Pragmatic muscle-strengthening programme in university employees: study protocol for a pre–post effectiveness trial in a real-world workplace setting

Background Insufficient physical activity and sedentary behaviour are associated with increased cardiometabolic and all-cause mortality risk. Although international guidelines recommend performing muscle-strengthening activities involving major muscle groups at least two days per week, the proportion of adults meeting these recommendations is very low, particularly in Europe. In workplace settings, exercise programmes have shown modest and heterogeneous benefits on cardiometabolic health and wellbeing, but studies focusing specifically on muscle-strengthening exercise and designed with a pragmatic approach remain scarce. Objective To describe the design and methods of a pragmatic pre–post study evaluating the effectiveness of a 12-week supervised muscle-strengthening training programme, integrated into a university-based exercise-for-health service, on body composition, cardiometabolic health, physical fitness and other health indicators in university employees. Methods This is a pragmatic, single-group, pre–post intervention study. The programme is offered as a free service to employees (academic and research staff and administrative and service staff) at King Juan Carlos University, who volunteer to participate. The intervention consists of two supervised muscle-strengthening sessions per week for 12 weeks, conducted in the university fitness facility, focusing on major muscle groups with individualised progression. The primary outcome is change in total fat mass (kg), measured by multifrequency bioelectrical impedance analysis. Secondary outcomes include other body composition indicators (fat mass percentage, fat-free mass, waist and hip circumferences), resting blood pressure, functional capacity (2-Minute Step Test and 6-Minute Walk Test), handgrip and lower limb strength, levels of physical activity and muscle-strengthening exercise (RAPA, short IPAQ, REGICOR short questionnaire, wrist-worn accelerometry), self-perceived fitness (IFIS), health-related quality of life (SF-36), and dietary habits (CFCGA). The sample size calculation was based on detecting a 1-kg decrease in total fat mass, considered clinically relevant, with a conservative standard deviation of 3.5 kg, a two-sided alpha of 0.05 and 90% power, requiring approximately 129 participants. Allowing for up to 20–25% attrition, the target sample size was set at 160 participants. Discussion This protocol describes a muscle-strengthening programme developed and implemented as a health service in a real-world university workplace setting. The study uses a pragmatic pre–post design without a concurrent control group, which limits causal inference but maximises external validity and applicability to other workplaces. Focusing on total fat mass as the primary outcome and combining objective and self-reported measures will allow a detailed characterisation of health changes associated with participation and adherence to the programme.