Afternoon, a debate with my roommate about the use of a dehumidifier indoors during the winter has lead me to look into optimal humidity levels for human lung function to try and understand if this is something that should be tuned for a given season or a given training modality;
fig 1 : a high humidity post training environment
fig 2 : a very low humidity post training environment
The images above are to illustrate the broad differences between environments for some of us when winter training.
The question I would like to answer is what is the optimal environment humidity for endurance training and V02 training both during and after exercise.
Anecdotally (and in the literature) cold temperatures can have a wild range of symptoms on athletes ranging from EIB to cough, malaise and reduced V02max. I wanted to open up the discussion to go one step further and isolate the humidity level specifically to see if there is any evidence that suggests that after a long aerobic session or a challenging V02max session there is a benefit to recovering in a high humidity environment and to also try to separate temperature from humidity in >0c environments where this is possible to understand if some benefit of sauna (for example) is a result of the humidity level and not just temperature.
In the 2023 study “Relative Humidity and Its Impact on the Immune System and Infections. Int J Mol Sci. 2023 May” the following chart from 1985 is referenced which seems to suggest that a level of 50% (far higher than outdoor ambient humidity or usual indoor humidity) Is optimal to prevent a wide range of complications to lung health.
However elite athletes are not sick people and can likely push the limits of several of these factors due to their environments being new construction, nicer, cleaner, hypoallergenic, devoid of pollutants, etc. All of which would generally point towards a higher humidity being more favorable.
All in all the humidity levels often advised in studies above or in general knowledge are in place to control environmental effects which may be damaging to the elderly or the very young but for which there are no strong studies on the very healthy or on elite athletes.
As a footnote, obviously pogacar doesn’t need to worry about controlling humidity level in his 150+ year old home to prevent the growth of toxic molds because his environment is likely not so dated, likewise there is probably not a historic pollution problem in his soil or ventilation system so certain “public knowledge best practices” may be missing the mark if the individual is not vulnerable to effects often associated with high humidity. For example chemical interactions are some of the risk factors associated with higher than 60% humidity, so too is allergic asthma (for which I am certain elite athletes are genetically devoid of and constantly monitored for and treated )
I welcome anecdotes and other discussion around sauna and the post exercise humidity like taking a long hot shower as well as any studies that I couldn’t find that show effects one way or another either in the very sick or the very active.