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Purpose <p>Heart rate variability (HRV) is a non-invasive marker of autonomic function, and cold-water ingestion effectively modulates HRV. However, no prior study has provided a unified time-resolved modeling framework capable of separating residual and stimulus-specific autonomic effects in repeated HRV stimulation paradigms.</p> Subjects and methods <p>Electrocardiograms from 39 healthy participants, exposed to two cold water ingestion (500&#xa0;ml at &#xa0;8<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(^o\)</EquationSource> </InlineEquation>C) separated by 30&#xa0;min, were analyzed. After segmenting recordings into 5–minute windows, HRV variables in time, frequency, and fractal domains were extracted. Linear mixed-effects models with linear and quadratic time components were used to characterize both transient and sustained responses.</p> Results <p>The first stimulus resulted in pronounced autonomic modulation: heart rate decreased by 8.8%, other time-domain HRV variables increased (SDNN: +27.8%, RMSSD: +42.4%, pNN50: +75.6%). Maximum responses reached within 17–30&#xa0;min, with recovery times of up to 60&#xa0;min. The second stimulus resulted in additional but attenuated responses (SDNN: +2.9%, RMSSD: +41.7%, pNN50: +76.2%), with shorter recovery times (25–32&#xa0;min), suggesting partial physiological adaptation. Frequency domain responses were smaller in magnitude but additive: with successive stimuli, ln(LF) response (+5.8% to +6.7%), and ln(HF) response increased (+9.2% to +10.5%). Fractal analysis revealed a decrease in short-term scaling (Alpha 1: −8.1% to −8.8%) without significant changes in long-term dynamics (Alpha 2).</p> Conclusions <p>The proposed time-resolved modeling framework effectively separates residual from stimulus-specific HRV effects, enabling quantification of repeated autonomic responses and providing a standardized approach for future repeated HRV stimulation studies.</p>

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Autonomic adaptation to repeated cold water ingestion: time-resolved HRV analysis

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Fırat Matur,
  • Gözde Hilal Öçalan,
  • Bora Büyüksaraç

摘要

Purpose

Heart rate variability (HRV) is a non-invasive marker of autonomic function, and cold-water ingestion effectively modulates HRV. However, no prior study has provided a unified time-resolved modeling framework capable of separating residual and stimulus-specific autonomic effects in repeated HRV stimulation paradigms.

Subjects and methods

Electrocardiograms from 39 healthy participants, exposed to two cold water ingestion (500 ml at  8 \(^o\) C) separated by 30 min, were analyzed. After segmenting recordings into 5–minute windows, HRV variables in time, frequency, and fractal domains were extracted. Linear mixed-effects models with linear and quadratic time components were used to characterize both transient and sustained responses.

Results

The first stimulus resulted in pronounced autonomic modulation: heart rate decreased by 8.8%, other time-domain HRV variables increased (SDNN: +27.8%, RMSSD: +42.4%, pNN50: +75.6%). Maximum responses reached within 17–30 min, with recovery times of up to 60 min. The second stimulus resulted in additional but attenuated responses (SDNN: +2.9%, RMSSD: +41.7%, pNN50: +76.2%), with shorter recovery times (25–32 min), suggesting partial physiological adaptation. Frequency domain responses were smaller in magnitude but additive: with successive stimuli, ln(LF) response (+5.8% to +6.7%), and ln(HF) response increased (+9.2% to +10.5%). Fractal analysis revealed a decrease in short-term scaling (Alpha 1: −8.1% to −8.8%) without significant changes in long-term dynamics (Alpha 2).

Conclusions

The proposed time-resolved modeling framework effectively separates residual from stimulus-specific HRV effects, enabling quantification of repeated autonomic responses and providing a standardized approach for future repeated HRV stimulation studies.