TerraMD Research Lab · Yogamu Institute Rishikesh

Measuring how practice shapes the autonomic nervous system.

VagalTone.org is the home of our ongoing research into vagal tone, heart rate variability (HRV), and the impact of different modalities—from breathwork and yoga to sound and cold exposure—on the human nervous system.

View research overview Experimental tools

What we measure

· Vagal tone & HRV (RMSSD, SDNN, pNN50)
· Resting heart rate & beat-to-beat dynamics
· Breathing rate & RSA (respiratory sinus arrhythmia)
· Coherence between breath, heart, and mind

All measurements are experimental, non-diagnostic, and used to better understand how different practices influence the autonomic nervous system over time.

Research overview

Project 1 · Modality Comparison

Project I · Which modalities produce the strongest HRV & vagal tone improvements?

Our first project systematically compares different practices and interventions to quantify their acute impact on HRV and vagal indices. Participants complete standardized baseline recordings and then repeat measurements after a defined modality.

Modalities under investigation

· Slow coherent breathing (e.g., 6 breaths/min)
· Box breathing / ratio breathing variants
· Classical yoga asana sequences
· Meditation vs. yoga nidra vs. mindful rest

· Sound-based practices (mantra, kirtan, singing bowls)
· Cold exposure & contrast hydrotherapy
· Gentle movement vs. brisk walking
· Custom TerraMD protocols (Ayurveda & integrative)

Primary metrics: RMSSD, SDNN, pNN50, vagal index, RSA coherence, breathing rate. Secondary metrics: subjective calmness, perceived stress, qualitative reports.

Key questions

· Which modalities reliably increase HRV in real humans?
· How much can vagal tone shift in 5–20 minutes?
· Does “inner experience” match measurable change?
· Which protocols are realistic for daily life?

Planned output: · A publicly accessible overview of modalities & their average HRV impact. · Whitepapers and, where appropriate, peer-reviewed publications.

Experimental tools

Online Experiments

Online Vagal Tone & HRV Estimator

This experimental tool uses your device’s camera to measure pulse waves (PPG) and estimate:

· Heart rate and beat-to-beat intervals
· HRV (RMSSD, SDNN, pNN50)
· Breathing rate from slow oscillations
· RSA coherence (breath–heart coupling)
· A composite vagal index (0–100)

This is not a medical device and not intended for diagnosis. It is a research instrument and a way for participants to contribute anonymous data to the VagalTone project.

Run Experimental Vagal Tone Test

How data is handled

· We do not store raw video; only derived HRV metrics may be stored for research.
· Participation in experiments is optional and requires explicit consent.
· Individual results are visible to you but are anonymized in aggregated analysis.

If you are a researcher, clinician, or engineer and would like to collaborate or review our methodology, please contact the TerraMD Research Lab.

About the VagalTone Project

TerraMD Research Lab

TerraMD is an integrative research & clinical initiative combining modern physiology, psychology, and Ayurveda. Our focus is to understand how sustainable, human-scale interventions modulate healthspan, mental wellness, and nervous system resilience.

The VagalTone Project is one of our core efforts to systematically quantify the effect of practices such as yoga, breathwork, meditation, sound, and behavioral interventions on measurable autonomic markers.

Yogamu Institute · Rishikesh, India

Yogamu Institute in Rishikesh serves as a physical hub for immersive practice, teaching, and data collection. It is one of the few places where traditional yoga, Ayurveda, and modern measurement techniques are combined under one roof.

Many of our protocols are first tested with students and retreat participants on-site before being adapted for remote experimental use via VagalTone.org.

Publications & whitepapers

This section will list formal outputs of the VagalTone project, from internal whitepapers and method notes to peer-reviewed publications.

Coming soon – planned 2025:

· “Comparative short-term HRV effects of 12 modalities in adults” (TerraMD cohort, 2024–2025)
· Methodology note on webcam-based PPG & HRV analysis (NeuroKit2 + custom peak detection)
· Case reports: HRV changes in intensive yoga/meditation retreats in Rishikesh

Participate

Join the modality impact study

If you regularly practice a specific modality (e.g., coherent breathing, cold exposure, yoga sequences, or sound practices), you can contribute anonymized data to help us map its HRV and vagal impact over time.

· Use the online test before and after your modality.
· Optionally log your practice details (duration, intensity, subjective effects).
· Allow us to include your anonymized metrics in aggregated research.

A dedicated participant portal will become available as the project expands. For now, you can express interest or propose collaborations via email.

Contact & collaboration

For research collaborations, data access discussions, or method review:

Email: (add your research contact here) Location: Rishikesh, India & international remote cohort

We are especially interested in collaboration with clinicians, neuroscientists, psychologists, yoga & meditation researchers, and engineers working on digital health tools.