by Joe Giandonato, MBA, MS, CSCS
A massive swath of the contiguous United States is once again enveloped by record breaking, near mercury solidifying temperatures. Actually, the aforementioned allegory is not that great of an exaggeration. Temperatures approaching -37°F, the point at which mercury begins to crystallize, have been recorded throughout the northern portion of the continental United States, most recently on Friday, February 13th in Watertown, NY, which experienced a low temperature of -30°F.
In addition to altering the properties of mercury, extremely cold environments are capable of impacting hypothalamic functioning, thereby triggering thermoregulatory functions which are governed by the body’s autonomic nervous system such as: voluntary shivering, non-shivering thermogenesis, and periperhal vasodilation. Each of these processes raises heat production, in turn, helping maintain body temperature closer to its physiological baseline, which in humans is 98.6°F.
When heat production via metabolic processes cannot satisfy heat losses, which largely transpire through water and air, conditions including chilblain, frostbite, or hypothermia may arise. Heat loss becomes magnified when the skin makes contact with colder water, as water possesses a thermal conductivity which is 25 times greater than that of air, meaning that heat loss occurs more rapidly when the body is exposed to water.
Exercise is rather limited in its capacity to offset heat losses associated with exercise. Thermal energy, more specifically, heat, is transferred through four key thermoregulatory processes:
- Conduction, which is mentioned above, involves direct contact with a cooler object. Individuals suffering from heat illnesses and those who are attempting to allay inflammation associated with physical activity often practice cold water immersion, or CWI, which serves a conductive medium that allows for the dissipation of heat. However, unintentional and prolonged CWI is not advisable while exercising.
- Convection, which involves the movement of air or water over the skin. This process occurs when individuals are running and/or biking during warmer weather and experience a breeze. This cooling breeze is actually created by their movement. The effects of radiation are magnified in colder weather.
- Radiation, which requires the surrounding temperature to be cooler than the body. If the air temperature is cooler than the body, than prolonged exposure may cause a drop in body temperature if voluntary and involuntary metabolic processes are unable to nullify heat losses.
- Evaporation, which occurs when perspiration and water evaporate from the skin.
Colder weather also presents significant challenges to the athlete and fitness and/or strength and conditioning professional, as it reduces exercise capacity, since a bulk of metabolic functioning is now being devoted to staving off heat losses. Instead of supporting exercise conducted at greater intensities, glycogen is being utilized to fuel shivering and non-shivering thermogenesis. Colder environments also make individuals more susceptible to exercise induced bronchospasms, as chilled air that is taken up by the mouth and nose and traveling through the airway may compromise pulmonary function. Further, aerobic capacity may be reduced as the body now has to “warm up” the cold air that is being inhaled, thus slightly delaying the delivery of oxygenated blood to thirsty muscles. Nervous system functioning, including activation, discharge frequency of motor neurons, and acetylcholine activity are impaired by colder environments.
Exercising in cold weather requires special care. The considerations below should be adhered to if decrements in performance and compromised safety are to be avoided:
- Clothing should be multilayered to better insulate the body, thus enhancing its ability to maintain core temperature. Layers should include: a base layer to transport moisture away from the skin and disperse it to above layers where it can evaporate. Non-wicking, synthetic textiles, such as polyester and polypropylene are suggested; a middle layer composed of a thicker or denser material such as wool or fleece to “trap” warm air close to the body. Wool and fleece are suggested due to their water resistant properties; lastly, an outer layer should shield you from the environment, which can include water and/or wind. Extremities should remain covered as a significant amount of heat loss occurs at the head. In colder weather, blood is shunted away from the extremities to preserve visceral functioning and health. Reduced blood flow inhibits strength and muscle function of the extremities, and more profoundly, makes them more susceptible to frostbite.
- Warm-ups should be lengthened and administered with gradual progressions in intensity as tolerated. The practice of overdressing can be utilized, which involves multiple layers of clothes and a subsequent removal based on comfort level and the achievement of maintenance of a body temperature is established. Additional measures to facilitate the warm-up may include: taking a warm shower prior to exercise, a useful practice, especially, if you do not have to travel a great distance or have to wait for a prolonged amount of time before exercising; cranking up the heat in your automobile, or applying certain topical liniments which promote vasodilation. Drinking warm beverages prior to exercising in the cold anecdotally seem to help, as does consuming caffeinated beverages, since caffeine stimulates the sympathetic nervous system and the triggers the activity of the apocrine glands, which produce sweat.
- If you have to train early in the morning, or are relegated to performing compound movements in the not-so comfort of a cold garage or gym, consider incorporating your assistance movements prior to the main lifts, provided they don’t significantly interfere with their safety performance. You may also use certain assistance exercises to activate dormant muscle groups and/or perform them in a circuit-like fashion with a number of exercises to elevate body temperature. Lightly loaded exercises and those performed with elasticized bands and bodyweight will often do the trick.
- Fueling and hydration strategies are still vitally important in ensuring optimal health and performance. Since energetic demands are increased in cold weather (up to 400 kcal / hour), it would be best to ingest more calorically dense foods and items that contain greater amounts of carbohydrates prior to, during, and following exercise. Hydration status also needs to be paid close attention. And since cold blunts an already misleading thirst mechanism, hydration strategies similar to exercising in warmer environments should be practiced.