Fitness status of people with axSpA : first results after implementing fitness assessments in axSpA exercise groups

Background: Public health recommendations for physical activity (PA) advise that a program of regular exercises include cardiorespiratory, muscle strength, flexibility and neuromotor exercise training at well-defined frequency, intensity and duration/repetitions, and regular evlaution over time (1). The 2018 EULAR recommendations for PA (2) state that this is also effective, feasible and safe for people with rheumatic diseases. Therefore, the Ankylosing Spondylitis Association of Switzerland (SVMB) has started to implement assessments for all four fitness dimensions in their exercise groups (n=68). Criteria for selection of an assessment were validity and feasibility for group setting, i.e. low costs and material requirements: Chester step test (CST) (3) for cardiorespiratory fitness; adapted Core Strength Endurance test battery (CSE) (4) for muscle strength; Bath AS Metrology Index (BASMI) (5) for flexibility; Single-Leg-Stance test (SLS) (6) for balance (as proxy for neuromotor activities). For all assessments, except CSE, norm values for healthy people are available. Objectives: To assess the fitness status of people with axSpA across four volunteering pilot groups and evaluate if between-subject variables of interest are associated with fitness status. Methods: A total of 30 participants were assessed at baseline and after 6 months on all four fitness dimensions. For each dimension, a linear mixed model with random intercept was fitted to the data with the within-subject variables time and measurement condition and the between-subject variables age, disease duration, disease activity (BASDAI) and PA level (weekly Metabolic Equivalent of Task MET) as explanatory variables. Results: Of 30 patients assessed, 10 (33%) were women, mean age was 58.8 (SD 9.68) years, mean disease duration was 32.6 (SD 9.68) years, mean disease activity was 3.1. (SD 2.36) and mean PA per week was 5013 (SD 3479.77) METs. Mean estimated VO2max for cardiorespiratory fitness was 35.2 (SD 6.