# Agreement between heart rate variability‐derived and lactate/ventilatory thresholds during a 4‐min stepwise incremental cycling test in male adults

## TL;DR

This study compares heart rate variability thresholds with traditional lactate and ventilatory thresholds during cycling to determine their reliability for endurance training.

## Contribution

The study evaluates the validity of HRVT1 and HRVT2 as alternatives to LT and VT in a 4-minute cycling test.

## Key findings

- HRVT2 showed stronger agreement with LT2/VT2 compared to HRVT1 with LT1/VT1.
- ANOVA revealed significant differences in heart rate between VT2 and LT2, and between VT2 and HRVT2.
- HRVT1 demonstrated poor agreement and reliability for determining LT1/VT1.

## Abstract

Accurate exercise intensity thresholds are key for endurance training prescription. The non‐linear heart rate (HR) variability (HRV) index DFAa1 has been proposed as a threshold determination marker, with DFAa1 values of 0.75 (HRVT1) and 0.5 (HRVT2) corresponding to aerobic and anaerobic thresholds, respectively. This study investigated the agreement between these novel HRVT's and the gold standard blood‐lactate (LT) and ventilatory thresholds (VT). Twenty‐one trained participants completed a 4‐min stepwise cycling test (starting 40 W, +30 W/stage) with continuous HR and gas exchange measurement. Capillary blood lactate was sampled after each stage. Agreement between corresponding thresholds was assessed for HR, power output (PO), and oxygen uptake (V̇O2) using (intraclass) correlation coefficients (ICC) and ANOVA. HRVT1 demonstrated poor agreement with LT1/VT1, while a more personalized determination method (HRVT1pers) rendered trivial to moderate correlations and poor ICC. Both exhibited substantial mean bias relative to LT1/VT1. Conversely, HRVT2 demonstrated stronger agreement with LT2/VT2, particularly for PO and V̇O2, with smaller mean biases but wide limits of agreement. ANOVA revealed significant HR differences between VT2 and LT2 and between VT2 and HRVT2. These findings support HRVT2 validity as a surrogate for LT2/VT2 in 4‐min stepwise protocols, whereas HRVT1 demonstrates insufficient reliability for determining LT1/VT1.