Historical snowfalls, cold temperatures and short days have been posing training challenges this winter. Recently, I have had a lot of runners ask what the keys to marathon training in the winter are, and if cold weather running is detrimental to their body.
Physiologic Response to Cold
Under normal circumstances and if appropriately dressed, it is extremely rare for people to reach their cold tolerance limit. The amount of heat one loses to the environment mostly depends on activity level and clothing, but the balance between heat generation/loss can change rapidly if one's activity level changes or if their clothes lose their insulative properties (getting wet is a common example of this). As temperatures drop, peripheral blood vessels (vessels supplying the limbs/appendices) constrict to reduce heat loss from blood near the body’s surface in order to maintain a core temperature of 36.5–37.5 °C or 97.7–99.5 °F through homeostasis or thermoregulation. In other words, your body will sacrifice your limbs in order to keep your vital organs running. A drop in just two degrees in core temperature signals the onset of hypothermia, which can lead to confusion, incoordination, organ failure and even death. The keys to staying safe while running in cold weather is to cover exposed skin, stay dry, use layers properly and protect your head and trunk. A number of studies have found that protecting athletes' faces and keeping the trunk warm was actually more effective at keeping the fingers warm than wearing gloves themselves. Carefully adding and subtracting layers as needed to stay warm can take some getting used to but will make long runs more manageable. If extremely cold, carrying reusable hot packs is not a bad idea either.
While cold weather itself doesn’t cause illness, hypothermia does suppress the immune system, which can lead to greater susceptibility to infection. Vasoconstriction (narrowing of blood vessels) close to the body surface, such as blood vessels in the nose, may compromise the nose’s ability to filter pathogens. It is not well understood how long it takes for the immune system to bounce back after a run; however, working out at the gym in tight quarters with members who don’t wipe off equipment when they are done using it may actually pose a bigger risk to one’s health (but that shouldn’t stop you from either activity).
Last week, I had a runner ask if he could be damaging his lung tissues when he runs outside in the extreme cold (he started coughing a lot after his runs). Even in the very coldest of places, research has demonstrated that runners are not at risk for damaging their lungs; by the time air enters our lungs, it has reached body temperature. Bitterly cold temperatures and/or dry air may act as an irritant/pathogen for some people, which results in an exaggerated inflammatory response that promotes changes in the airway such as coughing, increased mucus production and shortness of breath. If this sounds like something you experience, try wearing a scarf or neck-warmer to help warm and humidify the air before it enters your airways so that it is less likely to cause irritation.
Heat production is directly proportional to VO2 max, meaning the more conditioned one is, the fewer layers they will require when running in cold temperatures. Those who are more conditioned will also be able to run for longer periods of time safely in cold weather conditions. Scientists also believe that shivering releases a neurotransmitter (norepinephrine) that contributes to the body’s fight or flight response which jumpstarts the immune system, so it has been suggested that doing some shivering before you begin running could actually benefit the immune system.
Warming Up: Colder temperatures and slick roads can increase the risk of muscle strains, so include a longer warm up before starting your run.
Monitoring Your Exertion: Running in the snow and ice is similar to trail running in that it requires a lot more energy and stabilization demands on muscles. During the winter, I would avoid focusing on pace when the weather is rough and use heart rate and rate of perceived exertion to keep things reasonable – it will be very important for you to measure your body’s response to the stress load so that you are able to recover properly.
Dressing Properly: Invest in the right gear and layer up. High tech fabrics are essential for wicking away sweat and keeping you warm (stay away from cotton as a base layer). Don't forget to factor in wind chill too; have an outer windproof layer that can be vented and consider running into the wind on your way out and returning with the wind at your back. Find a good balaclava to protect your head, neck, and face (or a buff if you don’t like having things over your face) and a hood on your shell top. Don’t forget about eye protection and mittens. Consider a cold weather running shoe and wool socks.
Remain Visible: It is still quite dark early in the morning and in the evening. Make yourself visible to drivers and others you are sharing the sidewalks and roads with – wear contrasting and reflective clothing. Consider a flash light or bike lights at night or in the early morning. Always give cars plenty of space and warning.
Traction: Try YakTrax or running in trail shoes.
Be Smart: Carry your cell phone with you, run with a buddy if possible and let someone know your route and expected return time. Find areas to run where there is less traffic, even if you have to drive to these areas.
Treadmill: If you are anything like me, treadmill running can be mentally painful. I typically avoid it at all costs, but this winter weather has made running outside dangerous at times. The lack of stimulation during treadmill running typically had me ready to be done with my run after a mile if I don’t mix it up a bit. Here are some strategies I use to make treadmill running more bearable: With long runs, change the incline or speed every 1/4-1/2 mile (depending on the length of the run); every other mile, check an aspect of your running form (monitor where your foot is landing relative to your hip position, check that your knees are staying in line with your toes, make sure your shoulders are relaxed and that your arms are swinging parallel to one another). You can also check your cadence; increasing step rate by five to 10 percent may be helpful in correcting common problems. A cadence of 180 steps/min (90 steps per foot) is a good general recommendation, but optimal step rate will vary by individual and desired running speed.
Cross-training: Don’t forget that all of your running training doesn’t need to be running itself. See my previous post about injury prevention and the importance of strength and cross training.