# Nasal breathing in sport: the nasal valve, nitric oxide and the switching point

> The nose accounts for roughly half of total airway resistance - and gives you something in return. What physiology says about nasal breathing, and what external nasal dilators actually deliver.

The nose is the expensive route into the lungs: around half of total airway resistance is generated there. Evolution still built no shortcut. Switching to mouth breathing during exercise trades filtration, air conditioning and a gas your body makes for less resistance - a deal that doesn't always pay off.

## The nasal valve: where the resistance comes from

The narrowest point of the entire airway sits about a centimetre behind the nostril: the **nasal valve**, with a cross-section of only a few square millimetres per side. Under the Hagen-Poiseuille law, flow resistance scales with the fourth power of the radius - so a minimal widening at this spot has a disproportionate effect.

There is also a dynamic problem: at high inspiratory flow, pressure inside the narrow section drops and the lateral nasal wall is pulled inward. That is exactly what you feel when your nostrils collapse during hard breathing.

## What the nose delivers: NO, warmth, filtration

Lundberg et al. (1994) showed that human exhaled nitric oxide originates primarily in the nose - the epithelium of the paranasal sinuses continuously produces **NO**. Carried with inhaled air into the lungs, this gas locally dilates vessels and improves the match between ventilation and perfusion. Mouth breathing bypasses that source entirely.

The nasal passages warm incoming air to above 30 °C and almost fully saturate it with moisture before it reaches the trachea. Nasal hairs and mucosa trap particles and microorganisms. With mouth breathing both are lost: dry mucous membranes, greater water loss - and cold, dry air, a recognised trigger of exercise-induced bronchoconstriction.

## The switching point

Niinimaa et al. (1980) described how people spontaneously switch to oronasal breathing at a ventilation of roughly 35 to 45 litres per minute. Beyond that point, nasal resistance costs more than it returns. The conclusion is clear: at 100 litres per minute in a race, pure nasal breathing is physically impossible. The usable range is easy to moderate training, warm-ups, recovery - and sleep.

## What nasal dilators do - and what they don't

Dinardi et al. (2014) summarise the evidence: external strips enlarge the minimal cross-section of the nasal valve and measurably lower nasal airway resistance. Subjectively, users report less breathing effort, calmer sleep and less snoring.

What they do not reliably do is improve endurance performance. O'Kroy (2000) found no consistent effects on oxygen uptake or performance in exercise testing. The documented benefit is mechanical and subjective, not metabolic - knowing that, you use them properly.

## How WOO® Nasenstrips put this into practice

**[WOO® Nasenstrips](/en/shop/woo-nasal-strips)** are external nasal plasters: sprung plastic strips gently pull the nostrils apart and mechanically widen the nasal entrance. No active substance - and therefore none of the habituation that decongestant nasal sprays bring with prolonged use.

Application: clean the nose, dry it, apply the strip. 30 strips per pack. WOO® Nasenstrips suit anyone wanting to optimise nasal breathing in sport or during sleep.

## Frequently asked questions

**Do nasal strips make you faster?**
Measured directly against VO2max or time-trial performance: no. The benefit lies in comfort at low to moderate intensity, in warm-ups, and in sleep quality.

**Do they help with snoring?**
If the obstruction sits in the nasal valve, often yes. In obstructive sleep apnoea the throat collapses, not the nose - strips are not enough there, and that belongs in a doctor's hands.

**Why won't the strip stick?**
Almost always moisture, skin oil or cream. Wash the nose beforehand and dry it completely, and the adhesive holds overnight.

## Sources

Niinimaa V et al. (1980), Respiration Physiology - The switching point from nasal to oronasal breathing.
Lundberg JON et al. (1994), European Respiratory Journal - Primarily nasal origin of exhaled nitric oxide.
Dinardi RR et al. (2014), International Journal of General Medicine - External nasal dilators: definition, background and current uses.
O'Kroy JA (2000), Medicine & Science in Sports & Exercise - Oxygen uptake and ventilatory effects of an external nasal dilator during ergometry.

*WOO® Nasenstrips - in the NEMAPO shop.*