Abstract
Purpose This study explored the interrelationships between movement behaviors, compliance with 24-h recommendations, and their association with physical fitness in Portuguese youth. Methods A total of 263 Portuguese adolescents (51.3% boys), mean age 12.9 ± 1.0 years, participated in this cross-sectional study. Movement behaviors, moderate-to-vigorous physical activity (MVPA), screen time and sleep, were measured via accelerometers and self-reports. Physical fitness was assessed using the FITescola battery. Poisson regression with robust variance was used to examine interrelationships between movement behaviors. Linear regression models adjusted for age, sex, and accelerometer wear time were conducted to assess associations with fitness outcomes. Results Only 24.7% and 28.5% of participants met the MVPA and screen time recommendations, respectively, while 64.6% achieved sufficient sleep. MVPA compliance was substantially higher in boys than in girls. Meeting screen time recommendations was associated with a higher prevalence of meeting sleep recommendations (PR = 1.32; 95% CI: 1.18–1.56), whereas no significant associations were observed between MVPA and sleep. Compliance with MVPA was associated with higher aerobic fitness (B = 14.5 laps), upper-body strength (B = 2.1 push-ups), and lower-body strength (B = 10.9 cm). Meeting screen time recommendations was associated with lower body mass index (B = −1.1 kg/m 2 ). Adolescents meeting all three movement behavior recommendations showed better aerobic fitness (B = 10.7 laps), greater upper-body strength (B = 2.8 push-ups), and lower waist circumference (B = −5.0 cm). Conclusions Screen time may be a key component in the interrelationships among 24-h movement behaviors. Adolescents meeting all three movement behaviors recommendations presented more favorable fitness indicators. These findings support the relevance of an integrated 24-h movement behavior framework for promoting physical fitness in adolescents.