Asthma is the chronic inflammation of airways in the lungs, which results in episodes of coughing, wheezing, and chest tightness often associated with reversible airflow obstruction and affected by asthma triggers (Mims, 2015). Approximately 6% of children in the United States (US) are affected by asthma (Most Recent National Asthma Data, 2022). Severe persistent childhood asthma is associated with low physical activity (PA) participation. Despite recommendations that people with asthma participate in routine PA for positive health, children and adolescents with asthma are less able to engage in PA, and up to 20% of youth with asthma report exercise limitation (Román et al., 2019; Westergren et al., 2016; Lagiou et al., 2022; Faleiro et al., 2020). Only 20.6% of US youth met national PA guidelines in 2019 and 2020, including 60 min of aerobic activity a day (CAHMI, 2022). This is concerning, as PA is shown to reduce blood pressure, psychosocial stress, and depression (Lucas and Platts-Mills, 2005; Janssen and LeBlanc, 2010). PA is likely lower for youth with asthma due to discomfort from exercise-induced bronchoconstriction, dyspnea, and wheezing (Román et al., 2019; Westergren et al., 2016). PA is also reduced among youth with asthma due to parental or caregiver perceptions of risks associated with exercise (Eisenberg et al., 2020). Specifically, physical fitness and PA participation among youth with asthma may be associated with psychosocial factors, such as parental or caregiver fear that PA may exacerbate their child's asthma symptoms (Westergren et al., 2016; Dantas et al., 2014; Williams et al., 2008). Reduced PA is additionally linked to increasing asthma severity (Strine et al., 2007), and reduced physical fitness (Campbell et al., 2013), defined as the ability to perform PA and any bodily action that expends energy, and including multiple health-related components (Campbell et al., 2013). Low physical fitness is strongly associated with present and future chronic health conditions, placing individuals at risk for cardiovascular disease and mortality due to breast and colon cancer (Campbell et al., 2013; Ross et al., 2016).

Prior work has examined the physical fitness-asthma relationship among youth, finding an inverse association between fitness and asthma severity. A meta-analysis including both children and adults with asthma found that exercise training helped manage asthma control and improved lung function (Kuder et al., 2021). Exercise interventions that improved the physical fitness of children with asthma also demonstrated reduced severity of asthma symptoms (Lu and Forno, 2020). Physical fitness also has been associated with decreased likelihood of asthma morbidity in boys, but not girls (Lu et al., 2016). Two other longitudinal studies found an inverse relationship between fitness and asthma severity for individuals from childhood to adulthood (Guldberg-Møller et al., 2014; Rasmussen et al., 2000). Despite potential benefits of fitness on reducing asthma symptoms, some youth experience exercise-induced asthma which may limit PA, therein reducing their potential for fitness attainment (Román et al., 2019; Westergren et al., 2016; Campbell et al., 2013). However, limited longitudinal research has examined asthma severity as a predictor of physical fitness among youth. Research on the asthma severity-fitness relationship over time and across sociodemographic subgroups is needed to provide a more nuanced understanding and inform tailored PA programs to support the needs of children with asthma.

The aim of this study was to evaluate the longitudinal relationship between asthma severity and one-year lagged physical fitness in New York City (NYC) public school youth enrolled in grades 4–12. We hypothesized that youth with higher asthma severity would demonstrate lower fitness over time compared to youth with lower asthma severity or youth without asthma. We further hypothesized that the asthma severity-fitness association would vary across sociodemographic factors. Findings from this study can inform programs and interventions targeting fitness promotion among youth with asthma, particularly in urban settings.