Abstract
BACKGROUND: Chronic primary low back pain (CLBP) and fibromyalgia (FM) have complex etiologies and management approaches. Further research is needed, particularly on subgroups like individuals with CLBP who also report signs and symptoms of FM (CLBP/FM+) to better understand their pain mechanisms and clinical profile. Examining psychological, pain-related characteristics, and physical activity could help identify subgroups of individuals with CLBP/FM+ and guide the development of targeted interventions. This study aimed to compare physical activity practice, pain and psychological characteristics of individuals with CLBP without signs and symptoms of FM (CLBP/FM-), CLBP/FM + and FM to better understand similarities and differences between these chronic pain conditions. METHODS: Ninety-four individuals self-reporting CLBP (83% women) and 101 individuals self-reporting FM (96% women) were recruited online and completed a 30-min online survey. Among those with CLBP, 39 were classified as CLBP/FM+ and 55 as CLBP/FM-. Analyses of variance (ANOVAs) with polynomial contrasts were conducted to assess linear trends across the three groups on pain intensity (Numeric Rating Scale), psychological characteristics (Short Form-12, Tampa Scale for Kinesiophobia) and physical activity practice. RESULTS: Individuals with CLBP/FM- were more likely to participate in high-intensity physical activities. The analysis revealed a significant linear trend across the CLBP/FM-, CLBP/FM+, and FM groups for all pain and psychological characteristics except for the physical component of the quality of life and moderate-intensity physical activity. CONCLUSIONS: Individuals reporting a diagnosis of FM exhibit greater symptoms severity and engage less in high-intensity physical activities than individuals with CLBP/FM+ and CLBP/FM-. Identifying a subgroup of individuals with CLBP/FM+ may help recognize mixed pain profiles and inform more personalized tailor management strategies.