The Brazilian Portuguese Version of the Behavioral Regulation in Exercise Questionnaire 3 (BREQ-3) Is Reliable and Valid for Assessing Motivational Regulations and Self-Determination in Exercise Among Adults Aged 50 Years or Older: A Methodological S

The study aimed to investigate the reliability, construct, and discriminant validity of the Behavioral Regulation in Exercise Questionnaire 3 (BREQ-3) for evaluating motivational regulations and self-determination for exercise in Brazilian adults aged 50 years or older. The study assessed motivation for exercise, peripheral muscle strength, physical performance, functional capacity, cardiovascular fitness, and frailty phenotype. Two raters independently applied the BREQ-3. The reliability was evaluated using internal consistency, test-retest reliability, and agreement. Construct validity was tested with Spearman's correlation coefficient and discriminant validity with the Kruskal-Wallis test. Eighty individuals participated in the reliability study, and 136 participated in the validation study. Motivational regulation and Self-Determination Index (SDI) internal consistency ranged from 0.55 to 0.82. Test-retest reliability ranged from 0.77 (95% CI 0.64-0.85) to 0.91 (95% CI 0.85-0.94), and inter-rater ranged from 0.80 (95% CI 0.68-0.87) to 0.92 (95% CI 0.88-0.95), except for amotivation, which had poor inter-rater and test-retest reliability. Additionally, moderate to weak correlations between various types of motivation and physical function tests were found (<i>p</i> < 0.05). Frail and pre-frail participants had lower SDI, integrated, and intrinsic motivation regulation than non-frail individuals (<i>p</i> < 0.05). This study confirmed the reliability, construct, and discriminative validity of the Brazilian Portuguese version of the BREQ-3 for evaluating motivational regulations and self-determination for exercise in older adults.