The Full Respiratory Cycle and RMSSD

Series: Breathing, Body, Consciousness, and the Shifting of the Tensional Selves (Eus Tensionais)

Introduction — Brain Bee (first-person consciousness)

When I pay attention to my breathing, I realize it isn’t a single act.
It happens in phases.

Air comes in.
Air goes out.
There are brief instants when nothing seems to happen—yet something still shifts.

My heart responds to each of these steps.
Sometimes it speeds up. Sometimes it slows down. Sometimes it oscillates smoothly.

This is not emotion.
This is not thought.
It is physiology in motion.

The respiratory cycle as a functional sequence

Breathing is not only inhaling and exhaling.
A full respiratory cycle involves four functional moments:

1. Inhalation

2. Pause after inhalation (inspiratory hold)

3. Exhalation

4. Pause after exhalation (expiratory hold)

Even when we don’t consciously notice them, these phases exist—and each one “talks” differently with the heart and the autonomic system.

RMSSD: the sensitive marker of the breath–heart dance

RMSSD measures fast variations between successive heartbeats.
That’s why it is especially sensitive to what happens within a single breathing cycle.

While other HRV metrics reflect more global trends, RMSSD reveals:

• how the heart reacts moment by moment,

• how the vagus nerve enters and exits the scene,

• how much freedom the system has to oscillate.

Inhalation: temporary withdrawal of the vagal brake

During inhalation:

• vagal influence temporarily decreases,

• heart rate tends to rise,

• the sympathetic branch gains brief space.

Physiologically:

• RMSSD tends to drop slightly,

• variability narrows,

• the body enters readiness.

This is healthy.
Without it, there is no action.

The problem is not inhaling.
The problem is not being able to leave this state.

Inspiratory hold: tension and alertness

When air is held after inhalation:

• intrathoracic pressure increases,

• sympathetic activation becomes more evident,

• autonomic excitability rises.

Even short holds can:

• reduce RMSSD,

• increase vigilance,

• sustain alert-oriented Tensional Selves.

This may be functional during effort,
but becomes draining when repeated out of context.

Exhalation: the return of vagal influence

During exhalation:

• the vagus nerve reasserts itself,

• heart rate slows down,

• the body moves into regulation.

Here:

• RMSSD tends to rise,

• variability expands,

• physiology gains room for adjustment.

Exhalation is the main vagal portal of the breathing cycle.
That’s why it is not “relaxing” by definition—
it is organizing.

Passive expiratory pause: maximal sensitivity

When exhalation ends and the body naturally waits for the next inhale:

• CO₂ rises slightly,

• cerebral vasodilation increases,

• interoceptive sensitivity becomes high.

In that moment:

• RMSSD tends to reach higher values,

• the autonomic system enters fine balance,

• states of fruition and calm attention can emerge.

This pause should not be forced.
It appears when the body trusts its own rhythm.

The respiratory cycle and states of consciousness

Each phase of the cycle tends to favor different states of consciousness:

• Prolonged inhalation → action, readiness, narrow focus

• Inspiratory hold → vigilance, defense, alertness

• Long exhalation → regulation, openness, integration

• Passive expiratory pause → fruition, presence, sensitivity

These are not “psychological moods.”
They are temporary physiological configurations.

Tensional Selves and fixation in cycle phases

A Tensional Self can anchor itself in:

• short, repetitive inhalations,

• frequent holds,

• weak exhalations,

• or the absence of natural pauses.

When this happens:

• RMSSD loses variability,

• shifting between states becomes poorer,

• consciousness narrows.

Breathing reveals where the Self is stuck.

A technical basis for a physiological reading of consciousness

Observing the breathing cycle allows us to:

• infer autonomic state,

• understand HRV fluctuations,

• anticipate exhaustion or rigidity,

• read consciousness through the body, not through narrative.

This does not require intervention.
It requires perception.

Recognizing the cycle in yourself

Without correcting—just noticing:

• Where does my breath spend more time?

• Do I inhale quickly and then “lock”?

• Does exhalation have space?

• Is there a natural pause without anxiety?

These answers are living diagnostics—
often more precise than any questionnaire.

Closing

The respiratory cycle is not a technical detail.
It is the choreography of autonomic life.

RMSSD is the trace of this choreography in the heart.
Where there is variation, there is health.
Where there is rigidity, there is a request for space.

Learning to read the respiratory cycle
is learning to read states of consciousness through the body.

This text is part of the series Breathing, Body, Consciousness, and the Shifting of the Tensional Selves (Eus Tensionais), where different aspects of the same living system are approached from complementary angles.

References (post-2020)

Laborde, S., Mosley, E., & Thayer, J. F. (2022). Heart Rate Variability and Cardiac Vagal Tone in Psychophysiological Research. Biological Psychology.
→ Grounds RMSSD as a sensitive marker of beat-to-beat vagal modulation.

Shaffer, F., & Ginsberg, J. P. (2020). An Overview of Heart Rate Variability Metrics and Norms. Frontiers in Public Health.
→ Presents the relationship between HRV metrics and rapid physiological oscillations.

Kim, H. G., et al. (2021). Respiration–Heart Rate Coupling and Autonomic Regulation. Frontiers in Neuroscience.
→ Demonstrates how each respiratory phase directly alters heart rate.

von Rosenberg, W., et al. (2020). Respiratory Influences on Heart Rate Variability. IEEE Reviews in Biomedical Engineering.
→ Technically analyzes the impact of the full respiratory cycle on HRV.

Zaccaro, A., et al. (2022). How Breath-Control Can Change Your Life: A Systematic Review. Frontiers in Human Neuroscience.
→ Reviews how distinct respiratory phases modulate autonomic states.

Vlemincx, E., et al. (2020). Respiratory Variability and Autonomic Flexibility. Biological Psychology.
→ Links respiratory variability to healthy autonomic flexibility.

Grassmann, M., et al. (2021). Respiration, Interoception and Autonomic Regulation. Frontiers in Neuroscience.
→ Integrates breathing, interoception, and a physiological reading of consciousness.

Forte, G., et al. (2022). Heart Rate Variability, Interoceptive Awareness and Bodily States. Neuroscience & Biobehavioral Reviews.
→ Relates RMSSD to bodily awareness and physiologically modulated conscious states.