Components of 24-hour movement behavior and self-reported physical fitness in Ibero-American preschoolers, children, and adolescents during the COVID-19 pandemic

Objective To evaluate the association between the component of 24-h movement behaviors (24HMB) (physical activity—PA; screen time—ST; sleep) and self-reported physical fitness in Ibero-American preschoolers, children, and adolescents during the Coronavirus Disease 2019 (COVID-19) pandemic. Methods This cross-sectional study included 1,077 participants (3–17 years old) from Spain, Brazil, and Uruguay. The components of 24HMB were classified according to the Canadian Guidelines and the World Health Organization. Physical fitness was assessed using the International Physical Fitness Scale and dichotomized into high (good/very good) versus low (very poor/poor/medium) for general fitness, cardiorespiratory fitness, muscular fitness, speed/agility, and flexibility. Associations were assessed using generalized linear mixed models, reporting odds ratios (OR) and 95% confidence intervals (CI), adjusted for sex, age, and breadwinners’ educational level, with country as a random effect. Analyses were conducted in SPSS 25.0. Results In preschoolers, not meeting PA recommendations was associated with low general physical fitness (OR = 3.44; 95% CI: 1.20–9.88). In children, not meeting PA recommendations was associated with low general physical fitness (OR = 2.13; 95% CI: 1.29–3.53), muscular fitness (OR = 1.87; 95% CI: 1.12–3.12), and speed/agility (OR = 2.09; 95% CI: 1.25–3.51). Not meeting sleep recommendations was associated with muscular fitness only in partially adjusted models (OR = 1.91; 95% CI: 1.11–3.18). In adolescents, not meeting PA recommendations was associated with low general physical fitness (OR = 3.53; 95% CI: 1.69–7.41), cardiorespiratory fitness (OR = 3.52; 95% CI: 1.41–7.26), speed/agility (OR = 3.36; 95% CI: 1.54–7.32), and flexibility (OR = 2.94; 95% CI: 1.53–5.64). Not meeting ST recommendations was associated with lower odds of high cardiorespiratory fitness (OR = 0.35; 95% CI: 0.12–0.96). In age-stratified analyses, meeting fewer movement behavior recommendations was associated with poorer physical fitness among children and adolescents, although pooled analyses showed no significant associations. Conclusion Physical activity was the component of the 24HMB model most consistently associated with better self-reported physical fitness among Ibero-American youth, with stronger associations in older age groups. Sleep and ST showed less consistent associations, and low adherence to the recommendations was associated with poorer outcomes. These findings reinforce the importance of integrated 24-h strategies with a focus on physical activity.