Resistance exercise training improves heart rate variability in women with fibromyalgia.

Fibromyalgia (FM) is characterized by generalized muscle pain, low muscle strength and autonomic dysfunction. Heart rate (HR) variability (HRV) is reduced in individuals with FM increasing their risk for cardiovascular morbidity and mortality. We tested the hypothesis that resistance exercise training (RET) improves HRV, baroreflex sensitivity (BRS) and muscle strength in women with FM. Women with FM (n = 10) and healthy controls (n = 9), aged 27-60 years, were compared at baseline. Only women with FM underwent supervised RET 2 days per week for 16 weeks. Baseline and post-training measurements included HRV and spontaneous baroreflex sensitivity (BRS, alpha index) from continuous electrocardiogram and blood pressure (BP) recorded with finger plethysmography during 5 min in the supine position. RR interval, total power, log transformed (Ln) squared root of the standard deviation of RR interval (RMSSD), low-frequency power and BRS were lower (P<0.05), and HR and pulse pressure were higher (P<0.05) in women with FM than in healthy controls. After RET, mean (SEM) total power increased (387 +/- 170 ms(2), P<0.05), RMSSD increased (0.18 +/- 0.08 Ln ms, P<0.05) and Ln of high-frequency power increased (0.54 +/- 0.27 Ln ms(2), P = 0.08) in women with FM. Upper and lower body muscle strength increased by 63% and 49% (P<0.001), and pain perception decreased by 39% in women with FM. There were no changes in BRS, HR and BP after RET. Our study demonstrates that RET improves total power, cardiac parasympathetic tone, pain perception and muscle strength in women with FM who had autonomic dysfunction before the exercise programme.