Abstract
BACKGROUND: Personal trainers play a crucial role in the health promotion system by guiding the public in scientific exercise. This study aims to examine how the removal of mandatory occupational certification reshapes the professional structure, labor relations, and health promotion functions of personal trainers within a market-driven fitness industry. METHODS: This study adopts a tripartite perspective encompassing labor, capital, and consumers, and uses participant observation alongside semi-structured interviews with 42 participants to explore how, following the removal of mandatory occupational certification for personal trainers at the policy level, market mechanisms reshape labor relations and professional structures among personal trainers through interactions between consumers and gym operators, and to analyze the impact of this transformation on health promotion practices. RESULTS: The findings indicate that the national policy of abolishing mandatory occupational certification for personal trainers shifted control of the fitness industry back to the market. In this context, consumers’ demand for low-professional but highly emotional fitness guidance increasingly shapes the work content of personal trainers. Gym operators, in turn, translate these consumer demands into specific work requirements for trainers, effectively restructuring the labor relations between commercial fitness venues and personal trainers in practice. In this process, the erosion of trainers’ professional expertise not only undermines the scientific rigor and effectiveness of fitness instruction but also weakens the social foundation of health promotion. CONCLUSIONS: This study provides a new perspective for understanding the structural challenges faced by health promotion under market-oriented conditions and offers important empirical evidence to inform policy regulation of the fitness industry. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12889-026-26537-8.