Key result
DFAα1-derived thresholds overestimate gas exchange and respiratory compensation points by ~3.6 mL/kg/min during treadmill running.
Why the study?
The study evaluated whether DFAα1 values coincide with ventilatory thresholds, quantified DFAα1 during constant-speed running near the maximal lactate steady state (MLSS), and assessed its repeatability between MLSS trials.
Does the short-term scaling exponent of detrended fluctuation analysis (DFAα1) of heart rate variability accurately identify ventilatory thresholds and indicate systemic perturbation during prolonged exercise?
Observational (n=19)
No
Does the short-term scaling exponent of detrended fluctuation analysis (DFAα1) of heart rate variability accurately identify ventilatory thresholds and indicate systemic perturbation during prolonged exercise?
Effect estimate: Bias 3.6 (95% CI -9.1 to 1.9)
Absolute Event Rate: 42.3% vs 38.7%
p-value: p=<0.001
Fixed DFAα1 values of 0.75 and 0.50 do not accurately delineate exercise thresholds, but the metric's sensitivity to intensity and duration suggests utility in quantifying systemic perturbations during continuous exercise.
DFAα1 thresholds should not identify ventilatory thresholds in runners; leaves open utility for tracking systemic perturbations in prolonged exercise.
The short-term scaling exponent of detrended fluctuation analysis (DFAα1) applied to interbeat intervals may provide a method to identify ventilatory thresholds and indicate systemic perturbation during prolonged exercise. The purposes of this study were to i) confirm whether DFAα1 values of 0.75 and 0.5 coincide with the gas exchange threshold (GET) and respiratory compensation point (RCP), ii) quantify DFAα1 during constant-speed running near the maximal lactate steady state (MLSS), and iii) assess the repeatability of DFAα1 between MLSS trials. Seventeen runners performed an incremental running test, and eleven and ten runners also performed constant-speed running 5% below, at, and 5% above the MLSS, and a repeat trial at MLSS, respectively. GET (bias [LOA]: –3.6 [–9.1 to 1.9] mL·kg −1 ·min −1 ) and RCP (–3.5 [–14.1 to 7.2] mL·kg −1 ·min −1 ) were overestimated using DFAα1. DFAα1 responses during 30-min running trials near MLSS were variable (i.e., 0.27 to 1.24), and affected by intensity (p=0.019) and duration (p=0.001). No difference in DFAα1 was detected between MLSS trials (p=0.926). These results question whether DFAα1 values can accurately delineate exercise thresholds, but the dependency of DFAα1 on intensity and duration support its potential use to quantify systemic perturbations imposed by continuous exercise.
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Rassel et al. (2023) conducted an observational in Healthy runners (n=19). DFAα1 heart rate variability threshold estimation vs. Ventilatory gas exchange thresholds (GET and RCP) was evaluated on Agreement between DFAα1-derived threshold (HRVGET) and gas exchange threshold (GET) (Bias 3.6, 95% CI -9.1 to 1.9, p=<0.001). DFAα1-derived thresholds significantly overestimated the gas exchange threshold by 3.6 mL/kg/min and respiratory compensation point by 3.5 mL/kg/min during incremental treadmill running.
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