Physical Fitness in Patients With Ankylosing Spondylitis: Comparison With Population Controls

Background. Although flexibility traditionally has been the main focus for phys-ical therapy in patients with ankylosing spondylitis (AS), there is now evidence for an increased risk of cardiovascular diseases (CVDs) in this group. Objective. The purposes of this study were: (1) to compare physical fitness (cardiorespiratory fitness, muscular capacity, flexibility, and balance) in patients with AS and controls and (2) to explore associations between physical fitness and disease activity in the patient group. Design. This was a cross-sectional study. Methods. The physical fitness variables were cardiorespiratory fitness (treadmill test for estimation of peak oxygen uptake [V̇O2peak]), muscular capacity (push-ups test), balance (30-second single-leg stand and walking in a figure-of-eight pattern), and flexibility (Bath Ankylosing Spondylitis Metrology Index [BASMI]). The Ankylosing Spondylitis Disease Activity Score (ASDAS) was used to assess disease activity. Group differences and associations were tested with the chi-square test for categorical variables, the Mann-WhitneyU test for ordinal variables, and analysis of covariance fo