title: Reminder: RMSSD and SD1 are identical heart rate variability metrics.
abstract: Assessment of heart rate variability (HRV) is a common approach to examine cardiac autonomic nervous system modulation that has been employed in a variety of settings. Frequently, both the root mean square of successive differences (RMSSD) and SD1, which is a Poincaré plot component, have been used to quantify short-term heart rate variability. It is not typically appreciated, however, that RMSSD and SD1 are identical metrics of HRV. As a reminder to clinicians and researchers who use and study HRV, we show both empirically and mathematically that RMSSD and SD1 are identical metrics. Because the homology between RMSSD and SD1 is not commonly known, the inclusion of both measures has been reported in many recent publications. The inappropriate use of such redundant data may affect the interpretation of HRV studies. Muscle Nerve 56: 674-678, 2017.
authors.affiliation: Osness Human Performance Laboratories, Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, Kansas, 66045, USA.
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Ciccone
authors.affiliation: Department of Exercise Science and Pre-Health Professions, Creighton University, Omaha Nebraska, USA.
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Siedlik
authors.affiliation: Center for the Medical Consequences of Spinal Cord Injury, James J. Peters Veterans Affairs Medical Center, Bronx, New York, USA.|Department of Medicine and Rehabilitation Medicine, the Icahn School of Medicine, Mount Sinai, New York, New York, USA.
authors.forename: Jill M
authors.initials: JM
authors.lastname: Wecht
authors.affiliation: Osness Human Performance Laboratories, Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, Kansas, 66045, USA.
authors.forename: Jake A
authors.initials: JA
authors.lastname: Deckert
authors.affiliation: Center for the Medical Consequences of Spinal Cord Injury, James J. Peters Veterans Affairs Medical Center, Bronx, New York, USA.
authors.forename: Nhuquynh D
authors.initials: ND
authors.lastname: Nguyen
authors.affiliation: Osness Human Performance Laboratories, Department of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, Kansas, 66045, USA.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Weir
mesh_terms: D004562:Electrocardiography / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008962:Models, Theoretical
keywords: HRV; SD2; SDNN; autonomic; parasympathetic; sympathetic