# Phase-specific changes in anthropometric and physical fitness outcomes among Chinese upper-secondary students before, during, and after the COVID-19 pandemic: the moderating role of educational track

## TL;DR

The pandemic affected physical fitness in Chinese high school students differently depending on their education track and fitness domain.

## Contribution

This study reveals how pandemic disruptions differentially impacted physical fitness domains across educational tracks.

## Key findings

- Anthropometric indicators increased overall, with vocational students showing greater sensitivity to pandemic disruptions.
- Endurance and flexibility showed significant phase-dependent changes, including delayed differentiation and reduced disparities during the pandemic.
- Explosive power had small phase effects but large persistent differences between educational tracks.

## Abstract

The COVID-19 pandemic substantially disrupted school-based physical activity worldwide; however, how such disruptions differentially affect distinct domains of adolescent physical fitness across educational tracks remains insufficiently understood.

Using large-scale school-based fitness surveillance data collected before, during, and after the COVID-19 pandemic, we examined phase-specific changes in anthropometric indicators and physical fitness outcomes among Chinese upper secondary school students aged 15–18 years. Students were stratified by educational track (general academic vs. vocational education), and outcomes spanning explosive power, endurance, flexibility, and anthropometric measures were analyzed to assess phase effects and phase-by-school-type interactions.

Statistically robust phase-related variations and phase-by-school-type interactions were observed across all fitness domains, with highly domain-specific responses. Anthropometric indicators followed overall upward trajectories consistent with long-term secular patterns, although students in vocational education exhibited greater temporal sensitivity to pandemic-related disruption. Explosive power showed relatively small phase effects but large and persistent between-school differences, whereas endurance and flexibility displayed pronounced phase-dependent changes, including delayed differentiation in endurance performance and a temporary narrowing of between-school disparities in flexibility during the pandemic.

These findings demonstrate that large-scale societal disruptions, such as the COVID-19 pandemic, can alter adolescent physical fitness in domain- and context-specific ways, reshaping developmental patterns and inequality dynamics rather than uniformly depressing fitness levels. The educational track plays a critical role in moderating vulnerability and recovery across fitness domains, underscoring the need for fitness monitoring and intervention strategies that are sensitive to both domain-specific characteristics and the educational context.