What to Know about Marathon Pace Before Your Race
April 10, 2024
Depending on where you live, you may only deal with a couple of months of cold weather. Or, you may be bundling up for runs from mid-October to late April. Running in cold weather poses its own logistical challenges, from how to dress to possible increased injury risk. If it’s your first winter of running, running in the cold can be intimidating. For experienced runners, the season still may instill trepidation or cause a retreat to the treadmill. This article provides an evidence-based guide for running in cold weather (whether or not there is any snow on the ground).
Provided you are properly dressed and moving, running in cold weather is generally safe – to a certain point. Frostbite, hypothermia, and non-frostbite cold injury can all be concerns in the cold. However, as outlined in the 2021 American College of Sports Medicine Consensus Statement, dressing appropriately (including covering exposed skin) and moving the entire time you are outside can reduce the risk of cold injury.
There is a point where it may be more prudent to stick to the treadmill or indoor track. Around -4 degrees Fahrenheit/-20 degrees Celsius, many outdoor competitions (such as those with the International Ski Federation) are canceled. Based on the evidence, the risks outweigh any rewards when the windchill drops below -10 degrees Fahrenheit. (Here’s more on how cold is too cold to run.)
Your definition of cold may vary with your geographical location; a runner in Florida and a runner in Minnesota will define “cold” very differently. For simplicity’s sake, in this article “cold” refers to below-freezing temperatures (32 Fahrenheit/0 Celsius).
In temperatures between 0 and -20 degrees Celsius (32 to -4 degrees Fahrenheit), the cold air can cause up to a 5% reduction in performance as measured by VO2max, according to a 2015 study in Comprehensive Physiology. Likewise, a 2022 study in Medicine and Science in Sports and Exercise found that the 5K distance is the most affected by cold stress. Lower muscle temperature can cause increased lactate production, which may result in fatigue sooner. These effects will be more profound at higher intensities. You may feel a few seconds per mile slower in speedwork, but not notice any real difference on easy runs. (Read more in this article if you are racing in the cold.)
As described in greater depth below, mild hypothermia can result in a slower pace. Mild hypothermia (core temperature in the range of 89.6-95 degrees Fahrenheit/32-35 Celsius) causes elevated breathing rate and heart rate. If you continue to run, any pace will require more effort and you will likely slow down. You can mitigate the risk of hypothermia by dressing appropriately (see below) and making appropriate modifications such as minimizing stops along your route.
Cooler weather may feel better for hard workouts, but fast running may have more injury risk when the temperature drops too cold. Trail running expert coach David Roche recommends that hard workouts should be taken indoors when windchill drops below 15 degrees Fahrenheit. Why? While more research is required, limited evidence supports the theory that cold weather may increase the risk of musculoskeletal injury. Cold muscles have dampened neuromuscular function and fatigue sooner. In high-intensity workouts, cold weather could increase the risk of muscle or tendon strain.
Even between 15 degrees and 32 degrees Fahrenheit, you want to be more cautious about intervals and tempo runs in cold weather. Be mindful of dressing appropriately and fully warming up before you start. Jog any recoveries rather than standing still to minimize drops in muscle temperature between reps. If in doubt, consider taking your speed session to the treadmill instead.
Breathing in dry, cold air during exercise can cause asthma-like symptoms including coughing and wheezing -a condition known as exercise-induced bronchoconstriction. According to a 2019 study in BMC Pulmonary Medicine, up to 10% of the general population and 90% of asthmatic athletes deal with exercise-induced bronchoconstriction in cold weather.
If you experience symptoms, it is always worth first getting checked by your primary medical doctor. If you are prone to exercise-induced bronchoconstriction, using a gaiter to warm the air around your mouth may help (ultimately, defer to your doctor’s advice).
It is important to dress warmly enough that your muscles are warm. Cold skin and muscle temperature cause vasoconstriction, which may inhibit blood flow and oxygen delivery. Additionally, cold muscles are more likely to strain or tear. If you are shivering, you burn energy more quickly and may fatigue sooner.
Dressing appropriately can also reduce the risk of hypothermia, which can occur during prolonged exposure to cold temperatures. Hypothermia is more likely to happen if clothing is inadequate and there is wind or cold precipitation. (Think of the Boston Marathon in 2018, when cold conditions and rain led to many runners experiencing hypothermia.) Symptoms of hypothermia can range from shivering, rapid heart rate, rapid breathing rate, urinary urgency, and mild loss of coordination (for mild hypothermia) to poor judgment, slurred speech, weakness, clumsiness, fatigue, and apathy (moderate). Severe hypothermia can result in pulmonary edema, low blood pressure, low heart rate, irregular heartbeats, and muscle rigidity.
The metabolic heat you generate while running does increase core temperature, so you do not need to dress as warmly for running in the cold as you would for walking.
Importantly, you want to ensure you can change into warm and dry clothing as soon as possible after running in cold weather. As your core temperature drops after exercise cessation, cold and sweaty clothes could cause your core temperature to drop. If appropriate, bring a change of clothes for post-run brunch or sweats for the drive home.
This article delves into more detail about how to dress for running in cold weather! You can also find my picks for the best cold weather running gear here.
As discussed in a 2021 review in the International Journal of Environmental Research and Public Health, ensuring adequate glycogen availability is essential for cold weather training. If you go into a run (especially a run lasting one hour or longer) without adequate glycogen availability, you encounter the risk of slowing down due to low glycogen. While this isn’t great for performance in any season, in winter, slowing down mid-run leads to lowered production of metabolic heat – and that increases risk of hypothermia. Ensure that you eat appropriately during your runs and fuel well on runs longer than 90 minutes, even in the cold.
While fluid needs may not be as high in the winter as in summer (due to decreased sweat loss), you still lose fluids during winter runs. Fluid loss in the cold can occur both via sweat and as your body uses its fluid to humidity the cold dry air in your breathing passages. The cold may inhibit thirst mechanisms, so bring sports drink on any run longer than an hour and sip it at 10-15 minute intervals. Be sure to be well hydrated before runs as well to reduce the risk of dehydration.
(Got more questions about winter running? Read this article, which delves into chilblains, calorie burning in the cold, and more!)
Bubnis, M. A., & Hulsopple, C. (2022). Human performance and injury prevention in cold weather environments. Current Sports Medicine Reports, 21(4), 112–116. https://doi.org/10.1249/JSR.0000000000000946
Castellani, J. W., Eglin, C. M., Ikäheimo, T. M., Montgomery, H., Paal, P., & Tipton, M. J. (2021). ACSM expert consensus statement: injury prevention and exercise performance during cold-weather exercise. Current Sports Medicine Reports, 20(11), 594–607. https://doi.org/10.1249/JSR.0000000000000907
Dreßler, M., Friedrich, T., Lasowski, N., Herrmann, E., Zielen, S., & Schulze, J. (2019). Predictors and reproducibility of exercise-induced bronchoconstriction in cold air. BMC Pulmonary Medicine, 19(1), 94. https://doi.org/10.1186/s12890-019-0845-3
Gatterer, H., Dünnwald, T., Turner, R., Csapo, R., Schobersberger, W., Burtscher, M., Faulhaber, M., & Kennedy, M. D. (2021). Practicing Sport in Cold Environments: Practical Recommendations to Improve Sport Performance and Reduce Negative Health Outcomes. International Journal of Environmental Research and Public Health, 18(18), 9700. https://doi.org/10.3390/ijerph18189700
Mantzios, K., Ioannou, L. G., Panagiotaki, Z., Ziaka, S., Périard, J. D., Racinais, S., Nybo, L., & Flouris, A. D. (2022). Effects of weather parameters on endurance running performance: discipline-specific analysis of 1258 races. Medicine and Science in Sports and Exercise, 54(1), 153–161. https://doi.org/10.1249/MSS.0000000000002769
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