Why Do I Run Slower When it is Cold Outside?
Do you ever go out for a hard run on a cold day and notice that the effort to hit your pace is greater than expected? You nailed your workout on that 50℉ day last week, so it is unlikely that you’ve lost fitness since then. Maybe the harder effort and slower pace is attributable to the cold weather. In this article, Team RunRun explores some of the reasons you might run slower when it is cold outside.
How Cold is Cold?
Perception of what feels cold can be largely individual and can be influenced by your body’s adaptations to the environment you are most commonly exposed to. The definition of cold (or hot) for optimal endurance performance is temperatures that require our body to divert energy from performance to thermoregulation. A 1997 study in Medicine & Science in Sports & Exercise, that compared time to exhaustion at 70% of VO2max at 4 different ambient temperatures, reported best results at 52℉ with performance decreases at 39℉,70℉, and 88℉, respectively. A 2012 paper analyzing environmental conditions at six major marathons and the performance of nearly 1.8 million finishers over a 10 year period found that best results occurred when the temperature was between about 39℉ and 50℉. So if the mercury drops below 40 and you find yourself struggling to keep pace on your run, the data says you can cut yourself some slack because it is cold!
Blood Flow Making Me Slow… It Rhymes!
One of our body’s acute responses to cold exposure is to prioritize blood flow to the internal organs to keep them functioning at optimal temperatures, which diverts blood flow away from our less essential (to basic survival at least) extremities. We achieve this by blood vessels constricting in our limbs; however, this can be counterproductive for runners since our oxygen hungry, locomotive muscles are located in our legs and arms. Although blood flow remains sufficient enough to maintain activity, oxygen delivery to our working muscles is not quite as efficient as it might be in more optimal environmental conditions. Additionally, the rate of our motor neuron conduction decreases in cold temperatures, so the signal telling our muscles to run as swift as a hare catches a ride on the tortoise’s shell.
Mechanical Challenges of Picking Up the Pace
We often tense up and shiver when we are cold because these muscle contractions release heat as a by-product. Being tense when we are running can reduce both stride length and stride frequency, leading to slower running. In response to running in the cold, we often wear more layers of clothing to help keep warm. The added weight of clothing can reduce running economy and lead to slower running performances. Colder temperatures can also make the rubber and foam materials in running shoes more rigid, reducing the elastic properties that assist with maximizing energy return from the ground we are running on. Additionally, cold weather conditions can mean running on snow and ice which can greatly increase energy cost and might necessitate slowing down for safety in slippery conditions.
How to Get the Most Out of Your Cold Weather Workouts
Although there might be challenges associated with running fast on cold days, these tips can help you still crush an epic workout!
- Manage expectations in the cold by working to perceived effort rather than a specific pace. While pace can be a useful external measurement to estimate effort, our body makes physiological adaptations based on the level of stress applied and the duration the stress is applied; you don’t need your watch to ensure you get the desired adaptations!
- Wearing multiple layers of clothing can keep your body warm by creating an insulated micro-environment inside your layers. I recommend a long sleeve tech shirt, windproof jacket, full-length tights, gloves/mittens, and a hat that covers your ears. As you get warm during a workout, you can remove layers, but it is much harder to add layers after you are already too cold!
- Extend the warm-up before a hard workout on cold days to ensure that your body is primed for action and not putting too much energy into shivering for warmth.
- Keep moving, because your body will get cold quickly when you stop running.
Running in the cold is not all gloom and doom! Although there are multiple factors that might impact the paces you are able to hit on cold days, that does not mean that you are not making fitness gains that will ultimately translate to faster race performances down the road. Having an understanding of how your running is influenced by environmental factors outside your control provides you context for assessing your training. That flop of a workout I had last week when it was 35℉ and raining might have actually been a world record performance* at optimal running temperatures!
Maxx Antush is a coach with Team RunRun. To learn more about him or to work with Coach Maxx, check out his coaching page.