What question did this study set out to answer?

To evaluate the agreement between heart rate variability-derived thresholds (HRVT1 and HRVT2 via DFAa1) and standard blood-lactate and ventilatory thresholds during a 4-minute stepwise incremental cycling protocol.

February 19, 2026Physiological ReportsOpen Access

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

Q: What are the key findings of this study?

HRVT1 demonstrated poor agreement with standard aerobic thresholds, while HRVT2 showed better agreement with anaerobic thresholds during a 4-minute stepwise cycling protocol.

Q: What is the clinical evidence from this study?

Study design: Observational. Population: Healthy physically active adults (n=21). Intervention: Heart rate variability thresholds (HRVT1 and HRVT2) vs. Blood-lactate and ventilatory thresholds. Primary outcome: Agreement between heart rate variability thresholds and blood-lactate/ventilatory thresholds measured by Intraclass Correlation Coefficient (ICC) and mean bias (Poor ICC (0.07-0.35) for HRVT1; moderate ICC (0.65-0.68) for HRVT2 vs LT2/VT2 for power output and oxygen uptake).

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Key result

HRVT2 tracks anaerobic exercise thresholds better than HRVT1 identifies aerobic thresholds during incremental cycling.

Poor ICC (0.07-0.35) for HRVT1; moderate ICC (0.65-0.68) for HRVT2 vs LT2/VT2 for power output and oxygen uptake
n=21

Why the study?

Accurate exercise intensity thresholds are key for endurance training prescription, and the non-linear HRV index DFAa1 has been proposed as a marker, prompting investigation into its agreement with gold-standard blood-lactate and ventilatory thresholds.

Key Points

To evaluate the agreement between heart rate variability-derived thresholds (HRVT1 and HRVT2 via DFAa1) and standard blood-lactate and ventilatory thresholds during a 4-minute stepwise incremental cycling protocol.
Twenty-one trained male adults completed a 4-min stepwise cycling test (starting at 40 W, +30 W/stage; average duration 38 min 35 s) with continuous gas exchange and heart rate measurement.
Capillary blood lactate was sampled after each 4-min stage to identify physiological thresholds (LT1, LT2) alongside ventilatory thresholds (VT1, VT2).
Agreement between HRVT metrics (HRVT1, individualized HRVT1 pers, HRVT2) and LT/VT for heart rate, power output, and V̇O2 was assessed via ICC, Pearson correlation, ANOVA, and Bland–Altman limits of agreement.
HRVT1 showed poor agreement with VT1 and LT1 across heart rate, power output, and V̇O2 (ICC = 0.07 to 0.35; r = 0.07 to 0.38), with individualized HRVT1 pers yielding similarly low agreement (ICC = 0.08 to 0.33).
HRVT2 demonstrated moderate agreement with VT2 and LT2 for power output (ICC = 0.65 to 0.68; r = 0.67 to 0.68) and V̇O2 (ICC = 0.65 to 0.68; r = 0.68 to 0.73), exhibiting minimal mean biases (-10 to -2 W for power; -1 to 0 mL/kg/min for V̇O2).
Wide limits of agreement persisted for HRVT2 power output (-60 to 52 W) and V̇O2 (-9 to 8 mL/kg/min), and ANOVA identified significant heart rate differences between VT2 and HRVT2 (p < 0.05).

Study Design

Type

Observational (n=21)

Blinding

Blinded assessors

Multicenter

Structured PICO

Population

21 physically active young adult males completed a 4-minute stepwise incremental cycling test to validate heart rate variability thresholds against standard physiological thresholds.

Exposure

Assessment of exercise intensity thresholds using heart rate variability (HRV) derived non-linear index DFAa1 (HRVT1 at DFAa1=0.75, personalized HRVT1pers, and HRVT2 at DFAa1=0.5) during a 4-min stepwise maximal incremental cycling test (starting 40 W, +30 W/stage).

Comparator

Gold standard blood-lactate thresholds (LT1, LT2) and ventilatory thresholds (VT1, VT2) derived from continuous gas exchange and step-wise capillary blood sampling during the same incremental exercise test.

Outcome

Agreement between corresponding HRV, ventilatory, and lactate thresholds for heart rate (HR), power output (PO), and oxygen uptake (VO2), assessed using intraclass correlation coefficients (ICC), correlation coefficients, ANOVA, and Bland-Altman plots with 95% limits of agreement.surrogate

Main Result

Effect estimate: Poor ICC (0.07-0.35) for HRVT1; moderate ICC (0.65-0.68) for HRVT2 vs LT2/VT2 for power output and oxygen uptake

While HRVT1 is unreliable for detecting the first aerobic threshold in 4-min stepwise protocols, HRVT2 (DFAa1=0.5) is a valid group-level surrogate for the second anaerobic threshold, though wide individual variation limits its precise application for individuals.

Limitations

Inclusion of only trained male participants limits generalizability to females and untrained populations.
The 4-minute stage duration selected for lactate steady-state may have compromised ventilatory threshold assessment accuracy.
Did not directly assess the test-retest reliability of DFAa1-derived thresholds.
The 4-min stage duration, while optimal for lactate thresholds, may be suboptimal for ventilatory threshold detection.
The personalized HRVT1 method may be protocol-dependent and less effective in stepwise protocols.
Wide limits of agreement indicate considerable individual variability, suggesting caution for individual intensity prescription.

Implication

HRVT1 should not yet guide aerobic thresholds; leaves open prospective validation of HRVT2 as anaerobic surrogate in cycling.

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 (V̇O 2 ) using (intraclass) correlation coefficients (ICC) and ANOVA. HRVT1 demonstrated poor agreement with LT1/VT1, while a more personalized determination method (HRVT1 pers ) 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 V̇O 2 , 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.

Discussion

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Published by Physiological Reports · CC BY

Cite This Study

Anton et al. (2026) conducted an observational in Healthy physically active adults (n=21). Heart rate variability thresholds (HRVT1 and HRVT2) vs. Blood-lactate and ventilatory thresholds was evaluated on Agreement between heart rate variability thresholds and blood-lactate/ventilatory thresholds measured by Intraclass Correlation Coefficient (ICC) and mean bias (Poor ICC (0.07-0.35) for HRVT1; moderate ICC (0.65-0.68) for HRVT2 vs LT2/VT2 for power output and oxygen uptake). HRVT1 demonstrated poor agreement with standard aerobic thresholds, while HRVT2 showed better agreement with anaerobic thresholds during a 4-minute stepwise cycling protocol.

synapsesocial.com/papers/6996a83eecb39a600b3eeca7 https://doi.org/10.14814/phy2.70777

Topics

HFrEF treatment

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Implication

HRVT1 should not yet guide aerobic thresholds; leaves open prospective validation of HRVT2 as anaerobic surrogate in cycling.

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

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Figures from the paper

Cite This Study

Topics

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

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Figures from the paper

Cite This Study

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