Influences of a relaxation intervention on perceived stress and power spectral analysis of heart rate variability.
This study was designed to determine whether power spectral analysis (PSA) of heart rate variability (HRV) can detect change in autonomic tone following a relaxation intervention called therapeutic touch (TT). Thirty healthy subjects underwent TT by one of three TT practitioners using the steps developed by Krieger and Kunz (The Therapeutic Touch, Prentice-Hall, 1979). Both subjects and TT practitioners were monitored by continuous electrocardiographic monitoring (Holter) before (15 minutes), during, and after (15 minutes) TT was administered. Subjects and TT practitioners completed a visual analogue scale (VAS) of perceived stress before and after TT. Change scores for VAS and PSA of high-frequency/low-frequency (HF/LF) ratios were compared for the 2-minute interval before TT began and the end of TT and the end of the recovery period, using t tests. VAS scores decreased (less stress) from before to after TT for both subjects (p < 0.0005) and TT practitioners (p < 0.0005). Mean HF/LF ratios increased significantly to reflect greater parasympathetic dominance from before TT to the end of treatment for subjects (p = 0.006), but not for TT practitioners. However, further analysis revealed that this change was due to an exaggerated HF/LF response from four outliers (p < 0.0005). Data collected in this study did not reveal differences between these four subjects and the rest of the sample. There were no significant changes in HF/LF ratios from the end of TT to end of recovery for either group. Further research is needed to determine why some subjects may have greater change in autonomic tone in response to relaxation in order to be able to predict who will demonstrate physiologic response to relaxation interventions.