Heart rate variability in patients with low back pain: a systematic review.

There is limited evidence suggesting that chronic low back pain patients presented a lower vagal activity evidenced by HRV, when compared to healthy controls. The results of this systematic review should be interpreted with caution due to the restricted number of included studies, small sample sizes and different protocols used to measure HRV. The limited evidence about HRV alterations in low back pain also suggests the need of future studies to investigate if HRV parameters can be a useful measure in chronic pain samples or even if it can be used as an outcome in clinical trials aiming to investigate the effectiveness of interventions based on emotion regulation.