Physical activity (PA) during childhood is a key factor in long-term health. It contributes to the prevention of non-communicable diseases, increases muscle and bone strength, supports mental well-being, and improves overall quality of life (1–5).

The World Health Organization (WHO) and other prevention bodies highlight the benefits of health advice (HA) in promoting PA among patients, with exercise prescription as a relevant strategy to address sedentary behavior. They also recommend limiting screen use in children because of its association with physical inactivity and childhood obesity (6–9).

Sedentary lifestyles are linked to a wide range of health problems, including higher mortality, cardiovascular disease, obesity, hypertension, osteoporosis, and some cancers. Establishing global, evidence-based recommendations on physical activity for children and adolescents—adapted to individual capacities—is essential (4, 6–12). However, few studies have demonstrated, with sufficient methodological quality, the benefits of interventions aimed at increasing physical activity and reducing screen time in this population (13, 14).

In 2020, the World Health Organization (WHO) called for the integration of physical activity promotion and healthy diet counseling into routine primary care. In its guidelines, it recommends that children and adolescents aged 5–17 engage in at least 60 min of moderate- to high-intensity physical activity each day while limiting recreational screen time (8, 9). However, despite these clear recommendations, adherence remains low. Most children and adolescents still fail to meet these targets, showing low levels of physical activity and excessive screen exposure from the earliest stages of life (15).

These behaviors tend to cluster early, shaping lifestyle patterns that often persist over time (9, 16). Importantly, such early patterns are strongly influenced by the child's immediate social environment, particularly parental modeling, family routines, and opportunities for activity at home, school, and in the neighborhood (9, 16). Supporting this view, recent evidence from Spanish preschoolers shows that exceeding screen-time recommendations is associated with poorer health-related quality of life, whereas meeting physical-activity guidelines improves well-being (4).

The Spanish Association of Pediatrics (AEP) echoes this guidance, advising children in this age group to include both aerobic activity and muscle- and bone-strengthening exercises at least three times per week (17). Other national bodies, such as Previnfad, recommend introducing these habits during standard health check-ups from the age of two (10, 18). Similarly, the AEP suggests limiting daily screen use in children to under two hours and replacing sedentary time with active play or other physical routines (7, 10, 17–21).

International experiences have shown that exercise prescriptions can be effectively implemented in primary care. New Zealand's Green Prescription program—one of the longest-running national initiatives—enables healthcare providers to prescribe physical activity with individualized follow-up. Long-term evaluations have reported sustained increases in activity levels, better mental well-being, and improved quality of life up to three years after participation (22–25). These results highlight the potential of structured, follow-up–based prescriptions to promote lasting behavioral change in adults.

Recent meta-analytic evidence confirms that health professional–led interventions effectively increase physical activity in adults, reinforcing the rationale for adapting this approach to pediatric care (26).

Healthcare professionals play a central role in helping families adopt active lifestyles, particularly by engaging parents and supporting changes in daily routines. To promote PA among children, two strategies are most frequently used in clinical settings: brief health advice (HA) and the medical exercise prescription (MEP). These approaches differ in their level of personalization, duration, intensity, and the extent of follow-up involved (12).

HA involves brief counseling based on international recommendations, aimed at motivating patients to increase PA in their daily routines. It is typically delivered within a few minutes during a standard medical visit. In contrast, MEP involves additional time to create a tailored plan that considers the child's physical condition, motivation, and social context. It also includes setting specific goals and planning structured follow-up. Ideally, MEP should be provided by a trained healthcare professional (12).

Evidence on the effectiveness of primary care interventions to promote PA in children and adolescents is still limited (5, 12, 19, 27–30). Although numerous school, family, and community programs have sought to increase children's activity levels, their effects have generally been modest and short-lived (28–30). Few studies have tested strategies that can be realistically applied in children. Therefore, this trial was designed to address that gap by comparing two feasible approaches to promote PA and reduce screen time during routine pediatric consultations.

We hypothesized that both strategies would improve PA and reduce screen time over time, and that MEP would not differ significantly from HA in this pragmatic setting.

The study was approved by the Biomedical Research Ethics Committee on January 15, 2023, and conducted in accordance with the ethical principles of the Declaration of Helsinki and current data protection regulations. Written informed consent was obtained from parents or legal guardians, and assent was requested from children aged 12 years and older.

The bivariate analysis revealed no significant differences between MEP and HA groups across sociodemographic, anthropometric, lifestyle, or activity-related variables (Table 1). The randomization produced two well-balanced groups, reducing baseline confounding.

Table 2 shows the fixed effect estimates for the comparison between MEP and HA groups, adjusted for time. No significant differences were observed for any of the outcomes assessed, including weekly PA time, number of PA days, PA intensity, PA classification, or daily screen time. The two groups followed comparable trajectories throughout the study period.

Figure 2 shows the time-course evolution of the primary outcomes—PA time, PA days per week, PA intensity, and screen time—through marginal predicted means and probabilities for each group at baseline, 3 months, and 12 months.

Both MEP and HA groups showed significant increases in PA time and PA days per week at 3 and 12 months compared to baseline, with no significant difference between the two follow-up points. PA intensity also increased significantly over time in both groups. For screen time, a significant reduction was observed only between baseline and 12 months, while no relevant change occurred at 3 months. Bonferroni correction was applied to account for multiple comparisons.

This trial confirms that both HA and MEP effectively increased weekly physical activity in children. Beyond the rise in duration and frequency, more participants achieved the active classification threshold over time. We also found an inverse association between physical activity and screen time: children who spent more time in front of screens tended to be less active. This pattern, confirmed in multivariate analysis, suggests that reducing screen time may help promote healthier routines. Other studies have described this link, but when interventions took place in schools or homes, their impact was often modest (27, 28, 33–36). Most available evidence on school and community-based interventions—whether from trials or reviews—has shown some effect, but overall impact remains limited (30, 37–40).

In primary care, most studies have been rated as moderate to low quality in systematic reviews (26, 28, 29). Still, our findings align with prospective trials showing that exercise prescriptions can increase physical activity in children (5, 14). Compared to Ford's four-week follow-up, our 12-month design adds value in terms of long-term outcomes (14). Ortega-Sanchez et al. also reported 12-month data, but their multicenter approach and focus on older adolescents introduced variability (5). Our single-center design, with all sessions conducted by three trained pediatricians under a standardized protocol, ensured procedural consistency and strengthened internal validity.

Satisfaction levels were similar in both groups, suggesting that families responded positively regardless of the format or duration of the recommendation. This acceptance reinforces the practical value of integrating physical activity advice into routine pediatric care.

These findings support the implementation of physical activity advice in routine primary care. Both HA and MEP increased PA levels and sustained these improvements over time. Given this consistency, setting minimum standards for their delivery seems both feasible and necessary.

In practice, limited consultation time and doubts about the effectiveness of current recommendations often lead to inconsistent use. Offering clear, structured guidance may help overcome this barrier and integrate PA promotion into daily clinical work (25).

A short message delivered in just 2 min was enough to improve physical activity and reduce screen time over time. This effect likely reflects the trust many families place in their pediatrician or family doctor—a figure often seen as close, credible, and worth listening to. This effect may be mediated by family engagement, including parental support, shared routines at home, and the feasibility of incorporating physical activity into the child's daily environment. In primary care, this relationship may be key to sustained behavior change and long-term adherence.

MEP also maintained physical activity improvements over time. However, as it requires more time and involvement than HA, its use may be less efficient in routine consultations. Even so, its potential remains valuable, especially for children who require closer follow-up or additional motivation to maintain healthy habits. Delivered twice a year, MEP could reinforce recommendations, offer structure to unresponsive patients, and support those needing continued guidance. Exploring this approach through new trials would help define its role within broader primary care strategies against sedentary lifestyles and pediatric obesity.

Physical activity during school hours was not included in the analysis because of the wide variability among schools and programs. In some cases, physical education lessons focused mainly on theory or low intensity tasks, which could make comparisons between participants less reliable.

Another methodological consideration relates to the assessment of PA. Reported activities were not converted into metabolic equivalent tasks (METs), as the primary aim of the study was to evaluate changes in physical activity patterns over time rather than to estimate precise energy expenditure. This approach is consistent with the pragmatic design of the trial and its implementation in routine pediatric primary care.

Although more comprehensive, child-specific questionnaires are available and may provide a more detailed characterization of PA behaviors, their length and complexity can limit feasibility in busy clinical settings. We therefore used a brief adapted version of the IPAQ-A, which allowed repeated assessment over time with minimal burden in routine pediatric primary care.

Beyond this methodological aspect, several contextual limitations should also be acknowledged. Families who attend routine pediatric visits may differ from those who do not, which could influence the generalizability of the findings. Families living in disadvantaged areas often face barriers to accessing healthcare, transportation, or safe spaces for physical activity (25). Similar trends have been described in other countries, where families with fewer resources participate less in preventive and health promotion programs (40, 41). Yet these children may also benefit from brief counseling or an exercise prescription. Strengthening collaboration between healthcare teams, schools, and community organizations could help reduce these gaps and extend the benefits of brief interventions to more vulnerable families (42).

A key limitation of this study lies in its single-center design. Nonetheless, the intervention is easily replicable, and future multicenter trials could enhance heterogeneity and improve external validity. This study may serve as a starting point for developing standardized protocols and national guidelines for physical activity counseling and prescription in pediatric primary care.

Another limitation involves follow-up data collection, which relied on telephone interviews at 3 and 12 months. This method may introduce recall bias. In addition, self-reported data from children and parents could have introduced social desirability bias, possibly leading to an overestimation of physical activity or underestimation of screen time. However, using the same blinded investigator throughout follow-up helped minimize this effect and maintain internal validity.

Objective measures of physical activity, such as accelerometers or pedometers, were not used, which could have provided more precise estimates of activity levels. Additionally, objectifiable variables such as blood pressure or daily steps taken could have been measured, although this would have required electronic devices and much more stringent monitoring. Nevertheless, current evidence on the use of technology to monitor PA in children and adolescents remains insufficient (43–45).

This trial is among the few randomized controlled studies on physical activity and screen time in pediatric primary care. Its design captured both short- and long-term outcomes: improvements observed at 3 months persisted at 12 months. Contrary to initial expectations, PA levels did not decline over time, but remained above baseline. Our findings support the call by Sallis et al. for integrating evidence-based strategies into clinical and community settings to close the gap between knowledge and practice (46).

The sample (n = 130) included children with varied anthropometric and sociodemographic profiles, reflecting the diversity of the general pediatric population and supporting the external validity of our findings. Moreover, classifying physical activity by time and intensity (>250 vs. <250 effective minutes per week) allowed us to capture meaningful changes in activity levels throughout the study.

Our findings suggest that even brief counseling by a pediatrician—lasting just 2 min—can lead to sustained improvements in physical activity and screen time. In our context, standard health advice was as effective as a medical exercise prescription and represents a practical, low-cost approach to support healthier routines in children during routine primary care visits.

These results underscore the role of primary care professionals in shaping pediatric health through concise, well-delivered interventions. Taken together, these findings highlight the opportunity for pediatricians to integrate structured physical activity counseling into everyday consultations as a practical tool for sustained behavior change and health promotion.

Promoting healthier habits in pediatric care does not require complex strategies: a few minutes of clear, structured counseling during routine visits can foster lasting behavior change and help reduce sedentary time; it happens right where it matters most—the pediatric visit, a unique opportunity to offer trusted, evidence-based advice and support healthier routines in children. Future research should explore how to extend these benefits to other primary care settings and adapt interventions for children with greater needs.