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Swedish Cross Country Skiers suffer more asthma than their Norwegian Cousins...
pcoldski The Öppet Spår ("Open Track") race, 90 kilometer Vasaloppet Ski course in Dalarna, Sweden. Winter daytime max. temperatures may average -20 to -10 degrees centigrade in Sweden, which is some 10 degrees colder than in Norway, and this may explain the difference in exercise induced asthma prevalence between cross country skiiers of Norway and Sweden.
More about Cold Temperatures & Cross Country Skiing...
More about Vasaloppet...
Articles and Resources:-
Management of Exercise Induced Asthma in XC-Skiing
High Prevalence of Exercise Induced Asthma in Elite Swedish Cross Country Skiiers
Surgical Face Masks for Cross Country Skiiers!
Further Reading on Asthma.
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Management of Exercise Induced Asthma in XC-Skiing


By Clare-Louise Brumley B. Occ. Therapy, Grad. Dip. Nutrition/Medicine (Original Article: Australian Cross Country News Vol 18, no 1 Autumn / Winter 2003. Reprinted with author's permission).

"XC skiing is potentially a difficult sport for an asthmatic... From my personal perspective, I was previously considered to have severe exercise induced asthma to the extent that it stopped me from competing...."


CLBrumley


After a seven year break from racing and some serious work on managing this condition it is no longer such an obstacle, so I thought I'd share some of the strategies I use to manage my asthma and give the reasoning behind their effectiveness.


One in 7 Skiers may suffer...
Asthma is characterized by a wheeze, shortness of breath, a cough and chest tightness. However, not all these symptoms may be present, and in some athletes presenting with shortness of breath, the diagnosis may be missed. The prevalence of exercise-induced asthma (EIA) in the Australian population is thought to be 12%. Data from the 1996 summer Olympics stated that 14% of the USA team used anti-asthma medication. The prevalence in winter sports is likely to be much higher.


Triggered by rapid drying of the upper airways...
The most recognized theory on the cause of EIA is that increased ventilation rate leads to rapid drying of the upper airways and triggers bronchoconstriction. hence, the harder one breathes, and the colder and dryer the air, the risk of EIA increases. This combination of conditions is inherently part of cross country skiing. Asthmatics who exercise in 37 degrees temperature with 100 % humidity can almost completely block their EIA.

Buteyko breathing method. It's all through the nose!
Nose breathing can ameliorate the severity of EIA because inspired air is warmed by the blood vessels and tissues of the nose, and the air that hits the upper airways is warmer and more humidified. The Addition of a mask/balaclava further warms and moistens inhaled air. Another advantage of nose breathing is that air flow is more controlled than with mouth breathing which reduces the negative effect of rapid breathing on airway drying. Nose breathing in XC skiing is considered impossible given the amount of air that is required. However for the asthmatic, if nose breathing decreases symptoms, it far outweighs any possible advantage that mouth breathing may have.

Nose breathing has been recently popularized by the Buteyko breathing technique. A respected randomized placebo controlled trial of Buteyko technique(4) has demonstrated its clinical effectiveness in reducing symptoms and inhaler use. The method teaches a series of exercises for breathing correctly, and enables a sense of breathing control to be developed. The breathing exercises are a useful tool for managing symptoms even whilst racing.

Bronchoconstriction occurs 7 minutes into exercise, or at the end of exercise...
In most cases, broncho-constriction does not occur during the first few minutes of exercise. With continued exercise respiratory flow rates begin to fall after 6 to 8 minutes. The greatest drop in flow rates is often seen in the first few minutes after the cessation of exercise. Asthmatics commonly show a 20 to 40% decrease in lung function . Normal range is less than a 10% decrease.

Use your "Refractory period"!
Most athletes with mild EIA recover spontaneously within minutes or soon after treatment with a bronchodilator (e.g. Ventolin). However more severe broncho-constriction may persist. Interestingly, in more that 50% of patients, after an episode of EIA there is a period where further exercise is followed by a smaller episode of bronchoconstriction, or no bronchoconstriction at all. This "refractory period" may persist for up to 4 hours following the initial episode. This can be applied in a warm up prior to races whereby a period of skiing intensely provokes EIA which is then treated, and allows for the refractory period to be utilized during the race. Another hypothesis which re-enforces the need for a thorough warm up (especially prior to intensity work) is that some asthmatics talk of being able to "run through their asthma", whilst others can not. The idea behind this is that with continued exercise the mediators that cause bronchoconstriction are "burnt up". Medication management is critical in EIA.

Don't get discouraged!
Rules related to AOC and IOC legislation on asthma medications are currently changing so check out what you are taking with the Australian Sports Drug Advisory (PH 1800020 506) and you doctor. The variable nature of EIA is well known . When in very similar weather conditions and exertion levels, asthma severity can vary. So don't get discouraged by a bad period. Re-assess medication usage, work on overall immune function (e.g. to eliminate possible underlying viral situation) and experiment with nose breathing, masks and a thorough warm up. Sensibly thinking through different approaches may go a long way to minimizing symptoms of asthma and enjoying this fantastic sport.

References, Management of Exercise Induced Asthma in XC-Skiing:
  1. Brukner P, Khan k. Clinical Sports Medicine. Roseville:McGraw Hill Australia 2002: 743-750 (Astha Attacks: Triggers, Types & Management. Exercise-Induced Bronchospasm: Symptoms, Clinical Features & Treatment).
  2. Gillam I. Medical Conditions and exercise. Lecture Swinburne University Graduate School Integrative medicine 2001
  3. Nisar M, Spence DPS, West D, et al. A mask to modify inspired air temperature and humidity and its effect on exercise induced asthma. Thorax 1992; 47:446-50
  4. Bowler SD, Green A, Mitchell CA. Buteyko breathing technique in asthma: a blinded randomized controlled trial MJA 1998: 575-578

Exercise Induced Asthma in Elite Swedish Cross Country Skiiers

Exercise induced asthma in elite Swedish Cross country Skiers is phenomenally high! 36% of Swedish elite cross country skiiers routinely used asthma medication. Similar studies from Norway indicate a much lower level of asthma: In the order of 14%(2) . The authors quoted speculate that:
"Strenuous exercise at low temperatures entailing breathing large volumes of cold air is the most probable explanation of persistent asthma in skiers".
Mid-Swedish winter daytime maximum temperatures may average -20 to-10 degrees centigrade. Norwegian day time temperatures may average 10 degrees warmer, and this may explain the difference in exercise induced asthma between the two groups of skiers.

Experimental Group: Elite Skiers (Group size 42) None Skiers (group size 29)
Regular use of asthma drugs: 36% 0%
Symptoms of Asthma: 78% 4%

Note 1: These measurements did not change between summer and winter.

References, Exercise Induced Asthma in Elite Swedish Cross Country Skiers:
  1. Larsson K, Ohlsen P, Larsson L, Malmberg P, Rydstrom PO, Ulriksen H:
    High prevalence of asthma in cross country skiers.

  2. Sue-Chu M, Larsson L, Bjermer L:
    Prevalence of asthma in young cross-country skiers in central Scandinavia: differences between Norway and Sweden.



Surgical Face Masks!!!...

When temperatures dip to well below 10 degrees centigrade, Skiers may wish to manage their exercise induced asthma by the use of surgical face masks.
  1. Surgical Face Masks for Management of Exercise Induced Asthma

Further Reading on Exercise Induced Asthma relevant to Cross country Skiers...
  1. Three World-Class Athletes and Five national Medical Organizations Launch New National Asthma Education Program. Survey News Release. Asthma In America. September 28, 1999. Asthma information available online at: http://www.asthmainamerica.com/.
  2. Wilber RL et al. Incidence of Exercise-Induced Bronchospasm in Olympic Winter Sport Athletes. Medicine and Science in Sports and Exercise April 2000, Vol. 32, No. 4, p. 732-737. Available online at: www.acsm-msse.org.
  3. Asthma and Physical Activity in the School. National Heart, Lung, and Blood Institute, National Institutes of Health. NIH Publication No. 95-3651. September 1995. Available online at: http://www.nhlbi.nih.gov/ health/public/lung/asthma/ phy_astr.htm.
  4. Asthma and Exercise. Canadian Lung Association, 2001. Available online at: http://www.lung.ca/ asthma/exercise.
  5. Blood oxygenation improves 10 to 20% with nasal breathing: the nitric oxide connection... Nitric oxide produced in the nasal sinuses and mixed with air inhaled through the nose improves blood oxygenation. This effect is presumed due to dilation of arterioles in the lungs, but may also be due to relaxation of the smooth muscle in the bronchioles. http://erj.ersjournals.com/cgi/content/abstract/7/8/1501
  6. All Nitric Oxide in exhaled air of healthy subjects originates from the upper respiratory tract, with only a minor contribution from the lower airways. http://erj.ersjournals.com/cgi/content/abstract/7/8/1501
Exercise Induced Asthma in Cross-Country Skiers© Bruce Thomson, EasyVigour Project

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