Poincaré (Lorenz/Scatter) Plot HRV in Freedivers, Hypoxia–Insulin Hypothesis and Practical Use
Authors: Rosita Dangmann
DOI / Source: https://doi.org/10.13140/RG.2.2.24067.22562
Date: 26 December 2021
Reading level: Intermediate
Why This Matters for Freedivers
This piece suggests a simple, affordable way to “see” what your nervous system is doing during and after breath-holds using RR-interval data and a Poincaré/Lorenz HRV plot. It also highlights something safety-relevant: maximal statics can show patterns consistent with cardiac rhythm disturbances, and HRV plots may sometimes hint at that—so they should be interpreted carefully and never used to justify pushing harder.
Synopsis
This report explores the Poincaré/Lorenz (scatter) plot as a practical HRV tool for freedivers, framed around Rosita Dangmann’s hypoxia–insulin hypothesis. The Poincaré/Lorenz plot is built by plotting each RR interval against the next one, creating a cloud of points that can be summarized by an ellipse. The report focuses on three common ellipse metrics: - SD1 (short-term variability; essentially the same as RMSSD, often associated with parasympathetic/vagal activity), - SD2 (longer-term variability), - S (ellipse area; a broader “total HRV” indicator).
A small pretest is described using two subjects and a structured static-breath-hold protocol with phases: baseline, preparation, easy phase (no contractions), struggle phase (with diaphragm contractions), and recovery checks (15 min, 90 min, and later). RR intervals were recorded continuously (Polar device), and short segments were analyzed in Kubios.
The key reported pattern is: - During the easy phase, SD1 and SD2 tend to shrink, consistent with a stress load. - During the struggle phase, SD1 can increase sharply—but the report argues this may partly reflect arrhythmia-like point patterns in the Lorenz plot (e.g., ectopy or possible second-degree AV block patterns). The author notes that definitive identification would require ECG.
The report connects these observations back to the hypoxia–insulin hypothesis: insulin is proposed as a central regulator under hypoxic conditions, and the report notes insulin values in one subject decreased in the easy phase and increased in the struggle phase (with a caveat that the second subject’s insulin wasn’t measured due to lab issues). It also suggests HRV tracking could be useful in recovery monitoring and avoiding overtraining, with Kubios highlighted as an accessible analysis option.
Abstract
This report discusses the Poincaré/Lorenz (scatter) plot method for heart rate variability (HRV) analysis as a practical tool for freedivers, and links observed HRV changes during static breath-holding to the hypoxia–insulin hypothesis. Using short RR-interval segments across breath-hold phases (baseline, preparation, easy phase, struggle phase, and recovery), the author describes decreases in SD1/SD2 during the easy phase and increases during the struggle phase, while emphasizing that some struggle-phase plot patterns may reflect breath-hold–related arrhythmias rather than “healthy” vagal changes. The report proposes that Lorenz-plot HRV metrics—analyzable with accessible software such as Kubios—could help individualize training and monitor recovery, while cautioning that rhythm interpretation requires ECG confirmation.