Associations of Cumulative Wrist Accelerometer‐Derived Physical Activity and Proxies of Sedentary Behavior With Early Cardiac Remodeling in Healthy Adolescents

Background Physical inactivity and sedentary behavior are associated with adverse cardiac remodeling in adults, but evidence in adolescence remains limited. This study examined associations of cumulative accelerometer‐derived physical activity and proxies of sedentary behavior during adolescence with early subclinical cardiac features assessed by cardiovascular magnetic resonance. Methods A total of 111 adolescents (55.9% girls) wore a wrist‐worn triaxial accelerometer at ages 12, 14, and 16 years to measure physical activity and sedentary behavior proxies. A 3‐Tesla cardiovascular magnetic resonance scan was performed at final follow‐up to assess cardiac structure and function. Multivariable linear regression models examined associations between cumulative physical activity and sedentary behavior proxies and cardiovascular magnetic resonance–derived metrics. Results Daily step counts were positively associated with indexed end‐diastolic and end‐systolic volumes of the left ventricle (adjusted β per 1000 steps/d, 0.90 mL/m 2.7 [95% CI, 0.42–1.37]; 0.36 mL/m 2.7 [95% CI, 0.10–0.63], respectively) and the right ventricle (adjusted β per 1000 steps/d, 1.03 mL/m 2.7 [95% CI, 0.44–1.61]; 0.44 mL/m 2.7 [95% CI, 0.05–0.82], respectively), and with reduced right ventricular longitudinal strain (adjusted β per 1000 steps/d, 0.53% [95% CI, 0.16–0.91]). Greater time spent in sedentary bouts and a higher number of sedentary bouts were associated with increased left atrial active emptying fraction (adjusted β per 100 min/d, 8.21% [95% CI, 0.09–16.34]; adjusted β per 1 bout/d, 1.76% [95% CI, 0.17–3.35], respectively). Conclusions Physical inactivity and sedentary behavior proxies during adolescence were independently associated with early markers of ventricular and atrial remodeling. These findings highlight early cardiac adaptations related to lifestyle behaviors and underscore the importance of promoting active lifestyles from a young age.