PHYS-15 · Principle
Are my lungs my limiter, and is hard training at −10 °C bad for them?
Rarely the lungs, unless you are highly trained. Cold, dry air can narrow the airways of those prone to it; wheeze or a tight chest then is for a doctor.
How the body works, agreed across the reviews below; a study entry shows what one experiment measured.
Practical Application
Are my lungs my limiter, and is hard training at −10 °C bad for them? Rarely the lungs, unless you are highly trained. Cold, dry air can narrow the airways of those prone to it; wheeze or a tight chest then is for a doctor.
What it does not mean: that breathlessness proves a lung limit, or that breathing-muscle training is useless: it improved endurance performance in controlled trials, least in the fittest (REF-133).
Mechanism
The respiratory system is near ideally built for exercise in the healthy untrained young adult; underbuilt for a large cardiac output, as in highly trained endurance athletes, and with female sex, ageing and hypoxia, it limits oxygen transport and adds to leg fatigue (Dempsey 2020). Above about 85% VO2max held for long, fatiguing breathing-muscle work narrows leg vessels by a reflex in everyone, whatever their fitness (Amann 2012).
In 40-50% of elite endurance cyclists and runners arterial oxygen falls near VO2max, through ventilation-perfusion inequality and diffusion limits, not hypoventilation, and in the most affected it limits VO2max (Powers 1993).
Heavy breathing dries the airway surface, the accepted osmotic trigger, and cold air adds to it; long exposure to cold, dry air and pollutants makes bronchoconstriction commoner in high-performance athletes (Aggarwal 2018, full text), above all in endurance sports (Carlsen 2008). Breathing rate tracked perceived exertion more closely than heart rate (a perspective, REF-1084, C+).
Common misreading
"Breathless means my lungs are the limit"; "breathing-muscle training will show on my ramp test": it showed in constant-load tests and time trials, not in ramp tests (REF-133).
Safety (base practice): chest pain, or breathlessness out of proportion to the effort, goes to a doctor.