A friend of mine does not like running or the idea of running.
“What was chasing you?” he asked after hearing about a long run I just finished. Note he used “what”, instead of “who”.
It was a huge shock to him when he heard, for the first time, that people have to pay to run in a race. “Why would people pay so much money to get tortured? I can do that for free.” -His commented after hearing that I paid $200 to register for a marathon.
So I have been running regularly throughout Michigan winter, snow or shine, as far as the temperature is above -20°F. His remark was, “Your lungs will get frozen in that weather.”
He was not alone. Many worry that exercising in the cold weather will cause frozen lungs.
It has been known for a long time that winter athletes have higher rate of respiratory diseases. One prominent condition is called exercise-induced bronchoconstriction (EIB) or “sports asthma”, which represents narrowing of airways during sports. Affected people have asthmatic symptoms, such as cough, wheezing and difficulty in breathing, all of which is only triggered by exercise. According to a report in 2008, 15% of winter Olympic cross-country skiers have asthma, much higher than the 4% rate in armature skiers 1.
Researchers found signs of inflammation and injury to epithelial lining of airways in affected athletes. However, under the microscope, the pathological changes differ from what is seen in patients with asthma caused by allergy to environmental factors. Many affected athletes recovered from sports asthma after they retired from strenuous training.
On a side note, the group of athletes affected by sports asthma have significantly higher performance than the control group. We still don’t know why, although medicine used by athletes is not a contributing factor.
There have been many studies on this subject. It is believed that elite athletes undergo hyperpnea, or heavy breathing, which exposes them to many environmental insults, such as cold and dry air or pollutants.
At rest, a regular adult breathes in and out about 10 liters of air per minute. During moderate exercise, this can go up by 10 times. In elite athletes during intense training, however, up to 200 liters of air is exchanged through airways each minute, for extended period of time. This alone exposes athletes to irritation and pollutants from the air.
In fact sports asthma is not unique to elite winter athletes. It affects indoor Olympic swimmers to a similar extent. Exposure to chlorine-containing air from the pool during intense and prolonged training is responsible for swimmers’ asthma. In biathlon athletes who compete in both skiing and swimming, over 25% of them are affected by sports asthma.
At resting state, we breath calmly through the nose. The mucosa lining of our nasal tract warms and moisturizes the air. Thus the air reaches our body temperature by the time it passes our nasal cavity.
During moderate exercise in the cold air, we breath in more cold air through both mouth and nose, and our body faces the challenge from both exercise and low temperature.
This is due to engorgement of veins underlying nasal mucosa triggered by cold air. Cold air is low in humidity, therefore it has both cooling and drying effect on our airways. But most of these will resolve later during exercise.
Cold air also causes constriction of airways even during moderate exercise, which makes us feel shortness of breath. The mechanisms have not been fully understood, but include swelling of epithelial lining in airways, loss of the surface fluid, constriction of the smooth muscle controlling airways, and neuronal reflex when our face is being cooled down 2.
However, this response triggered by cold is transient. Air that reaches our lung is is at body temperature due to warming and conditioning by airways.
The occasional cough and shortness of breath a healthy individual feels during cold weather exercise is not asthma. In fact, asthma is not more prevalent in cold regions compared to warm regions. Risk for asthma is not elevated by regular exercise such as recreational skiing, or working outdoors in the cold air 3.
Surprisingly, compared to research on athletes, much fewer studies have been conducted on long-term effects of moderate cold-weather sports among regular people. This is probably expected, as research on professional athletes would be more likely to gain support from funding agencies and companies.
Nevertheless, long-term benefits of moderate exercise have been well- established. It has been shown that consistent moderate exercise led to increase in anti-inflammatory response, with improved immunity and resistance to upper respiratory tract infection 4. The well-known benefits of exercise outweigh the discomfort of exercising in the cold weather. For instance, in recreational downhill skiers who ski regularly, overall improvement in both physical and mental health has been described 5.
In this fascinating photo in the Atlantic before the 2018 Pyeongchang Winter Olympic, the German skier Maren Hammerschmidt is using a device called Heat and Moisture Exchanger (HME). The device retains the heat and moisture from exhaled air and adds them back to the inhaled air. A recent study by Austrian scientists in Sport Science reported that an HME device not only reduced respiratory symptoms such as coughing and difficulty in breathing, but also improved lung functions and sport performance of athletes during intense exercise at -4°F 6.
Shall we use HME for exercising in winter? After I read the research article above, I found out that the device now is available online for $50. But I won’t need one. While running outside, the chance of getting frostbites is higher than hurting my lungs.
Exposure to fresh air in winter makes us healthier and stronger, as mothers in Finland have believed for generations 7. Finnish babies as young as two weeks old sleep outdoors once a day in winter. Similarly, most Swedish daycares let babies rest outside everyday at below freezing temperature, as reported by BBC.
Being outside is simply part of our winter life. It is worth enjoying.
1. Fitch KD, Sue-Chu M, Anderson SD, et al. Asthma and the elite athlete: Summary of the International Olympic Committee’s Consensus Conference, Lausanne, Switzerland, January 22-24, 2008. Journal of Allergy and Clinical Immunology 2008;122(2):254-260.e7.
2. Koskela HO. Cold air-provoked respiratory symptoms: the mechanisms and management. International Journal of Circumpolar Health 2007;66(2):91–100.
3. Kotaniemi J-T, Latvala J, Lundbäck B, Sovijärvi A, Hassi J, Larsson K. Does living in a cold climate or recreational skiing increase the risk for obstructive respiratory diseases or symptoms? Int J Circumpolar Health 2003;62(2):142–57.
4. Pedersen BK, Toft AD. Effects of exercise on lymphocytes and cytokines. Br J Sports Med 2000;34(4):246–51.
5. Burtscher M, Federolf PA, Nachbauer W, Kopp M. Potential Health Benefits From Downhill Skiing. Frontiers in Physiology [Internet] 2018 [cited 2019 Dec 7];9. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6340074/
6. Frischhut C, Kennedy MD, Niedermeier M, Faulhaber M. Effects of a Heat and Moisture Exchanger on Respiratory Function and Symptoms Post Cold Air Exercise. Scandinavian Journal of Medicine & Science in Sports [Internet] [cited 2019 Dec 1];n/a(n/a). Available from: https://onlinelibrary.wiley.com/doi/abs/10.1111/sms.13603
7. Tourula M, Isola A, Hassi J. Children sleeping outdoors in winter: parents’ experiences of a culturally bound childcare practice. Int J Circumpolar Health 2008;67(2–3):269–78.
I received my MD from PUMC in Beijing China and my Ph.D. in Biochemistry from Stony Brook University on Long Island. Over the years, I have worked in the fields of genetic research and clinical medicine in different parts of the US, including PA, MO, CT, FL, NY and MI. My research has been published in multiple scientific journals. Currently I live in Ann Arbor, MI with my husband and our children and Mango the orange tabby. I love hiking, running, baking, cooking and biking.