Just as hot, muggy summer days have a detrimental effect on your running, cold weather has an impact on your running performance as well. Unfortunately less attention is given to cold weather performance than hot weather so many runners do not train with this knowledge.
The effects of hot weather on your running are quite clear – you will need to slow your pace, put very focused attention on hydration, and watch for warning signs of heat exhaustion.
In short, your performance in hot temperatures is not the same as it would be on an optimal 50°F day. You’ll run slower and maybe not able to run as far as you planned.
But what about cold temperatures? How much is your performance impacted? Is it safe? Can your lungs freeze? Humans are actually warm weather mammals and we only thrive in colder climates with clothing and ability to shelter ourselves from prolonged exposure to the cold.
As a result there are impacts to your running when the temperature drops, but they are for different reasons than hot weather performance declines.
Impact of Cold Weather on Performance
As the temperature decreases below 50°F your performance can be subject to decline. The good news is that the difference is negligible as long as the air temperature is above freezing 32°F/0°C. At an air temperature at the freezing point, you can expect just a 1-2% increase in your pace per mile. As the temperature drops, the impact to your performance becomes more noticeable:
The reason for the increased pace is three fold.
Reduced Muscle Contractions
At colder temperatures your muscles do not contract with the same intensity as they do in warmer temperatures. As the temperature gets colder your nervous system that transmits the impulses to move your muscles slows down. Since your muscle contractions are not as powerful as they are in warmer temperatures you slow down as a result.
The cold can also reduce the blood flow to chilled areas of your body. Cold muscles can’t perform at the same level as a muscle that is warm.
Changes in Energy Sourcing
The second reason for increased pace is how your body uses energy at lower temperatures. As the temperature drops your body increases carbohydrate consumption as a source of fuel and reduces the reliance on fat consumption. As carbohydrates are an important source for energy for distance running you drain your reserves faster than you would at warmer temperatures.
Your body also becomes less efficient in using oxygen as a fuel source resulting in more oxygen being used in cold conditions compared to the same effort in ideal conditions.
Increased Lactate Production
When running your body either operates in an aerobic or anaerobic state. In an aerobic state your body uses oxygen as a primary fuel source and it is very efficient in producing the energy needed for running.
When your pace is faster than your body can sustain aerobically your body taps the anaerobic system which does not use oxygen but instead breaks down carbohydrates to create lactic acid to fuel your running until a point is reached where the lactic acid build up slows your pace due to excess hydrogen byproducts.
As mentioned above your body consumes carbohydrates faster at lower temperatures which increases lactic acid production as a consequence. Since carbohydrates are burned faster at cold temperatures this increases the pace per mile that is sustainable at a given temperature. This is in addition to the disadvantage of having less efficient oxygen usage.
Other Performance Considerations
In addition to your pace per mile being negatively impacted, there are other impacts to your performance when the temperature drops.
At lower temperatures your body has to work harder to maintain your core temperature. The result of this is more energy has to be expended simply for maintaining core temperature compared to ideal conditions or warm weather. This increased energy consumption comes at the expense of your running performance as less overall energy is available. Quite simply there are more demands for the same amount of available energy when it is cold.
When running in cold conditions it is important to keep your muscles warm and your core temperature maintained at all times. If you become chilled on a run or allow yourself to cool down for any length of time your body is unable to get back to the prior temperature without returning to a warmer environment. As a result, your performance will suffer.
This is critically important when starting a race. If you head into the cold and do not keep yourself warm and ready to go but allow yourself to cool down you will be at an even greater disadvantage that cannot be overcome. Allowing yourself to get to the point of shivering will quickly rob your body of energy as shivering is produced by your body engaging in the most inefficient muscle contractions it can to generate heat.
Hydration needs are impacted in colder conditions. When the temperature drops your blood pressure rises as your blood flow is constricted. To counter this your body removes excess water in the form of urine. In colder temperatures you do not sweat as much and your body does not trigger thirst the same way it does in warm conditions. As a result, it is very easy to become dehydrated.
Minimal intake of fluid can cause the feeling of needing to urinate, even if it is a small amount.
The same rules apply for hydrating in cold weather as in warm weather:
Running in the cold requires paying attention to signals from your body. Unlike in warm weather if you become overheated you can slow or stop activity to prevent heat related illness or heat exhaustion. In cold weather, the onset of hypothermia is a real risk and can only be treated by warming the body by immersing yourself in warmer temperatures. Advanced signs of hypothermia include slowed or slurred speech, loss of concentration and loss of coordination.
There is also the risk of frost nip or frost bite, especially in very cold conditions where sweat can freeze to the skin.
Many runners fear that in very cold temperatures their lungs or airway tissues can freeze and cause damage. Some runners experience pain or stinging in their lungs when exercising in the cold.
Fortunately this is one concern that is largely unfounded. Your body is incredibly efficient in heating air before it makes it to your lungs so the risk of sub-freezing air killing tissue or freezing your lungs is not a concern. But some do struggle with breathing in cold weather.
Much of the time this is due to dry air being inhaled rather than cold air. You might try inhaling through your nose as much as possible or purchasing a running mask to help warm and moisten the air before you inhale it.
By knowing the impact of running in cold weather, you can plan your training, racing and pacing effectively and set realistic expectations for your performance. You can’t control the conditions, but you can optimize your planning and approach.
For tips on how to run comfortably in cold weather, click here.