In brief: Heart rate variability reflects how adaptable your nervous system is, and higher HRV is linked with better recovery, sleep and stress resilience. The vagus nerve drives the rest-and-recover side of the nervous system, while nitric oxide supports circulation, endothelial health and vagal signalling. As nitric oxide declines with age and metabolic dysfunction, HRV often falls too. Humming, nasal breathing, exercise, sauna, slow breathing and dietary nitrates may help support nitric oxide, vagal tone and HRV.
The Hidden Connection Between Circulation, Recovery and Healthy Aging
Heart Rate Variability is emerging as one of the most important biomarkers in modern health optimisation.
Tracked by devices like WHOOP, Oura Ring, Garmin and Apple Watch, HRV reflects how adaptable and resilient the nervous system is.
Higher HRV is generally associated with:
- better cardiovascular health
- improved recovery
- better sleep
- lower inflammation
- stronger stress resilience
- healthier aging
Low HRV is commonly associated with:
- metabolic disease
- chronic stress
- obesity
- poor sleep
- cardiovascular disease
- inflammation
- aging
What is becoming increasingly interesting is the central role nitric oxide and the vagus nerve may play in this entire system.
Understanding the Autonomic Nervous System
The autonomic nervous system controls many of the body’s automatic functions, including:
- heart rate
- blood pressure
- breathing
- circulation
- digestion
- inflammation
- recovery
It has two major branches:
The Sympathetic Nervous System
Often called:
“fight or flight”
This system prepares the body for stress and action by increasing:
- heart rate
- blood pressure
- adrenaline
- alertness
Short-term activation is healthy and necessary.
However, chronic sympathetic dominance — common in modern life due to stress, poor sleep, inflammation and metabolic dysfunction — is associated with:
- fatigue
- anxiety
- high blood pressure
- poor recovery
- lower HRV
The Parasympathetic Nervous System
Often called:
“rest, digest and recover”
This system helps the body:
- recover
- repair
- lower inflammation
- improve digestion
- conserve energy
- restore balance
The major nerve controlling this system is:
the vagus nerve
The Vagus Nerve: The Body’s Recovery Highway
The vagus nerve is the longest cranial nerve in the body, travelling from the brainstem through:
- the heart
- lungs
- digestive tract
- liver
- intestine
It acts as a communication highway between the brain and body.
One of its most important roles is regulating parasympathetic activity.
When vagal activity increases:
- heart rate slows
- breathing becomes calmer
- inflammation decreases
- recovery improves
- HRV rises
This is often referred to as:
“vagal tone”
Higher vagal tone is strongly associated with:
- higher HRV
- improved stress resilience
- better cardiovascular health
- better emotional regulation
- improved recovery
What Is HRV?
HRV measures the variation in time between heart beats.
A healthy heart does not beat like a metronome. Instead, it constantly adjusts in response to:
- breathing
- movement
- stress
- recovery
- nervous system input
Higher HRV generally reflects:
- greater nervous system flexibility
- stronger vagal activity
- healthier autonomic balance
Lower HRV often reflects:
- sympathetic dominance
- chronic stress
- inflammation
- reduced resilience
Where Nitric Oxide Fits In
Nitric oxide is one of the body’s most important signalling molecules.
It helps regulate:
- blood vessel dilation
- circulation
- oxygen delivery
- mitochondrial function
- endothelial health
- autonomic nervous system balance
As we age, nitric oxide production tends to decline significantly.
This decline is associated with:
- endothelial dysfunction
- higher blood pressure
- reduced circulation
- poorer recovery
- lower HRV
- increased cardiovascular risk
Research increasingly shows nitric oxide plays a major role in autonomic regulation and vagal signalling.
Studies suggest nitric oxide:
- improves endothelial flexibility
- supports vagal neurotransmission
- improves baroreflex sensitivity
- reduces sympathetic dominance
- enhances parasympathetic activity
This may explain why interventions that improve nitric oxide production often also improve HRV.
The Connection Between Nitric Oxide, HRV and Aging
One of the clearest patterns in modern health research is that metabolic dysfunction impairs nitric oxide production.
Conditions such as:
- insulin resistance
- obesity
- inflammation
- sedentary lifestyle
- poor sleep
are all associated with reduced nitric oxide availability and lower HRV.
This creates a potential cascade:
metabolic dysfunction → impaired nitric oxide → endothelial dysfunction → autonomic imbalance → reduced HRV → increased cardiovascular risk
This may help explain why improving nitric oxide production can have broad effects on:
- cardiovascular health
- energy
- recovery
- stress resilience
- healthy aging
Humming: A Powerful Nitric Oxide and Vagus Nerve Stimulator
Listen to this track daily and hum along with the frequencies to naturally calm the nervous system, boost nitric oxide and hence increase HRV.
One of the most fascinating discoveries in nitric oxide research is the effect of humming.
Research has shown humming can increase nasal nitric oxide production dramatically — up to 15-fold higher than quiet exhalation.
This appears to occur through:
- vibration of the sinus cavities
- increased airflow exchange
- nitric oxide release from the nasal passages
At the same time, humming may stimulate the vagus nerve through:
- vibration near vagal pathways
- slower breathing
- longer exhalation
- parasympathetic activation
Studies on humming and slow breathing have demonstrated improvements in HRV markers associated with:
- increased vagal tone
- reduced stress
- improved autonomic balance
This may explain why many people notice:
- deeper relaxation
- calmer mood
- lower resting heart rate
- improved sleep
- better recovery
after humming or breathwork practices.
Natural Ways to Support Nitric Oxide and HRV
Many evidence-based interventions that improve HRV also appear to support nitric oxide production and vagal function.
These include:
Nasal Breathing
Supports nitric oxide intake from the nasal passages and improves breathing efficiency.
Humming
May dramatically increase nasal nitric oxide while stimulating vagal activity.
Exercise
Aerobic exercise strongly stimulates endothelial nitric oxide production.
Nitrate-Rich ingredients
Extracts like:
- beetroot
- arugula
- spinach
provide dietary nitrates that can be converted into nitric oxide.
L-Citrulline
Supports nitric oxide production by increasing arginine availability.
These ingredients available in Ultimate 4
Sauna
May improve endothelial nitric oxide synthase activity and vascular flexibility.
Meditation and Slow Breathing
Increase parasympathetic activity and support vagal tone.
Why nitric oxide, HRV and vagal tone matter for healthy ageing
The emerging science suggests nitric oxide sits at the intersection of:
- circulation
- mitochondrial health
- nervous system regulation
- recovery
- inflammation
- cardiovascular resilience
At the same time, HRV provides a measurable window into how well these systems are functioning together.
The vagus nerve appears to be one of the key regulators connecting these systems.
As nitric oxide declines with aging and metabolic dysfunction, autonomic balance and HRV often decline as well.
This may be one of the reasons interventions that support nitric oxide production — including humming, nasal breathing, exercise and targeted nutrition — can have such broad effects on energy, recovery and healthy aging.
While more large-scale human studies are still needed, the current evidence strongly suggests that supporting nitric oxide production and vagal function may be one of the most overlooked strategies for improving resilience, recovery and long-term cardiovascular health.
Frequently asked questions
What is heart rate variability (HRV)?
HRV measures the variation in time between heartbeats. A healthy heart does not beat like a metronome but constantly adjusts to breathing, movement, stress and recovery, so higher HRV generally reflects greater nervous system flexibility and stronger vagal activity.
How does nitric oxide affect HRV?
Nitric oxide helps regulate circulation, endothelial health and autonomic nervous system balance. Studies suggest it supports vagal neurotransmission and baroreflex sensitivity, which may explain why interventions that improve nitric oxide production often also improve HRV.
What does the vagus nerve do?
The vagus nerve is the longest cranial nerve, travelling from the brainstem through the heart, lungs and digestive tract. It acts as a communication highway between brain and body and regulates parasympathetic activity, slowing heart rate and supporting recovery.
Does humming increase nitric oxide?
Research has shown humming can increase nasal nitric oxide up to 15-fold compared with quiet exhalation. Humming may also stimulate the vagus nerve through vibration, slower breathing and longer exhalation.
How can I improve my HRV naturally?
Practices that support both nitric oxide and vagal function include nasal breathing, humming, aerobic exercise, sauna, meditation and slow breathing. Nitrate-rich ingredients such as beetroot, arugula and spinach, along with L-citrulline, also help support nitric oxide production.
If you are interested in getting started on my protocols, take the assessment first.
Second, join my community where I regularly discuss these matters and you can ask me any questions. Join here.
References & Research
- Lehrer P & Gevirtz R. Heart rate variability biofeedback. Frontiers in Psychology, 2014.
- Bonaz B, et al. The vagus nerve at the interface of the microbiota-gut-brain axis. Frontiers in Neuroscience, 2018.
- Lundberg JO & Weitzberg E. Nitric oxide and the autonomic nervous system. Cardiovascular Research, 2019.
- Thayer JF, et al. The relationship of autonomic imbalance, heart rate variability, and cardiovascular disease. International Journal of Cardiology, 2010.