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DFAα1 as an intensity-sensitive biomarker for exercise prescription: a prospective cross-sectional study in healthy
Yuxiao Deng1, Chunxue Tang1, Xianxiang Zeng1
1Department of Exercise Physiology, Beijing Sport University, Beijing, 100084, P.R. China.
Background:
While heart rate variability (HRV) offers a non-invasive alternative for ventilatory thresholds (VTs) estimation, its conventional linear parameters (e.g., RMSSD) exhibit a "floor effect" limiting utility. DFAα1 is a promising non-linear HRV parameter, reflecting the complex pattern of autonomic regulation. This study evaluated DFAα1 for threshold estimation, intensity monitoring, and recovery assessment.
Methods:
27 healthy adults underwent an incremental cycle ergometer test. VTs were determined via standard criteria, while HRV thresholds (HRVTs) were determined using multiple parameters. A subset (n = 19) then performed low to severe intensity exercise tests (E1-E4) to validate HRV sensitivity and dynamic responses.
Results:
For HRVT1 vs. VT1: DFAα1-derived HRVT1 exhibited the highest ICC (> 0.60) among all parameters but with a systematic bias; for HRVT2 vs. VT2: DFAα1-derived HRVT2 exhibited moderate-to-high ICC (> 0.60) and RMSSD-derived achieved the highest ICC (0.88-0.95). During E1-E4, DFAα1 and the natural log of RMSSD (LnRMSSD) both decreased during exercise and increased during recovery. During exercise, DFAα1 in E1 and E2 exceeded in E3 and E4, while LnRMSSD was higher in E1 than in E2-E4 (all P < 0.05). During recovery in E2-E4, DFAα1 exceeded baseline, and this rebound was delayed with intensity, while LnRMSSD was lower than baseline with a downward trend.
Conclusions:
DFAα1 showed potential for estimating both VTs, retained sensitivity across intensity domains, and showed recovery dynamics proportional to prior intensity. Despite individual variability suggesting use for broad zoning rather than precise estimation, DFAα1 serves as an intensity-sensitive biomarker for individualized exercise prescription.
