SDT-Based Intervention for Exercise Motivation in Female Students

Measured using the Behavioral Regulation in Exercise Questionnaire-3 (BREQ-3). The Relative Autonomy Index (RAI) was calculated by weighting the six regulation subscales (Amotivation -3, External -2, Introjected -1, Identified +1, Integrated +2, Intrinsic +3) and summing the weighted mean scores.

Higher (positive) scores indicate more autonomous forms of motivation, whereas lower (negative) scores reflect more controlled forms of regulation.

Because the RAI is computed from mean subscale scores, its theoretical limits depend on the 0-4 response scale and the weighting structure; for typical BREQ-3 scoring, values fall approximately between -12 and +12.

Measured using the Basic Psychological Need Satisfaction and Frustration Scale (BPNSFS).

This instrument assesses both satisfaction and frustration of the three basic psychological needs, autonomy, competence, and relatedness, within the framework of Self-Determination Theory.

Items are rated on a 5-point Likert scale ranging from 1 (not at all true) to 5 (completely true). Subscale scores were computed as the mean of the corresponding items, resulting in scores ranging from 1 to 5 for each dimension.

Higher scores on the satisfaction subscales indicate greater need satisfaction, whereas higher scores on the frustration subscales reflect greater need frustration.

The scale demonstrates a six-factor structure, comprising autonomy, competence, and relatedness satisfaction and frustration dimensions.

Physical activity was assessed using the International Physical Activity Questionnaire-Short Form (IPAQ-SF). This instrument evaluates the frequency (days per week) and duration (minutes per day) of walking, moderate-intensity, and vigorous-intensity physical activity performed during the previous 7 days.

Total physical activity was expressed in metabolic equivalent minutes per week (MET-min/week), following the official IPAQ scoring protocol. MET-min/week values were obtained by multiplying the assigned MET coefficient of each activity category by the corresponding minutes and days: walking (3.3 METs), moderate-intensity activity (4.0 METs), and vigorous-intensity activity (8.0 METs), and summing the results across all categories. Total scores range from 0 MET-min/week to theoretically unbounded values, depending on the volume of physical activity accumulated. Higher scores indicate higher levels of physical activity.

Body appreciation was assessed using the Body Appreciation Scale-2 (BAS-2), a 10-item measure of positive body image. Items are rated on a 5-point Likert scale ranging from 1 (never) to 5 (always). Scores were computed as the mean of all items, resulting in a total score ranging from 1 to 5. Higher scores indicate greater body appreciation, reflecting acceptance, respect, and positive attitudes toward one's body. The BAS-2 has demonstrated strong psychometric properties and a robust unidimensional factor structure across different populations.

Disordered eating attitudes were assessed using the Eating Attitudes Test-26 (EAT-26). The instrument consists of 26 items assessing symptoms and concerns characteristic of eating disorders. Items are scored on a 6-point Likert scale, which is recoded into a 4-point scale ranging from 0 to 3 (Always = 3, Usually = 2, Often = 1, and Sometimes/Rarely/Never = 0), following standard scoring procedures. Total scores are obtained by summing all items, resulting in a range from 0 to 78. Higher scores indicate greater eating-related concerns and a higher risk of disordered eating. A total score of 20 or higher is commonly used as a screening cut-off indicating elevated risk and the potential need for further clinical evaluation.