The results from this study report varying patterns of association between muscle-building exercise and concurrent substance use behaviors among U.S. adolescents. While there were significant findings among the overall sample, stratified analyses emphasized that the relationship between muscle-building exercise and patterns of concurrent substance use were particularly driven males. Specifically, high engagement (6–7 days) in muscle-building exercise was associated with any single use, any dual use, and over two-fold greater relative risk of triple use, compared to no use. Similarly, moderate engagement (3–5 days) in muscle-building exercise was associated with any single use and any dual use, compared to no use. Taken together, these findings contrast with prior research in the U.S., which has shown that male and female dual users of e-cigarettes and cigarettes have a lower likelihood of muscle-building exercise [8]. However, these findings align with research in Canada showing associations between muscle-building exercise and vaping among males [35].

The findings from this study underscore that muscle-building exercise, unlike other forms of physical activity [8] and sports participation [11], may not be protective of substance use behaviors, including vaping, cigarette use, and cannabis use, particularly among males. In fact, muscle-building exercise was associated with a higher risk of any single use and any dual use among males even at moderate participation rates, which generally align with recommended guidance from the American Academy of Pediatrics (i.e., 2–3 non-consecutive days per week) [27]. However, it is concerning that males who reported high engagement in muscle-building exercise, that is engaged 6–7 days per week, which is thus outside the recommended guidance, had greater risk of all substance use patterns, underscoring a potentially problematic clustering of behaviors as outlined by problem behavior theory [20,21]. These findings add the list of potential risk factors of substance use behaviors among adolescents [2].

Prior research has shown that adolescent use of vaping and cigarettes are mechanisms for appetite control or weight loss, and connected with weight concerns [36,37]. Thus, given the sociocultural prominence of the muscular and lean body ideal among males [16,38], vaping, cigarette use, and cannabis use may be adjunct behaviors to muscle-building exercise intended to achieve this body ideal. Additionally, adolescent males may use muscle-building exercise and substance use behaviors to display their adherence to masculine gender norms, such as strength, toughness, and risk-taking behavior [22]. Indeed, future research is needed to explicate the mechanisms (i.e., sensation seeking, peer influence, attempts to adhere to masculine norms) underlying the associations found in this study, as well as whether these substance use behaviors are associated with other forms of muscularity-oriented behaviors (e.g., protein overconsumption, muscle-building supplement and substance use). Indeed, muscle-building exercise may also be a proxy for other behaviors (i.e., energy drink use), which have been shown to be associated with vaping, cigarette use, and cannabis use [39,40].

Strengths of this study include a large, nationally representative sample of U.S. adolescents. Despite these strengths, several limitations should be noted. The YRBS data are cross-sectional, which limits directional associative inference. Additionally, there were differing time frames assessed by the vaping, cigarette use, and cannabis use measures, as well as the muscle-building exercise measure (i.e., within the past 30 days versus within the past 7 days). Thus, there may be gaps between the substance use and engagement in this form of exercise, leading to an attenuation in the current associations. Future research should utilize a prospective cohort study to assess and identify how the associations occur and evolve over time. All items were based on retrospective self-report, which may increase the risk of reporting and recall bias. Additionally, given small cell sizes, we were unable to investigate whether muscle-building exercise was associated with individual, mutually exclusive substance use categories (i.e., vaping only, cigarette use only, etc.) in adjusted analyses, which is a line of inquiry for future research. The YRBS is conducted only in the United States, which limits external validity to other populations (i.e., countries). Lastly, there is the potential for unmeasured confounders, such as sensation seeking and peer influence, that may have influenced the findings.

Considering these limitations, the findings from this study have important implications. Adolescents, particularly males, should seek professional instruction and oversight when participating in muscle-building exercise to ensure proper and safe engagement, potentially reducing other problematic behaviors (i.e., concurrent substance use). Education and training for professionals, including coaches and physical trainers, are needed to bring awareness of the potential risks of concurrent substance use associated with muscle-building exercise. Coaches and physical trainers may also require training on proper intervention strategies, such as assessment and referral processes, to aid adolescents who participate in moderate and high levels of muscle-building exercise and are susceptible to concurrent substance use. Despite potential benefits of muscle-building exercise, healthcare providers should be aware of the unique relationship between this form of exercise and substance use behaviors when treating adolescent males, particularly when engagement in muscle-building exercise is moderate or high. Public health professionals should consider including information on concurrent substance use into physical activity education for adolescents.