Factors associated with adherence to the muscle-strengthening activity guideline among adolescents

Purpose: We aimed to explore associations between guideline-concordant muscle-strengthening activity (MSA) and demographic, biological, psychosocial, and behavioral factors among Australian adolescents. Methods: We used baseline data from the ‘Resistance Training for Teens’ cluster randomized controlled trial (collected April–June 2015). Adolescents (n = 602, mean age = 14.1 ± 0.5 years, 50% female) from 16 schools in New South Wales, Australia self-reported their sex, primary language spoken at home, postal code (for socioeconomic status), resistance training (RT) self-efficacy, motivation for RT, perceived strength, moderate-to-vigorous physical activity (MVPA), screen-time, and sleep. Participants also completed tests of height, weight, cardiorespiratory and muscular fitness, flexibility, and RT skills. MSA was self-reported and participants were dichotomized as ‘meeting’ (3–7 days) or ‘not meeting’ (0–2 days) the MSA guideline. Binary logistic regression with odds ratios (OR) was used to determine associations with adolescents' MSA. Results: Analyses for each variable group explained a small-to-moderate proportion of the variance in MSA. Sex, muscular fitness, RT self-efficacy, perceived strength, and total MVPA emerged as statistically significant factors. However, only RT self-efficacy (OR = 2.48 [1.37 to 4.50]) and total MVPA (OR = 1.48 [1.22 to 1.79]) were associated with guideline-concordant MSA in the full model, which explained 52% of the variance. Conclusions: Our study adds to the limited understanding of adolescents' MSA behavior. RT self-efficacy and total MVPA were independently associated with guideline-concordant MSA among Australian adolescents. The findings have implications for the design and delivery of future interventions targeting adolescents’ MSA behavior.