Detrended fluctuation analysis to determine physiologic thresholds, investigation and evidence from incremental...

Area of Science:

• Exercise Physiology
• Sports Science
• Biomedical Engineering

Background:

• Gas-exchange thresholds (GET) are standard for assessing training zones.
• Heart rate variability (HRV) analysis offers potential for indirect GET determination.
• Detrend fluctuation analysis (DFA α1) is one such HRV method.

Purpose of the Study:

• To evaluate the agreement between DFA α1 and ventilatory thresholds (VT1 and VT2) in well-trained cyclists.
• To assess the reliability of DFA α1 for determining GET compared to traditional methods.

Main Methods:

• Eighteen female and 38 male sub-elite cyclists underwent maximal incremental cycling tests.
• Continuous gas exchange and heart rate (HR) were measured.
• Agreements between DFA α1-derived thresholds (HRVT1, HRVT2) and ventilatory thresholds (VT1, VT2) were analyzed using Bland-Altman analysis for power output (PO), oxygen uptake (VO2), and HR.

Main Results:

• Significant and large limits of agreement were found between VT1 and HRVT1 for VO2, HR, and PO.
• Low agreement was also observed between VT2 and HRVT2 for VO2, HR, and PO.
• Women showed poorer predictions from DFA α1 compared to men for HR and PO at VT1 and VT2.

Conclusions:

• The DFA α1 method demonstrates unsatisfactory agreement for determining VT1 and VT2 in well-trained cyclists of both sexes.
• DFA α1 is not a reliable indirect method for GET determination in this population.
• Further research may be needed to refine HRV analysis for accurate training zone prescription.