Preliminary Evidence of Altered Biomechanics in Adolescents With Juvenile Fibromyalgia

Juvenile Fibromyalgia (JFM) is a chronic pain condition characterized by widespread musculoskeletal pain and several associated symptoms that contribute to significant functional disability (1, 2) that persists over time (3). Regular participation in moderate to vigorous physical activity and muscle strengthening exercises at least two times a week is recommended for pain management in patients with JFM, but adherence to these recommendations is poor (4, 5). In fact, a majority of pediatric and adult patients with fibromyalgia have been found to engage in extended periods of inactivity (6, 7), and based on objective activity monitoring, adolescents with JFM were found to remain very sedentary even after completing cognitive-behavioral treatment that significantly reduced their self-reported functional disability (8). Prolonged engagement in sedentary behavior can contribute to physical deconditioning and loss of confidence in patients’ ability to engage in physical activity (9). In particular, fear of movement is a prevalent concern for adults with fibromyalgia and is associated with poorer physical performance, muscle weakness, and increased pain sensitivity (10, 11). As such, pain-related fear may reinforce patients’ activity avoidance, exacerbate pain, and contribute to functional deficits, which can further contribute to physical deconditioning (11, 12). Due to their reduced participation in physical activities, adolescents with JFM may be susceptible to functional deficits that affect the fundamental movements necessary to re-engage in physical activity. For example, adults with fibromyalgia and youth with rheumatic conditions are weaker in lower extremity strength compared to healthy controls (13–16). Such biodynamic deviations can alter their joint mechanics, exacerbate chronic pain, and consequently increase their risk of falls as demonstrated in adults with fibromyalgia (9, 17–19) and adolescents with other rheumatic or chronic pain conditions (20–22). The increased risk for functional deficits and pain flares with physical activity for patients with JFM can interfere with their ability to safely engage in exercise, and contribute to a downward progression of disability, pain-related fear, and activity avoidance into adulthood. There is a need to better understand the types of biomechanical and biodynamic deviations prevalent in adolescents with JFM so that tailored exercise-based treatments can be designed to meet their specific needs. The use of three-dimensional (3-D) biomechanical analyses to assess a range of functional abilities, from walking gait to more dynamic maneuvers like jumping, can provide valuable insight regarding the nature of functional deficits associated with musculoskeletal pain conditions such as JFM. Biomechanical assessments of gait are increasingly used to identify functional deficits in patients with a variety of health conditions (23, 24). In fact, quantitative data from gait analyses has guided the development of targeted interventions resulting in improved postoperative gait in children requiring orthopedic surgery (25). On tasks requiring higher levels of skill and coordination, the drop vertical jump test (DVJ) commonly has been used to identify poor neuromuscular control (26) and predict risk of lower extremity injury (27, 28). Biomechanical and biodynamic assessments provide an ideal methodology to better understand functional deficits associated with high levels of physical impairment in JFM. The primary aim of this study was to objectively assess a spectrum of functional abilities progressing in difficulty from walking gait and strength to functional performance. We hypothesized that adolescents with JFM would demonstrate altered gait and deficiencies in lower extremity strength and performance compared to healthy controls. Patients with JFM also were expected to demonstrate higher levels of self-reported functional disability, pain intensity, depressive symptoms, and pain-related fear of movement than healthy controls.