RESUMEN
OBJECTIVE: To assess aerobic capacity and cardiac autonomic modulation in juvenile fibromyalgia syndrome (JFM) patients at diagnosis in response to graded exercise text. METHODS: A multicenter cross-sectional study included 25 JFM patients and 25 healthy controls. Both groups participated only in physical education classes at school. A treadmill graded cardiorespiratory test was performed and the heart-rate (HR) response during exercise was evaluated by the chronotropic reserve (CR). Pain, functional ability, and health-related quality of life (HRQL) were assessed. RESULTS: The median current age was similar in JFM and controls (15 vs. 15 years, p = 0.890), as well as body mass index (p = 0.332), female gender (p = 1.000), and Tanner stages (p = 0.822). The medians of HRQL parameters (total score/physical health/psychosocial health) were significantly lower in JFM vs. controls according to patient and parent self-reports (p < 0.001). The median of peak HR [181 (150-198) vs. 197 (181-202)bpm, p < 0.001], chronotropic reserve [84 (53-98) vs. 99 (84-103)%, p < 0.001], and resting to peak [96 (65-181) vs. 127 (61-185)bpm, p = 0.010] were significantly lower in JFM compared to controls. The median of ΔHRR1 [15 (3-39) vs. 35 (9-52)bpm, p < 0.001], ΔHRR2 [37 (20-57) vs. 51 (32-94)bpm, p < 0.001], peak VO2 [32.34 (24.24-39.65) vs. 36.4 (28.56-52.71)ml/kg/min, p = 0.005], peak speed [5 (4-6.3) vs. 5.9 (4.0-6.3)mph, p = 0.001], time to exhaustion [11.5 (8.5-14.5) vs. 14 (11-18)min, p < 0.001], and working capacity on power [3.37 (2.04-5.6) vs. 3.89 (2.91-6.55)W/kg, p = 0.006] were significantly lower in JFM compared to controls. The frequency of chronotropic incompetence (≤80%) was significantly higher in JFM vs. controls (p = 0.0006). CONCLUSIONS: This study identified chronotropic incompetence and delayed HR recovery in JFM patients, indicating autonomic dysfunction. Aerobic exercise training should be considered in all JFM patients and may improve cardiac autonomic impairment, thus reducing cardiovascular risk.