Longitudinal Outcomes of the COVID-19 Pandemic on Youth Physical Fitness.

Importance: The COVID-19 pandemic led to a decline in physical activity levels among youths, which could have a negative impact on their fitness. Objective: To examine longitudinal changes in cardiorespiratory fitness (CRF) and musculoskeletal fitness (MSF) among students at schools participating in a school-based physical activity program during fall 2019 through spring 2023. Design, Setting, and Participants: This longitudinal cohort study included US schools reporting CRF and MSF data at least once during the pandemic (fall 2020 to fall 2021) and at least 1 additional time before or after. In a subset of schools for which learning modality data was available, the association between in-person vs remote or hybrid environments and fitness was examined. Exposures: COVID-19 pandemic status and school learning modality. Main Outcomes and Measures: CRF and MSF results were entered into the fitness assessment software by school staff. Estimated maximal oxygen consumption (milliliters per kilogram per minute) was categorized into 1 of 3 groups (healthy fitness zone [HFZ], needs improvement, and health risk), whereas MSF was categorized into 2 groups (HFZ or needs improvement) according to age-specific and sex-specific criterion-referenced standards. Mixed-effects logistic regression was used to estimate adjusted HFZ odds ratios (ORs) for CRF (vs needs improvement and health risk) and MSF (vs needs improvement). Results: The sample consisted of 264 schools and 152 094 students (77 818 boys [51.2%]) across 21 states. Compared with the prepandemic and postpandemic periods, students were significantly less likely to achieve the CRF HFZ (OR, 0.72; 95% CI, 0.66-0.78) and MSF HFZ (OR, 0.82; 95% CI, 0.75-0.89) during the pandemic. Adjusted CRF was 0.55 mL/kg/minute lower in girls (95% CI, 0.36-0.74 mL/kg/minute) and 0.86 mL/kg/minute (95% CI, 0.63-1.10 mL/kg/minute) lower in boys during the pandemic (P < .001). Among students at 116 schools with available learning modality by week, those in remote or hybrid environments for 15 to 22 weeks were significantly more likely to achieve the CRF HFZ compared with those who were hybrid or remote for shorter periods of time (15-22 vs 0-4 weeks, OR, 1.26; 95% CI, 1.06-1.50; 15-22 vs 5-14 weeks, OR, 1.34; 95% CI, 1.10-1.63). Conclusions and Relevance: In this cohort study of schools, a COVID-19-related decline in youth physical fitness was observed. Compared with prepandemic and postpandemic periods, CRF and MSF HFZ achievement were significantly lower during the pandemic, but the reduction did not appear to be associated with extended remote or hybrid environments.