Estimation of Runners' Lactate Threshold Heart Rate and Speed by Heart Rate Variability.

Area of Science:

• Exercise Physiology
• Autonomic Nervous System Function
• Sports Science

Background:

• Accurate training intensity measurement is key for endurance performance.
• Lactate threshold (LT) is a critical performance indicator but requires invasive methods.
• Heart rate variability (HRV) offers a non-invasive approach to assess autonomic nervous system activity.

Purpose of the Study:

• To evaluate the validity of various HRV metrics in predicting LT heart rate and speed.
• To compare HRV thresholds against LT during graded exercise tests (indoor and outdoor).
• To identify potential non-invasive predictors for optimizing endurance training.

Main Methods:

• 19 recreational runners performed indoor and outdoor graded exercise tests.
• LT heart rate and speed were determined using standard methods.
• HRV thresholds (HRVT1-HRVT6) were calculated using SD1, SD2, DFA exponents, SDNN, and RMSSD via the Dmax method.

Main Results:

• Indoor tests: HRV thresholds often underestimated LT heart rate; most HRV thresholds differed significantly from LT.
• Indoor tests: Moderate correlations found for SDNN (HRVT5HR, r=0.66) and DFA exponents (HRVT3speed, r=0.70) with LT speed.
• Outdoor tests: Most HRV thresholds showed no significant difference from LT; moderate correlations (r=0.54-0.7) observed for HRV speed thresholds with LT speed.

Conclusions:

• HRV thresholds and LT may represent distinct physiological markers.
• Certain HRV metrics, especially DFA exponents, show potential as non-invasive predictors of LT in recreational runners.
• HRV offers a promising, non-invasive tool for monitoring training intensity and optimizing performance.