The road-racing season is upon us, and it appears that the team buses continue to be plagued by snoring cyclists. What’s more, these athletes seem to forget time and again to remove their remedial nose strips come the morning.
Alternatively, there might be some notion that these nose strips improve performance. In case of the latter, I thought I might go over the theory and research behind this practice.
The more formal term for breathing, i.e. inhaling and exhaling.
In this context, the term respiration is used in reference to pulmonary respiration, which refers to the transport of oxygen & carbon dioxide from the atmosphere to body tissues.
Airflow is governed by the Pressure difference at either end of the airway, divided by the Resistance to flow (ΔP/R)1. When we breathe in, we expand our chest and decrease the air pressure in our lungs relative to atmospheric air, causing an inflow of air. The other part of the equation (Resistance) is effectively the result of airway diameter (or rather, airway radius, according to Poiseuille’s law). The relationship is such that doubling airway radius would result in a 16-fold decrease in resistance (i.e. resistance increases with radius to the fourth power). We can adjust the resistance of the oral airway (by opening/closing our mouth), but the resistance of the nasal passage is fairly fixed7,8.
NB: while the mouth is generally considered the lower resistance breathing route, this is only necessarily the case when the mouth is wide open12. For example, breathing orally with pursed-lips results in a similar air resistance to nasal breathing13.
Breathing through the nose is useful in that it warms, filters, and humidifies incoming air2. Yet, its greater resistance (compared to an open mouth) means that its use can incur additional respiratory muscle work4. This is less than you might expect, however, as nasal airway resistance falls substantially during exercise5 (e.g.by as much as 40-50%)11.
It should come as no surprise that as we transition from rest to exercise we switch from almost exclusive nasal breathing to oronasal (mouth + nose) breathing6. The exact nature of this switch is highly variable between individuals, but quite consistent within individuals4,6,9. One study quotes that breathing is ~85% nasal at rest, which is reduced to ~50% when cycling at 150 Watts9. This percentage might decrease further with increasing intensity, but (again) this is highly variable.
The exact distribution of oral and nasal breathing reflects, in part, physiological drives (e.g. ventilatory demands, perceived effort of breathing, airflow resistance etc.)9, though there is also a likely psychological component4—for example, being told to “breathe in through the nose, and out through the mouth”. In one study (conducted in the late 1970s), 4/10 of the *student participants reported that they intentionally breathed through their nose during exercise, and 7/10** believed there was an advantage to doing so4.
The variability in oronasal breathing during rest and exercise. Each line represents a different individual’s response. [adapted from ref. 9]
By and large, in healthy individuals (at sea level), the capacity of the respiratory system exceeds the demands placed on it during heavy exercise14. Breathing capacity per se isn’t a limiting factor during exercise (which I would imagine is most athlete’s justification for wearing nasal strips). This is evidenced by the fact that blood oxygen saturation seldom drops below 90%, even during maximal exercise23. (Have you ever seen someone turn blue while exercising?)
NB: There is one small exception, which is a small subset of highly-trained athletes, particularly runners, who experience an unusually large, and as yet unexplained, drop in blood oxygen saturation during maximal exercise18,19.
As ventilation increases, there is a disproportionate increase in respiratory muscle work and, thus, oxygen uptake (VO2)14. In other words, as breathing depth and rate rises, the demands placed on the muscles involved in breathing increase to a greater extent. As a result, about 10–15% of maximal oxygen uptake (VO2max) might be attributed to the work of the respiratory muscles15.
Sustained, high-intensity exercise (80–85% max HR or greater)18,20 can cause the respiratory muscles to become mechanically limited and/or fatigued15, particularly the diaphragm16. The demands of the respiratory muscles are prioritised above those of the working limbs, such that respiratory muscle fatigue causes diversion of blood away from the working muscles17,18, which can expedite fatigue.
Therefore, if nasal splints can reduce nasal airway resistance*, the same level of airflow could be achieved with less respiratory muscle work21. This might also delay/attenuate respiratory muscle fatigue.
*As with everything, there are both responders and non-responders to the effects of nose strips. Specifically, those with lower baseline levels of nasal airflow resistance are less likely to see any effect from a nasal dilator21. In addition, there is also substantial variation in the actual dilation achieved with a nose strip (e.g. 0–50% change in cross-sectional area)22.
Those with higher levels of baseline nasal resistance generally benefit more from a nose strip [adapted from ref. 21]
So the theory is reasonably sound, but do nose strips actually enhance exercise performance in practice?
Put simply, no.
Despite an abundance of anecdotes, the research is fairly unanimous in it’s rejection of nasal dilators as an ergogenic aid (e.g. 24–27). No significant effects have been observed across a wide range of physiological measures (e.g. VO2max, ventilatory parameters, heart rate, work output…etc.). Even the perceptual benefit (i.e. the feeling that breathing is enhanced) hasn’t stood up to the scrutiny of placebo-controlled studies24,25.
“Coaches and athletes are always seeking new ways to enhance performance. Although nose strips may be popular with athletes, current research concludes that nose strips do not provide any cardiorespiratory or perceptual advantage during rest, submaximal and maximal exercise, or recovery conditions.” — Baker & Behmn, 199924
- Powers SK and Howley ET. Respiration During Exericse. Exercise Physiology: Theory And Application To Fitness And Performance. 8th Edn. New York: Mcgraw-Hill, 2012, p. 218.
- Proctor DF. The Upper Airways. I. Nasal Physiology And Defense Of The Lungs. The American Review Of Respiratory Disease. 115: 97–129, 1977.
- Dempsey JA and Fregosi RF. Adaptability Of The Pulmonary System To Changing Metabolic Requirements. The American Journal Of Cardiology. 55: D59–D67, 1985.
- Saibene F, Mognoni P, Lafortuna CL and Mostardi R. Oronasal Breathing During Exercise. Pflugers Archiv. 378: 65–69, 1978.
- Olson LG and Strohl KP. The Response Of The Nasal Airway To Exercise. The American Review Of Respiratory Disease. 135: 356–359, 1987.
- Wheatley JR, Amis TC and Engel LA. Oronasal Partitioning Of Ventilation During Exercise In Humans. J. Appl. Physiol. 71: 546–551, 1991.
- Cole P, Forsyth R and Haight JS. Respiratory Resistance Of The Oral Airway. The American Review Of Respiratory Disease. 125: 363–365, 1982.
- Strohl KP, Butler JP and Malhotra A. Mechanical Properties Of The Upper Airway. Comprehensive Physiology. 2: 1853–1872, 2012.
- Chadha TS, Birch S and Sackner M. Oronasal Distribution Of Ventilation During Exercise In Normal Subjects And Patients With Asthma And Rhinitis. Chest Journal. 92: 1037–1041, 1987.
- Ferris BG Jr, Mead J and Opie LH. Partitioning Of Respiratory Flow Resistance In Man. J. Appl. Physiol. 19: 653–658, 1964.
- Strohl KP, Decker MJ, Olson LG, Flak TA and Hoekje PL. The Nasal Response To Exercise And Exercise Induced Bronchoconstriction In Normal And Asthmatic Subjects. Thorax. 43: 890–895, 1988.
- Amis T, O’neill N and Wheatley J. Oral Airway Flow Dynamics In Healthy Humans. The Journal Of Physiology. 515: 293–298, 1999.
- Rodenstein DO and Stanescu DC. Absence Of Nasal Air Flow During Pursed Lips Breathing. The Soft Palate Mechanisms. The American Review Of Respiratory Disease. 128: 716–718, 1983.
- Guenette J and Sheel A. Physiological Consequences Of A High Work Of Breathing During Heavy Exercise In Humans. Journal Of Science And Medicine In Sport. 10: 341–350, 2007.
- Aaron EA, Seow KC, Johnson BD and Dempsey JA. Oxygen Cost Of Exercise Hyperpnea: Implications For Performance. J. Appl. Physiol. 72: 1818–1825, 1992.
- Johnson BD, Babcock MA, Suman OE and Dempsey JA. Exercise-Induced Diaphragmatic Fatigue In Healthy Humans. The Journal Of Physiology. 460: 385–405, 1993.
- Sheel AW, Derchak PA, Morgan BJ, Pegelow DF, Jacques AJ and Dempsey JA. Fatiguing Inspiratory Muscle Work Causes Reflex Reduction In Resting Leg Blood Flow In Humans. The Journal Of Physiology. 537: 277–289, 2001.
- Amann M. Pulmonary System Limitations To Endurance Exercise Performance In Humans. Experimental Physiology. 97: 311–318, 2012.
- Dempsey JA, Hanson PG and Henderson KS. Exercise-Induced Arterial Hypoxaemia In Healthy Human Subjects At Sea Level. The Journal Of Physiology. 355: 161–175, 1984.
- Wetter TJ, Harms CA, Nelson WB, Pegelow DF and Dempsey JA. Influence Of Respiratory Muscle Work On VO2 and Leg Blood Flow During Submaximal Exercise. J. Appl. Physiol. 87: 643–651, 1999.
- Gehring JM, Garlick SR, Wheatley JR and Amis TC. Nasal Resistance And Flow Resistive Work Of Nasal Breathing During Exercise: Effects Of A Nasal Dilator Strip. J. Appl. Phsyiol. 89: 1114–1122, 2000.
- Kirkness JP, Wheatley JR and Amis TC. Nasal Airflow Dynamics: Mechanisms And Responses Associated With An External Nasal Dilator Strip. The European Respiratory Journal. 15: 929–936, 2000.
- Powers SK, Lawler J, Dempsey JA, Dodd S and Landry G. Effects Of Incomplete Pulmonary Gas Exchange On Vo2 Max. J. Appl. Physiol. 66: 2491–2495, 1989.
- Baker KM and Behm DG. The Ineffectiveness Of Nasal Dilator Strips Under Aerobic Exercise And Recovery Conditions. J. Strength Cond. Res. 13: 206–209, 1999.
- Case S, Redmond T, Currey S, Wachter M and Resh J. The Effects Of The Breathe Right Nasal Strip On Interval Running Performance.* J. Strength Cond. Res. 12: 30–32, 1998.
- O’kroy JA, James T, Miller JM, Torok D and Campbell K. Effects Of An External Nasal Dilator On The Work Of Breathing During Exercise. *Med. Sci. Sports Exerc**.* 33: 454–458, 2001.
- Thomas DQ, Larson BM, Rahija MR and Mccaw ST. Nasal Strips Do Not Affect Cardiorespiratory Measures During Recovery From Anaerobic Exercise. J. Strength Cond. Res. 15: 341–343, 2001.