Testing the Youth Physical Activity Promotion Model (YPAP) in Brazilian Adolescents

Minutes per day spent in sedentary, light, moderate, and vigorous intensity, measured using ActiGraph GT3X accelerometers and classified according to Evenson cut-points.

Total body mass will be measured using a digital electronic scale Filizola (model ID 1500; capacity: 150 kg; accuracy: 100 g). Measurements will be recorded in kilograms (kg).

Standing height will be measured using a vertical stadiometer Sanny (model ES2020; millimetric scale; range up to 2.20 m), with the participant standing barefoot in the orthostatic position and the head aligned in the Frankfurt plane. Values will be recorded in centimeters (cm).

Body Mass Index (BMI) will be calculated using measured total body mass and standing height, following World Health Organization (WHO) criteria (2007). Participants will be classified according to age- and sex-specific BMI nutritional status categories. Values will be expressed in kg/m².

Waist circumference will be measured using a metal measuring tape. Values will be recorded in centimeters (cm).

The waist-to-height ratio will be calculated using measured waist circumference and standing height.

Body fat percentage will be assessed by Dual-Energy X-ray Absorptiometry (DXA) using a Lunar scanner from GE Healthcare. The device will be calibrated according to manufacturer guidelines. Participants will remain in the supine position, motionless, with upper and lower limbs aligned. Scans will be performed in high resolution and analyzed by the same trained technician.

Cardiorespiratory fitness will be assessed using the Yo-Yo Intermittent Recovery Test Level 1 adapted for children (YoYo IR1C). The protocol consists of repeated 16-meter shuttle runs interspersed with a 4-meter active recovery zone and 10-second rest periods. Running pace is controlled by audio cues from a dedicated application, with progressive speed increments until voluntary exhaustion. Maximum heart rate (HRmax) will be recorded using a heart rate sensor Polar Electro (model H10). Test termination will occur when the participant fails to reach the designated line twice consecutively or demonstrates significant fatigue. Results will be used to estimate maximal oxygen uptake (VO2max) and HRmax.

Motor competence will be assessed using the Körperkoordinationstest für Kinder (KTK), developed by Klaus Kiphard and Friedhelm Schilling. The battery consists of four subtests evaluating distinct components of motor coordination:

(1) dynamic balance through walking on beams of different widths; (2) speed and rhythm through two-foot lateral jumps performed for 15 seconds; (3) strength and motor control through single-leg jumps over progressively higher foam obstacles; and (4) lateral agility using two moving platforms over a fixed 20-second interval. Raw scores from each subtest will be converted into age- and sex-adjusted standardized scores and summed to generate a global motor index. All assessments will be conducted by trained evaluators to ensure procedural standardization and data reliability.

Cognitive function will be assessed using the three-disk Tower of Hanoi task. The test consists of a base with three pegs and three disks of different sizes and colors, initially stacked on the left peg with the smallest disk on top.

Participants must transfer the entire tower to the right peg while following two rules: only one disk may be moved at a time, and a larger disk may not be placed on top of a smaller one. The entire procedure will be video recorded to allow quantification of the total number of moves and the total time required to complete the task.

Perceived health status will be assessed through a single question using a 5-point Likert scale. Adolescents will classify their health as: (1) poor, (2) fair, (3) good, (4) very good, or (5) excellent. Higher scores indicate better perceived health.

Motivation for physical activity will be assessed using the Behavioral Regulation in Exercise Questionnaire (BREQ-2), adapted for Portuguese. The questionnaire consists of items distributed across subscales evaluating amotivation, external regulation, introjected regulation, identified regulation, integrated regulation, and intrinsic motivation. Participants will respond on a 5-point Likert scale ranging from "Not true for me" to "Very true for me." Scores will be calculated for each regulatory style to characterize participants' motivational profile toward physical activity.

Self-perception will be assessed using the Escala de Autopercepção de Harter para Adolescentes (EAPH-A), the Brazilian adaptation of the Self-Perception Profile for Adolescents (SPPA). The instrument comprises five specific domains of self-perception-school competence, social competence, athletic competence, physical appearance, and behavioral conduct-along with a global self-esteem score. The scale uses a structured alternative-response format with four response levels, in which participants first choose which of two hypothetical descriptions best resembles them and then indicate whether the statement is "very true for me" or "somewhat true for me." This response structure reduces social desirability bias and enhances self-reflection.

Social support for physical activity will be assessed using a 12-item scale that captures different forms of support provided by parents and friends. Considering a typical week, adolescents will report the frequency (never, rarely, often, always) with which parents and friends encourage them, practice together, watch, comment, discuss, invite them to be active, or provide/arrange transportation to physical activity locations. Higher scores reflect greater perceived social support for engaging in physical activity.

Perception of the environment for physical activity will be assessed using a scale composed of three domains. An overall score will be created by summing the items within each domain. Scores will then be divided into tertiles, with higher tertiles indicating more favorable perceptions of the environment for engaging in physical activity.

Attitude toward physical activity will be assessed using a five-item semantic differential scale. Two items evaluate affective/emotional aspects and three evaluate instrumental aspects. Participants will rate bipolar adjective pairs (safe-unsafe, fun-boring, important-unimportant, healthy-harmful, good-bad) on a 4-point scale. Higher scores indicate a more positive attitude toward physical activity

Self-efficacy for physical activity will be measured using a 12-item scale assessing confidence to engage in physical activity when facing commonly reported barriers. Items are rated on a 4-point Likert scale ranging from 1 ("strongly disagree") to 4 ("strongly agree"). Higher scores indicate greater self-efficacy to be physically active.

Examination of whether networks of YPAP correlates differ between boys and girls.

Analysis of networks across socioeconomic categories to determine whether demographic moderators influence YPAP pathways. Socioeconomic status will be classified using the Critério Brasil, developed by the Associação Brasileira de Empresas de Pesquisa (ABEP). The instrument assesses household assets, access to services, and the educational level of the head of household, categorizing participants into economic strata ranging from A to E.

Maturational status will be estimated using the Peak Height Velocity (PHV) prediction equation (Maturity Offset), which uses anthropometric variables including standing height, body mass, sitting height, leg length, chronological age, and sex. The method provides an estimate, in years, of the time before or after the individual's PHV.