Why a Blocked Nose Makes Training Feel Harder Than It Should

Most people think of a blocked nose as an inconvenience. Something annoying, but easy to push through. In reality, nasal congestion can have a meaningful impact on how you train, how quickly you fatigue, and how you feel both during and after exercise.

If you have ever felt unusually groggy, flat, or out of breath during a session while congested, there is a physiological reason for it.

The nose plays a bigger role than we realise

Your nose is designed to optimise breathing. It filters incoming air, warms and humidifies it, and supports the production of nitric oxide, a molecule that helps regulate blood flow and oxygen delivery in the body. Research shows that the nasal airway accounts for over 50 percent of total respiratory resistance in healthy individuals, which means small changes in nasal airflow can have a disproportionate impact on breathing efficiency.

Nasal breathing has also been shown to support aspects of post-exercise recovery. In controlled studies, recovery markers such as muscle oxygenation and vascular function improved more quickly when nasal breathing was maintained compared to mouth breathing, likely linked to nitric oxide availability.

When the nasal passages are blocked, airflow resistance increases and the body naturally shifts toward mouth breathing. This bypasses many of the nose’s functions and leads to less efficient breathing mechanics overall.

Congestion increases effort and speeds up fatigue

From a training perspective, restricted nasal airflow means the respiratory system has to work harder to meet the same oxygen demand. Studies examining nasal obstruction have found associations with reduced ventilation efficiency, lower VO₂max, and higher perceived breathlessness during exercise.

In one treadmill-based study, participants exercising under restricted nasal breathing conditions reached exhaustion around 20–25 percent sooner compared to conditions where airflow was improved. When nasal patency was supported (i.e. better airflow), time to exhaustion increased by over 30 percent in some protocols.

In simple terms, congestion makes the same workload feel harder. As perceived effort rises, time to fatigue shortens, particularly during aerobic or high-volume training where breathing efficiency matters most. This is one of the reasons athletes often report feeling “heavy” or underpowered when training with a blocked nose, even if their conditioning has not changed.

 

Why congestion leaves you feeling groggy

The impact does not stop when training ends. Persistent nasal obstruction is associated with poorer sleep quality, increased mouth breathing at night, and more frequent sleep disruption. Even modest reductions in sleep efficiency are known to impair cognitive sharpness, mood, and perceived energy levels the following day.

This helps explain why congestion often leaves you feeling foggy or flat, even after what should have been a normal night’s sleep. So the groggy feeling that accompanies congestion is not just about oxygen during training. It is also about recovery quality, nervous system load, and cumulative fatigue.

The bigger picture

Nasal congestion might seem minor, but its effects can cascade across performance and wellbeing:

• Breathing becomes less efficient
• Training feels harder at lower intensities
• Fatigue arrives sooner
• Sleep and recovery are compromised

Taken together, this helps explain why athletes and high performers often notice a real drop in training quality when nasal breathing is restricted.

Breathing well is not just about getting air in. It is about how efficiently the system works under load. Keeping the nasal airway clear is one of the simplest ways to support that system, both in training and in recovery.

References:

Dallam, G.M., McClaran, S.R. and Cox, J.L. (2018) ‘Effect of nasal versus oral breathing on exercise performance and recovery’, International Journal of Exercise Science, 11(4), pp. 110–123.

Ferris, B.G., Mead, J. and Opie, L.H. (1964) ‘Partitioning of respiratory flow resistance in man’, Journal of Applied Physiology, 19(4), pp. 653–658.

Koutsourelakis, I., Safakas, K., Roussos, C. and Zakynthinos, S. (2008) ‘Nasal obstruction and sleep quality’, European Respiratory Journal, 32(6), pp. 1509–1514.

Kujanpää, T., Virkkula, P. and Leppänen, T. (2023) ‘Nasal obstruction and aerobic performance in athletes’, Rhinology, 61(3), pp. 215–223.

Surda, P. and Walker, A. (2018) ‘Upper airway inflammation and its impact on athletic performance’, Current Allergy and Asthma Reports, 18(6), 31.

Tong, T.K., Fu, F.H., Chung, P.K., Eston, R.G. and Lu, Y. (2001) ‘The effect of nasal dilatation on ventilatory capacity and exercise performance’, Medicine & Science in Sports & Exercise, 33(4), pp. 609–615.