Changes in Physical Activity Patterns from Childhood to Adolescence: Genobox Longitudinal Study

International Journal of Environmental Research and Public Health Article Changes in Physical Activity Patterns from Childhood to Adolescence: Genobox Longitudinal Study Francisco Jesús Llorente-Cantarero 1,2 , Francisco Javier Aguilar-Gómez 3, Augusto Anguita-Ruiz 2,4,5 , Azahara Iris Rupérez 2,6 , Rocío Vázquez-Cobela 7, Katherine Flores-Rojas 3, Concepción M. Aguilera 2,4,5 , Esther M. Gonzalez-Gil 2,4,6, Mercedes Gil-Campos 2,3,* , Gloria Bueno-Lozano 2,6,8 and Rosaura Leis 2 1Department of Specific Didactics, Faculty of Education, University of Córdoba, 14071 Córdoba, Spain; [email protected] 2CIBEROBN, (Physiopathology of Obesity and Nutrition) Institute of Health Carlos III (ISCIII), 28029 Madrid, Spain; [email protected] (A.A.-R.); [email protected] (A.I.R.); [email protected] (C.M.A.); [email protected] (E.M.G.-G.); [email protected] (G.B.-L.); [email protected] (R.L.) 3Metabolism and Investigation Unit, Reina Sofia University Hospital, Institute Maimónides of Biomedicine Investigation of Córdoba (IMIBIC), University of Córdoba, 14004 Córdoba, Spain; [email protected] (F.J.A.-G.); katherine1.flor[email protected] (K.F.-R.) 4Department of Biochemistry and Molecular Biology II, Institute of Nutrition and Food Technology “JoséMataix”, Center of Biomedical Research, University of Granada, Armilla, 18016 Granada, Spain 5Instituto de Investigación Biosanitaria IBS, 18012 Granada, Spain 6GENUD Researchgroup, University of Zaragoza, Instituto Agroalimentario de Aragón (IA2), Instituto de Investigación Sanitaria (IIS), 50009 Aragón, Zaragoza, Spain 7Unit of Investigation in Nutrition, Growth and Human Development of Galicia, Department of Pediatrics, University Clinical Hospital of Santiago, University of Santiago de Compostela, 15701 Santiago de Compostela, Spain; [email protected] 8Pediatric Endocrinology Unit, Lozano Blesa University Clinical Hospital of Zaragoza, Faculty of Medicine, University of Zaragoza, 50009 Zaragoza, Spain *Correspondence: mer[email protected] Received: 8 August 2020; Accepted: 29 September 2020; Published: 2 October 2020   Abstract: Longitudinal changes of physical activity (PA) from childhood into adolescence have not been accurately described yet for the Spanish population. The aim of this study is to evaluate the changes of PA, assessed by accelerometry and anthropometric measures in a cohort of 213 children from the prepubertal to pubertal period, focusing on those with valid data from both time points (n=75) . Sedentary time (ST) increased about 50%, while all PA intensities declined from the pre-pubertal to pubertal period. Light PA (LPA) was the major contributor, decreasing by about 30%. Boys were more active than girls in both periods, but they showed a higher decline in PA, especially moderate-to-vigorous PA (MVPA). The proportion who reached the recommendation of 60 min of MVPA decreased by 33.3% in boys and 4.6% in girls. Children with obesity or overweight had lower MVPA than those with normal-weight in the pre-pubertal period, but no differences were found in the pubertal period. This study shows a decrease of PA and an increase of sedentarism in the transition from childhood to adolescence, particularly in boys. Regardless of body weight, adolescents tend to be less active. Therefore, prevention programs should be implemented to achieve optimal PA and reduce sedentarism during infancy considering the differences found by sex. Keywords: childhood; obesity; physical activity; pubertal status; sedentary time Int. J. Environ. Res. Public Health 2020,17, 7227; doi:10.3390/ijerph17197227 www.mdpi.com/journal/ijerph Int. J. Environ. Res. Public Health 2020,17, 7227 2 of 14 1. Introduction Physical activity (PA) improves cardiorespiratory fitness and strengthens the musculoskeletal system, contributing to maintain an adequate body composition and preventing childhood obesity [ 1 , 2 ]. In this context, the World Health Organization (WHO) and other entities [ 3 – 6 ] have recommended at least 60 min per day of moderate-to-vigorous physical activity (MVPA) for children and adolescents [7,8] . A recent systematic review also highlighted the potential benefits of total PA and light PA (LPA), especially in the improvement of cardio-metabolic biomarkers [9]. On the other hand, sedentarism has been proposed as an independent risk factor of unhealthy outcomes, such as overweight or obesity, especially in adults. However, evidence in youth is less conclusive to date [ 10 , 11 ]. Sedentary behavior is characterized by a very low energy expenditure ( ≤ 1.5 of metabolic equivalents of task (METS)) in a sitting, reclining, or lying posture [ 12 ]. However, there are no recommendations for sedentary time (ST) but a suggestion to limit screen time (a component of ST) to no more than 2 h per day. A recent review revealed that less than 50% of European children and adolescents meet the WHO recommendations regarding PA when measured subjectively [ 13 ], but even those who achieve the 60 min of MVPA may also spend a high proportion of their time being sedentary [14]. In addition to these findings, the practice of PA seems to decrease progressively during childhood and adolescence, coupled to the increase of ST [ 15 ]. Although the reduction of MVPA has always received attention, the latest research has focused also on the importance of LPA decline [ 9 , 15 ]. There are several factors associated with the PA decline: biological, psychosocial, and environmental. Specifically, the influence of gender, pubertal status, or body mass index (BMI) have not been accurately described yet. Moreover, most of these studies include self-reported PA and/or a cross-sectional design [16–19], being few those with longitudinal data. During childhood and adolescence, boys seem to perform more PA than girls [ 13 ], although the rate of decline by gender varies between studies especially related with social factors and others. This reduction in adolescents seems to occur earlier in girls (9–12 years) and later in boys (13–16 years) [ 17 , 20 ], suggesting that it may be related with pubertal status more than with chronological age. It seems that young people become less physically active as they progress along the maturation process [ 16 – 19 ]; thus, puberty could be a critical lapse for PA [ 21 ]. The appearance of secondary sexual characteristics, the changes in body composition, hormonal imbalance, and self-perception are related to the practice of PA in boys and girls [ 22 ]. So, puberty timing (e.g., the age of menarche or peak of high velocity) related to age and gender may be relevant in explaining the decrease in the practice of exercise. A recent review [ 23 ] revealed that the practice of MVPA is significantly lower in children and adolescents with obesity than in their normal-weight peers, although differences are relatively small and both groups are below the recommendations. Moreover, no differences have been found in ST between BMI groups, without any information regarding total PA or LPA. The relationships between changes in body composition, gender, or puberty and PA, remain under investigation. This is of special importance for addressing population-based interventions. Based on these previous observations, it is important to describe changes of PA and ST according to the presence or absence of pubertal development, as well as to corroborate if the differences previously reported in other countries, such as United Kingdom [ 15 ], between genders and BMI groups remain similar for the Spanish population. The aim of the present study is to analyze the time spent on all intensities of PA, measured by accelerometry, and ST in a cohort of children followed from pre-pubertal to pubertal status, focusing also on gender differences and BMI changes. 2. Materials and Methods 2.1. The Cross-Sectional Study Design The present study was carried out under the framework of the GENOBOX study [ 24 , 25 ]. GENOBOX is a cross-sectional case-control, multicentre study carried out in children from 2012–2015. After assessing Int. J. Environ. Res. Public Health 2020,17, 7227 3 of 14 them in a first visit at the primary care centre, the children fulfilling the inclusion criteria and their parents were invited to the Endocrine Departments of the Reina Sof í a University Hospital in C ó rdoba, University Clinical Hospital in Santiago de Compostela, and Lozano Blesa University Clinical Hospital in Zaragoza, obtaining a similar sample distribution among three regions. Nine hundred and fifty-three prepubertal children were assessed based in the sample size estimation for the GENOBOX study [ 24 , 25 ]. Out of them, a subsample of 213 (27 from C ó rdoba, 104 from Santiago de Compostela, and 82 of Zaragoza) children (105 boys) was selected based on the following inclusion criteria for the present study: to have valid blood samples including sex hormones (follicle-stimulating hormone, luteinizing hormone, testosterone in boys, and estradiol in girls); being aged between 5–14 years and being in a pre-pubertal stage (Tanner I confirmed with sex hormones: follicle-stimulating hormone (<5.0 U/L), luteinizing hormone (<8 U/L), testosterone in boys (<0.5 ng/mL), and ostradiol (<10 pg/mL) in girls) at baseline, with an absence of endogenous obesity and metabolic diseases at recruitment, no use of medications for controlling blood pressure (BP), glucose, or lipid metabolism levels, and valid data for the present study variables; especially, with data from an accelerometer according to the protocol. 2.2. The Longitudinal Study Design Two measurements were conducted on the selected children before and after the onset of puberty, being all of them part of the previously mentioned cross-sectional study population. All these children were first recruited as prepubertal children during the year period (2012–2015), baseline, and called again for follow-up medical consultation in 2018. All subjects with clinical signs of puberty at follow-up (at least Tanner II, confirmed with sex hormones), were included in the longitudinal study. Finally, 75 children presented valid data of PA, measured by accelerometers, at both prepubertal and pubertal stage. During the whole course of the study (2012–2018), children remained under regular medical monitoring by the same pediatricians. Children and parents or custody holders were informed about the purpose and procedures of the study, giving the children their assent to participate. Signed written consents were obtained from the parents after the Ethics Committees of all participating institutions approved the study. We complied with the Declaration of Helsinki [ 26 ] and followed the recommendations of the Good Clinical Practice of the CEE (Central and Eastern Europe) (Document 111/3976/88 July 1990) and the legal, in-force Spanish regulation, which regulates Clinical Investigations in human beings (RD 223/04 on Clinical Assays). 2.3. Anthropometric and Clinical Measurements Medical history and a physical examination including the evaluation of sexual maturity according to Tanner’s five-stage scale [ 27 ] were assessed in both visits, at prepubertal and pubertal stages, and confirmed with sexual hormone measurements. Anthropometric measurements were taken by a single examiner within each hospital. Body weight was measured using a standard beam balance. Height was measured using a precision stadiometer. Waist circumference (WC) was measured in fasting state by applying an inelastic tape horizontally midway between the lowest rib margin and the iliac crest of the standing child at the end of a gentle expiration. BMI was calculated (kg/m 2 ), and overweight and obesity were defined using age and sex-specific BMI cut-offpoints of the International Obesity Task Force, equivalent to adult values of 25 kg/m 2 for overweight and 30 kg/m 2 for obesity [ 28 ]. In this study, three BMI groups were created to test differences in PA between them in the two time points (baseline and follow-up): normal-weight (NW), overweight (OW), and with obesity (OB). For the analysis of the changes in PA between the two time points, BMI-change groups were created as follows: NW-no change group, OW/OB-no change group, improving-BMI group (for those who changed from OB to OW or NW, and from OW to NW), and worsening-BMI group (for those who changed from NW to OW or OB, and from OW to OB). Int. J. Environ. Res. Public Health 2020,17, 7227 4 of 14 Systolic and diastolic blood pressure (BP) were measured three times by the same examiner using an electronic manometer (Omrom, M6 AC) and following international recommendations [ 29 ], and the mean of the three measurements was considered the current value. 2.4. Biochemical Analysis Blood samples were drawn from the antecubital vein between 08:00 and 09:30 h after an overnight fast. Routine blood tests were analyzed at the general laboratory of each participating hospital. Glucose (CV =1.0%) was analyzed using the glucose oxidase method in an automatic analyzer (Roche-Hitachi Modular P and D Autoanalyzer; Roche Laboratory Systems, Mannheim, Germany), and plasma insulin was analyzed by radioimmunoassay (RIA) (CV =2.6%) using an automatic microparticle analyzer (AxSYM; Abbott Laboratories, Abbott Park, IL, USA). Insulin resistance (IR) was calculated by the homeostatic model assessment of IR (HOMA-IR). Serum triacylglycerols (TAG) (CV =1.5%), total cholesterol (CV =0.9%), high density lipoprotein cholesterol (HDL-c) (CV =0.8%), and low-density lipoprotein cholesterol (LDL-c) (CV =1.5%) were measured using an automatic analyzer (Roche-Hitachi Modular P and D Autoanalyzer; Roche Laboratory Systems, Mannheim, Germany). The sex hormones follicle-stimulant hormone (FSH) (CV =3.6%); luteinizing hormone (LH) (CV =3.1%), testosterone (CV =2%), and estradiol (CV =1.8%) were measured by chemiluminescence using an automatic analyzer (Architec I4000, Abbott Laboratories, Abbott Park, IL, USA). 2.5. Accelerometry ActiGraph GT3X+accelerometers (ActiGraph; Pensacola, FL, USA) were used to assess PA levels in this study. Accelerometers were placed over the right iliac crest and held in place using an adjustable elastic belt for 24 h a day and could be removed only to shower or for nocturnal rest (if the instrument caused discomfort in sleeping). It was programmed for 15 epochs (period of 15 s), as previously recommended [30]. Accelerometry data were processed using the Actilife v6.13.3 program. Two rules were used for excluding data: (a) all negative counts were replaced by a missing data code, and (b) periods of 20 min or more of consecutive zero counts were replaced by a missing data code prior to further analysis, as recommended by Treuth et al. [ 31 ]. The output generated by the ActiGraph GT3X+included the total volume of PA and each PA intensity as defined by the cut-points of the following counts per minute (CPMs) based in Evenson et al. [ 32 ] classification: sedentary: ≤ 100 CPM, light (LPA): >100–<2296 CPM, moderate (MPA): >2296–<4012 CPM, and vigorous PA (VPA): ≥ 4012 CPM. A minimum of 8 h of monitoring per day for at least 3 days including at least 1 weekend day was considered acceptable for the evaluation of PA and sedentary time. After meeting these conditions, differences in time measured between the two timepoints may have been different and overor underestimated in absolute values, so relative values of each PA intensity were calculated as follows: % of LPA =(min of LPA measured/min of total time measured) × 100, as previously [33]. 2.6. Statistical Analyses All continuous variables were tested for normality using the Kolmogorov test, and all were transformed through natural log, or square root or rank-based inverse normal transformation. Heteroscedasticity between groups was explored with the Levene test. Differences in the characteristics of the participants for prepubertal and pubertal periods were tested using Chi-square or t-paired tests. In the cross-sectional study, the two-way ANOVA and Kruskal–Wallis were employed to assess group differences in the measurements according to standard statistical assumptions. In addition, the Dunn tests were applied conveniently as post-hoc analyses adjusted by age to determine which experimental groups differed from each other for the ANOVA. A p-value ≤ 0.05 was considered significant. Int. J. Environ. Res. Public Health 2020,17, 7227 5 of 14 In the longitudinal study, mean (SD) differences in the time of ST/PA (all intensities), between the two time points were assessed for all subjects and separately by gender, BMI groups, and BMI-change groups, using paired t-tests, paired Wilcoxon signed rank tests, and Dunn tests conveniently, adjusted by age. Absolute values would overestimate the differences between prepubertal and pubertal time; thus, relative values of each level of PA were also calculated (min of intensity level of PA with regard to the total measured time, expressed as percentage). On the other hand, differences between prepubertal and pubertal stage ( ∆ ) were calculated for BMI z-score and the PA variables. After that, given the co-linearity found between PA variables, several multivariable regression tests selecting changes in BMI-Z score as dependent variable, and changes in the different physical activity intensities as independent variables, as well as age, Tanner status, and gender were included in the model carried out; (Supplementary Table S1). A p-value ≤ 0.05 was considered as significant. All statistical procedures were conducted by using SPSS (IBM SPSS Statistics for MacOS, Version 25.0. Armonk, NY, USA). 3. Results Measurements of PA with an Actigraph device were collected from 52.8% of children at baseline (n=112) , 67.6% of children at follow-up (n=142), and 35.2% of children at both time points (prepubertal and pubertal stages) (n=75) (Figure 1). Table 1shows the characteristics of the population in the group with both measurements. The number of days with valid PA data recorded was lower in prepubertal time than in pubertal time, although both of them were above the recommendations. The proportion of girls was a little higher, and it remained around 50% for each BMI group (data not shown). At baseline, 69% were children with overweight and obesity. The mean of the BMIZ-score in prepubertal children showed no significant difference to that at pubertal stage. At the end of follow-up, about 3/4 of adolescents showed no BMI group changes and the others had an improvement to a normal weight, or a worsening to obesity. Figure 1. Design of the study. Total min of PA detected by the accelerometer were significantly higher at the pubertal (891.1 ± 169.6 min) than at prepubertal stage (771.8 ± 79.4 min). In Table 2, PA is presented for both times as the mean of measured min/day and relative values of these measurements for both groups. Absolute and relative values of ST were significantly higher in pubertal time compared with basal time, with no gender differences. In the adolescents, average ST increased by 66.9 min. LPA, MPA, and MVPA were lower in pubertal measures than in prepubertal. At baseline, only MVPA shows statistical differences in absolute values (p=0.03) and, MPA and MVPA for relative values (p=0.027 and p=0.025, respectively). At the pubertal stage, only VPA showed significant gender differences. The decline of MPA and MVPA Int. J. Environ. Res. Public Health 2020,17, 7227 6 of 14 from prepubertal to pubertal period was higher in boys than girls. In contrast, VPA in boys was the only PA intensity which increased in absolute values between times (1.6 min/day). Table 1. Characteristics of the longitudinal sample (n =75) at prepubertal and pubertal periods and evolution in weight status. Prepubertal Pubertal p Days of Physical activity 4.65 ±0.70 6.52 ±0.86 <000.1 Age (years) 8.46 ±1.37 13.84 ±1.88 <000.1 Females (%) 42 (56.0) BMI (Kg/m2)21.92 ±4.86 25.80 ±6.78 0.001 BMI Z-Score 1.79 ±1.95 1.63 ±1.89 0.610 Cole groups (%) Normal-weight 23 (30.6) 29 (38.6) Overweight 19 (25.3) 18 (24.0) With Obesity 33 (44.0) 28 (37.3) Changes in BMI No changes (%) 55 (73.3) Normal-weight 21 Overweight 9 Obesity 25 Improvement (%) 15 (20) Obesity to overweight 7 Overweight to normal-weight 7 Obesity to normal-weight 1 Worsening (%) 5 (6.7) Normal-weight to overweight 2 Overweight to obesity 3 Normal-weight to obesity 0 Data are expressed as mean ±DS. Differences between groups are presented in pcolumn. As Table 3shows, around 60% of boys accomplished the recommendation of 60 min/day of MVPA at prepubertal period, while only 28% of girls did. In pubertal period, the proportion of adolescents who met this recommendation decreased in both genders, however, the decline was greater for boys than girls (33.3% vs. 4.6%, respectively). Table 4shows PA data according to BMI groups. At baseline, there were no differences in ST between BMI groups. NW children showed higher MPA, VPA, and MVPA values than OW and OB children. In fact, only NW prepubertal children reached 60 min of MVPA. At the pubertal stage, there were no differences between BMI groups for ST or any PA intensity. As seen previously, ST increased about 16% in relative values for all BMI groups, with a decline in PA, especially in LPA. This reduction in LPA, MPA, VPA, and MPVA tended to be higher for NW children than OW and OB children, with a tendency of similarity between BMI groups in the pubertal period. Table 5shows the PA measurements from the longitudinal analysis according to BMI-change groups. Subjects who did not change their BMI increased their ST for up to 70% of the time measured (about 15% more in relative values), which means about 1 h more per day of ST in pubertal stage. Those who improved their BMI had the highest increase in ST (about 18.8% in relative values). In contrast, those whose BMI worsened showed the shortest increase in ST (about 6%). Int. J. Environ. Res. Public Health 2020,17, 7227 7 of 14 Table 2. Differences in physical activity levels between prepubertal and pubertal periods measured in mean minutes and relative percentages in the longitudinal sample (n =75). Mean Values (min ±SD) Relative Values (% ±SD) Prepubertal Pubertal ∆(%) pPrepubertal Pubertal ∆(%) p Sedentary All 443.3 ±74.1 636.8 ±164.2 +43.6 <0.001 56.0 ±6.7 71.1 ±8.2 +15.1 <0.001 Boys 445.2 ±78.1 661.9 ±146.4 +48.6 <0.001 56.1 ±6.3 71.6 ±7.0 +15.5 <0.001 Girls 441.8 ±71.6 617.1 ±176.1 +39.6 <0.001 55.9 ±7.0 70.7 ±9.1 +14.8 <0.001 Light PA All 286.8 ±47.8 200.6 ±50.1 −32.0 <0.001 36.7 ±5.6 23.4 ±6.9 −13.3 <0.001 Boys 281.5 ±43.7 202.7 ±60.1 −27.9 <0.001 35.9 ±4.8 22.5 ±5.6 −13.4 <0.001 Girls 291.0 ±50.8 199.0 ±51.5 −31.6 <0.001 37.3 ±6.2 24.1 ±7.8 −13.2 <0.001 Moderate PA All 40.9 ±13.3 31.1 ±12.3 −23.9 <0.001 5.2 ±1.6 3.6 ±1.5 −1.6 <0.001 Boys 43.7 ±14.8 31.7 ±13.3 −27.4 <0.001 5.7 ±1.7 3.6 ±1.5 −2.1 <0.001 Girls 38.6 ±11.7 30.6 ±11.6 −20.7 0.003 4.9 ±1.3 δ3.6 ±1.5 −1.3 δ<0.001 Vigorous PA All 15.3 ±9.2 15.2 ±11.0 −0.6 0.965 1.9 ±1.1 1.7 ±1.2 −0.2 0.255 Boys 17.4 ±10.5 19.0 ±10.2 +9.1 0.379 2.1 ±1.2 2.1 ±1.3 0 0.809 Girls 13.6 ±7.8 12.2 ±8.9 λ−10.2 κ0.296 1.7 ±0.9 1.4 ±1.0 δ−0.3 0.139 MVPA All 56.1 ±20.4 45.5 ±18.0 −18.8 <0.001 7.1 ±2.5 5.3 ±2.3 −1.8 <0.001 Boys 61.4 ±22.4 49.3 ±18.9 −19.7 0.024 7.9 ±2.8 5.6 ±2.4 −2.3 0.001 Girls 52.1 ±18.1 δ42.6 ±16.9 −18.2 0.008 6.6 ±2.1 δ5.1 ±2.2 −1.5 δ0.001 PA: physical activity; MVPA: moderate-to-vigorous PA; Data of PA for both periods and variation between them are presented for total sample with absolute (mean) and relative values. Mean values are expressed as mean of min/day of each level of PA ± SD. Relative values are expressed as ((mean of min/day of any level of PA measured/mean of total min/day of PA measured) × 100) ± SD. Differences between sex are indicated in girls’ rows of “prepubertal”, “pubertal”, and “ ∆ ” columns. Differences between periods for all, boys and/or girls are indicated in pcolumn. Differences are expressed with: δfor p<0.05; λfor p<0.01; κfor p<0.001. Table 3. Distribution in percentage of children by gender in prepubertal and pubertal periods, related with moderate-to-vigorous physical activity in the longitudinal sample (n=75). Boys (%) Girls (%) MVPA (min) Prepubertal Pubertal Prepubertal Pubertal <30 3 (9.0) 7 (21.2) 4 (9.5) 12 (28.5) 30–59.9 10 (30.3) 17 (51.5) 26 (61.9) 20 (47.6) 60–89.9 15 (45.4) 9 (27.2) 11 (26.1) 10 (23.8) >90 5 (15.1) 0 1 (2.3) 0 Regarding PA, the biggest increase in ST was replaced by a decline in LPA (about 88% of ST, which means about 35–40 min less per day), being statistically significant for all of them, except the worsening BMI group. The improving and not-changing BMI groups decreased MPA and MVPA in absolute and relative values, but VPA did not show differences in any of them. The worsening group did not show any difference between prepubertal and pubertal time in any group of PA intensities. Int. J. Environ. Res. Public Health 2020,17, 7227 8 of 14 Table 4. Comparison of physical activity levels and minutes of practice between prepubertal and pubertal periods according to BMI groups in the longitudinal sample (n=75). Total Sample (n =75) Mean Values Relative Values Prepubertal Pubertal ∆(%) pPrepubertal Pubertal ∆(%) p Sedentary NW 429.3 ±63.1 641.3 ±174.5 δ+49.3 <0.001 55.5 ± 7.3 73.2 ± 8.1 +17.7 <0.001 OW 428.1 ±68.1 695.5 ±120.5 λ+62.4 <0.001 56.5 ± 8.1 72.9 ± 5.7 +16.4 <0.001 OB 444.9 ±85.0 624.9 ±152.6 +40.4 κ<0.001 55.9 ± 6.4 71.1 ± 8.0 +15.2 <0.001 Light PA NW 279.5 ±46.6 186.2 ±52.5 δ−33.3 δ<0.001 36.1 ± 5.3 21.7 ± 6.7 −14.4 <0.001 OW 279.1 ±52.9 208.4 ±58.2 −25.3 <0.001 36.8 ± 6.6 21.9 ± 5.1 −14.9 <0.001 OB 290.1 ±54.7 204.1 ±56.0 δ−29.6 <0.001 37.1 ± 5.8 23.7 ± 6.4 −13.4 <0.001 Moderate PA NW 45.4 ±13.6 κ27.6 ±12 δ−39.2 κ<0.001 5.8 ±1.6 κ3.2 ±1.5 −2.6 <0.001 OW 36.7 ±15.4 31.7 ±12.5 −13.6 0.004 4.8 ±1.9 3.3 ±1.2 −1.5 <0.001 OB 39.7 ±12.4 λ30.5 ±14.0 −23.1 δ<0.001 5.1 ±1.4 λ3.5 ±1.5 −1.6 <0.001 Vigorous PA NW 18.8 ±12.2 λ15.1 ±10.2 −19.6 δ0.009 2.4 ±1.4 κ1.7 ±1.2 −0.7 <0.001 OW 13.1 ±9.7 16.6 ±11.9 +26.7 δ0.012 1.7 ±1.1 1.7 ±1.1 0 1.000 OB 14.2 ±7.5 λ13.2 ±10.8 −7.0 0.405 1.7 ±0.9 κ1.5 ±1.2 −0.2 0.143 MVPA NW 61.9 ±21.2 λ42.0 ±18.8 −32.1 δ<0.001 8.2 ±2.9 κ4.9 ±2.4 −3.3 <0.001 OW 49.8 ±23.6 47.9 ±19.9 −3.8 0.482 6.5 ±2.8 5.0 ±1.9 −1.5 <0.001 OB 54.8 ±17.6 δ42.3 ±19.7 −22.8 <0.001 6.9 ±2.1 λ5.0 ±2.4 −1.9 <0.001 PA: physical activity; MVPA: moderate-to-vigorous PA; NW: children normal-weight; OW: children with overweight; OB: children with obesity. Data of PA for each period and variation between them are presented with absolute (mean) and relative values. Mean values are expressed as mean of min/day of each level of PA ± SD. Relative values are expressed as ((mean of min/day of any level of PA measured/mean of total min/day of PA measured) × 100) ± SD. Differences between periods for NW, OW, and/or OB are indicated in ∆ column. Differences between NW and OW are indicated in NW row. Differences between OW and OB are indicated in OW row. Differences between OB and NW are indicated in OB row. Differences are expressed with: δfor p<0.05; λfor p<0.01; κfor p<0.001. Int. J. Environ. Res. Public Health 2020,17, 7227 9 of 14 Table 5. Comparison of physical activity levels between prepubertal and pubertal periods according to BMI-change groups in the longitudinal sample (n =75). Total Sample (n=75) Mean Values Relative Values Prepubertal Pubertal ∆(%) pPrepubertal (%) Pubertal (%) ∆(%) p Normal-Weight No Changes (n=21) Sedentary 423.0 ±60.6 595.0 ±183.1 +40.6 0.001 55.2 ±6.3 69.9 ± 9.3 +14.7 β<0.001 Light 279.7 ±42.0 196.2 ±56.2 −29.8 β<0.001 3.6 ±4.6 24.1 ± 7.7 −12.4 <0.001 Moderate 44.8 ±10.5 30.5 ±12.4 −31.9 0.001 5.8 ±1.3 3.8 ±1.7 −2.0 β0.001 Vigorous 17.9 ±9.7 16.5 ±10.0 −7.8 0.523 2.3 ±1.2 2.0 ±1.2 −0.2 0.384 MVPA 62.7 ±19.2 47.0 ±18.9 −25.0 0.007 8.2 ±2.4 5.8 ±2.6 −2.3 0.007 Overweight/With Obesity No changes (n=34) Sedentary 445.8 ±79.1 639.1 ±162.1 +43.3 <0.001 55.4 ±6.3 70.5 ± 7.4 +15.1 β<0.001 Light 300.7 ±45.7 210.5 ±51.8 −29.9 β<0.001 37.6 ±6.2 24.0 ± 6.5 −13.5 β<0.001 Moderate 40.0 ±12.4 32.2 ±12.1 −19.5 0.016 5.0 ±1.2 3.7 ±1.3 −1.3 0.001 Vigorous 15.2 ±9.6 14.9 ±11.5 −1.9 0.885 1.8 ±1.0 1.6 ±1.1 −0.2 0.294 MVPA 56.3 ±19.6 47.5 ±18.8 −15.6 0.066 6.9 ±2.2 5.3 ±1.9 −1.6 0.005 Improving (n=15) Sedentary 465.4 ±70.4 728.6 ±119.1 +56.5 <0.001 57.6 ±5.4 76.5 ± 6.7 +18.8 β<0.001 Light 274.9 ±44.2 178.1 ±62.6 −35.2 β<0.001 35.8 ±4.0 19.2 ± 6.2 −16.5 β<0.001 Moderate 37.5 ±15.9 26.0 ±10.0 −30.6 0.020 4.8 ±2.1 2.6 ±0.7 −2.1 β0.003 Vigorous 13.4 ±7.8 13.9 ±9.8 +3.7 0.813 1.6 ±1.0 1.5 ±1.1 −0.1 0.626 MVPA 50.6 ±22.9 39.0 ±15.9 −22.9 0.045 6.4 ±3.0 4.1 ±1.6 −2.2 0.010 Worsening (n=5) Sedentary 444.6 ±100.6 521.3 ±85.3 +17.2 0.285 58.5 ±12.8 64.4 ± 5.6 +5.8 δ,λ,κ0.329 Light 263.1 ±78.7 226.1 ±20.7 −14.0 δ,λ,κ0.354 34.5 ±9.6 28.1 ± 2.8 −6.3 λ,κ0.252 Moderate 41.8 ±20.8 43.1 ±14.4 +3.1 0.834 5.4 ±2.5 5.3 ±1.7 −0.1 δ,κ0.932 Vigorous 10.4 ±7.2 16.0 ±16.8 +53.8 0.306 1.3 ±0.9 1.9 ±2.0 +0.5 0.383 MVPA 42.3 ±16.3 46.5 ±13.0 +9.9 0.630 6.8 ±3.2 7.3 ±3.7 +0.5 0.595 MVPA: moderate-to-vigorous physical activity; Improving: Subjects with overweight or obesity in prepubertal time and changed to overweight or normal-weight, respectively, in pubertal time. Worsening: Subjects who were normal-weight or overweight in prepubertal time and changed to overweight or obesity, respectively, in pubertal time. Data of PA and variation between periods are presented for total sample with absolute (mean) and relative values. Mean values are expressed as mean of min/day of each level of PA ± SD. Relative values are expressed as ((mean of min/day of any level of PA measured/mean of total min/day of PA measured) × 100) ± SD. Differences between BMI-change groups (p<0.05) according to “ ∆ ” for each level of PA intensity are expressed in “ ∆ ” column. Differences regarding “Normal-weight no changes” group are expressed with δ ; differences regarding “OW/OB no changes group” are expressed with λ ; differences regarding “Improving group” are expressed with κ ; differences regarding “Worsening” group are expressed with β. Finally, the results of the multivariable regression test are showed in the Table S1. 4. Discussion Changes of PA and ST according to the presence or absence of pubertal development, as well as the differences between genders and BMI groups have been studied in this Spanish sample. The performance of PA in this Spanish cohort decreased from childhood to adolescence, being replaced by a rise in sedentarism. The time spent on all intensities of PA has been measured objectively by accelerometry, focused also on gender differences, and especially related with BMI changes. This increase in ST which accounted for 72% of the total measured time in pubertal adolescents (Table 2), has been previously reported to be about 40 min per day than the baseline values, or reaching 90 min per day for British and North Americans [ 15 , 33 – 35 ]. Parallel to the increased ST, LPA was the main contributor in the reduction of PA, with a 14% decrease in relative values, while MPA, and especially VPA, remained stable (Table 2). Some researchers also found that the rise of ST matched the decrease in LPA in adolescence, while MVPA remained relatively constant during this stage [ 15 , 34 – 36 ]. Previous studies focused on MVPA as the most important contributor to the decrease of PA and its association with health benefits [ 1 , 20 , 37 ]. However, our data suggest that MVPA plays a small role in this reduction, at least in older children. It seems that VPA and MVPA levels were already low at the prepubertal time in our cohort, especially in girls, and only boys at baseline accomplished