How Does Cold Weather Affect the Athlete?

Cold weather exposure of the airway is a form of chronic trauma that can lead to exercise-induced asthma and other adverse health effects such as rhinorhea, rhinitis, nasal stuffiness, and cough. Scientific studies indicate that up to 50% of athletes who exercise in cold weather experience some respiratory symptoms, including a decline in lung function compatible with exercise-induced asthma. (Storms W. Review of Exercise-Induced Asthma, Medicine and Science in Sports and Exercise, 2003; 35:1464-1470). Many of these athletes have neither a prior history of asthma nor a family history of asthma.

Cold exercise-induced asthma and respiratory symptoms likely involve thermal (warmth related) osmotic (dryness related) and mechanical mechanisms acting on the airway (Helenius I. et al. Asthma, Airway Inflammation and Treatment in Elite Athletes, Sports Medicine, 2005; 35:565-574). According to research studies, a counter measure for decreasing the occurrence of cold related, exercise-induced asthma is to increase warmth and moisture of the airway without increasing resistance when breathing rates are high (Prevention of Cold Injuries During Exercise, Position Stand, American College of Sports Medicine, Medicine and Science in Sports and Exercise, 2006; 38:2012-2029). In addition to cold air affecting the airways, stimulation of the facial skin by cold air has an effect on airway responsiveness (Heindl S. et al. Effect of Facial Cooling and Cold Air Inhalation on Sympathetic Nerve Activity in Men, Respiratory Physiology and Neurobiology, 2004; 142:69-80). The American College of Sports Medicine’s position on prevention of cold injuries during exercise states that breathing dry air combined with skin and facial cooling act in synergy to trigger exercised-induced bronchospasm (Prevention of Cold Injuries During Exercise, Position Stand, American College of Sports Medicine, Medicine and Science in Sports and Exercise, 2006; 38:2012-2029).

Can Exercise in Cold Weather Affect the Immune System?

Cold weather combined with endurance exercise can alter the immune system. Athletes performing in cold weather may thus experience a window of immunologic vulnerability, increasing the risk for viral infections of the respiratory tract. In an animal experiment, exposure to cold air altered immunologic responses for 48 hours following the exercise. This was associated with increased expression of inflammatory mediators circulating in the blood (cytokines) that suppress cell-mediated immunity. In this animal study, continued increases in the expression of interleukin IL-5 and IL-10 and the pro-inflammatory cytokines IL-1, IL-6, and IL-8 were detected 24 hours after exercising while breathing cold air. Forty-eight hours after exercising the expression of IL-10 was still higher than that of the controls, and the expression of tumor necrosis factor (TNF-?lpha) was significantly increased 48 hours after exercising. Such findings suggest a similar window of immunologic vulnerability for athletes, increasing their risk for respiratory viral infections that could negatively affect theri performance. (Davis M et al. Influx of Neutrophils in Persistence of Cytokine Expression in Airways of Horses After Performing Exercise While Breathing Cold Air, American Journal of Veterinary Research, 2007; 68:185-189). Human studies have also found that athletes who perform strenuous exercise are predisposed to post exercise viral infections, particularly of the respiratory tract (Davis M et al. Cold Weather Exercise and Airway Cytokine Expression, Journal of Applied Physiology, 2005; 98:2132-2136; Karjalainen E et al. Evidence of Airway Inflammation and Remodeling in Ski Athletes with and without Bronchial Hyper-responsiveness to Methacholine, American Journal of Respiratory and Critical Care Medicine, 2000;161:2086-2091). Exercise in cold environments also causes disturbances in immunity in humans during recovery from exercise (McFarlin B. and Mitchell B. Exercise in Hot and Cold Environments: Differential Effects on Leukocyte Number and NK-Cell Activity, Aviation, Space, and Environmental Medicine, 2003;74:1231-1236).

Does Cold Weather Exercise Affect Performance?

Exercise capacity has been studied with regards to exercise-induced bronchoconstriction in a cold environment as measured by peak oxygen uptake (VO₂ peak), peak ventilation (VE peak) and peak running speeds in subjects who have been diagnosed with exercise-induced bronchospasm. Results of this study indicated that the VO₂ peak decreased 6.5% in the cold environment, and running speed was significantly lower. The post-exercise reduction in lung function (FEV1.0) was significant (Stensrud T et al. Exercise Capacity and Exercise-Induced Bronchoconstriction in a Cold Environment, Respiratory Medicine, 2007; 101:1529-1536). Only a few studies have even investigated the whole body effects of exposure to cold air upon exercise capacity and/ or lung function in asthmatic subjects. Since up to 50% of athletes may have some type of cold exercise-induced asthma, the effect on athletic performance could reasonably be hampered even if the athlete is not experiencing obvious respiratory symptoms. Since exercise capacity measured by VO₂ peak and peak running speed decreased significantly during exercise studies in a cold environment as compared with regular environmental conditions, such results could apply to most athletes. These findings supported other studies that demonstrate that facial cooling combined with cold air inhalation causes the greatest exercise-induced bronchospasm compared with the isolated challenge of cold air inhalation alone (Zeitoun M et al. Facial Cooling Enhances Exercise-Induced Bronchoconstriction in Asthmatic Children, Medicine and Science in Sports and Exercise, 2004; 36:767-771). Other studies have concluded that exercise-induced bronchospasm is more common in cross-country skiers than in non-athletic controls, and that even mild asthma decreases maximal performance of winter sport athletes (Pohjantahti H et al. Exercise-Induced Bronchospasm Among Healthy Elite Cross-Country Skiers and Non-Athletic Students, Scandinavian Journal of Medicine, Science, and Sports, 2005;15:324-328.).

Does Humidity Help Performance in Cold Weather?

Another important factor found to have an effect on airway inflammation is the humidity of inhaled air. Humidity influences exercise capacity in subjects with exercise-induced bronchoconstriction and one study examined the effect of changing humidity upon exercise capacity measured by peak oxygen uptake (VO₂ peak), peak running speed, VE peak, and peak ventilation (Stensrud T et al. Humidity Influences Exercise Capacity in Subjects with Exercise-Induced Bronchoconstriction, Respiratory Medicine, 2006;100;1633-1641). The results demonstrated that the VO₂ peak and VE peak increased significantly as relative humidity of the inhaled air increased, thus supporting the hypothesis that airway dryness is a critical factor negatively affecting exercise capacity.

Summary

Chronic cold weather exposure of the airway and face is a form of trauma that can potentially lead to inflammation, to exercise-induced bronchospasm, immunologic vulnerability, and a reduction in defined performance parameters. The immunologic vulnerability induced by cold exposure has the potential to negatively affect energy expenditure and savings via induction of some level of fatigue associated with inflammation, increased systemic concentrations of pro-inflammatory cytokines, alteration in natural killer cell activity, and an increased risk of respiratory and viral infections. Protecting the facial skin and airway from cold exposure, and from low humidity induced by cold air, while allowing adequate ventilation with no resistance could help prevent or reduce airway inflammation and improve athletic performance. The American College of Sports Medicine states that a counter measure for decreasing the occurrence of exercise-induced bronchospasm in cold weather athletes is to increase warmth and moisture of the airway without increasing resistance when ventilation rates are high (Prevention of Cold Injuries During Exercise, Position Stand, American College of Sports Medicine, Medicine and Science in Sports and Exercise, 2006; 38:2012-2029).