and Trondal conclude with possible ‘design implications’ of said findings (chapter 9). Their ‘organizational approach’ focuses on the impact of selected organizational characteristics on decision‐making in and on behalf of government organizations in policy‐making generally (‘public governance’) and administrative politics more specifically (‘meta‐governance’). The authors concentrate on three sets of ‘classical’ organizational characteristics: structure (mainly vertical and horizontal specialization), demography (personnel composition), and locus (geographical location). The conceptual part of the volume convincingly summarizes ‘formal organization matters’—arguments from the literature for each of the individual organizational factors. Their main, already well‐established argument is that the way an organization is formally set up makes some (reform) decisions more likely than others—a line of reasoning that the authors present as neglected in governance literature.
In the following five empirical chapters, the authors show that aspects of horizontal and vertical specialization—mainly operationalized by Gulicks’ principles of horizontal specialization and the idea of primary versus secondary affiliation of staff—affect organizational behaviour. Readers learn that whether government levels are organized according to a territorial or non‐territorial principle impacts the power relationship between levels: non‐territorial organization at the supranational level tends to empower the centre against lower levels of government. There are two chapters on the decision‐making behaviour of commissioners and officials in the European Commission, both showing that organizational affiliation trumps demographic background factors such as nationality, even with temporary staff.
Chapter 5 addresses coordination dynamics in the European multi‐level system and finds that coordination at the territorially organized national level thwarts non‐territorially organized coordination at the supranational level, resulting in the phenomenon of ‘direct’ national administration bypassing their national executives. Further, the authors show that vertical specialization—while controlling for other factors such as issue salience—has an effect on officials’ behaviour at the national level: agency officials in Norway report significantly less sensitivity towards political signals from the political executive than their colleagues in ministries. Chapter 7 discusses the relevance of geographical location for the relationship between subordinated organizations and their political executive. The authors find that the site of Norwegian agencies does not significantly affect their autonomy, influence, or inter‐institutional coordination with the superior ministry.
The last empirical chapter focuses on the effect of formal organization on meta‐governance, that is, administrative politics. Based on a qualitative case study of a reorganization process in Norway in 2003 involving the synchronized relocation of several agencies after many failed attempts, the authors conclude that administrative reforms can be politically steered and controlled through the organization of the reform process. They argue that amongst other factors the strategic exclusion of opposing actors from the reform process as well as the deliberate increase in situations demanding quick decisions (‘action rationality’, p. 119) by political leaders helps explain the reform's unexpected success. The last chapter is dedicated to the synthesis of the results and to design implications. Supported by new data from a 2016 survey among Norwegian public officials, the authors conclude that organizational position is the most important influencer of decision‐making behaviour, with educational background and previous job experience also playing a large role (p. 135). Consequently, their suggestions for practitioners involved in meta‐governance processes concentrate on aspects of the deliberate crafting of organizational specialization to shape organizational positions, and spend less time discussing location and employee demographics. The authors illustrate and contextualize their recommendations with the help of three empirical examples: organizing good governance by balancing political control and independence in the case of agencification, organizing for coping with boundary‐spanning challenges such as climate change through inter‐organizational structural arrangements, and designing permanent organizational structures for innovative reforms in the public sector (pp. 137 ff.).
This volume is an excellent compilation of theoretically informed applications of the all too often undefined ‘organization matters’ argument. It juxtaposes—particularly in the theory chapter and in the last chapter on design implications—organizational arguments against other explanations of organizational change like historical institutionalism or the garbage can model of decision‐making. However, two major aspects of the book's approach are less convincing. First, supplementary explanations such as the garbage can model that are discussed in the reflections on meta‐governance are neither argumentatively nor empirically applied to public governance; why should, for example, the ‘solutions in search of a problem’ idea only be applicable to decisions on reform policy, but not to decisions in all other policy areas? Similarly, it would have been nice to read more on the authors’ idea on the interaction between organizational factors and between them and other explanations in the empirical cases on public governance—this would have allowed the reader to get a better idea about how much formal organization matters. The view on bureaucrats’ demographic background is slightly confusing: it is presented as a competing approach (p. 7), but also as one of the main organizational factors (p. 12).
Second, as the authors themselves state, the concept of governance is about ‘steering through collective action’ (p. 3) and focuses on interactive processes, and explicitly includes non‐governmental actors in the policy‐making equation. Against this background it seems unfortunate that most of the work presented in the book takes an exclusively governmental perspective and the justification for it remains rather superficial. It would be preferable and even necessary to see the organizational arguments—at least theoretically or through discussing appropriate literature—applied to interactive governance processes involving other actors and/or to non‐bureaucratic organizations.
Regarding its methodology, the specifics of the proposed approach deserve to be addressed more systematically and critically in the book. Except for chapters 2, 3 and 5 (literature‐based studies) as well as chapter 8 (single case study), the empirical studies follow a quantitative logic and are informed by data on self‐reported behaviour through large‐N panel surveys with public officials. In terms of analysis, descriptive statistics or basic inferential statistics (linear regression) are employed. Certainly, the authors are aware of the limitations of their data sources, such as the results being possibly affected by social desirability, and they discuss and justify them in the chapters individually (e.g., on pp. 47, 89). Still, their approach could be strengthened with a more cautious account on the extent to which their choice of data and methods is able to uncover the ‘causal impact of organizational factors in public governance processes’ (p. 131, emphasis added) and with some suggestions for widening their methodological toolbox in the future. On this note, the survey method presented as new on p. 135 is not a particularly convincing choice. The authors do not lay out a research agenda; a surprising omission. This is, however, somewhat made up for by the concluding chapter's stimulating discussion of the possible real‐world implications of their findings and perspective, skilfully using organization theory as a ‘craft’ (p. 29).
Arboreal epiphytes (plants residing in forest canopies) are present across all major climate zones and play important roles in forest biogeochemistry. The substantial water storage capacity per unit area of the epiphyte "bucket" is a key attribute underlying their capability to influence forest hydrological processes and their related mass and energy flows. It is commonly assumed that the epiphyte bucket remains saturated, or near-saturated, most of the time; thus, epiphytes (particularly vascular epiphytes) can store little precipitation, limiting their impact on the forest canopy water budget. We present evidence that contradicts this common assumption from (i) an examination of past research; (ii) new datasets on vascular epiphyte and epi-soil water relations at a tropical montane cloud forest (Monteverde, Costa Rica); and (iii) a global evaluation of non-vascular epiphyte saturation state using a process-based vegetation model, LiBry. All analyses found that the external and internal water storage capacity of epiphyte communities is highly dynamic and frequently available to intercept precipitation. Globally, non-vascular epiphytes spend <20% of their time near saturation and regionally, including the humid tropics, model results found that non-vascular epiphytes spend similar to 1/3 of their time in the dry state (0-10% of water storage capacity). Even data from Costa Rican cloud forest sites found the epiphyte community was saturated only 1/3 of the time and that internal leaf water storage was temporally dynamic enough to aid in precipitation interception. Analysis of the epi-soils associated with epiphytes further revealed the extent to which the epiphyte bucket emptied-as even the canopy soils were often <50% saturated (29-53% of all days observed). Results clearly show that the epiphyte bucket is more dynamic than currently assumed, meriting further research on epiphyte roles in precipitation interception, redistribution to the surface and chemical composition of "net" precipitation waters reaching the surface.
Purpose of review In addition to the currently available lysosomotropic drugs and autophagy whole-body knockout mouse models, we provide alternative methods that enable the modulation and detection of autophagic flux in vivo, discussing advantages and disadvantages of each method. Recent findings With the autophagosome-lysosome fusion inhibitor colchicine in skeletal muscle and temporal downregulation of autophagy using a novel Autophagy related 5-short hairpin RNA (Atg5-shRNA) mouse model we mention two models that directly modulate autophagy flux in vivo. Furthermore, methods to quantify autophagy flux, such as mitophagy transgenic reporters, in situ immunofluorescent staining and multispectral imaging flow cytometry, in mature skeletal muscle and cells are addressed. To achieve clinical benefit, less toxic, temporary and cell-type-specific modulation of autophagy should be pursued further. A temporary knockdown as described for the Atg5-shRNA mice could provide a first insight into possible implications of autophagy inhibition. However, it is also important to take a closer look into the methods to evaluate autophagy after harvesting the tissue. In particular caution is required when experimental conditions can influence the final measurement and this should be pretested carefully.
Sortases are enzymes occurring in the cell wall of Gram-positive bacteria. Sortase A (SrtA), the best studied sortase class, plays a key role in anchoring surface proteins with the recognition sequence LPXTG covalently to oligoglycine units of the bacterial cell wall. This unique transpeptidase activity renders SrtA attractive for various purposes and motivated researchers to study multiple in vivo and in vitro ligations in the last decades. This ligation technique is known as sortase-mediated ligation (SML) or sortagging and developed to a frequently used method in basic research. The advantages are manifold: extremely high substrate specificity, simple access to substrates and enzyme, robust nature and easy handling of sortase A. In addition to the ligation of two proteins or peptides, early studies already included at least one artificial (peptide equipped) substrate into sortagging reactions - which demonstrates the versatility and broad applicability of SML. Thus, SML is not only a biology-related technique, but has found prominence as a major interdisciplinary research tool. In this review, we provide an overview about the use of sortase A in interdisciplinary research, mainly for protein modification, synthesis of protein-polymer conjugates and immobilization of proteins on surfaces.
A wide variety of processes controls the time of occurrence, duration, extent, and severity of river floods. Classifying flood events by their causative processes may assist in enhancing the accuracy of local and regional flood frequency estimates and support the detection and interpretation of any changes in flood occurrence and magnitudes. This paper provides a critical review of existing causative classifications of instrumental and preinstrumental series of flood events, discusses their validity and applications, and identifies opportunities for moving toward more comprehensive approaches. So far no unified definition of causative mechanisms of flood events exists. Existing frameworks for classification of instrumental and preinstrumental series of flood events adopt different perspectives: hydroclimatic (large-scale circulation patterns and atmospheric state at the time of the event), hydrological (catchment scale precipitation patterns and antecedent catchment state), and hydrograph-based (indirectly considering generating mechanisms through their effects on hydrograph characteristics). All of these approaches intend to capture the flood generating mechanisms and are useful for characterizing the flood processes at various spatial and temporal scales. However, uncertainty analyses with respect to indicators, classification methods, and data to assess the robustness of the classification are rarely performed which limits the transferability across different geographic regions. It is argued that more rigorous testing is needed. There are opportunities for extending classification methods to include indicators of space-time dynamics of rainfall, antecedent wetness, and routing effects, which will make the classification schemes even more useful for understanding and estimating floods. This article is categorized under: Science of Water > Water Extremes Science of Water > Hydrological Processes Science of Water > Methods
We summarize the current state of observations of circumplanetary dust populations, including both dilute and dense rings and tori around the giant planets, ejecta clouds engulfing airless moons, and rings around smaller planetary bodies throughout the Solar System. We also discuss the theoretical models that enable these observations to be understood in terms of the sources, sinks and transport of various dust populations. The dynamics and resulting transport of the particles can be quite complex, due to the fact that their motion is influenced by neutral and plasma drag, radiation pressure, and electromagnetic forcesall in addition to gravity. The relative importance of these forces depends on the environment, as well as the makeup and size of the particles. Possible dust sources include the generation of ejecta particles by impacts, active volcanoes and geysers, and the capture of exogenous particles. Possible dust sinks include collisions with moons, rings, or the central planet, erosion due to sublimation and sputtering, even ejection and escape from the circumplanetary environment.
The protein fractions of cocoa have been implicated influencing both the bioactive potential and sensory properties of cocoa and cocoa products. The objective of the present review is to show the impact of different stages of cultivation and processing with regard to the changes induced in the protein fractions. Special focus has been laid on the major seed storage proteins throughout the different stages of processing. The study starts with classical introduction of the extraction and the characterization methods used, while addressing classification approaches of cocoa proteins evolved during the timeline. The changes in protein composition during ripening and maturation of cocoa seeds, together with the possible modifications during the post-harvest processing (fermentation, drying, and roasting), have been documented. Finally, the bioactive potential arising directly or indirectly from cocoa proteins has been elucidated. The state of the art suggests that exploration of other potentially bioactive components in cocoa needs to be undertaken, while considering the complexity of reaction products occurring during the roasting phase of the post-harvest processing. Finally, the utilization of partially processed cocoa beans (e.g., fermented, conciliatory thermal treatment) can be recommended, providing a large reservoir of bioactive potentials arising from the protein components that could be instrumented in functionalizing foods.
We review our current knowledge of comet 67P/Churyumov–Gerasimenko nucleus composition as inferred from measurements made by remote sensing and in-situ instruments aboard Rosetta orbiter and Philae lander. Spectrophotometric properties (albedos, color indexes and Hapke parameters) of 67P/CG derived by Rosetta are discussed in the context of other comets previously explored by space missions. Composed of an assemblage made of ices, organic materials and minerals, cometary nuclei exhibit very dark and red surfaces which can be described by means of spectrophotometric quantities and reproduced with laboratory measurements. The presence of surface water and carbon dioxide ices was found by Rosetta to occur at localized sites where the activity driven by solar input, gaseous condensation or exposure of pristine inner layers can maintain these species on the surface. Apart from these specific areas, 67P/CG’s surface appears remarkably uniform in composition with a predominance of organic materials and minerals. The organic compounds contain abundant hydroxyl group and a refractory macromolecular material bearing aliphatic and aromatic hydrocarbons. The mineral components are compatible with a mixture of silicates and fine-grained opaques, including Fe-sulfides, like troilite and pyrrhotite, and ammoniated salts. In the vicinity of the perihelion several active phenomena, including the erosion of surface layers, the localized activity in cliffs, fractures and pits, the collapse of overhangs and walls, the transfer and redeposition of dust, cause the evolution of the different regions of the nucleus by inducing color, composition and texture changes.
Sentence comprehension requires that the comprehender work out who did what to whom. This process has been characterized as retrieval from memory. This review summarizes the quantitative predictions and empirical coverage of the two existing computational models of retrieval and shows how the predictive performance of these two competing models can be tested against a benchmark data-set. We also show how computational modeling can help us better understand sources of variability in both unimpaired and impaired sentence comprehension.
One commonly proposed method to limit flood risk is land-use or zoning policies which regulates construction in high-risk areas, in order to reduce economic exposure and its vulnerability to flood events. Although such zoning regulations can be effective in limiting trends in flood risk, they also have adverse impacts on society, for instance by limiting local development of areas near the water. In order to judge whether proposed land-use or zoning policies are a net benefit to society, they should be accepted or rejected based on a societal cost-benefit analysis (CBA). However, conducting a CBA of zoning regulation is complex and comprehensive guidelines of how to do such an analysis are lacking. We offer guidelines for good practice. In order to assess the costs and benefits of zoning as a climate change adaption strategy, they should be assessed at a societal level in order to account for public good features of flood risk reduction strategies, and because costs in one area can be benefits in another region. We propose a multistep process: first, determine the spatial extent of the zoning policy and how interconnected the zoned area is to other locations; second, conduct a CBA using monetary costs and benefits estimated from an integrated hydro-economic model to investigate if total benefits exceed total costs; third, conduct a sensitivity analysis regarding the main assumptions; fourth, conduct a multicriteria analysis (MCA) of the normative outcomes of a zoning policy. A desirable policy is preferred in both the CBA and MCA. This article is categorized under: Engineering Water > Planning Water Human Water > Value of Water Science of Water > Water Extremes Human Water > Methods
Ecological effects of alien species can be dramatic, but management and prevention of negative impacts are often hindered by crypticity of the species or their ecological functions. Ecological functions can change dramatically over time, or manifest after long periods of an innocuous presence. Such cryptic processes may lead to an underestimation of long-term impacts and constrain management effectiveness. Here, we present a conceptual framework of crypticity in biological invasions. We identify the underlying mechanisms, provide evidence of their importance, and illustrate this phenomenon with case studies. This framework has potential to improve the recognition of the full risks and impacts of invasive species.
Large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking. Most moderate‐ and large‐magnitude earthquakes trigger landslides, ranging from small failures in the soil cover to massive, devastating rock avalanches. Some landslides dam rivers and impound lakes, which can collapse days to centuries later, and flood mountain valleys for hundreds of kilometers downstream. Landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows. Cracks and fractures can form and widen on mountain crests and flanks, promoting increased frequency of landslides that lasts for decades. More gradual impacts involve the flushing of excess debris downstream by rivers, which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency, settlements, ecosystems, and infrastructure. Ultimately, earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales. Two recent events have attracted intense research into earthquake‐induced landslides and their consequences: the magnitude M 7.6 Chi‐Chi, Taiwan earthquake of 1999, and the M 7.9 Wenchuan, China earthquake of 2008. Using data and insights from these and several other earthquakes, we analyze how such events initiate processes that change mountain landscapes, highlight research gaps, and suggest pathways toward a more complete understanding of the seismic effects on the Earth's surface.
We evaluated the effectiveness and acceptability of metacognitive interventions for mental disorders. We searched electronic databases and included randomized and nonrandomized controlled trials comparing metacognitive interventions with other treatments in adults with mental disorders. Primary effectiveness and acceptability outcomes were symptom severity and dropout, respectively. We performed random-effects meta-analyses. We identified Metacognitive Training (MCTrain), Metacognitive Therapy (MCTherap), and Metacognition Reflection and Insight Therapy (MERIT). We included 49 trials with 2,609 patients. In patients with schizophrenia, MCTrain was more effective than a psychological treatment (cognitive remediation, SMD = -0.39). It bordered significance when compared with standard or other psychological treatments. In a post hoc analysis, across all studies, the pooled effect was significant (SMD = -0.31). MCTrain was more effective than standard treatment in patients with obsessive-compulsive disorder (SMD = -0.40). MCTherap was more effective than a waitlist in patients with depression (SMD = -2.80), posttraumatic stress disorder (SMD = -2.36), and psychological treatments (cognitive-behavioural) in patients with anxiety (SMD = -0.46). In patients with depression, MCTherap was not superior to psychological treatment (cognitive-behavioural). For MERIT, the database was too small to allow solid conclusions. Acceptability of metacognitive interventions among patients was high on average. Methodological quality was mostly unclear or moderate. Metacognitive interventions are likely to be effective in alleviating symptom severity in mental disorders. Although their add-on value against existing psychological interventions awaits to be established, potential advantages are their low threshold and economy.
Objective: The purpose of this systematic review and meta-analysis was to examine the effects of exercise on depression and anxiety in people living with HIV (PLWH), and to evaluate, through subgroup analysis, the effects of exercise type, frequency, supervision by exercise professionals, study quality, and control group conditions on these outcomes. Method: A literature search was conducted through four electronic databases from inception to February 2019. Considered for inclusion were randomized controlled trials (RCTs) investigating exercise interventions and depression or anxiety as outcomes in people living with HIV (>= 18 years of age). Ten studies were included (n = 479 participants, 49.67% females at baseline), and the standardized mean difference (SMD) and heterogeneity were calculated using random-effect models. An additional pre-post meta-analysis was also conducted. Results: A large effect in favor of exercise when compared to controls was found for depression (SMD = -0.84, 95%CI = [-1.57, -0.11], p = 0.02) and anxiety (SMD = -1.23, 95%CI = [-2.42, 0.04], p = -0.04). Subgroup analyses for depression revealed large effects on depression for aerobic exercise only (SMD = -0.96, 95%CI = [-1.63, -0.30], p = 0.004), a frequency of >= 3 exercise sessions per week (SMD = -1.39, 95%CI = [-2.24, -0.54], p < 0.001), professionally supervised exercise (SMD = -1.40, 95%CI = [-2.46, -0.17], p = 0.03]), and high-quality studies (SMD = -1.31, 95%CI = [-2.46, -0.17], p = 0.02). Conclusion: Exercise seems to decrease depressive symptoms and anxiety in PLWH, but other larger and high-quality studies are needed to verify these effects.
Background Small-sided games have been suggested as a viable alternative to conventional endurance training to enhance endurance performance in youth soccer players. This has important implications for long-term athlete development because it suggests that players can increase aerobic endurance through activities that closely resemble their sport of choice. Data Sources The data sources utilised were Google Scholar, PubMed and Microsoft Academic. Study Eligibility Criteria Studies were eligible for inclusion if interventions were carried out in male soccer players (aged < 18years) and compared the effects of small-sided games and conventional endurance training on aerobic endurance performance. We defined small-sided games as modified [soccer] games played on reduced pitch areas, often using adapted rules and involving a smaller number of players than traditional games. We defined conventional endurance training as continuous running or extensive interval training consisting of work durations>3min. Study Appraisal and Synthesis Methods The inverse-variance random-effects model for meta-analyses was used because it allocates a proportionate weight to trials based on the size of their individual standard errors and facilitates analysis whilst accounting for heterogeneity across studies. Effect sizes were represented by the standardised mean difference and presented alongside 95% confidence intervals. Results Seven studies were included in this meta-analysis. Both modes of training were effective in increasing endurance performance. Within-mode effect sizes were both of moderate magnitude [small-sided games: 0.82 (95% confidence interval 0.05, 1.60), Z=2.07 (p=0.04); conventional endurance training: 0.89 (95% confidence interval 0.06, 1.72), Z=2.10 (p=0.04)]. There were only trivial differences [0.04 (95% confidence interval -0.36, 0.43), Z=0.18 (p=0.86)] between the effects on aerobic endurance performance of small-sided games and conventional endurance training. Subgroup analyses showed mostly trivial differences between the training methods across key programming variables such as set duration (>= or < 4 min) and recovery period between sets (>= or< 3min). Programmes that were longer than 8 weeks favoured small-sided games [effect size=0.45 (95% confidence interval -0.12, 1.02), Z=1.54 (p=0.12)], with the opposite being true for conventional endurance training [effect size=-0.33 (95% confidence interval -0.79, 0.14), Z=1.39 (p=0.16)]. Programmes with more than 4 sets per session favoured small-sided games [effect size=0.53 (95% confidence interval -0.52, 1.58), Z=0.98 (p=0.33)] with only a trivial difference between those with 4, or fewer, sets [effect size=-0.13 (95% confidence interval -0.52, 0.26), Z=0.65 (p=0.52)]. Conclusions Small-sided games are as effective as conventional endurance training for increasing aerobic endurance performance in male youth soccer players. This is important for practitioners as it means that small-sided games can allow both endurance and skills training to be carried out simultaneously, thus providing a more efficient training stimulus. Small-sided games offer the same benefits as conventional endurance training with two sessions per week, with4 sets of 4 min of activity, interspersed with recovery periods of 3min, recommended in this population.