Which indices of cardiorespiratory fitness are more strongly associated with brain health in children with overweight/obesity?

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY 4.0 https://creativecommons.org/licenses/by/4.0/ Which indices of cardiorespiratory fitness are more strongly associated with brain health in children with overweight/obesity? © 2023 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd. Published version Haapala, Eero A.; Lubans, David R.; Jaakkola, Timo; Barker, Alan R.; Plaza‐Florido, Abel; Gracia‐Marco, Luis; Solis‐Urra, Patricio; Cadenas‐Sanchez, Cristina; Esteban‐ Cornejo, Irene; Ortega, Francisco B. Haapala, E. A., Lubans, D. R., Jaakkola, T., Barker, A. R., Plaza‐Florido, A., Gracia‐Marco, L., Solis‐ Urra, P., Cadenas‐Sanchez, C., Esteban‐Cornejo, I., & Ortega, F. B. (2024). Which indices of cardiorespiratory fitness are more strongly associated with brain health in children with overweight/obesity?. Scandinavian Journal of Medicine and Science in Sports, 34(1), Article e14549. https://doi.org/10.1111/sms.14549 2024 Scand J Med Sci Sports. 2023;00:1–12. | 1 wileyonlinelibrary.com/journal/sms Received: 3 October 2023 | Revised: 28 November 2023 | Accepted: 30 November 2023 DOI: 10.1111/sms.14549 ORIGINAL ARTICLE Which indices of cardiorespiratory fitness are more strongly associated with brain health in children with overweight/obesity? Eero A.Haapala1,2 | David R.Lubans1,3,4 | TimoJaakkola1 | Alan R.Barker5 | AbelPlaza- Florido6,7 | LuisGracia- Marco6,8 | PatricioSolis- Urra6,9,10 | CristinaCadenas- Sanchez6,8 | IreneEsteban- Cornejo6,8,11 | Francisco B.Ortega1,6,8 1Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland 2Institute of Biomedicine, School of Medicine, University of Eastern Finland, Kuopio, Finland 3Centre for Active Living and Learning, School of Education, The University of Newcastle, Callaghan, Australia 4Active Living Research Program, Hunter Medical Research Institute, New Lambton Heights, Australia 5Children's Health and Exercise Research Centre, Public Health and Sports Sciences, University of Exeter, Exeter, UK 6Department of Physical Education and Sports, Faculty of Sport Sciences, Sport and Health University Research Institute (iMUDS), University of Granada, Granada, Spain 7Pediatric Exercise and Genomics Research Center, Department of Pediatrics, School of Medicine, University of California at Irvine, Irvine, California, USA 8CIBER de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, Granada, Spain 9Nuclear Medicine Services, "Virgen de Las Nieves", University Hospital, Granada, Spain 10Faculty of Education and Social Sciences, Universidad Andres Bello, Viña del Mar, Chile 11Instituto de Investigación Biosanitaria ibs.GRANADA, Granada, Spain Correspondence Eero A. Haapala, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland. Email: eero[email protected]i Francisco B. Ortega, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Granada, Spain. Email: [email protected] Funding information European Commission; European Regional Development Fund; Fundación Alicia Koplowitz; Juho Vainion Säätiö; Spanish ministry of economy and competitiveness Abstract Purpose: To compare the strength of associations between different indices of cardiorespiratory fitness (CRF) and brain health outcomes in children with overweight/obesity. Methods: Participants were 100 children aged 8–11 years. CRF was assessed using treadmill exercise test (peak oxygen uptake [VO2peak], treadmill time, and VO2 at ventilatory threshold) and 20- metre shuttle run test (20mSRT, laps, running speed, estimated VO2peak using the equations by Léger etal., Mahar etal., and Matsuzaka etal.). Intelligence, executive functions, and academic performance were assessed using validated methods. Total gray matter and hippocampal volumes were assessed using structural MRI. Results: VO2peak/body mass (β = 0.18, 95% CI = 0.01–0.35) and treadmill time (β = 0.18–0.21, 95% CI = 0.01–0.39) were positively associated with gray matter volume. 20mSRT laps were positively associated with executive functions This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2023 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd. Clinical trial registration: ClinicalTrial.gov ID: NCT02295072. Section Specialty Area: Section III: Health, Disease & Physical Activity, Senior Section Editor: Mark Hamer. 2 | HAAPALA etal. 1 | INTRODUCTION Nearly 30% of children in European countries are living with overweight/obesity, and the prevalence may be increasing.1 Childhood overweight/obesity is associated with impaired brain health.2 Some evidence also suggests that higher levels of cardiorespiratory fitness (CRF) are associated with improved executive functions, academic performance, and enhanced brain characteristics, such as improved functional connectivity and increased hippocampal volume (hereafter referred to as brain health outcomes) in children and adolescents.3,4 However, the variety of methodologies used to assess CRF3,4 may have clouded our understanding of the importance of CRF for young people's brain health outcomes. Previous research has identified positive associations between CRF assessed using the 20- metre shuttle run (20mSRT) or treadmill exercise tests and brain health outcomes in youth.5 Alternatively, studies that have used other measures of CRF, such as peak power output in the cycle ergometer exercise test, have not observed such associations.6–11 Moreover, CRF assessed by a 1.6- km run, but not CRF assessed by physical work capacity at a heart rate of 170, was positively associated with academic performance in a random sample of apparently healthy children.7 This issue is further complicated with the different equations used to calculate VO2peak from indirect submaximal and maximal exercise testing.12 For example, there are at least 15 different equations used to estimate VO2peak using results from the 20mSRT.13 The use of different estimation equations may increase the uncertainty in the associations between CRF and brain health outcomes.10 Most studies that have explored associations between directly measured VO2peak and brain health outcomes have used VO2peak normalized for body mass (BM).14 However, the ratio standard approach has been criticized in the literature because it is often invalid in removing the effect of body size on VO2peak15 leading to underestimated VO2peak in children with overweight/obesity.15 Therefore, normalizing the indicators of CRF using allometrically modeled lean body mass (LBM) has been recommended.16 Some studies suggest no association between VO2peak normalized for LBM and brain health outcomes,6,17 yet others have observed such a link.18 To our knowledge, the effects of the scaling approach on the associations between directly measured VO2peak and brain health outcomes have yet to be comprehensively investigated in children with increased adiposity. Compared to maximal exercise, submaximal exercise testing is better tolerated, safer, and more appropriate for children with increased adiposity.19 Therefore, submaximal testing may be a more feasible approach for investigating the link between CRF and brain health outcomes in this population, but submaximal indices of CRF have been almost completely omitted in previous studies.3,18 VO2 at the ventilatory threshold (VT) is widely used submaximal indicator of CRF20 and could have a different association with brain health outcomes than VO2peak. However, to the best of our knowledge, only one study has investigated the associations between VO2 at the VT and brain health outcomes in youth with normal weight, showing a positive association between VO2 at the VT and brain health outcomes.18 While we have previously observed that laps completed in the 20- metre shuttle run test and estimated (β = 0.255, 95% CI = 0.089–0.421) and academic performance (β = 0.199–0.255, 95% CI = 0.006–0.421), and the running speed was positively associated with executive functions (β = 0.203, 95% CI = 0.039–0.367). Estimated VO2peak/Léger etal. was positively associated with intelligence, executive functions, academic performance, and gray matter volume (β = 0.205–0.282, 95% CI = 0.013–0.500). Estimated VO2peak/Mahar etal. and VO2peak/Matsuzaka etal. (speed) were positively associated with executive functions (β = 0.204–0.256, 95% CI = 0.031–0.436). Conclusion: Although VO2peak is considered the gold standard indicator of CRF in children, peak performance (laps or running speed) and estimated VO2peak/Léger etal. derived from 20mSRT had stronger and more consistent associations with brain health outcomes than other indices of CRF in children with overweight/obesity. KEYWORDS brain, child, cognition, pediatric obesity, physical fitness 16000838, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/sms.14549 by University Of Jyväskylä Library, Wiley Online Library on [15/12/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License | 3 HAAPALA etal. VO2peak are positively associated with brain health outcomes in children with overweight/obesity,8–11 no previous study has comprehensively investigated the magnitude of the associations between several indices of CRF and a broad set of brain health outcomes. The present study contributes to the existing evidence by comparing the associations of different CRF indices with brain health outcomes, specifically focusing on (1) laboratory versus fieldbased; (2) measured versus estimated VO2peak; (3) different equations to estimate VO2peak; (4) different scaling approaches; (5) VO2peak versus peak performance; and (6) maximal versus submaximal indices. Therefore, the aim of our study is to compare the strength of associations between different indices of CRF and brain health outcomes, including intelligence, executive function, academic performance, and total gray matter and hippocampal volumes in children with overweight/obesity. 2 | METHODS 2.1 | Study design and population We used baseline data from the ActiveBrains trial (Clini calTr ial. gov ID: NCT02295072),21 conducted in children aged 8–11 years with overweight/obesity. The recruitment occurred mainly at the pediatric units of the two main hospitals in Granada, Spain, from November 1, 2014 to June 30, 2016. The assessments in the study were carried out in three waves and over 5–6 days for different outcome measures in the following order: (1) brain health outcomes, (2) fieldbased physical fitness testing, (3) cardiometabolic risk factors, (4) maximal incremental treadmill test, (5) laboratorybased strength testing, questionnaires, and body composition (note that in the first wave, consisting 20% of the whole sample, body composition was assessed at the same day than the cardiometabolic risk factors). Children with any medical condition that would affect the results of the evaluations or that limit the normal capacity to do exercise were excluded. A total of 100 children (40 girls) had complete data and were included in the analyses of the present study. For the current analyses, we estimated that 97 observations were needed to observe the correlation of 0.25 at the power of 0.80 when statistical significance level was set at p < 0.05. The parents or legal guardians of the children provided written informed consent to participate in the trial. The ActiveBrains project was approved by the ethics committee of the University of Granada (Reference: 848, February 2014). 2.2 | Assessment of indices of cardiorespiratory fitness 2.2.1 | Maximal indices obtained from the incremental treadmill exercise test VO2peak and a treadmill time were assessed during a maximal incremental treadmill test (h/p/cosmos sports and medical gmbh, Nussdorf- Traunstein, Germany) at the Andalusian Centre of Sports Medicine. Respiratory gas exchange was analyzed using a calibrated gas analyzer (General Electric Corp), and the breathby- breath data were averaged over 10 s. Participants walked on a treadmill at a constant speed (4.8 km/h) with a 6% slope with grade increments of 1% every minute until volitional exhaustion. We defined a maximal effort in the incremental treadmill exercise test as meeting three out of four following criteria: achieving >85% of agedpredicted maximal heart rate, a respiratory exchange ratio of ≥1.0, volitional fatigue (i.e., >8 points in the OMNI scale), and a plateau in the VO2 during the last two exercise work rates (<2.0 mL × kg BM−1 × min−1).21 Heart rate was measured an electrocardiogram. Before the treadmill exercise test, the OMNI scale was explained to children to ensure that they understood the meaning of each category of the scale. However, because of uncertainty about the secondary indicators of maximal effort in children,22 we performed the analysis with the complete sample that performed the incremental treadmill exercise test and provided VO2peak values. We also ran sensitivity analyses in the subsample of children that met the criteria for maximal effort. VO2peak (L/min) was ratio scaled for BM (VO2peak mL × kg BM−1 × min−1) and allometrically modeled BM (VO2peak mL × kg body mass−b × min−1) and LBM (VO2peak mL × kg lean mass−b × min−1). Allometric scaling of VO2peak was performed by the loglinear regression model23 with BM or LBM as an independent variable and VO2peak as a dependent variable. VO2peak, BM and LBM were logtransformed, and least squares regression with the equation ln (VO2peak) = lnY/b ln(X) was used to obtain the scaling exponent b. The scaling exponent b for BM was 0.70 (95% confidence interval [CI] = 0.60–0.81) and for LBM 0.87 (95% CI = 0.77–0.98). These power function ratios removed the associations of VO2peak with BM (r = −0.023, 95% CI = −0.219 to 0.174, p = 0.810) and LBM (r = −0.016, 95% CI = −0.212 to 0.181, p = 0.872), suggesting the validity of scaling CRF for body size. To test if the slope of the association of BM or LBM with VO2peak was similar in boys and girls, we added the interaction term to the model. The interaction of sex with BM or LBM to VO2peak was not statistically significant (p > 0.122). 16000838, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/sms.14549 by University Of Jyväskylä Library, Wiley Online Library on [15/12/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 4 | HAAPALA etal. 2.2.2 | Maximal indices obtained from the 20- metre shuttle run test Twentymetre SRT was performed at the Sport and Health University Research Institute (iMUDS), University of Granada, and supervised by experienced researchers. Participants were required to run between two lines 20- m apart while keeping pace with a prerecorded audio. The participants performed the test individually. One researcher ran with the participant to help keep the pace and reach maximal effort. The initial speed was 8.5 km/h, which was increased by 0.5 km/h each minute (1 min = approximately 1 stage). The CRF was recorded as completed laps and the speed at the final stage. We also estimated VO2peak using the equations by Léger et al.,24 Mahar et al.,25 and Matsuzaka et al.26 to assess whether using different equations to estimate VO2peak can be used interchangeably to investigate the associations between estimated CRF and brain health outcomes. The equation by Léger etal.24 is the most widely used equation to estimate VO2peak in youth, allowing comparisons between previous studies. Furthermore, the equations by Mahar etal.25 and Matsuzaka etal.26 have been suggested to provide better prediction accuracy of VO2peak than other equations.13,25 2.2.3 | Submaximal indices obtained from the incremental treadmill exercise test VO2 at VT was determined using the data acquired during the maximal incremental treadmill test by two sports physicians. The VT was defined as a point where the increase in the ventilatory equivalent for VO2 occurs without an increment in the ventilatory equivalent for carbon dioxide production. The threshold was confirmed by inspecting the nonlinear increase in ventilation relative to oxygen uptake. VO2 at VT was normalized for BM and allometrically modeled LBM using the VO2peak approach.18 2.3 | Assessment of brain health outcomes Brain health outcomes were assessed at the Mind, Brain, and Behavior Research Centre, at the University of Granada, by trained researchers. Total intelligence was assessed using the Spanish version of Kaufman Brief Intelligence test measuring verbal and nonverbal intelligence.21 Normal scores from verbal and nonverbal intelligence subtests were used to calculate a composite intelligence score. Executive functions including cognitive flexibility, inhibition, and working memory were assessed using the Design Fluency Test and the Trail Making Test, a modified version of the Stroop Color- Word Test (paperpencil version), and a modified version of the Delayed Non- Match- to- Sample computerized task, respectively. The executive function composite z score was calculated as the renormalized mean of the z scores for cognitive flexibility, inhibition, and working memory.8 Academic performance was assessed using the Spanish version of the Woodcock- Johnson III Tests of Achievement. Total academic performance was defined as an overall performance based on reading, mathematics, and writing.11 Total gray matter volume (cm3) and hippocampal (mm3) volume were assessed by structural magnetic resonance imaging (Siemens Trio de 3 T, Magnetom Trio, Siemens Medical Systems, Erlangen, Germany). All images were collected on a 3.0 Tesla Siemens Magnetom Tim Trio scanner (Siemens Medical Solutions, Erlangen, Germany) with a 32- channel head coil. Highresolution T1- weighted images were acquired using a 3D MPRAGE (magnetizationprepared rapid gradient echo) protocol.9 Acquisition parameters were as follows: repetition time (TR) = 2300 ms, echo time (TE) = 3.1 ms, inversion time (TI) = 900 ms, flip angle = 9°, field of view (FOV) = 256 × 256, acquisition matrix = 320 × 320, 208 slices, resolution = 0.8 × 0.8 × 0.8 mm, and scan duration of 6 min and 34 s. The MRI images were analyzed with FreeSurfer software version 5.3.0 (http:// surfer. nmr. mgh. harva rd. edu) and FMRIB's Software Library (FSL) version 5.0.7. (FMRIB analysis group, Oxford, UK). We used the standard processing pipeline known as reconall that has been previously described and wellvalidated to assess total and gray matter volume27–29 and a semiautomated modelbased subcortical segmentation tool which uses the Bayesian framework from shape and appearance models obtained from manually segmented images of hippocampal volumes described in detail previously.30 Before preprocessing, we visually checked each individual image for acquisition artifacts and four children were excluded due to motion noise. In addition, outputs were visually inspected by two assessors and when an additional opinion was needed, another assessor inspected the outputs. 2.4 | Assessment of body size and composition BM (kg) and height (cm) were measured using an electronic scale (SECA861, Hamburg, Germany) and a precision stadiometer (SECA225, Hamburg, Germany), respectively. Both measurements were performed twice and averaged. Dual energy X- ray absorptiometry (DXA) was used to measure whole body fat mass (kg), body fat percentage (BF%), and LBM (kg). The Norland XR- 46 (software version 3.9.6, 16000838, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/sms.14549 by University Of Jyväskylä Library, Wiley Online Library on [15/12/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License | 5 HAAPALA etal. Medical System, Inc., Fort Atkinson, Wisconsin) scanner was used in the first wave (16 participants) while the Hologic Discovery Wi (software version APEX 4.0.2, Hologic Series Discovery QDR, Bedford, Massachusetts) was used in the second and third wave (84 participants). Subsequent analyses were completed by the same researcher following recommendations from the International Society of Clinical Densitometry.31 These analyses were performed separately for each DXA device to eliminate the potential error associated with using two different DXA devices. 2.5 | Other assessments Somatic maturity status in terms of time to peak height velocity was calculated using the equations by Moore etal.32 The participants were classified as pre- (<−1 years), circa (−1 to 1 years), and post (>1 years) peak height velocity. Parental education was reported as: no elementary school, elementary school, middle school, high school, and university completed. Parents responses were combined into a trichotomous variable: none, one of the parents, or both had a university degree. 2.6 | Statistical analyses Statistical analyses were performed using the SPSS statistical software, version 27.0 (IBM corp. Armonk, NY, USA). All continuous variables were checked for normality by observing histograms and using the Kolmogorov– Smirnov test. The associations between the indices of CRF and brain health outcomes were investigated using linear regression analyses adjusted for sex, somatic maturity status, and parental education. These data were further adjusted for BF%. We further investigated the modifying effects of sex and BF% on the associations between indices of CRF and brain health outcomes including sex × CRF or BF% × CRF interaction term to the model. The data were reported using standardized regression coefficients and 95% confidence intervals. We considered standardized regression coefficients between 0.10 and 0.29, between 0.30 and 0.49 are medium, and ≥0.50 to describe small, medium, and large effect sizes, respectively.33 3 | RESULTS 3.1 | Characteristics of participants Participants' characteristics are reported in Table1. A total of 66 of 100 (%) children met the criteria for maximal effort in the treadmill exercise test. Specifically, 95%, 29%, 88%, and 67% of children met the criteria for heart rate, respiratory exchange ratio, volitional fatigue, and plateau in the VO2, respectively. Children who did not meet the criteria for maximal effort did not differ in absolute VO2peak, VO2peak normalized for kg LBM, treadmill time, absolute or normalized VO2 at VT, or in maximal OMNI score from those who met the criteria (p > 0.115). However, those who did not meet the criteria for maximal effort had lower peak respiratory exchange ratio (mean difference −0.05, 95% CI = −0.07 to −0.03, p < 0.001), peak heart rate (mean difference − 6.9, 95% CI = −11.7 to −2.1, p = 0.006), and higher VO2peak normalized for kg BM−1 (mean difference 3.0, 95% CI = 1.1–4.9, p = 0.002) than those who met the criteria. 3.2 | Associations of indices of cardiorespiratory fitness with brain health outcomes The associations between indices of CRF and brain health outcomes are presented in Figure1. VO2peak normalized for kg BM−1 or kg BM−0.70 and a longer treadmill time were positively associated with total gray matter volume. Brain health outcomes were not statistically significantly associated with VO2peak or VO2 at VT measured during the incremental treadmill exercise test. Laps completed in the 20mSRT were positively associated with executive functions and academic performance. Higher speed at the final stage of the 20mSRT was associated with better executive functions. Estimated VO2peak/Léger et al. was positively associated with intelligence, executive functions, academic performance, and gray matter volume. Higher estimated VO2peak/Mahar et al. and VO2peak/Matsuzaka et al. (speed) was positively associated with executive functions. All statistically significant associations were small in magnitude (standardized regression coefficient ranging from 0.183 to 0.256). Most of the abovementioned associations between the indices of CRF with brain health outcomes remained materially unchanged after further adjustment for BF% (Table2). However, the association of VO2peak normalized for kg BM−1 or kg BM−0.70, a treadmill time, and estimated VO2peak/Léger etal. with total gray matter volume were no longer statistically significant after adjustment for BF%. 3.3 | Sex and body fat percentage as moderators of the associations between indices of cardiorespiratory fitness and brain health outcomes In girls, completed laps and final speed on the 20mSRT, and estimated VO2peak/Leger etal. were positively associated 16000838, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/sms.14549 by University Of Jyväskylä Library, Wiley Online Library on [15/12/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 6 | HAAPALA etal. TABLE 1 Characteristics of participants. All Girls Boys Age (years)a10.1 (9.2–11.0) 9.9 (8.9–10.5) 10.3 (9.3–11.2) Height (cm) 144.0 (8.3) 142.8 (9.4) 144.7 (7.4) Weight (kg) 55.8 (11.0) 54.5 (11.5) 56.7 (10.7) Lean mass (kg) 29.2 (5.2) 27.8 (5.7) 30.1 (4.6) Fat mass (kg) 24.5 (7.0) 24.6 (7.0) 24.4 (7.1) Body fat percentage 43.9 (5.6) 45.3 (6.0) 43.0 (5.2) Prevalence of overweight, % 74.0 75.0 73.3 Prevalence of obesity, % 26.0 25.0 26.7 Time to peak height velocity (years) −2.3 (1.0) −1.6 (1.0) −2.7 (0.8) Prepeak height velocity, <−1 years (%) 90 75 100 Circa peak height velocity, −1 to 1 years (%) 10 25 0 Post peak height velocity, >1 years (%) 0 0 0 Parental education (university degree, %) Neither parent 66 57.5 71.7 One parent 18 20.0 16.7 Both parents 16 22.5 11.7 Cardiopulmonary exercise test Plateau in VO2 during incremental treadmill exercise test (%) 67 75 61.7 Peak respiratory exchange ratio 0.96 (0.06) 0.98 (0.06) 0.94 (0.05) Peak heart rate (beats/minute) 193 (12) 198 (10) 189 (12) OMNI score (min – Max)b10 (3–10) 10 (3 to 10) 10 (4 to 10) Proportion of children meeting the criteria for maximal effort (%)1 66 75 60 VO2peak (mL/min−1) 2058 (359) 1984 (351) 2108 (359) VO2peak (mL × BM−1 × min−1) 37.4 (4.7) 36.9 (4.3) 37.7 (5.0) VO2peak (mL × BM−0.70 × min−1) 123.8 (13.8) 121.4 (12.0) 125.5 (14.8) VO2peak (mL × LBM−0.87 × min−1) 110.4 (9.8) 111.3 (9.3) 109.8 (10.1) Treadmill time (min)a8.1 (6.4 to 10.0) 8.4 (6.6 to 9.3) 8.0 (6.3 to 11.0) VO2 at VT (mL × min−1) 1696 (339) 1.601 (341) 1759 (325) VO2 at VT (mL × min- 1)/VO2peak (mL/min−1) (%)* 83.8 (79.8 to 87.7) 81.6 (77.5 to 85.5) 84.7 (80.1 to 88.2) VO2 at VT (mL × BM−1 × min−1) 30.8 (4.9) 29.8 (4.8) 31.5 (5.0) VO2 at VT (mL × LBM−0.81 × min−1)a110.2 (105.0 to 117.0) 108.5 (104.9 to 113.7) 111.7 (105.0 to 119.7) 20- metre shuttle run test Peak heart rate during 20- metre shuttle run test, n = 98 197 (10.2) 200 195 20- m SRT laps (n)a14 (11 to 20.8) 12 (10 to 17) 14.5 (12.0 to 23.8) 20- m SRT speed (minutes)a8.5 (8.5 to 9.0) 8.5 (8.5 to 9.0) 8.8 (8.5 to 9.5) VO2peak/Léger etal. 40.8 (0.3) 40.7 (2.8) 40.8 (2.8) VO2peak/Mahar etal. 34.4 (5.1) 31.8 (4.3) 36.2 (4.9) VO2peak/Matsuzaka etal. (speed) 34.8 (4.6) 33.2 (4.4) 35.7 (4.6) VO2peak/Matsuzaka etal. (laps) 29.5 (2.9) 28.8 (2.9) 29.9 (3.0) Brain health outcomes Total gray matter volume (cm3) 729.1 (65.0) 692.6 (57.3) 753.5 (58.3) Hippocampal gray matter volume (mm3) 7050.2 (693.6) 6757.5 (630.1) 7245.3 (669.3) 16000838, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/sms.14549 by University Of Jyväskylä Library, Wiley Online Library on [15/12/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License | 7 HAAPALA etal. with academic performance with medium to large effect sizes (TableS1). In boys, these associations were statistically nonsignificant with small effect sizes (TableS1). Laps in the 20mSRT were directly associated with executive functions with medium effect sizes in children with lower BF% (below median) but the associations in children with higher BF% (at or above median) were weak and statistically nonsignificant (TableS2). Laps and speed at the final stage in the 20mSRT had positive association with medium effect size with academic performance in children with higher BF% but the association in children with lower BF% was weak and statistically nonsignificant. VO2peak/Leger etal. was positively associated with gray matter volume with medium effect size in children with higher BF% but not in children with lower BF%. 3.4 | Sensitivity analyses The associations between the indices of CRF and brain health outcomes remained materially unchanged after excluding children who did not reach three of four criteria for maximal effort during the incremental treadmill exercise test from the analyses (TableS3). 4 | DISCUSSION Our main findings were that (1) directly measured VO2peak and VO2 at VT were not associated with behavioral brain health outcomes, (2) VO2peak estimated from 20mSRT performance using the equation by Leger etal. in 198824 had stronger and more consistent associations with brain health outcomes than other indices of CRF, and (3) five out of six indices derived from the 20mSRT were positively associated with executive functions. Collectively, our findings suggest that while CRF is positively associated with brain health in children with overweight/obesity, not all measures of CRF are associated with brain health. Furthermore, the effect sizes for all associations were considered small. Consistent with some previous studies in children,3,7,34 we found positive associations of CRF with brain health outcomes, particularly with executive functions. The high All Girls Boys Total intelligence score 98.0 (11.9) 99.9 (12.0) 96.7 (11.7) Total executive functions −0.03 (0.75) −0.20 (0.70) 0.09 (0.77) Total academic performance 109.1 (11.8) 109.3 (13.4) 109.0 (10.7) Abbreviations: 20- m SRT, 20- metre shuttle run test; LBM, lean body mass; mL, milliliter; BM, body mass; VO2, oxygen uptake; VO2peak, peak oxygen uptake; VT, ventilatory threshold. Note: The data are means and standard deviations. p Value for the differences between girls and boys from Student's ttest, Mann–Whitney U- test, or chisquare test. Maximal effort was defined as meeting three out of four following criteria: achieving >85% of agedpredicted maximal heart rate, a respiratory exchange ratio of ≥1.0, volitional fatigue (i.e., >8 points in the OMNI scale) and a plateau in the oxygen uptake during the last two exercise work rates (<2.0 mL/kg/min). VO2peak/Léger etal., VO2peak/Mahar etal., VO2peak/Matsuzaka etal. (speed), and VO2peak/Matsuzaka etal. (laps), peak oxygen uptake estimated from the 20- metre shuttle run test using the equations by Léger etal.,24 Mahar etal.,25 and Matsuzaka etal.,26 respectively. aMedians and interquartile ranges. bMedian and minimum and maximum values. TABLE 1 (Continued) FIGURE 1 Associations of indices of cardiorespiratory fitness with brain health outcomes. Data are standardized regression coefficients with their 95% confidence intervals adjusted for sex, time to peak height velocity, and parental education. VO2peak, peak oxygen uptake; mL, milliliter; BM, body mass; LBM, lean body mass; VO2, oxygen uptake; VT, ventilatory threshold; 20- m SRT, 20- metre shuttle run test;VO2peak/Léger etal., VO2peak/Mahar etal., VO2peak/Matsuzaka etal. (speed), and VO2peak/Matsuzaka etal. (laps), peak oxygen uptake estimated from the 20- metre shuttle run test using the equations by Léger etal.,24 Mahar etal.,25 and Matsuzaka etal.,26 respectively. 16000838, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/sms.14549 by University Of Jyväskylä Library, Wiley Online Library on [15/12/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 8 | HAAPALA etal. malleability of executive functions and their sensitivity to changes in CRF in childhood3,35,36 may explain why we observed the most consistent associations between CRF and executive functions. Nevertheless, supporting the evidence from one previous study,7 we observed that peak performance in the fieldbased running tests is more strongly associated with behavioral brain health outcomes than laboratorymeasured indices of CRF. Different determinants of peak performance and measured VO2peak may explain our findings. Maximal stroke volume and cardiac output are the strongest determinants of VO2peak, whereas a combination of VO2peak, body composition, agility, motivation, and selfregulation determining 20mSRT performance may contribute to its stronger associations with brain health outcomes.37 However, VO2peak normalized for body mass has been positively associated with executive functions and academic performance in children with overweight and low levels of CRF (mean VO2peak = 27 mL × kg BM−1 × min−1).14 While the reason for these contrasting findings is unclear, a higher directly measured VO2peak may contribute to brain health, particularly in children with very low CRF. Furthermore, the larger sample size may have contributed to the statistically significant associations found in the study by Davis and Cooper.14 VO2peak normalized for BM, treadmill time, and estimated VO2peak/Léger etal. were the only indices of CRF positively associated with gray matter volume. However, the associations of VO2peak normalized for BM and treadmill time with gray matter volume were explained by BF%. As we also observed that VO2peak normalized for LBM was not associated with gray matter volume, our results suggest that body adiposity is an important confounder for the associations between CRF and brain health outcomes in children with overweight/obesity. Previous studies in children and adults reporting positive associations between CRF and gray matter volume after controlling for several confounding factors partially supported our findings.9,38,39 However, it is important to note that none of these studies considered DXA- derived BF% in their analyses. Nevertheless, peak performance in the 20mSRT quantified by laps or running speed was not associated with gray matter volume. Gray matter plays an important role in the controlling functions related to memory, emotions, and movement.40,41 However, it also has complicated maturationrelated development and associations with behavioral brain health outcomes, such as executive functions.40,41 Although our results suggest that a phenotype with high peak performance and favorable body composition may benefit brain health, further longitudinal studies with larger sample sizes clarifying the role of different indices of CRF in the gray matter volume are warranted. In contrast to some previous findings,42,43 we found no associations between the different indices of CRF and TABLE 2 Associations of indices of cardiorespiratory fitness with brain health outcomes. Intelligence Executive functions Academic performance Gray matter volume Hippocampal volume VO2peak (mL × BM−1 × min−1) 0.019 (−0.280 to 0.241) 0.137 (−0.092 to 0.366) 0.123 (−0.137 to 0.383) 0.082 (−0.058 to 0.321) −0.058 (−0.325 to 0.208) VO2peak (mL × BM−0.70 × min−1) 0.000 (−0.238 to 0.238) 0.058 (−0.153 to 0.268) 0.086 (−0.153 to 0.324 0.175 (−0.041 to 0.392) 0.012 (−0.232 to 0.256) VO2peak (mL × LBM−0.87 × min−1) 0.003 (−0.184 to 0.191) 0.091 (−0.074 to 0.256) 0.107 (−0.080 to 0.294) 0.095 (−0.077 to 0.267) −0.022 (−0.215 to 0.170) VO2 at VT (mL × BM−1 × min−1) 0.025 (−0.191 to 0.240) 0.130 (−0.059 to 0.320) 0.037 (−0.180 to 0.253) 0.041 (−0.158 to 0.239) −0.153 (−0.373 to 0.066) VO2 at VT (mL × LBM−0.81 × min−1) 0.032 (−0.157 to 0.220) 0.101 (−0.064 to 0.267) 0.035 (−0.154 to 0.224) 0.070 (−0.103 to 0.243) −0.122 (−0.314 to 0.070) Treadmill time (min) −0.064 (−0.301 to 0.174) 0.146 (0.063 to 0.354) 0.082 (−0.157 to 0.320) 0.138 (−0.079 to 0.355) −0.078 (−0.321 to 0.166) 20- m SRT laps 0.046 (−0.194 to 0.287) 0.364 (0.164 to 0.564) 0.295 (0.061 to 0.530) −0.004 (−0.226 to 0.218) 0.041 (−0.206 to 0.288) 20- m SRT speed 0.104 (−0.134 to 0.342) 0.297 (0.094 to 0.500) 0.282 (0.049 to 0.515) 0.053 (−0.167 to 0.273) 0.081 (−0.163 to 0.326) VO2peak/Léger etal. 0.270 (0.001 to 0.539) 0.291 (0.055 to 0.527) 0.379 (0.115 to 0.644) 0.187 (0.063 to 0.437) 0.167 (−0.113 to 0.444) VO2peak/Mahar etal. 0.054 (−0.249 to 0.358) 0.496 (0.247 to 0.745) 0.385 (0.091 to 0.680) −0.089 (−0.368 to 0.190) −0.008 (−0.320 to 0.303) VO2peak/Matsuzaka etal. (speed) 0.167 (−0.140 to 0.475) 0.444 (0.186 to 0.702) 0.392 (−0.092 to 0.692) −0.080 (−0.364 to 0.204) −0.019 (−0.337 to 0.298) VO2peak/Matsuzaka etal. (laps) 0.087 (−0.193 to 0.367) 0.043 (−0.206 to 0.292) 0.035 (−0.247 to 0.317) −0.159 (−0.415 to 0.098) −0.137 (−0.424 to 0.150) Abbreviations: 20- m SRT, 20- metre shuttle run test; BM, body mass; LBM, lean body mass; mL, milliliter; VO2, oxygen uptake; VO2peak, peak oxygen uptake; VT, ventilatory threshold. Note: The data are standardized regression coefficients and their 95% confidence intervals adjusted for sex, estimated time to peak height velocity, parental education, and body fat percentage. VO2peak/Léger etal., VO2peak/Mahar etal., VO2peak/Matsuzaka etal. (speed), and VO2peak/Matsuzaka etal. (laps), peak oxygen uptake estimated from the 20- metre shuttle run test using the equations by Léger etal.,24 Mahar etal.,25 and Matsuzaka etal.,26 respectively. Statistically significant associations are bolded. 16000838, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/sms.14549 by University Of Jyväskylä Library, Wiley Online Library on [15/12/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License