Physical activity in students and its association with attention. A systematic review

. Despite the recommendations for physical activity in children and adolescents, sedentary behaviors that may affect health are frequent in today's schools. Evidence suggests that physical activity has a beneficial effect on the development of attention, however, there is no clarity on the characteristics that physical activity should have to optimize the improvement of attention in schoolchildren. A search for articles in databases published between 2013 and 2023 was performed, and after applying the inclusion and exclusion criteria and after analyzing their results, thirty-three articles were identified. The results suggest that the practice of physical activity has a positive effect on attention, mainly selective attention, but it is not possible to establish the characteristics in relation to frequency, time, intensity, or type of exercise that yield the best results, probably due to the heterogeneity of the interventions and populations studied. More experimental studies are therefore required to help identify the characteristics of physical activity that best contribute to the development of attention as a cognitive indicator.


Introduction
The World Health Organization (WHO) published guidelines on physical activity (PA) and sedentary behaviors (SB), where it recommends the amount of PA that children and adolescents should perform, describing the values to be considered in frequency, intensity, and duration.The document recommends that children and adolescents aged five to 17 years accumulate at least 60 minutes of moderate to vigorous intensity physical activity (MVPA) per day, with muscle strengthening activities at least three days per week (WHO guidelines on physical activity and sedentary behaviour., 2021).In turn, Miko et al. (2020) defines PA as activity that includes any form of movement in which the contraction of skeletal muscles results in increased energy consumption.Similarly, SB are defined as those characterized by an energy expenditure ≤1.5 MET (Metabolic rate unit of measure) in a sitting, reclining, or lying posture.(Tremblay et al., 2017).
PA seems to have a positive effect on some cognitive indicators (CI) such as attention, especially selective attention (Martínez-López et al, 2018;Rosa et al., 2020;Ruiz-Ariza et al., 2021).Despite this evidence, educational centers generally focus their teaching-learning processes on prolonged periods of time in a seated position, thus, causing a prevalence of SB in most of the school timetable (Ma. J et al., 2015;Van den Berg et al., 2018).In the current school context, where students are influenced by multiple distractors, maintaining the attention span of children and adolescents has become a challenging task for teachers and managers of educational institutions (Gunnell et al., 2019).According to global estimates, children can have up to eight hours of SB daily (Bauman et al., 2018), and may experience various problems of concentration in learning, especially in primary schools, due to excessive use of technological devices (Komari et al., 2024), therefore, being able to replace teaching -learning activities with high SB with movement-based learning activities could contribute to the physical health (Ruiz-Ariza et al., 2021) and attentional processes of schoolchildren.(Altermann & Gröpel, 2022).
The school is recognized as an important space to promote the health and well-being of children (Kuzik et al., 2022;Maldonado et al., 2023) and the physical education (PE) class provides the enabling context for the development of strategies such as the promotion of PA and exercise (Alvarado et al., 2019;Romero-Martínez et al., 2024).However, outside the PE class, long periods of SB occur in schoolchildren that are unfavorably associated with body composition, physical fitness, prosocial behavior and self-esteem (Saunders et al., 2022) therefore, for managers and teachers to implement PA programs in the classroom, they need to be convinced that these programs benefit students and facilitate academic processes (Mahar, 2019).In this sense, the practice of PA and exercise becomes a strategy supported by great scientific evidence that demonstrates a broad impact on strengthening health (WHO guidelines on physical activity and sedentary behaviour., 2021), and CI such as attention (Altermann & Gröpel, 2023;Gallotta et al., 2015;Polevoy, 2022;Rosa et al., 2021;Tseng et al., 2021).
Attention is defined as a cognitive process that allows selective concentration on one aspect of the environment while ignoring others (Rodríguez-Negro & Yanci, 2021) and generates a control mechanism that plays a fundamental role in the hierarchical organization of not only neurocognitive but also motivational processes (Rosa et al., 2020).Similarly, Hillman et al. (2003) defines attention as a crucial mental process that participates in the learning process of both simple and complex skills, being a central mediator of cognition.Likewise, De Greeff et al. (2017) states that attention participates in the selection, integration, and comprehension of a vast amount of contextual information, which underpins the learning process.Attention is, therefore, a vital component for learning, and it deserves to be promoted in schools through PA-oriented interventions (Schmidt et al., 2015).
Attention is classified according to Sohlberg, cited by Lai & Chang (2020) in five dimensions, sustained attention, selective attention, focused attention, alternating attention, and divided attention.For this review, selective attention and sustained attention have been considered, as they are the main dimensions addressed in the articles reviewed.Thus, selective attention has been defined as the cognitive function that directs attention to objects or stimuli that are relevant and avoids distraction from those that are not (Introzzi et al., 2019).As for sustained attention, it is defined as a type of voluntary attention that responds to the ability to maintain the same behavior over time and fatigue (Maureira Cid & Flores, 2017).
Few systematic reviews and meta-analyses have delved into the effects of PA on attention as a CI.The systematic review by Hajar et al. (2019) analyzed the relationship of PA with sustained attention, describing beneficial effects in the participants of most studies, while De Greeff et al. (2017) in their meta-analysis, addresses intervention studies that investigated the effects of PA in different domains, showing positive effects on attention in children and preadolescents who participated in acute PA programs, similarly, describes effects of longitudinal PA on the domains of executive functions, academic performance and attention.Researchers such as Domínguez-González et al. (2018) and Rosa et al. (2019) have found positive relationships between physical condition, especially cardiorespiratory fitness and selective attention, however, scientific evidence shows no conclusive results, since studies are presented with PA programs with different designs and applications that do not reveal positive effects in the domains of attention (Gelabert et al., 2023;Gilbert et al., 2023).Thus, the present review stands out for its innovative approach in the analysis of recent studies with distinctive designs and methodologies, addressing different domains of attention, with emphasis on selective and sustained attention.
Having described the above, the present review documentarily analyzed the scientific evidence on PA interventions and their relationship with attention as a CI, determining whether the effects are acute or chronic.Therefore, this article aims to: i) Determine whether there is a dose-response relationship between PA and selective or sustained attention as CI in schoolchildren aged six to 18 years.ii) Demonstrate whether the results presented by the studies reflect a change in relation to the type of PA used, duration of activity, intensity, and frequency of the interventions.

Method
This review was registered in the Prospero international prospective registry of systematic reviews with ID CRD42023447339.For its methodological development and the organization of variables, the PICO strategy was used (P = Population "schoolchildren aged six to 18 years", I = Intervention "PA and exercise", C = Comparison "compared with usual activity", O = Outcomes "improves attention as CI") (Oviedo & Soria Viteri, 2015), also following the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses-PRISMA (Page et al., 2021).The review focused on the search and analysis of original articles published in peer-reviewed journals that examined the measurement or implementation of PA programs in schoolchildren aged six to 18 years and their association with domains of attention such as CI.

Search strategy.
The databases consulted for the selection of articles were PubMed, Scopus, and Web of Science (WOS).The search was performed in PubMed as it is the most important database in health-related, Scopus and WOS as they are the databases with the largest number of articles from high impact research journals.The search was restricted to the last 10 years (January one, 2013 -March 30, 2023) and included original articles in English and Spanish.Reviews, meta-analyses, and case studies were not included.
To perform the search in the databases, the words (physical activity, exercise, attention, cognitive and school indicators) were required to appear in the title, keywords or abstract of the article.Boolean operators AND and OR were used to better delimit the search and the filters of full text article, time, language and human studies were applied.The search equations are shown in table one.

Scopus
("physical activity" OR "exercise")) AND (("attention" OR "cognitive function")) AND (("schoolchildren" OR "students" OR "adolescents"))) 588 Web Of Science ("physical activity" OR "exercise") AND ("attention" OR "cognitive function") AND ("schoolchildren" OR "students" OR "adolescents") 333 For the article selection process, the exploration was carried out by applying the search filters in the three databases described above, identifying 1062 articles, then the metadata of the articles were exported to the Rayyan collaboration and research platform for systematic reviews.In this platform, eighty articles were identified and eliminated due to duplicity, leaving 982 documents.Subsequently, the following steps were carried out: i) Blind reading by the researchers, taking into account the title and abstract for the selection of articles, ii) After consensus by the researchers, 933 articles that were not directly related to the subject were excluded, iii) finally, 49 articles were added to the Mendeley bibliographic manager for full text reading and subsequent application of the inclusion and exclusion criteria, leaving 33 studies for the systematic review.
Table 2. Criteria for inclusion or exclusion of articles. N.
Inclusion criteria 1 Study design: Original articles in English and Spanish of experimental type, randomized clinical trials (RCT), quasi-experimental and observational, that allow the analysis of the evaluation or application of physical activity programs and their association with attention as a cognitive indicator.2 Study population: Studies with school population between 6 and 18 years of age. 3 Intervention: Articles that address the evaluation or implementation of physical activity or exercise programs and their association with attention as a cognitive indicator.4 Results: Studies presenting conclusions on the impact of the evaluation or implementation of physical activity or exercise programs, and their association with the different dimensions of attention.
Exclusion criteria 1 Articles that address interventions in students with health alterations, pathologies, or special cognitive capacities. 2 Studies that do not directly present the relationship between physical activity or exercise and attention.3 Articles that are published outside the delimited time frame.4 Review articles, meta-analysis, abstracts of academic events, theses, monographs, or reports.5 Articles that do not meet the inclusion criteria.

Results
Figure 1.Prisma flow diagram of the selection of studies.

Evaluation of the methodological quality of the studies
The methodological quality and measurement of bias were assessed using Cochrane RevMan software.Due to the low homogeneity of the studies included in the systematic review, the Forest Plot was performed considering only the randomized clinical trials that used the D2 test tool to measure attention as a CI.show I² = 0 %, suggesting high homogeneity in these five studies.In the study by (Martínez-López et al, 2018), the sedentary population of the experimental group was considered for the data to elaborate the forest plot.Similarly, figure three shows the risk of bias plot made according to the criteria of two researchers, and in the case of discrepancy, the opinion of a third researcher was considered.

Main characteristics of the studies
To respond to the objectives set out in the study, an analysis matrix was prepared in the Microsoft Excel program where the data of the articles were included as follows: main author, year of publication, country, population size and ages, sex, type and duration of PA, attention evaluated and type of effect (acute or chronic), the attention evaluation instrument and the main conclusions.In this graph, in addition to describing the main characteristics of the selected studies, they have been organized by year of publication, starting from the oldest to show the progress and analysis of the information over the last 10 years.See table three.
Of the 1062 articles found in the databases, 33 original articles were finally analyzed, 25 of them experimental and eight observational, including 12.133 schoolchildren aged six to 18. Twenty studies were conducted with children aged six to 13 years, six studies with adolescents aged 14 to 18 years and seven studies present a general population of children and adolescents.
The research was carried out in twenty countries, with Spain being the country where the relationship between PA and attention was examined the most, with six studies (see Figure four).Similarly, it is important to highlight that the same study was developed in six European countries (Vanhelst et al., 2016).The most used tool (16 of the 33 articles, 48 %) to measure attention and its dimensions was the D2 attention test and its recent version D2-R, this tool determines the ability to pay attention to a stimulus, while omitting distracting letters (Gall et al., 2018).The overall results of the studies analyzed show that the dose-response relationship between PA and attention presents facilitating effects on performance in several domains of attention (25 of 33 items.76 %).In relation to articles that evaluated physical fitness, the studies by Rosa et al. (2021) and Pérez-Lobato et al. (2016) argue that adolescents who had better aerobic fitness and physical fitness respectively presented better selective attention.No study reported a decrease in attention after PA implementation.Eight of the articles analyzed in this review, did not evidence significant changes in attention (Gall et al., 2018;García-Hermoso et al., 2020;Gelabert et al., 2023;Gilbert et al., 2023;Leong et al., 2015;Lima et al., 2017;Van den Berg et al., 2018;Vanhelst et al., 2016).
The results of the studies show benefits of the practice of PA and exercise in dimensions of attention such as selective, sustained, divided, and executive attention, among others.Regarding the types of attention, selective attention was the dimension that was most evaluated in the studies with 19 of the 33 articles (57%).Of the 19 articles that evaluated selective attention, 12 (63%) claimed an improvement in its levels in relation to the initial parameters, these interventions varied in number of sessions between one single session (Rosa et al., 2021) up to 12 weeks (about three months) with two weekly sessions (Martínez-López et al, 2018).Similarly, the intensities and timing of the applications varied, ranging from four minutes of high-intensity activities (Ma. J et al., 2015) to 90 minutes (about one and a half hours) of light activity.(Tseng et al., 2021).Sustained attention was evaluated in four studies (12%), where conclusions evidencing changes in sustained attention were presented in two studies (50%) from activities involving physical effort accompanied by cognitive effort (Gallotta et al., 2015) and practice of 60 minutes of open dexterity activity (racket) (Gallotta et al., 2020).
In relation to intensity, the results presented by the studies evidence improvements in attention with high intensity interventions (Ma. J et al., 2015;Rosa et al., 2020).In the same line, Martínez-López et al ( 2018) implemented a high-intensity intervallic training (HIIT) program, where they found that the experimental group (EG) increased selective attention by 14, 2% in relation to the control group (CG).
For their part, Booth et al. (2013) evaluated the PA of 4,755 children between the ages of 11 and 13 years and concluded that MVPA may be beneficial for attention processes in adolescence and especially in boys.Interventions with moderate intensities also had favorable effects on attention in children and adolescents; studies such as the one developed by Ruiz-Ariza et al. (2021) affirm that both high and low intensity active breaks have a significant effect on attention immediately after the stimulus ends.
In terms of frequency, there are studies that showed improvements in attention with a single session (Schmidt et al., 2015).The study by Rodríguez-Negro & Yanci (2021) also with a daily session, but for eight weeks (about two months) found that PA based on the tactical games model, has specific effects on attention.López-Vicente et al. (2016) suggests that children who exercise twice a week present better levels of attention than those who exercise once a week.Altenburg et al. (2015) highlights in their study that two daily sessions of 20 minutes of MPA could improve selective attention in children aged 10 to 13 years and maintain its effect up to 110 minutes (about two hours) after the end of the activity, a conclusion similar to that described in the studies by Samuel et al. (2017) and Schmidt et al. (2015) who concluded that the practice of PA can improve attention 60 and 90 minutes (about one and a half hours) after the effort has been made.
Of all PA interventions that showed positive effects on attention domains, six presented one session per week and ranged from one week to two months, six studies applied two sessions per week and ranged from one week to five months.The intervention by Spitzer & Hollmann (2013) developed three sessions per week for four months and evidenced improvements in attention following physical exercise.The studies by Ma. J et al. (2015) and Martínez-López et al (2018) found acute effects on selective attention after applying high-intensity interventions, while Altenburg et al. (2015) and Rosa et al. (2021) found acute effects on selective attention with MPA interventions, Ruiz-Ariza et al. ( 2021) evidenced acute effects on selective attention with both high and low intensity active breaks, likewise, Gallotta et al. (2020) found acute effects, but on sustained attention with racquet practice activities.
Regarding the duration of the sessions and the interventions applied in the studies, as was the case with the frequency and intensity variables, they presented extremely high heterogeneity, and some studies lack detailed information.To highlight the study by Vanhelst et al. (2016) who made an anthropometric measurement and PA assessment for seven days to 273 adolescents aged 12 to 17 years in different countries in Europe, and presented data suggesting that the PA thresholds that best discriminated attention span were 41 minutes for MPA, 12 minutes per day for VPA and 58 minutes per day for MVPA.Interventions that affected attention as CI ranged from four minutes (Ma. J et al., 2015), to two studies that conducted a 90-minute intervention per session (Rodríguez-Negro & Yanci, 2021;Tseng et al., 2021).
Regarding the duration of the intervention programs, there were three studies of one single session, one with two sessions, one with two weeks, the largest number of studies with interventions of equal time were five studies and eight weeks (about two months).Polevoy (2022) was the longest duration with five months.

Karate
Karatekas were compared to nonkaratekas.

Selective attention
Test Stroop (Teresa, 2014;Graf, 1995;Treneri, 1989) The results show that there is a notable difference between 8 to 10 students who practice Karate and those who do not practice Karate, and a marginally significant difference in 11-year.2002).

Van den
The study concluded that there were no significant effects of the exercise on selective attention.Exercises based on speed and strength.
(PE) class twice a week for 40 minutes, for three months.
Ability to change attention.

Method of numbers
Indicators of attentional change in 13-14-year will improve if they perform speed and strength physical exercises in the physical education lesson at school.The intervention did not produce significant results in sustained or selective attention.The aim was to establish whether their chronic effects.

Discussion
The differences presented in the conclusions of the studies, may be a result of the heterogeneity of the intervention duration periods, the frequency and intensity of PA, the ages of the participating population, the dimensions and attention assessment tools used by the researchers, as well as by the socioeconomic conditions of the population, example of this, is evidenced in the studies by Gall et al. (2018) and García-Hermoso et al. (2020).This heterogeneity in the studies makes their analysis difficult and does not allow us to deliver data that responds concretely to the stated objectives.
Regarding the discussion of the main objective of this review that sought to determine the relationship between PA and attention as CI, we can highlight the studies that presented a benefit in attention after the practice of PA that involved a cognitive load in its development.Studies such as the one conducted by Rodríguez-Negro & Yanci (2021) that compared two teaching models in PE and concluded that the game-based model was more effective in improving attention than the traditional model of direct instruction, by involving aspects of higher cognitive load, which is close to what was presented by Latino et al. (2021) and Schmidt et al. (2015) who pointed out that the intervention of practices based on coordination exercises, which involve a higher cognitive load, present an increase in attention in relation to traditional exercise.
In the same line of the previous discussion, the study of Gallotta et al. (2015), who developed an intervention with three groups of elementary school students with the aim of evaluating attention before and after performing a PA session, stands out.The first group performs cognitive work, the second group, traditional PE class and the third group receives PE class with cognitive stimulation, concluding that the third group presents better results just after the end of the test and 50 minutes after the end of the test.
Another study that strengthens this argument is also presented by Gallotta et al. (2020) when they show that open sport exercises such as racquet practice, which involves cognitive stimuli such as temporal precision, reaction time and coordination, may present a superior relationship in attentional performance compared to closed, continuous and repetitive practices such as running.
The above results may be associated with biological mechanisms of activation of cognitive functions induced by PA (Rosa et al., 2020) and manifested in increased blood flow and cerebral oxygenation (Faulkner et al., 2016), high cardiorespiratory fitness associated with healthier neural tissue (García-Hermoso et al., 2020), increased levels of neutrophic factors such as brain-derived neurotrophic factor (BDNF), a protein that enhances synapses (Hillman et al., 2009;Vanhelst et al., 2016), improved neurophysiological activity (Flores et al., 2019) and favors changes in brain activity that facilitate cognitive functions (Gallotta et al., 2020).
Many the studies analyzed in this review were carried out in school environments, which represented a difficulty for some researchers due to situations such as nonattendance of students due to different circumstances on the days of intervention and the unwillingness of some teachers to apply the various scientific designs (Spitzer & Hollmann, 2013).

Conclusions
The results of the studies analyzed in this review suggest that the practice of PA and exercise have a positive relationship with attention, mainly selective attention, and especially with activities of moderate to vigorous intensity; likewise, it can be observed that activities with greater cognitive load seem to have greater efficacy.However, it can be observed that the interventions with positive effects on attention vary in duration (from four minutes to 90 minutes), intensity (high intensity, moderate and low intensity PA), frequency (a single session, up to two months with three weekly sessions), which prevents the delivery of conclusive results that allow determining the most favorable characteristics for the improvement of attention.
As described above, it is suggested that more experimental research be conducted, especially in school settings, to learn more about this topic.
Based on the findings, it is suggested that educational institutions consider the implementation of more appropriate activities and environments within their curricula to comply with international recommendations on the practice of PA, not only because of the already proven effects on health, but also because of the possible effects on CI such as attention.Likewise, it is hoped that this review will contribute to the advancement of this important subject of study.

Strengths and limitations
One of the review's strengths was that it gave an overview of the topic by including articles with different research designs and methods, allowing it to be approached in greater depth and covering a larger population.Likewise, an updated review is presented, which could be useful in the field of study and guide future research.
A limitation of the review is the inability to provide conclusive results that fully answer concerns about the optimal characteristics for improving attention.
Selective Attention as a Cognitive Indicator", which is part of his research in the Doctoral Program in Education at Universidad de La Sabana, Colombia.
Figure two shows the forest plot comparing PA vs non-PF interventions; the forest plot data

Table 3 .
Article analysis matrix.