We performed cross-sectional analyses of baseline data from participants in the FUPRECOL study, which was focused on the associations between fitness, health, and non-communicable diseases. We published a complete description of the FUPRECOL study design, methods, and primary outcomes for our current cohort (Ramírez-Vélez, Ojeda-Pardo et al., 2016). The sample comprised of 8,000 healthy Colombian children and adolescents aged 9-17.9 years. In this study, we included a sub-sample (N = 7,714; boys, n = 3,379; girls, n = 4,335). The participants were recruited between April 2012 and June 2015. The children and adolescents were of low to middle socioeconomic status (SES 1-3, as defined by the Colombian government), enrolled in public elementary and high schools (grades 5-11), and resided in the capital district of Bogota in a municipality in the Cundinamarca Department in the Andean region. A convenience sample of volunteers was included and grouped by sex and age in 1-year increments (a total of 9 groups). Individuals with endocrine disorders, psychiatric disorders, pregnancy, cardiovascular disease, systemic infections, asthma, or other physical impairments that made them unable to participate in this study, as well as individuals using any prescribed drugs or actively using illegal or illicit drugs, were excluded from this investigation.

Bullying victimization. This content was assessed by means of the Revised Bully/Victim Questionnaire. A previous study has reported a good reliability and validity (Solberg & Olweus, 2003). Youths were asked how often they had been bullied at school in the past couple of months in a variety of different ways: (1) Physical bullying: hitting, kicking, pushing, shoving around, or locking indoors); (2) Verbal bullying: calling mean names and making fun of or teasing in a hurtful way; (3) Social exclusion bullying: socially excluding others and spreading rumors; (4) Sexual harassment: sexual comments, jokes, gestures, or looks; and (5) Cyberbullying: bullying using a computer or e-mail messages or pictures, and bullying using a cell phone. The questionnaire consists of seven items answered on a five-point scale: “none”, “only once or twice”, “2 or 3 times a month”, “about once a week”, and “several times a week”. Bullying victimization was categorized as traditional bullying (physical, verbal, social exclusion, and sexual harassment) and cyberbullying. A previous study recommended the cut-point of “2 or 3 times a month” to code a student as bullied or non-bullied (Solberg & Olweus, 2003). The scale presents a Cronbach's alpha of .75.

Anthropometric assessment. All data was collected at the same time in the morning, between 7:00 a.m. and 10:00 a.m. Body weight and height were measured following standard procedures using an electronic scale (Tanita® BC544, Tokyo, Japan) and a mechanical stadiometer platform (Seca® 206, Hamburg, Germany), respectively. Body Mass Index (BMI) was calculated as body weight in kilograms divided by the square of height in meters. BMI was classified as underweight, normal weight, overweight, or obese using the International Obesity Task Force criteria for age and sex (Monasta, Lobstein, Cole, Vignerová, & Cattaneo, 2011). In all measures, we found almost excellent test-retest reliability (body weight [intraclass correlation coefficient [ICC] = .98], height [ICC = .97], and BMI [ICC = .89].

Physical Fitness Assessment. The musculoskeletal component used is appropriate for this age group and has shown acceptable validity and reliability (Ramírez-Vélez, Martínez et al., 2016; Ramírez-Vélez, Morales et al., 2017). Handgrip strength was assessed as an indicator of upper-body MF using an adjustable analogue handgrip dynamometer, T-18 TKK SMEDLY III® (Takei Scientific Instruments Co. Ltd., Niigata, Japan). Students were shown a brief demonstration of technique, and were given verbal instructions on how to perform the test. The dynamometer was adjusted according to the child's hand size per predetermined protocols. Youth were classified as fit or unfit based on the sex-and age cut-points established among Colombian children and adolescents (Ramírez-Vélez, Peña-Ibagon et al., 2017). Handgrip measurement in a subsample (n = 229, similar in demographics and biological characteristics to the whole sample) was recorded to ensure reproducibility on the day of the study. The reproducibility of our data was R = .96 to the handgrip test.

Cardiorespiratory fitness (CRF) was assessed with the 20 meter Shuttle Run Test (20mSRT) (Ramírez-Vélez, Palacios López et al., 2016). This test requires participants to run back and forth between two lines set 20 m apart. Running speed started at 8.5km/h and increased by 0.5km/h each minute, reaching 18.0km/h per minute. Each level was announced on a recorded audio. The participants were instructed to keep up with the pace until exhausted. The test was finished when the participant failed to reach the end lines concurrent with the audio signals on two consecutive occasions. Otherwise, the test ended when the subject stopped because of fatigue. The participants received verbal encouragement from the investigators to achieve maximum performance to keep running as long as possible. The number of shuttles performed by each participant was recorded. To estimate VO2max using the 20mSRT, the equation developed by Barnett equation for boys and girls, VO2max = 25.8 × [6.6 × G × 0.2 × (body mass + 3.2 × (final speed)], where G is gender (male = 0; female = 1) and final speed (8 + 0.5 × last stage completed), was used (Barnett, Chan, & Bruce, 1993). Youth were classified as fit or unfit based on the sex-and age cut-points established among Colombian children and adolescents (Ramírez-Vélez, Correa-Bautista, Mota, & Garcia-Hermoso, 2018). The reproducibility of our data was R = .84. Intra-rater reliability was assessed by determining the ICC (.96, CI 95% .95 to .97).

Screen time. Screen time was assessed by asking participants to report the number of hours per typical day in the past seven days with a question: “Approximately how many hours a day do you usually watch television in your free time?”. Television use was dichotomized (< 2h/day; ≥2h/day) based on international guidance on limiting pediatric screen time (Bar-On et al., 2001). Previous studies have been related the screen time with higher bullying victimization (Merrill & Hanson, 2016).

Maturation Status Assessment. Maturation status (self-reported) was assessed by the classification described by Tanner (five stages: I–V) (Tanner & Whitehouse, 1976). Each participant entered into an isolated room where, using a set of images exemplifying the various stages of sexual maturation, they categorized the development of their own genitalia (for boys), breasts (for girls), armpits (for boys), and pubic hair (for both sexes). The reproducibility of our data was R = .84.

The study protocol was explained verbally to the participants and their parents/guardians before they gave their written consent. Participation in the study was fully voluntary and anonymous, with no incentives provided to participants. The Review Committee for Research on Human Subjects at the University of Rosario (code No. CEI-ABN026-000262) approved all study procedures. The protocol was in accordance with the latest revision of the Declaration of Helsinki and current Colombian laws governing clinical research on human subjects (Resolution 008430/1993 Ministry of Health).

The normality of the variables was verified using histograms and Q-Q plots. VO2max and handgrip strength/weight had skewed distributions and were log-transformed prior to analyses. To aid interpretation, data was back-transformed from the log scale for presentation in the results. Since no significant interaction (i.e., p>.10) was observed between age group (children or adolescents; e.g., age group x bullying victimization) to increase statistical power, all the statistical analyses were performed with both age groups together.

First, we tested associations between traditional bullying, cyberbullying, age, sex, pubertal status, BMI, excessive television use, cardiorespiratory fitness, and muscular strength by computing zero-order correlations using Pearson correlations.

Differences were analyzed using the chi-square test (χ2) in order to explore each group (fit vs. unfit). Analyses of covariance (ANCOVA) were used to assess the differences between mean cardiorespiratory fitness (ml/kg/min) and handgrip strength/weight according to bullying victimization categories (non-bullied vs bullied), adjusted for age, pubertal status, overweight/obesity, and excessive television use (≥ 2h/day).

To examine the odds of bullying victimization (Odds Ratio [OR] and 95% confidence interval) in fit but overweight/obesity youths compared to unfit and overweight/obesity peers, we used multinomial logistic regression. The first model was not adjusted. The second model was adjusted for age, pubertal status, and excessive television use (≥ 2h/day). We used SPSS V. 21.0 software for Windows (SPSS, Chicago, IL, USA). Statistical significance was set at p < .05.