Gymnastik- och idrottshögskolan, GIH

AIM: Investigate the longitudinal relationship between physical activity, organised physical activity, fitness, screen time and academic performance among Swedish adolescents.

METHODS: Data from 1139 adolescents at age 13, included vigorous physical activity (accelerometry), fitness (submaximal ergometer test), screen time and organised physical activity participation (self-reported) and academic performance (math and Swedish grades at ages 13 and 16 from registry). Academic performance at age 16 was categorised as A-D (higher grades or pass) or E, F (fail or at-risk of failing). Multilevel logistic regression models were used to examine the relationships while adjusting for gender, parental education, parental country of birth and academic performance at age 13.

RESULTS: Higher fitness at age 13 was associated with increased odds of receiving A-D at age 16 (OR: 1.04 per mL, 99% CI 1.00, 1.07, p = 0.003). High screen time during weekdays was associated with reduced odds (OR: 0.40, 99% CI 0.20, 0.81, p = 0.001) compared to low screen time.

CONCLUSION: Academic performance at the end of compulsory school (age 16) was related to fitness and screen time 3 years earlier. These findings create a paradigm for future randomised controlled trials to explore how influencing these factors might affect academic performance.

It remains unknown whether dietary nitrate and breakfast may enhance working memory (WM) performance by augmenting physiological mechanisms and subjective psychological well-being. We performed a 3-arm randomised within-subject crossover study, with pretest-posttest comparisons, to test whether nitrate consumption via breakfast with a beetroot juice shot or regular breakfast compared to no breakfast improved WM (measured with n-back tests) and cognitive task-related changes in prefrontal cortical haemodynamic response (oxygenated- and deoxygenated-haemoglobin derived from functional near-infrared spectroscopy). In addition, effects on peripheral vascular function and self-reported psychological factors were assessed. In 60 adolescents (13-15 years old; 66% girls), WM improved in all conditions, with no intervention effects. Intervention effects were seen for oxygenated-haemoglobin changes, such that it increased after the breakfast with a nitrate shot during the WM tests and decreased after the regular breakfast. Thus, different neurophysiological mechanisms may be at play to preserve WM in adolescents depending on their breakfast composition. The trial was registered in the ISRCTN registry (ISRCTN16596056) on 21/02/2022.

Gymnastik- och idrottshögskolan (GIH) har sedan 2017 arbetat i en serie forskningsstudier finansierade av Stiftelsen för kunskaps- och kompetensutveckling, KKS. Studierna har fokuserat på både barn, vuxna och äldre. Sedan 2021 finns vid GIH ett forskningscentrum med fokus på fysisk aktivitet och hjärnhälsa, det vill säga goda kognitiva funktioner och god psykisk hälsa, kallat E-PABS (Center of Excellence in Physical Activity, Healthy Brain Functions and Sustainability). Forskningen inom E-PABS täcker många ämnesområden och innefattar epidemiologi, beteendeförändring, kognitiv neurovetenskap, fysiologi och molekylär biokemi.

Denna rapport bygger på studier inom projektet ”Fysisk aktivitet och hälsosamma hjärnfunktioner hos skolungdomar”, som genomfördes under 2017–2023. Projektet hade tre delar, en epidemiologisk, en fysiologisk och en etnografisk del som tillsammans syftade till att svara på frågorna ”Vilket är sambandet mellan fysisk aktivitet, stillasittande beteende, kost och hälsosamma hjärnfunktioner hos barn och ungdomar, och hur kan fysisk aktivitet som främjar sunda hjärnfunktioner långsiktigt hållbart implementeras i skolor?”

Introduction

The family is assumed to be fundamental in youth socialization processes and development, connected to social and cultural practices such as healthy lifestyles and physical activity. However, gender patterns in physical activity among adolescents and the structural drivers of gender inequality (e.g., parentage and siblingship) are poorly understood. The aim of this study was to explore further how gender structures relate to adolescents' time spent being sedentary and physically active, using contemporary gender theory.

Methods

This cross-sectional study involved 1,139 adolescents aged 13-14 and their parents, including 815 mothers and 572 fathers. Physical activity and time spent sedentary were assessed through accelerometry among adolescents and through a self-report questionnaire for parents validated against accelerometry.

Results

The results showed significant relationships between mothers' moderate-to-vigorous physical activity (MVPA) and girls' MVPA on weekdays and weekends, and fathers' MVPA was significantly related to girls' MVPA on weekdays. Our results imply that the relationship between Swedish parents' and adolescent girls' physical activity in higher intensities are to some extent gendered practices. However, time spent sedentary does not seem to show any patterns of being performed according to binary ideas of gender. Further, our exploratory analyses suggest that these results somewhat intersect with parents' educational level and relate to intra-categorical aspects of doing gender. The results also indicate slight gendered patterns in the “doing” of brotherhood for time spent sedentary, however, for boys only on weekends.

Discussion 

The study contributes to the understanding of gender norms as constraints and enablers for adolescents' participation in physical activity. The results can spur public health and physical activity research to apply a contemporary gender theory approach, and to expand the research agenda connected to what relates to gender inequalities in physical activity practices.

There is public health concern regarding physical activity levels and sedentary behavior among adolescents. Only a small proportion meet the daily physical activity recommendations, while most spend most of their time being sedentary. There is a lack of studies examining the associations between physical activity, fitness, sedentary behaviors, and healthy brain functions, particularly in adolescents while using robust measures. The aim of this thesis was, therefore, to investigate how accelerometer-measured physical activity, sedentary time, sports participation, fitness, and screen time were associated with healthy brain functions (mental health, cognitive, and academic performance), in a cohort of Swedish adolescents. Further, to examine how physiological factors underpinning healthy brain functions change acutely when prolonged sitting is interrupted with physical activity breaks.

Paper I had a cross-sectional design and examined how accelerometer-measured physical activity and sedentary time, sports participation, and screen time were associated with mental health (anxiety and health-related quality of life) in 1139 Swedish adolescents (mean age 13.4). The results showed that adolescents who engaged in high levels of moderate-to-vigorous physical activity, particularly during leisure time, reported better mental health. In contrast, those with high levels of sedentary time or screen time during leisure time reported poor mental health.

In Paper II, cross-sectional associations between device-measured physical activity, fitness, and cognitive or academic performance were studied in the same cohort (n=1139, mean age 13.4). The results showed that adolescents with high fitness levels had better cognitive performance (in working memory and episodic memory tasks) and better academic performance (grades in math and Swedish). No significant association between accelerometer-measured physical activity and cognitive or academic performance was found. 

Paper IV investigated longitudinal associations in the same cohort (n=1139). The aim was to study how accelerometer-measured physical activity, sports participation, fitness, and screen time at baseline (mean age 13.4) were associated with academic performance three years later (mean age 16.0). The results showed that higher fitness levels or low screen time on weekdays at age 13 were associated with higher school grades three years later. No significant associations between accelerometer-measured physical activity or sports participation at age 13 and academic performance three years later were found. 

Paper III was based on an acute intervention study, the adolescents (n=17, mean age 13.6 years) performed three 80-minute lab sessions in randomized order. The sessions consisted of 80 minutes of prolonged sitting, with three-minute breaks every 17th minutes (either simple resistance activities, SRA, step-up exercise, STEP, or remain seated, SOCIAL). Changes in cerebral blood flow (oxygenated hemoglobin, Oxy-Hb, in the prefrontal cortex) were assessed before and after each session, using functional near-infrared spectroscopy during a working memory task. The results showed that following the physical activity breaks, cognitive performance improved during the most difficult cognitive task, these improvements were seen in parallel with an increase in Oxy-Hb in the prefrontal cortex. In contrast, no cognitive improvements were observed during the most difficult task after the prolonged sitting condition (SOCIAL), and Oxy-Hb levels significantly decreased.

In conclusion, device-measured physical activity was associated with some aspects of healthy brain function (mental health), but not all (cognitive and academic performance). However, incorporating physical activity breaks during prolonged periods of sitting seems to benefit cognitive performance, potentially through improved cerebral blood flow. The findings also suggest that adolescents with low levels of physical activity or high screen time were more likely to experience poor mental health. Furthermore, adolescents with high screen time at age 13 tended to have lower school grades three years later, at the end of compulsory school. These findings contribute to the current understanding of how physical activity, fitness, and sedentary behaviors relate to healthy brain function in adolescents and are of importance to researchers, parents, and professionals working with this age group.

Populärvetenskaplig sammanfattning

Det övergripande målet med denna avhandling var att undersöka samband mellan accelerometer-mätt fysisk aktivitet, stillasittande, idrottsdeltagande, kondition och skärmtid och hjärnhälsa (psykisk hälsa, kognition och skolbetyg) hos 1139 svenska skolungdomar i början på högstadiet (årskurs 7). Ungdomarna följdes även upp i slutet av grundskolan (årskurs 9). Dessutom syftade avhandlingen till att undersöka hur fysiologiska faktorer som påverkar hjärnhälsa förändras när man bryter långa perioder av stillasittande med korta rörelsepauser, och om dessa pauser kan gynna kognitiv prestation.

Avhandlingen visade att de ungdomar som var fysiskt aktiva, särskilt under fritiden, rapporterade bättre psykisk hälsa, medan de som hade mycket stillasittande eller hög skärmtid rapporterade sämre psykisk hälsa (artikel I). Dessutom hade ungdomar med högre kondition bättre kognition och högre betyg i matte och svenska. Dock fanns inget samband mellan fysisk aktivitet och kognition eller skolbetyg (artikel II).

När ungdomarna följdes upp i årskurs 9 visade resultaten att de med hög kondition eller låg skärmtid på vardagarna i årskurs 7 hade större sannolikhet att få godkända skolbetyg i slutet på grundskolan. Däremot fanns det inga samband mellan fysisk aktivitet, idrottsdeltagande eller skärmtid på helgen i årskurs 7 och betyg tre år senare.

I en mindre labbstudie undersöktes effekterna av att bryta upp långvarigt stillasittande med korta rörelsepauser. Resultaten visade att de korta rörelsepauserna förbättrade kognitionen och ökade syresättningen i blodet i hjärnans främre pannlob.

Sammanfattningsvis visade avhandlingen att det fanns samband mellan fysisk aktivitet och vissa aspekter av hjärnhälsa, som psykisk hälsa, men inte kognition och skolbetyg. Däremot visade resultaten att rörelsepauser som bryter upp långvarigt stillasittande kan gynna kognitionen, troligen genom ökad syresättning i hjärnan.

Vidare visade resultaten att det är vanligare att ungdomar med sämre psykisk hälsa också hade låg fysisk aktivitet och/eller hög skärmtid. Dessutom hade ungdomar med hög kondition och låg skärmtid i årskurs 7 bättre skolbetyg i slutet av grundskolan. Avhandlingens resultat är viktiga för forskare, samhällsaktörer, föräldrar och yrkesverk-samma som arbetar med skolungdomar.

PURPOSE: Physical activity (PA) breaks during school lessons have been suggested as a promising strategy to improve working memory performance in children and adolescents. There is a lack of studies investigating the underlying physiological mechanisms of PA on cognition, especially among adolescents. This study aimed to investigate the effects of different types of short frequent PA on adolescents' cognitive task-related changes in cerebral blood flow in the prefrontal cortex (PFC) and working memory performance compared to prolonged sitting.

METHODS: In this randomized crossover study, adolescents visited the laboratory on three different occasions for 80-minute sessions of prolonged sitting interrupted by four breaks for three minutes of simple resistance training (SRA), step-up at a pre-determined pace (STEP), or remaining seated (SOCIAL). Before and after each session, cognitive task-related changes in cerebral blood flow (oxygenated-hemoglobin, Oxy-Hb) during working memory tasks (1-, 2-, 3-back tests) were measured using functional near-infrared spectroscopy in the PFC. Accuracy and reaction time were derived from the working memory tasks. Linear mixed-effect models were used to analyze the data.

RESULTS: A total of 17 students participated (mean age 13.6 years, 11 girls). Significant time x condition interactions were noted for Oxy-Hb in the most demanding working memory task (3-back), with a decrease following prolonged sitting in the SOCIAL condition compared to both the SRA (β 0.18, 95% CI 0.12, 0.24) and the STEP (β 0.11, 95% CI 0.05, 0.17). This was observed in parallel with improvements in reaction time following SRA (β -30.11, 95% CI -59.08, -1.13) and STEP (β -34.29, 95% CI -69.22, 0.63) although this was only significant for the SRA and no improvements in the SOCIAL condition.

CONCLUSION: We found that short frequent PA breaks during prolonged sitting among adolescents can prevent the decrease in cognitive task-related changes in cerebral blood flow that occur following prolonged sitting. This was observed simultaneously with improvements in working memory, indicating that changes in cerebral blood flow could be one factor explaining the effects on working memory. Future studies should investigate the efficacy of implementing these PA breaks in schools.

TRIAL REGISTRATION: Retrospectively registered on 21/09/2020, ClinicalTrial (NCT04552626).

Gymnastik- och idrottshögskolan (GIH) har sedan 2017 arbetat i en serie forskningsstudier finansierade av Stiftelsen för kunskaps- och kompetensutveckling, KKS. Studierna har fokuserat på både barn, vuxna och äldre. Sedan 2021 finns vid GIH ett forskningscentrum med fokus på fysisk aktivitet och hjärnhälsa, det vill säga goda kognitiva funktioner och god psykisk hälsa, kallat E-PABS (Center of Excellence in Physical Activity, Healthy Brain Functions and Sustainability). Forskningen inom E-PABS täcker många ämnesområden och innefattar epidemiologi, beteendeförändring, kognitiv neurovetenskap, fysiologi och molekylär biokemi.

Denna rapport bygger på studier inom projektet ”Fysisk aktivitet och hälsosamma hjärnfunktioner hos skolungdomar”, som genomfördes under 2017–2023. Projektet hade tre delar, en epidemiologisk, en fysiologisk och en etnografisk del som tillsammans syftade till att svara på frågorna ”Vilket är sambandet mellan fysisk aktivitet, stillasittande beteende, kost och hälsosamma hjärnfunktioner hos barn och ungdomar, och hur kan fysisk aktivitet som främjar sunda hjärnfunktioner långsiktigt hållbart implementeras i skolor?”

Purpose: Beneficial acute effects of dietary nitrate have been demonstrated on working memory in adults, with changes in cerebral blood flow (CBF) being a potential mechanism. However, these effects have not been studied in adolescents. Moreover, having breakfast compared to skipping may also exhibit positive effects on working memory. Therefore, this randomized crossover trial investigated the acute effects of nitrate and breakfast on working memory and changes in task-related CBF in adolescents.  Methods: This trial will recruit at least 43 adolescents (13–15 years old). There were three experimental breakfast conditions: (1) none, (2) regular, and (3) regular breakfast with high nitrate in the form of concentrated beetroot juice. Working memory (1-, 2-, 3-back tests) and task-related CBF (prefrontal cortex oxygenated and deoxygenated-hemoglobin changes estimated using functional near-infrared spectroscopy) were measured immediately after breakfast and 130 min later. The data collection for this study is ongoing, thus results for 35 adolescents are presented here and due to blinding of the researcher we are unable to report at this time in which condition these effects occurred, but will be revealed by the time of the conference, as well as for the results on changes in CBF.  Results: Preliminary results from the ongoing study showed that from pretest to posttest there was a statistically significant improvement in reaction time in all three conditions for all three n-back tests, but no intervention effects. Accuracy, however, improved from pretest to posttest in only one condition, for all three nback tests (β [95% confidence interval] from linear mixed-effects models with subject as random effect: 1-back 2.8[1.2-4.3], 2-back 2.6[0.9-4.2], 3-back 3.6[2.2-5.0]), and there was a tendency towards an intervention effect between this breakfast condition and another on the accuracy of the 3-back test (P for time-by-condition interaction 0.07).   Conclusions: The results from this study will increase our understanding into the effects of breakfast and its composition (i.e., nitrate-rich) on acutely improving working memory in adolescents and the potential mechanisms. In turn, the results will inform on whether policies on providing breakfast in schools should be considered to improve students' cognitive performance.

BACKGROUND: Inorganic nitrate has been shown to acutely improve working memory in adults, potentially by altering cerebral and peripheral vasculature. However, this remains unknown in adolescents. Furthermore, breakfast is important for overall health and psychological well-being. Therefore, this study will investigate the acute effects of nitrate and breakfast on working memory performance, task-related cerebral blood flow (CBF), arterial stiffness, and psychological outcomes in Swedish adolescents.

METHODS: This randomised crossover trial will recruit at least 43 adolescents (13-15 years old). There will be three experimental breakfast conditions: (1) none, (2) low-nitrate (normal breakfast), and (3) high-nitrate (concentrated beetroot juice with normal breakfast). Working memory (n-back tests), CBF (task-related changes in oxygenated and deoxygenated haemoglobin in the prefrontal cortex), and arterial stiffness (pulse wave velocity and augmentation index) will be measured twice, immediately after breakfast and 130 min later. Measures of psychological factors and salivary nitrate/nitrite will be assessed once before the conditions and at two-time points after the conditions.

DISCUSSION: This study will provide insight into the acute effects of nitrate and breakfast on working memory in adolescents and to what extent any such effects can be explained by changes in CBF. This study will also shed light upon whether oral intake of nitrate may acutely improve arterial stiffness and psychological well-being, in adolescents. Consequently, results will indicate if nitrate intake from beetroot juice or if breakfast itself could acutely improve cognitive, vascular, and psychological health in adolescents, which can affect academic performance and have implications for policies regarding school meals.

TRIAL REGISTRATION: The trial has been prospectively registered on 21/02/2022 at https://doi.org/10.1186/ISRCTN16596056. Trial number: ISRCTN16596056.

AIM: Physical activity patterns in adolescents have been associated with general health. Stress, screen-time and sleep are other factors associated with physical activity that influence health in adolescents. Physical activity accounts for several health benefits; however, the impact of organised sports participation to achieve the same health benefits are less explored. This study explored the associations of organised sports participation with general health, stress, screen-time and sleep-duration in adolescents.

METHODS: For this cross-sectional study, data from 1139 adolescents (age 13-14 years) from 34 schools were analysed. Data were collected during autumn 2019. Data collection consisted of self-reported questionnaires and standard methods for height and weight measurements.

RESULTS: Adolescents with organised sports participation ≥3 times/week were twice as likely to report better general health (OR: 2.11, CI: 1.45-3.07) and lower screen-time (OR: 1.98, CI: 1.43-2.74). Adolescents with organised sports participation ≥3 times/week were less likely to meet the recommended sleep-duration on weekdays (OR: 0.43, 95% CI: 0.29-0.65).

CONCLUSIONS: Adolescents with frequent organised sports participation had better general health, lower amounts of screen-time and shorter sleep-duration on weekdays than those with no participation. Although the causal relationships remain unknown, these results can be relevant when developing strategies promoting physical activity and health in adolescents.