Cold Acclimation and the Effect on Sport Performance

Original Editor - User Name

Top Contributors - Kapil Narale  

Introduction

In an extreme cold environment, even though behavioural or psychological adaptations may act to maintain a sufficient amount of body heat, it is possible that core or peripheral skin temperature can be decreased to a point where metabolic and physiologic functions are no longer sufficient and damage to skin and other tissues may occur.

Environmental cooling power is not only determined by the ambient wet bulb temperature, but is also influenced by the wind and wet clothing. The wind can produce heat loss through convection, while wet clothing increases heat loss through evaporation. Water temperature and currents, with water activities, can contribute to a cooling effect. Inhalation of cold air can also have negative effects for asthmatic healthy athletes.

Various Conditions

Hypothermia and Sport

In sporting events like the Winter Olympics, there can be a vast range in cold temperature, ranging from <-5^oC and >+5^oC. The production of metabolic heat during exercise surpasses the rate of body heat loss in similar and colder environments. In winter sports which involve displacement in a straight line, such as Alpine skiing or snowboarding, factors such as wind and low air-temperature, at high athlete movement speeds, expose the athletes to even apparent colder conditions. However, the production of metabolic heat is quite high during such an activity. In fact, athletes who are participating in events that last around 2 hours, such as Nordic skiing, have a metabolic heat production that is even higher, about 13-18 METS. With this kind of metabolic heat production, the loss of body heat is dissipated, decreasing the chance of suffering experiencing hypothermia during the activity in the respective cold conditions.

When considering open body water temperature in swimming events, even in the summer, there is a minimum lower limit for the water temperature. Body heat loss with water immersion can be much greater than that lost in air of the same temperature, making hypothermia more likely. The lower limit of water temperature is 16^oC. If the temperature of the water, 1m below the surface, is below the 16^oC limit, such an event will not go ahead. Thermoregulatory modelling helps indicate that open water swimmers, swimming at race speeds, in water ≥16^oC, will not experience a significant reduction in body temperatures. However, a group of athletes suggest that the 16^oC limit may not be high enough.

The cold water could also be causing an arrhythmogenic effect. When the actions of exposure to cold water, holding your breath, and immersion of your face, can cause increased sympathetic and parasympathetic activity, which could lead to premature ventricular contractions, thus could cause fatal outcomes.

Frostbite and Sport

When the skin temperature drops below 0^oC, frostbite can occur. The risk of frostbite is seen to increase with wind, which increases convective heat loss at areas of exposed skin. This accounts for the windchill factor, which can be seen on pg. 773 of Bergeron et al (2012). Similar to the wind that contributes to a greater difference between air temperature and metabolic heat production, activities such as running or skiing would result in wind being produced across the body, resulting in a greater windchill factor. When the windchill temperature is below -27^oC, any exposed skin can experience frostbite within 30 minutes.

There are examples of different athletes that are at a risk of developing frostbite. Nordic skiers and biathletes can travel at speeds of 24-27km/h. At this wind speed speed, there is a risk of frostbite since it is likely that air temperatures are below -20^oC. With Alpine skiing and sliding activities, athletes experience speeds of up to 60-100km/h. At this wind speed, there can be a risk of an athlete experiencing a frostbite at an air temperature of -15^oC. Each session of these activities are completed within 3 minutes, so it is unlikely for a frostbite to occur.

Since this is only a risk for exposed skin, therefore windproof clothing would help mitigate the risk of frostbite. It is seen that the athletes have a much lower risk when they are in motion, but while stationary, and for other individuals such as staff and coaches, who are more or less stationary and don't have a high metabolic heat production, there could be a high risk of frostbite.

Cold Exposure and Respiratory Problems in Athletes

It is seen that ≥50% of elite cross-country skiers and swimmers may experience Exercise-Induced Asthma (EIA), and Bronchial Hyper-Responsiveness (BHR). EIA is seen to be caused by heat loss and water loss from respiration. The inhalation of cold air steeply increases the magnitude of exercise-induced bronchoconstriction (EIB), thus decreasing athletic performance. Regardless of inhaling warm air, cold fascial temperatures can increase EIB, thus causing a parasympathetic nervous reflex.

There is a high prevalence of asthma in athletes with exposure to cold air who are participating in endurance sports such as cross-country skiing, Nordic skiing, biathlon, and speed skating. This may occur due to epithelial damage of the respiratory mucosa. Inflammation of the airway, which is denoted by percentage of neutrophils in induced sputum, is associated to the number of hours per week spent on training for cross-country skiers and swimmers. However, age and number of competitive years in cross-country skiers is correlated with intensity of BHR. As seen in bronchial biopsies in young skiers, with or without asthma, there was a significant increase in airway inflammation in competitive cross-country skiers over the winter season. There was a noted increased parasympathetic activity in athletes with a positive metacholine BHR compared to a negative metacholine BHR, who presented with decreased excretion of sweat, production of saliva, and flow of tears. The protection against EIB by inhaled ipratropium bromide in cross-country runners exercising at cold temperatures was marked by greater parasympathetic (vagal) activity.

Many of these respiratory conditions are primarily caused by respiratory epithelial damage in endurance athletes. There is an increase in airway inflammation with the increased exposure to the cold. It is seen that epithelial bronchial culture cells from asthmatics have a slower healing process subsequent to scarring. Though the healing can be accelerated by adding steroids to a cell culture.

Cutaneous vasoconstriction prompted by cold water exposure

can increase venous return, leading to an increase in blood

pressure and central vascular volume. Reportedly, this can

result in acute pulmonary oedema and hemoptysis in swimmers,

similar to swimming-induced or immersion-related pulmonary

congestion.63 64

Resources

• bulleted list
• x

or

1. numbered list
2. x