Transfer Test Research Articles

Experimental study on heat transfer and resistance of round tube with tube sheet under ultrasonic action

AbstractEnergy is vital to the survival and development of human beings. In the era of ‘carbon neutrality’, all walks of life around the world are upgrading their technological capabilities to reduce carbon emissions. As a new type of active strengthening technology to improve the comprehensive performance of heat exchangers, ultrasonic technology has attracted the attention of more and more scholars. From the actual installation situation, a set of ultrasonic enhanced heat transfer test device with tube sheet round tube was built. After experimental research and data analysis, the influence of ultrasonic sound intensity, frequency, and position on heat transfer, flow resistance, and comprehensive performance of heat exchange tube under different working conditions and without ultrasonic wave is studied. The results show that the ultrasonic enhanced heat transfer and drag reduction capacity increases with the decrease of ultrasonic frequency, and under the action of ultrasonic waves of different frequencies, the critical sound intensity of its enhanced heat transfer and drag reduction performance is different. The drag reduction performance of the ultrasonic heat exchange tube is increased by 18.41%, the heat transfer performance is increased by 36.53%, and the overall performance is increased by 20.57%.

Short-Term Effect of Attributional Versus Non-Attributional Negative Normative Feedback on Motor Tasks: A Double-Blind Study

Augmented feedback can alter motor performance. We examined if presenting attributional versus non-attributional negative normative feedback differently impacted short-term motor performance. With a double-blind experimental design, 49 students (36.7% female, Mage = 17.14 and SD = ±0.35) were assigned to the following two groups: G1: Attributional Negative Normative Feedback group (n = 24) and G2: Non-Attributional Negative Normative Feedback group (n = 25), with the dependent variable being the score obtained on a dart-throwing test. The results showed that those participants who received negative social comparative feedback presented in an attributional way (internal, controllable, and unstable) obtained higher scores in the dart throwing task than those who received negative social comparative feedback presented in a non-attributional way. Furthermore, these differences were maintained in the retention and transfer tests conducted 24 h after the practice phase. These findings have practical implications in motor behavior learning and performance.

Evaluation of bacterial anti-adhesion and sustained antimicrobial abilities of chlorhexidine gluconate-loaded phase-transited lysozyme nanoparticle suspension on dentine: An exvivo study.

To evaluate the effect of chlorhexidine gluconate-loaded phase-transited lysozyme (CHG@PTL) coating on inhibiting bacterial adhesion and biofilm formation in an exvivo root canal dentine model. The physicochemical and structural characteristics of CHG@PTL nanoparticle suspension and its coating formed on the dentine surface were analysed by thioflavin T fluorescence assay, transmission electron microscopy and confocal laser scanning microscopy (CLSM). The sustained chlorhexidine release profile of the CHG@PTL coating on the dentine surface was compared with that of the 2% CHG solution. By comparing with phosphate-buffered saline, 1% sodium hypochlorite and 2% CHG solutions, the sustained antibacterial ability of the CHG@PTL coating and its effects on adhesion and biofilm formation of three types of bacteria (E. faecalis, S. mutans, and A. viscous) were analysed in exvivo root canal dentine models using the serial plate transfer test (SPTT) and CLSM with live/dead bacterial staining, respectively. CHG promoted the lysozyme protein to form a higher proportion of β-sheet structure during phase transition. In the CHG@PTL nanoparticle suspension, characteristic drug-loaded nanospheres with a high concentration of CHG molecules inside and an outer PTL nanofilm were observed, and they formed a thinner and tighter coating on the dentine surface. The CHG@PTL coating on the dentine surface showed a significantly higher cumulative release amount of chlorhexidine than that of 2% CHG (p < .05). The results of SPTT showed that the CHG@PTL coating had a longer antibacterial duration than the control groups. After 12 h of incubation, a higher number of bacteria were agglutinated on the CHG@PTL coating surface compared to the control groups (p < .05). After 7 days of incubation, the number of agglutinated bacteria significantly decreased. At two time points, the percentage of dead bacteria on the CHG@PTL coating surface was the highest among all experimental groups based on CLSM observation (over 99.9% for all three bacteria, p < .001). CHG@PTL nanoparticle suspension could form an antimicrobial coating on the surface of dentine with a novel 'agglutinating bacteria and sterilizing' mode.

Thermal-deformation behaviors of the primary sealants in double, triple, and multi glazed insulating glass units

Polyisobutylene (PIB), commonly used as the primary sealant of double, triple, and multi glazed insulating glass units (IGUs), provides the key moisture barrier function and determines the expected lifespan of the IGUs and even the entire glass curtain wall systems (GCWSs). Slipping and debonding of the PIB, caused by temperature changes, have resulted in numerous instances of premature failure of building envelopes. However, available research is inadequate in accurately evaluating the service environment of IGUs and thermal-deformation behaviors of this energy-saving building material. This paper presented a simplified method for analyzing the thermal environment of IGUs, considering outdoor air temperature, solar radiation, wind speed, and angle to the horizontal. A numerical modeling method was proposed and validated with the heat transfer tests. Three finite element (FE) models were built and utilized for the precise analysis of temperature-induced deformations of double, tripled, and quadruple glazed IGUs. Simplified calculation formulas for the maximum thermal deformation of PIB in the X and Y directions under different temperature conditions were obtained, taking a new concept “cavity-to-pane ratio” into consideration. Finally, the relationship between the PIB’s temperature-induced deformation and its probability was proposed. The results show that the IGUs in Beijing suffer more than 22 % of their time in harsh service conditions where the difference between indoor and outdoor temperatures exceeds 20 °C. For DIGUs, the maximum temperature-induced deformations of the PIB in X (along the short side of the panel) and Y (along the long side of the panel) directions are 0.142 and 0.214 mm, respectively, corresponding to shear strains of 28.4 % and 42.8 % for the PIB with a thickness of only 0.5 mm. For TIGUs, the maximum deformations increase to 0.159 and 0.239 mm, corresponding to shear strains of 31.8 % and 47.8 %. For QIGUs and the other multi-glazed IGUs, these values can increase to 36.8 % and 55.4 % or more. The methodology proposed in this paper aims to lay the groundwork for further addressing premature failure issues and optimizing edge bond constructions of multi-glazed IGUs.

Determining the optimal challenge point for learning motor skills in children with attention deficit/hyperactivity disorder

The purpose of this study was to investigate the optimal challenge point for learning motor skills in children with and without attention deficit/hyperactivity disorder (ADHD). Ninety-six 9- to 10-year-old children, including 48 children with ADHD and 48 neurotypical children, were randomly assigned to one of four practice groups with varying levels of nominal and functional task difficulty. They performed 63 trials of a dart throwing task in the acquisition phase and 18 trials in the retention and transfer tests a day later. The results showed that neurotypical children outperformed children with ADHD in all phases of the study. Both groups improved in the acquisition phase and performed better in the retention and transfer tests. Interestingly, low nominal task difficulty was associated with better learning for both groups, despite lower average performance for children with ADHD. Thus, despite their performance differences, we did not find a difference in the effective challenge point between children with ADHD and their neurotypical peers.

Does Embodiment in Virtual Reality Boost Learning Transfer? Testing an Immersion-Interactivity Framework

This study investigates the role of embodiment when learning a technical procedure in immersive virtual reality (VR) by introducing a framework based on immersion and interactivity. The goal is to determine how increasing the levels of immersion and interactivity affect learning experiences and outcomes. In a 2 × 2 factorial design, 177 high school students were assigned to one of four experimental conditions, varying levels of immersion (learning in immersive virtual reality wearing a head-mounted display (VR) vs. learning via a computer screen (PC)) and interactivity (directly manipulating objects using controllers/mouse and keyboard (congruent) vs. indirectly manipulating objects with a laser pointer to select a course of action (incidental)). The main outcome measure was a transfer task in which students were required to perform the task they had learned in the virtual environment using concrete objects in real life. Results demonstrated that students in the VR conditions experienced significantly higher levels of presence, agency, location, body ownership, and embodied learning compared to participants in the PC conditions. Additionally, students’ performance during the virtual lesson predicted their real-life transfer test. However, there were no significant effects of immersion or interactivity on any of the transfer measures. The results suggest that high immersion in VR can increase self-reported measures of presence, agency, location, body ownership, and embodied learning among students. However, increased embodiment—manipulated by adding immersion and congruent manipulation of objects did not improve transfer.

Theoretical and experimental study on the effect of the heat shield on the trough solar cavity receiver in alpine areas

The large heat loss of the cavity receiver limits its application in parabolic trough collectors, matching the environmental factors in alpine areas, in this paper, adding a glass cover plate as a heat shield at the aperture of the trough inverted trapezoidal cavity receiver is investigated. To quantify the optimization of the system performance by adding, an analytical study is carried out for the cavity receiver using theoretical calculations of heat transfer and indoor experimental tests, while “thermal uniformity” is introduced as an indicator of the temperature distribution inside the cavity, and further verifies experimentally by the outdoor real-area environment. The findings indicate that adding a heat shield is significantly effective in reducing heat loss in windy areas. At the flow rate of 250 L/h and inlet temperature of 323 K, the maximum experimental heat loss value is significantly reduced by 70.01 % in the range of 1–5 m/s wind speeds compared to the one without a heat shield. When the wind direction is from −60° to 60°, the heat loss inside the cavity is small after adding, forming a stable stratified flow, and the thermal uniformity decreases by only 0.02, indicating that the stability of the temperature field inside the cavity is high. Furthermore, outdoor validation experiments demonstrate a slower change in heat loss rate with adding the heat shield compared to without, the growth rate of the former is close to 1/3 that of the latter, with a maximum suppressed heat loss rate of 23.49 %. This study provides the theoretical basis and data guidance for optimizing cavity receiver performance in alpine areas.

The Effect of Contextual Interference on the Acquisition and Learning of Motor Skill with an Emphasis on Cognitive Flexibility

Background: The effect of contextual interference (CI) on motor skill learning may be influenced by various factors, such as cognitive abilities. Objectives: The purpose of the current research was to investigate the effect of CI on the acquisition and learning of soccer skills, with an emphasis on the role of cognitive flexibility (CF). Methods: Eighty students, aged 9 - 12 years, were randomly selected and administered the Wisconsin Card Sorting Test. From this group, 60 students who scored the highest and lowest points were selected as the final subjects. After completing the pre-test on Moore-Christine's pass, shoot, and dribble skills, the subjects were divided into four groups of 15 participants each (high CF with Random Practice (RP) and Blocked Practice (BP), low CF with RP and BP). The subjects then engaged in practice sessions according to their assigned protocols for three sessions, with each session consisting of three blocks of 12 trials across all three skills—passing, shooting, and dribbling. Following the practice, acquisition, immediate retention, delayed retention, and transfer tests were conducted. Results: The results showed that practice in all four groups had significant beneficial effects on the acquisition and learning of skills. Additionally, the high CF with RP group demonstrated better performance in all skills compared to the other groups. Conclusions: Therefore, it can be concluded that RP may be more beneficial for individuals with higher CF. Teachers and educators should consider this when teaching sports skills.

Pure copper extrusion additive manufacturing of lattice structures for enabling enhanced thermal efficiency in hydrogen production

The high geometrical complexity allowed by Additive Manufacturing (AM) of pure copper can support the development of more efficient catalytic supports that can enable the design of efficient reactors for key processes for energy transition, i.e., hydrogen production with methane steam reforming or CO2 conversion to synthetic methane, thanks to the enhanced thermal conductivity of the catalytic support. Low relative density lattice geometries with open cell copper geometries can be adopted as catalyst supports in the new generation chemical reactors to improve the heat transfer. This work presents a manufacturability study about pure copper lattice filters produced via metal Extrusion AM i.e., via feedstock 3D printing and sintering. The results show that feasible parts design can be reached and produced and that heat-exchange performances can be increased with respect to conventional supports, as confirmed by lab-scale heat transfer tests. A specific metrological assessment based on CTscan data is implemented on the printed parts to qualify them and to ensure a good thermal coupling between the printed filters and the heat exchanger main tube elements.

Thermal characteristics of cementitious building materials with carbon and PCM for improved heat storage performance

The thermal properties of cementitious building materials were analyzed by integrating phase change materials (PCMs) and carbon materials to improve their heat storage performance. Four types of carbon materials, namely activated carbon (AC), carbon nanotubes (CNT), exfoliated graphite nanoplatelets (xGnPs), and graphene, were dispersed in PCMs and impregnated into artificial lightweight aggregates via vacuum impregnation to create cement building materials. Various parameters including compressive strength, differential scanning calorimetry (DSC), hydration heat, thermal conductivity, and dynamic heat transfer were evaluated According to the results, the thermal conductivity of PCM was significantly improved by incorporating carbon materials, and the specimen with CNT showed a result of 0.8386 W/m∙K, which is about 20 % higher than that of the specimen without carbon materials. Although the compressive strength decreased with the addition of PCMs, it remained above 20 MPa, thereby ensuring structural integrity. In the dynamic heat transfer test, the carbon/PCM specimen maintained a higher temperature during heat dissipation. It showed a high peak temperature and a time delay of about 2.5 hours during free cooling. The results showed that integrating PCMs and carbon materials into cementitious building materials could effectively improve their thermal performance, potentially saving building energy.

The Development and Optimization of a New Wind Tunnel Design for Odour Sampling

The characterization of passive area sources, emitting odours due to wind-driven convection, poses significant challenges. The present experimental study aims to evaluate the performance, in terms of fluid dynamics and mass transfer, of a recently developed wind tunnel, with a more compact design and reduced weight, compared to the one proposed by the Italian regulations. The results show that the new design outperforms the Italian standard in several aspects. From a fluid dynamic point of view, the new wind tunnel exhibits a slightly more homogenous and uniform velocity distribution, and it does not reveal airflow preferential channels inside the central body. The pressure tests highlight that the presence of fillers in the new wind tunnel does not significantly alter the pressure inside the hood and therefore the gas–liquid equilibrium conditions; actually, the slight overpressure may help to prevent the infiltration of external air. Finally, mass transfer tests on the standard device show a vertical concentration gradient along the outlet duct, highlighting concentration values that differ up to a factor of two depending on the measurement point. The new design has almost completely solved this issue, thanks to the use of fillers that promote mixing of the outlet flow.

The impact of extremely brief meditation and brief mindfulness interventions on assisted reproductive technologies success rates: A randomised controlled trial

ObjectiveTo investigate the effect of extremely brief meditation (EBMI) or brief mindfulness interventions (Brief MI) on pregnancy rate in women undergoing Assisted Reproductive Technology (ART). MethodsThis is a prospective, three-armed, randomized controlled trial with women undergoing ART cycle, age ranging from 18 to 50 years. In the day of embryo transfer, the patients randomized to Brief MI group received a 15-minute audio of mindfulness. They were instructed to practice it daily, starting from the day of embryo transfer to the day of the pregnancy test, leading to a total of 180–210 minutes. Women randomized to EBMI met once a week during the waiting time between the embryo transfer and pregnancy test day in the same virtual room with a meditator instructor for 40 minutes, totalizing two sessions (80 minutes). The pregnancy rate was assessed via a blood test to measure hCG performed 2 weeks after embryo transfer. ResultsA total of 68 women aged 37.5 ± 4.3y were included (EBMI, n = 24; Brief MI, n = 22 and CG, n = 22). Pearson's Chi-square test and Student's t-test for independent samples showed no significant differences between intervention and control groups. Both EBMI and Brief MI had no significant effect on pregnancy rate in women undergoing ART. ConclusionThis randomized control trial revealed that the extremely brief meditation (EBMI) or self-managed brief mindfulness intervention (Brief MI) had no significant effect on pregnancy rates in infertile women undergoing ART cycles. Trial registration number: NCT04058262.

The Effect of Internal and external imagery on learning badminton long serve skill: The role of visual and audiovisual imagery

This study aimed to examine the impact of internal and external audiovisual imagery on the learning of the badminton long serve skill. A lot of 42 right-handed novice women were selected using availability sampling. Participants were categorized into four groups based on their scores from the visual imagery ability questionnaire and Bucknell auditory questionnaire: Visual-Internal imagery, Visual-External imagery, AudioVisual-Internal imagery and AudioVisual-External imagery groups. To generate an auditory pattern, the shoulder joint’s angular velocity of a skilled individual was recorded and translated into sound based on frequency characteristic changes. Subjects underwent four sessions of 40 trials each and subsequently participated in retention and transfer tests. Performance accuracy of the badminton long serve was assessed using the Scott and Fox standard test and repeated measures ANOVA was employed to compare performance across groups during test stages. While no significant differences were noted between groups during the acquisition stages, indicated that subjects in the AudioVisual imagery conditions outperformed those in Visual imagery during the retention test. Additionally, the AudioVisual-Internal Imagery group demonstrated superior performance compared to other groups. Internal imagery groups also exhibited better performance in the later stages of acquisition, retention and transfer tests compared to external imagery groups. These findings suggest that the incorporation of audiovisual imagery utilizing movement sonification, alongside physical practice, improves skill development more effectively than visual imagery alone.

Thermal performance and Feasibility Study Using a Straw-Based Thermal Insulation in Geothermal systems

Straw is the part of the stem (or stubble) of certain grasses, known as "straw cereals", and is most often a by-product or waste product of cereal production. In northern Algeria, it is produced in all cereal growing regions. It is generally used for animal feed. In this study, straw waste is used as a bio-material for thermal insulation in bioclimatic constructions and especially in geothermal applications, and the thermal insulation needs in a geothermal system is discussed. Furthermore, thermal performance of wheat straw aggregates bio-based material is tested for several thicknesses until stable results are achieved, using conduction heat transfer tests or heating flat plate. This method is based on the temperature difference measuring across the sample (inlet and outlet) and finally, compared it with other commercial geothermal insulation materials. Obtained results give us an idea of the energy gains to be expected from the bio-based materials manufacture to be used in geothermal systems comparing to conventional materials. It is noted that, the optimum thickness of the insulation material based on straw is 2cm, giving a temperature gradient around 9°C versus 16°C for conventional materials. Straw organic waste material is a promising candidate as an alternative insulating material for low-carbon and green buildings targets. Which are in line with the objectives set by the Algerian government as part of the fight against climate change, in particular the development of renewable energies, the promotion of energy efficiency as well as clean technologies and waste recycling.

Demo2Test: Transfer Testing of Agent in Competitive Environment with Failure Demonstrations

Demo2Test: Transfer Testing of Agent in Competitive Environment with Failure Demonstrations

The reliability and validity of the Lie‑To‑Sit‑To‑Stand‑To‑Walk transfer test in total knee arthroplasty.

Total knee arthroplasty (TKA) is the standard procedure for treating end-stage knee osteoarthritis. Nevertheless, some residual issues can persist, leading to various problems, including pain, compromised strength, impaired proprioception, postural instability, dynamic balance issues, and gait deficiencies. The Lie-to-Sit-to-Stand-to-Walk Transfer Test (LSSWT) implements a multi-faceted methodology to evaluate basic transfer abilities. The purpose of this study is to investigate the validity, reliability, and minimal clinically important difference of the LSSWT in TKA patients. Twenty-two patients with TKA were enrolled in this study. The patients were administered the LSSWT, the Timed Up and Go Test (TUG), and the Hospital for Special Surgery (HSS) knee score. Patients rested between the tests for an hour to prevent fatigue. The mean age was 68.1 ± 2.59 years and the mean HSS Knee Score was 85.43 ± 3.47 of the patients. The relative (ICC coefficient) and absolute (SEM and SRD95) reliability values were 0.88, 1.21, and 3.33 respectively. The Spearman correlation coefficient of the LSSWT with the TUG was 0.63. The LSSWT displays excellent reliability and high validity in assessing fall risk, complex dynamic balance, and mobility required for daily activities in patients post-TKA. The low MCID value (3.33) indicates its sensitivity and ability to identify minor changes in a patient's status over time or in response to rehabilitation applications. Therefore, it is recommended to use the LSSWT when evaluating fall risk, dynamic balance, and mobility for community living, discharge planning, or facility admission.

Development of a Stable Lyophilized Cyclophosphamide Monohydrate Formulation Using Non-Aqueous Solvents.

To ensure product stability, it is critical to maintain the monohydrate state of cyclophosphamide following lyophilization, as this is the most stable solid form of the Cyclophosphamide. On the other hand, because of their limited aqueous solubility and stability, non-aqueous solvents are preferred for determining the composition and stability of bulk solutions. Hence, the purpose of this study was to use non-aqueous solvents for determining the composition and stability of bulk solutions, and to shorten the lyophilization process by retaining the cyclophosphamide monohydrate. Furthermore, prior to selecting the solvent for the bulk solution consisting of 90:10 tertiary butyl alcohol (TBA) and acetonitrile (ACN), various factors were taken into account, including the freezing point, vapor pressure of solvents, solubility, and stability of cyclophosphamide monohydrate. The concentration of the bulk solution was adjusted to 200mg/mL in order to optimize the fill volume, enhance sublimation rates at lower temperatures during primary drying, and eliminate the need for secondary drying. The differential scanning calorimetry (DSC) measurements of bulk solution were used to improve the lyophilization cycle. The lyophilization cycle opted was freezing at a temperature of -55°C with annealing step at -22°C by which the reconstitution time was significantly reduced. The drying was performed at below - 25°C while maintaining a chamber pressure of 300 mTorr. The complete removal of non-aqueous solvents was achieved by retaining water within the system. The presence of cyclophosphamide monohydrate was confirmed using X-ray diffraction (XRD). The reduction of lyophilization process time was established by conducting mass transfer tests and evaluating the physicochemical properties of the pharmaceutical product. Using non-aqueous solvents for freeze-drying cyclophosphamide is a viable option, and this study provides significant knowledge for the advancement of future generic pharmaceuticals.

A Bi-Temporal Airborne Lidar Shrub-to-Tree Aboveground Biomass Model for the Taiga of Western Canada

Monitoring aboveground biomass (AGB) is critical for carbon reporting and quantifying ecosystem change. AGB from field data can be scaled to the region using airborne lidar. However, lidar-based AGB products emphasize upland forests, which may not represent the conditions in rapidly changing peatland complexes in the southern Taiga of western Canada. In addition, to ensure that modeled AGB changes do not incorporate systematic error due to differences between older and newer lidar technologies, model transfer tests are required. The aim of this study was to develop one bi-temporal lidar-based AGB model applicable to (1) vegetation structures at varying vertical and horizontal continuity in this region and to (2) data collected with an earlier generation lidar system for which Canada-wide aerial coverage is available. Goodness-of-fit metrics show that AGB can be modeled with moderate (R2 = 48%–58% Taiga Shield, peatlands) to high accuracies (R2 = 83%–89% Taiga Plains, upland/permafrost plateau forests including ecotones) by using the point clouds average height and 90th height percentile within a weighted approach as function of modeled AGB and calibrating the earlier lidar data. These results are important for quantifying climate change effects on forest to peatland ecotones.

Health and non-health benefits and equity impacts of individual-level economic relief programs during epidemics/pandemics in high income settings: a scoping review

BackgroundEconomic relief programs are strategies designed to sustain societal welfare and population health during a regional or global scale infectious disease outbreak. While economic relief programmes are considered essential during a regional or global health crisis, there is no clear consensus in the literature about their health and non-health benefits and their impact on promoting equity.MethodsWe conducted a scoping review, searching eight electronic databases from January 01, 2001, to April 3, 2023, using text words and subject headings for recent pathogens (coronavirus (COVID-19), Ebola, Influenza, Middle East Respiratory Syndrome (MERS), severe acute respiratory syndrome (SARS), HIV, West Nile, and Zika), and economic relief programs; but restricted eligibility to high-income countries and selected diseases due to volume. Title and abstract screening were conducted by trained reviewers and Distiller AI software. Data were extracted in duplicates by two trained reviewers using a pretested form, and key findings were charted using a narrative approach.ResultsWe identified 27,263 de-duplicated records, of which 50 were eligible. Included studies were on COVID-19 and Influenza, published between 2014 and 2023. Zero eligible studies were on MERS, SARS, Zika, Ebola, or West Nile Virus. We identified seven program types of which cash transfer (n = 12) and vaccination or testing incentive (n = 9) were most common. Individual-level economic relief programs were reported to have varying degrees of impact on public health measures, and sometimes affected population health outcomes. Expanding paid sick leave programs had the highest number of studies reporting health-related outcomes and positively impacted public health measures (isolation, vaccination uptake) and health outcomes (case counts and the utilization of healthcare services). Equity impact was most often reported for cash transfer programs and incentive for vaccination programs. Positive effects on general well-being and non-health outcomes included improved mental well-being and quality of life, food security, financial resilience, and job security.ConclusionsOur findings suggest that individual-level economic relief programs can have significant impacts on public health measures, population health outcomes and equity. As countries prepare for future pandemics, our findings provide evidence to stakeholders to recognize health equity as a fundamental public health goal when designing pandemic preparedness policies.

The effectiveness of different attentional foci on the acquisition of sport-specific motor skills in healthy adults: a systematic review with network meta-analysis.

The acquisition of motor skills is a key element in many sports. A motor learning principle, which is frequently used to support skill acquisition is the application of different attentional foci. The effectiveness of different attentional foci on performance and the learning of motor skills has been investigated in various sports using randomised controlled trials. The aim of the present study was to investigate the effectiveness of different attentional foci (such as external (EFA) and internal attentional foci (IFA), but also holistic and switching foci) on the performance and learning of a sport-specific motor task in healthy individuals. This study was a systematic review with network meta-analysis. We followed the Prisma reporting guideline and the Cochrane handbook for systematic reviews. Cinahl, Embase, Medline and Cochrane Central were searched for eligible studies. Network meta-analyses were performed for the post-acquisition, retention and transfer test endpoints. Twelve studies were included in the review. At post-acquisition an EFA was the most effective intervention compared to the control intervention (SMD: 0.9855; 95% CI [0.4-1.57]; p: 0.001). At the retention and transfer test endpoints, a holistic focus of attention had the highest effectiveness compared to an IFA (SMD 0.75; 95% CI [-0.1 to 1.6]; p: 0.09) and (SMD 1.16; 95% CI [0.47-1.86]; p: 0.001). For all three endpoints, we analysed a greater effectiveness of an EFA and holistic focus compared to an IFA. Several promising different attentional focus interventions were identified. The largest effects were analysed for a holistic focus. However, only one study used this intervention and therefore there remains uncertainty about the effectiveness. With regard to the inconsistency observed, the analysis at post-acquisition should be interpreted with caution. Modified versions of the EFA were the imagined and the dynamic EFA. Both were only explored in single studies and should therefore be investigated in further follow-up studies that directly compare them.