How to Run a Marathon

    Body Temperature  

During training runs, with the exception of extremely cold or hot days, maintain body temperature is not a crucial part of the workout. The point of a workout is to stress the body. Working harder when the weather is less than ideal allows the body to acclimatize to either hot or cold weather conditions. However, On unusually warm days one should still pay a particular attention to the heat index to prevent over heating.

Being aware of your body temperature can be critical to one's success during a race. Your body will use more energy trying to maintain its core temperature in extreme hot or cold temperature. If you actively help maintain your bodies temperature, that energy can be applied to the effort of the race, instead of using the energy to heat or cool your body.

Studies have shown the most efficient temperature to run at is in the mid 50s. There is a host of other factors, such as humidity and wind to consider. A 70 degree day with very high humidity can feel much hotter than a 70 degree day with no humidity and a light breeze in one's face.

The Body.

The body generates its own heat. Any exercise has the capacity to raise the core body temperature. The more vigorous the exercise, the more heat that is generated. This core temperature can rise several degrees over the course of the workout.

As the core body temperature rises, the body will take steps to maintain its core temperature. The primary method is though the use of sweating. When one sweats, moisture is produced which allows for evaporation which in turns cools the skin. If everything is working properly, as one works harder the more one will sweat which in turn allows for even more evaporation.

It is necessary to examine how evaporation works. Cooling occurs when the liquid water your body produces is tuned into water vapor. There are several factors that influence this process. The most obvious one is how hot it is the air temperature. When temperatures are higher outside the rate of evaporation increases.

Related to that is the temperature of the liquid. The higher the temperature of the liquid, in this case sweat, the higher rate of evaporation. The next vital factor is the outside relative humidity. The higher the humidity the lower the rate of evaporation. It becomes increasingly difficult to add more water to air already containing more water moisture. This is also one of the reasons why it feels hotter on humid days.

Another factor is how much liquid your body produces. As it gets hotter, more liquid allows for more evaporation.

If you maintain a proper ratio of liquid intake to sweating, theoretically you should be able to maintain your body temperature indefinitely.

Another factor is humidity. On extremely humid days evaporation off skin is more difficult. On extremely dry hot days, the opposite problem occurs. As the water evaporates quickly, it will not allow for the conduction phase of the evaporation to occur. Conduction is the cooler water transferring the lower temperature back to the body.

Another process is called convection. This is a factor of the air blowing over the body. Ironically the faster you run, the more efficient your body becomes at cooling itself. Conversely, if one is getting too tired and hot and they come to a complete stop then there is less air is flowing over the body. This will cause the body temperature to rise even further. This is a crucial concept. If you come to a complete stop to recover, you may increase your bodies core temperature thus pushing yourself into heat exhaustion.

Each factor plays a part in maintaining your body temperature. The first part is how much you sweat. This can vary from person to person. You will produce a greater amount of sweat the hotter your body temperature is which in turn helps maintain the core temperature at a lower level. Understanding how the body tries to regulate its own temperature is noteworthy because it will influence how to prepare for both hot and cold conditions. It is necessary to understand each of above factors to help determine the best course of action.


There are multiples ways to influence your body temperature in the heat. On hot days, the first rule is to make sure you are properly hydrating yourself. Be aware the hotter the temperature the more you will need to maintain your liquid intake. Besides evaporation, the other way to cool your body is through the use of conduction. Simply pouring water on the top of the head and down the back of the neck can help keep the body cool. For women that have longer hair, it is best to leave your hair down as the water in the hair will act like a heat sink and will not dissipate as quickly. On especially hot days bring a bandana or other cloth that you can wet a drape around your neck can prove advantages.

In the early stages of the run if you are sweating properly and it is not too hot do not dump water over the entire body. Cold water interferes with the evaporation process. Confine the water you pour on yourself to your head and neck area. Most of the blood will circulate through the main arteries in the neck. This is one of the reasons to keep your neck cool.

In weather hotter than normal, slow your pace down from the onset. The amount you slow down is based on how hot the temperature will be on the latter stages of the race. Do not wait for your body to become overheated.

Waiting will cause you to slow down 3-4 times more than if you picked the right pace from the beginning.

The choice of clothing is also crucial. Darker clothes absorb more heat than lighter colors. Also, pay attention to the fabric. On extremely hot humid days, you want fabric that will whisk moisture away from the body and allow for maximum convection. Consider clothing that expose more of the arms such a tank top or singlet. Consider wearing more, not less coverage on extremely hot dry days This is because the rate of evaporation exceeds the body's ability to produce water. It is counter intuitive, but examine how the Desert Bedouin dress. They cover most of their body. The fabric they wear allows for the water to remain on the skin for longer periods of time. In extremely hot and dry conditions wearing a legionnaire hat can be beneficial. This hat has a flap/neck drape that one can constantly dump cool water over to help maintain a lower body temperature.


Cold is much easier to deal with than heat. Simply wearing a heavier fabric with Long sleeves or adding another light layer of clothing is usually sufficient for most races. The body generates heat. With this added layer, there should be enough heat to trap against the body. If the race is in very cold conditions, then dressing in additional layers should be considered. Be aware that most heat is lost through the heads and hands. In very cold conditions light gloves to protect your hands are a must. Consider bringing a Thermal hat made of fleece or wool.

When adding clothes it is necessary to dress in a fashion that one can moderate one's temperature as they run. For instance, if you are wearing a wind breaker make sure there is a zipper that can be opened up. The long-sleeve shirt should be loose enough to able to be pushed or rolled up to expose your arms.


A person that is coming from a winter climate will be more uncomfortable in a race conducted in 70 degree temperatures than a runner that comes from the desert that was training in high temperatures. This link documents the effect. . The general consensus is it takes about 14 days to acclimate properly. Generally this concept applies to the extreme temperatures on both end of the scale.

Most of the tips that are given here are to be used during race conditions. During the short training runs, with the exceptions of very hot or cold days, it usually is not necessary to try and mitigate the heat or your body temperature. The run is usually over before your body temp can rise too far. So in effect one can practice acclimatization with out too may adjustments.

The Race

Hot conditions.

There is not a single approach to planning a race. There is a host of factors such as conditioning, acclimatization, race day conditions and other factors to consider. To find the best approach one needs to find the weather report and then set up a personal game plan.

These are some factors to consider.

1, Temperature prior to the race.

2 Temperature at the start of the race.

3, Temperature at the later stages of the race.

4 The heat index.

5 Wind conditions.

6. How heat affects you personally.

7. How acclimatized you are to the weather conditions

The above factors will allow you to dress properly for the race. For instance if the heat index is high with very high humidity then wearing an outfit that allows your body to sweat is very important.On a bright, hot sunny day, then wearing a light colored top is imperative. If the morning temps are cool, then it is necessary to dress in layers and dispose of the top layer once the temperature rises.

Proper Hydration is the single most crucial factor that is in your control. There is a difference between proper hydration and over-hydration. Stocking up on too much water prior to the race is not only counter productive it can be down right dangerous and lead to Hyponatremia.

Prior to a race, the adrenal glands will kick in which will in turn divert the blood to the extremities. This is usually the cause of why so many people desperately need to use the restroom prior the race. This can create a vicious cycle. If you end up urinating more than normal before the race because of this excess water, you can deplete the proper Salt/potassium balance. This in effect makes you more thirsty which causes you to drink more water which in turn makes you even more thirsty.

Besides causing premature fatigue, this can cause severe health problems and even death. In some studies, some of the deaths that have occurred in marathons were attributed to water poisoning(Hyponatremia), not heat stroke.

On potentially hot day, it is a good idea to bring a water bottle to the starting line. Light drinking in the minutes before the race can be beneficial. Avoid "stocking "up in the hours before a race.

Once the race starts it is best to start hydrating early. Waiting until you get thirsty is simply to late. If the temperature is expected to top 70 degrees, then it is best to start dumping water on your head within the first several miles, well before you feel the effects of the heat.

On a very hot day, It is necessary to adjust your expectations. For example if the temperature is over 80 degrees and you run a 9 minute mile you could reasonably expect your time to drop by a minute a mile. If you are facing a hot day, slow down before you start feeling heat. Remember, your core body temperature is also a function on how hard your body is working. If you keep the pace slower than originally planned, you can actually forestall the negative effects of the heat.

As a loose guideline, expect your pace to drop by 20 seconds per mile for every 5 degree rise in the heat index. This is calculated for runners in the 4 hour range. Runners in the 3 hour range may see only 10 second drop while runners in the 5 hour plus range may see a drop of 30 seconds or more per mile.

If you can make that compensation early in the race, you will have an overall net gain in time compared to runners that ignore the effects of the heat.

Conditions can change during the race. Be aware of those conditions and be flexible enough to change. Temperatures will generally rise as the race progresses. If you are running close to your max capability early in the race, be aware that this factor alone may be enough to send you into a downward spiral.

It is possible that you may not keep up with the hydration to keep your self sweating properly. Be aware of this. If the temperature has not dropped, and you are not sweating as much as before then you may be heading for trouble. To mitigate the effects of less sweating, when you come to an aid station dump more water over your entire body, not just your head. Instead of evaporation, the body can now be cooled through conduction. Look for spray areas and try and keep your clothing doused with cool water. Many people offer water along the course. Take advantage of this. Slow down.

Aid Stations

During the race, aid station will usually be placed at or near every mile marker. On a warm to hot day, it is essential to use these early in the race. For example if the heat index of the race is over 70 degrees it is best to start using these stations by mile 2. Water is almost always the first drink that is offered. Grab he first cup and dump it on your head and neck. This will  help with the conduction phase of cooling. The next cup you grab is the liquid you will drink. Many marathons also supply a sports drink. It is vital to find out which drink are being offered so you can sample it in advance of the race to make sure your body is OK with it. In the early stages in the race, your body may only want a sip or two. If it is exceedingly hot,it may be necessary to take more than one drink at each aid station. For some people that incorporate walk breaks, this may be the perfect opportunity to walk.

But be careful!

If your walk is significantly slower than the run, be aware that one's body temperature may actually rise during the break. This is because of the convection effect. By standing or walking slowly, there is less air moving over the body. This will reduce the amount of evaporation, which in turn cause the body to heat up. One trick that does not take up too much energy is move your arms away from your body. While you are walking slowly move your arms in large circles. This will have the effect of flowing air flow over your  body and help keep you cool.

As the race progresses, it is essential to monitor your condition. Finishing the race is always the goal, but your health is always more important. Heat exhaustion and Heat stroke can be deadly. Both can occur in runners that are in excellent shape that ignored the symptoms.


Heat exhaustion

During a hard run or race, we are often pushing our bodies to the max. This effort can raise our core body temperature several degrees.

If you add high temperatures and humidity coupled with the lack of water, or host of other factors one can push their body into dangerous areas. Everyone should be aware of the signs of heat exhaustion. Not only for themselves but for their fellow runners around them.

Below is a list of warning signs to watch out for.

  • heavy sweating
  • paleness
  • muscles Cramps
  • tiredness
  • weakness
  • dizziness
  • headache
  • nausea or vomiting
  • fainting

The skin may be cool

It is crucial to pay attention to the above symptoms. During a race, these symptoms tend to be progressive. If your symptoms progress past the point of cramping and feeling weak, it is time to stop and seek help. Pushing your body further can lead to serious consequences.

Heat Stroke

Heat stroke is a dangerous and potentially fatal condition.

The body has lost all ability to self regulate itself. Generally a person suffering for Heat stroke is past the point of being able to self monitor or help themselves. Any person suffering form heat stroke will need immediate medical assistance. Many of the symptoms mirror those of Heat Exhaustion. The difference is these symptoms tend to be more severe. One significant difference is the color of the skin. Instead of being cool and pale the skin may appear hot, red and dry. A person in this state needs more than a cup of water and rest. They need medical assistance. If you observe a person in this condition then it is necessary to call 911 if there isn't any one around to help.

 Hyponatremia (water poisoning)

This is another potentially dangerous and even deadly condition. A simplistic description of this, is overhydation. This can occur because the water intake is not balanced the proper amount of sodium and electrolytes. Ironically this over abundance of water causes one to be more thirsty.

Some of the symptoms are similar to Heat exhaustion such as headaches and vomiting. The one symptom that truly stands out on the onset is bloating. It may be impossible to remove rings from the fingers of a person suffering from Hyponatremia. Hands and other extremities can be visibly swollen.

Generally this is rare and can easily be avoided by supplementing your water intake with a sport aid type of liquid with your water intake. For those that do not like those types of drinks, it is necessary to supplement your water intake with Gels, snack foods or power bars.

Early in the race moderate your water intake. Take sips of water. Listen to your body. If you take a sip or two of water early in the race and your body does not appear to want more to do not force more down because you think you need to stock up for later.

Hyponatremia is entirely avoidable. Do not stock up on water before a race. Normal hydration is suitable. If you are running on an unusually hot day, make sure mix your water intake with sport drinks or food that contains salt and complex carbohydrates.

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