What could be the reason that someone during cycling on colder days (under 15°C or 60°F) needs to invest effort in breathing out as to push the air against something. On the other hand breathing in is easy.


  1. The feeling is similar to blowing up a balloon and it's only in the mouth and cheeks. It's exactly like meeting higher pressure outside my mouth.

  2. In my habitual breathing in rest the I:E is close to 1 and my breathing rate is very low, sometimes as low as 2 per minute. In intense dynamic exercise my breathing rate is still quite low - it could go up 12 as opposed to 30 in many fit people around me. In this case my breathing out is much longer and much more noticeable.


Exhaling through tightly pressed lips is called pursed lip breathing, in which the effort of exhaling is felt only in the lips and cheeks. This way you increase the pressure in the small airways, which expand and thus allow easier elimination of the carbon dioxide from the lungs.

Heavy exercise can be associated with excessive inhalation and therefore lung hyperinflation, in which carbon dioxide accumulates in your lungs. Additionally, forced expiration during exercise often collapses the bronchial wall (Virginia Department of Health).

In such physiological (non-pathological) situations, pursed lip breathing, which widens small airways, can help eliminate excessive air from your lungs. It can also help in stress-related hyperventilation syndrome (Breathe).

Uses of pursed lip breathing in pathological conditions:

1. Exercice-induced bronchoconstriction, which may or may not be a part of chronic asthma;... Stimuli for asthma attack may include: cold air, stress, physical effort...Exercise-induced bronchoconstriction appears to be common in endurance athletes, who have allergic rhinitis, are female, or who exercise in cold [and dry] weather (Breathe).

2. Emphysema, which is a type of chronic obstructive pulmonary disease (COPD), with partially collapsed airways (Physiotherapy Journal, 2018 ; PubMed, 2015)

In summary, pursed lip breathing can be the reaction to normal physiological hyperinflation of the lungs during heavy exercise or due to an obstructive pulmonary disease.


Breathing in is a an active action requiring muscle. Expiration is passive, so occurs more slowly.

Breathing in - inhalation - takes less time than exhalation.

Normal I:E [Inspiration:Experation] ratio at rest and while asleep is 1:2 or less. On exertion the I:E ratio is 1:1. Inspiration is normally an active process (requiring work). Expiration is passive, and usually longer than the time required for exhalation, resulting an a no-flow period. When breathing spontaneously, the work of breathing is minimised by keeping inspiratory times short and tidal volumes low - just enough to get rid of the produced CO2. To minimise collapse, sighs are taken from time to time.

Inhalation involves (unconscious) respiratory muscle use, most commonly the diaphragm, but also the chest wall muscles and even neck muscles. As I said, it's all done unconsciously, and it's done about 28,000 times a day. these muscles are doing this constantly and are well toned to do it.

The work of breathing is done by the diaphragm, the muscles between the ribs (intercostal muscles), the muscles in the neck, and the abdominal muscles. ... The process of breathing out (called exhalation or expiration) is usually passive when a person is not exercising.

Exhalation under normal conditions is passive. It requires no effort from muscles; in fact, it's the opposite: the muscles relax, and you exhale as they do.

The process of breathing out (called exhalation or expiration) is usually passive when a person is not exercising. The elasticity of the lungs and chest wall, which are actively stretched during inhalation, causes them to return to their resting shape and to expel air out of the lungs when inspiratory muscles are relaxed. Therefore, when a person is at rest, no effort is needed to breathe out.

When exercising, in order to speed O2 delivery to muscles that need it, you must actively assist exhalation. When you need to decrease the expiratory phase duration, you need to actively use muscles not normally used to exhale.

During vigorous exercise, however, a number of muscles participate in exhalation. The abdominal muscles are the most important of these. Abdominal muscles contract, raise abdominal pressure, and push a relaxed diaphragm against the lungs, causing air to be pushed out.

That's not "normal" in relaxed exhalation, therefore the use of these muscles to exhale more actively is noticable.

Control of Breathing

  • 3
    Although I trust your knowledge from seeing your many answers on various stacks, I think this answer could use some references for support. Dec 21 '18 at 4:31
  • 1
    @BryanKrause - Fair enough. Done. Dec 21 '18 at 15:34
  • I'm unsure about this answer. For one, OP particularly mentions the cold weather conditions, which you have not addressed yet. Secondly, I find the claim unconvincing that during vigorous exercise, the respiratory exhalation is aided by respiratory exhalation aiders, while the inspiration aiders (M. serratus anterior, Mm. pectoralis major et minor, Mm. scaleni, Mm. serratus posteriores, M. sternocleidomastoideus) are completely ignored. People who are breathless often sit in the cart driver position to aid the M. pectoralis major, which is all about inspiration, not expiration.
    – Narusan
    Dec 23 '18 at 12:02
  • The way I understand your answer is that you state that during exercise, additional muscles are needed for expiration, hence one breathes out more heavily. But as additional muscles are used for inspiration as well, one does also breathe in more heavily.
    – Narusan
    Dec 23 '18 at 12:05
  • @Narusan - There are several things I ignored about the OP's Q: That he breaths twice a minute for one. I answered a general question, I did not try to diagnose the OP. About your second point, you can argue with the references. Pick any good teaching article about inspiration and expiration. I didn't mention the additional muscles of inspiration because 1. that wasn't the question, and 2. I don't think it's relevant. Please add a better answer; I'll look forward to reading it. Dec 23 '18 at 12:16

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