Detrended Fluctuation Analysis

Over the past couple years a novel method for analyzing athletic ‘readiness’ has emerged. The short-term scaling exponent alpha1 of Detrended Fluctuation Analysis (DFA a1), a heart rate variability (HRV) index representing the degree of fractal correlation properties of the cardiac beat sequence, may be a convenient method of assessing the effects of exercise load on the athlete. At low intensities DFAa1 are typically in a correlated range >1.0.  With increasing intensity DFAa1 declines to 0.75 at moderate loads and drops below 0.5 at very high workloads (Gronwald et al., 2020). As exercise intensity increases there is a parasympathetic withdrawal and augmentation of sympathetic activity, both of which are signaled by a change in HRV including DFAa1. DFAa1 is a reflection of multiple biological systems hence indicating a broad internal load on the body.  

An update published this month in Frontiers in Physiology suggested using DFAa1 in conjunction with external loads may serve as a valuable tool signifying performance degradation in terms of autonomic nervous system imbalance (Rogers and Gronwald, 2022). Smartphone apps exist that allow live capture of DFAa1. Likewise upper end Garmin watches will soon have this feature. Access to this data in real time would allow the athlete to assess their system’s readiness as well as their aerobic and anaerobic thresholds. Heeding the signals may mean shifting training to best suit the body’s fluctuating capacity. Leveraging data such as DFAa1 is a powerful tool to assist in optimizing the dose and timing of the training stimulus. Can’t ‘beat’ that!