The relationship between fatigue and muscle strength and endurance of lower extremity, core endurance, sleep quality, cardiopulmonary capacity in patients with ankylosing spondylitis and comparison with healthy individuals

Ankylosing spondylitis is an inflammatory disease that primarily affects the axial skeleton, typically manifesting as inflammatory low back pain, leading to structural deformities and decreased quality of life. Fatigue is the most common symptom in patients with ankylosing spondylitis, after pain and stiffness. This study aimed to evaluate the relationship between fatigue and core endurance, lower extremity muscle strength and endurance, sleep quality, and cardiopulmonary capacity in patients with ankylosing spondylitis and to compare it with a healthy control group. Our study included 42 male patients diagnosed with ankylosing spondylitis according to Assessment of Spondyloarthritis International Society criteria and 49 healthy male patients. The patients' sociodemographic data were recorded. The ankylosing spondylitis group was administered the Bath Ankylosing Spondylitis Disease Activity Index and the Ankylosing Spondylitis Quality of Life Scale to assess disease activity and quality of life. All participants underwent the Fatigue Severity Scale to assess fatigue, the isokinetic test to assess lower extremity muscle strength, the McGill core endurance test to assess trunk endurance, the Pittsburgh Sleep Quality Index to assess sleep quality, the pulmonary function test and the six-minute walk test to assess cardiopulmonary capacity. Data were compared between the groups. Age distribution and body mass index were similar between the groups. The fatigue severity scale, isokinetic assessment, core endurance test, pulmonary function test, and the six-minute walk test showed significant differences between the ankylosing spondylitis and control groups (p<0.05). In the ankylosing spondylitis group, fatigue was found to be related to disease activity, quality of life, and sleep quality (p<0.05). Given that fatigue is a multifactorial symptom, comprehensive studies with larger series may provide a better understanding of fatigue symptoms in patients with ankylosing spondylitis and enable the development of treatment strategies.