Temporal trends and developmental trajectories of physical fitness among university students: a 13-year accelerated...

University represents a critical developmental stage during which physical fitness may undergo substantial changes. However, evidence regarding long-term physical fitness trajectories and cohort differences among university students remains limited, particularly in the context of the COVID-19 pandemic.

This study used annual physical fitness surveillance data collected from 2013 to 2025. Partial follow-up data from the 2012 enrollment cohort were additionally included to reconstruct developmental trajectories across university years using an accelerated longitudinal design. A total of 50,158 students contributing 143,292 observations were included. Interrupted time-series analyses were conducted to assess temporal changes in physical fitness before and after 2020. Linear mixed-effects models were used to examine developmental trajectories and compare enrollment cohorts between 2012-2019 and 2020-2025. Additional BMI-stratified analyses were performed to explore heterogeneity in trajectory patterns.

Most physical fitness indicators showed continuous improvement during 2013-2019, whereas these improvements generally became attenuated after 2020. Developmental trajectories differed significantly between enrollment cohorts. Compared with the pre-2020 (2012-2019) cohorts, the post-2020 (2020-2025) cohorts generally demonstrated higher baseline levels for several indicators but weaker developmental trajectories across academic grades. BMI-stratified analyses further revealed substantial heterogeneity in developmental trajectories across BMI groups, particularly for endurance- and strength-related indicators.

Physical fitness among university students showed substantial temporal changes between 2013 and 2025. Although the post-2020 cohorts demonstrated relatively higher baseline performance for several indicators, their subsequent developmental trajectories across university years were generally weaker than those of the pre-2020 cohorts. These findings highlight the importance of continuous physical fitness monitoring and targeted health promotion strategies tailored to different physical fitness components and BMI groups.