Physical Activity and Immunity in Pediatric Populations: A Comprehensive Review

Physical activity in childhood is a powerful, scalable determinant of immune health that complements vaccination, nutrition, and sleep in pediatric care. Regular moderate exercise enhances mucosal, innate, and adaptive immunity, while sedentary behavior and obesity promote chronic inflammation and impaired host defense. These changes reduce upper respiratory tract infections (URTIs) and improve vaccine response. Mechanistically, moderate exercise mobilizes natural killer and CD8⁺ T cells, enhances neutrophil function, and increases salivary secretory IgA, improving viral clearance without causing prolonged immunosuppression seen in adults. Children show blunted stress hormone responses and rapid immune recovery, suggesting lower immunosuppressive risk. Epidemiologic studies show each additional 1,000 daily steps reduces URTI symptoms by about 4 days, explaining a significant portion of infection variability. Higher training frequency links to fewer infections; higher screen time increases lower respiratory infections. These findings support daily movement as a core infection prevention strategy. Clinically, age-appropriate aerobic activity (~60 minutes moderate-to-vigorous daily) should be prescribed alongside vaccination and nutrition. For children with obesity or chronic illness, tailored exercise programs reduce inflammation and restore immune homeostasis. As research advances, integrating mechanistic and practical approaches will optimize “movement as immune medicine” through childhood and adolescence