Marathon Training Sanity Check: Nerd Facts - What actually happens to the body during a marathon?

The marathon is only three weeks away! So, for the final Nerd Facts post, I've decided to research exactly what happens to the human body during a marathon. Since I now have some experience with long runs, I started the research expecting to find cut and dry scientific articles on water and sodium loss, etc.

Instead, I was greeted with article names such as, "The Terrifying Hell a Marathon Inflicts on the Human Body," and subheadings such as, "Sudden Death," and "What about Blood-Pissing?"

All of the articles consisted of subsections based on the worst case scenarios. So, I will stick with that format here. I mean, it is Halloween season and all.

Hyperthermia

The most obvious condition that can result from running a marathon is hyperthermia, or, greatly increased body temperature. This can result from dehydration, climate, running at a faster pace inducing higher metabolic rates, or a combination of factors. Let's begin with dehydration, the most familiar issue thanks to an $8 billion sports drink industry.

The average sweat rate for runners is 1.2 liters per hour. Thus, one way to prevent against dehydration is to drink as much as you are losing. However, this is easier said than done during a marathon.

I'm incredibly impressed by those runners that just fly through the water stations, throwing back fluids without reducing their pace. I, on the other hand, enjoy slowing down to a walk, to make sure that the fluids make it down my throat, as opposed to all over my face and shirt.

A less intuitive method of avoiding dehydration, but perhaps not a less lucrative business, is stripping off layers of clothing. During the NYC marathon in particular, the first mile is on a windy, chilly bridge. However, once your body warms up and you hit the warmer city streets, you don't need the same amount of clothing that you did while standing around waiting for the race to start. Keeping too many articles of clothing on will just increase how much you sweat. So marathoners, this is the perfect time to legitimately get your strip on!

Many consider dehydration as the main cause of hyperthermia in marathoners. However, studies have shown that the increase in metabolic rates actually has a stronger correlation to increased body temperature. Most marathoners pick up their pace in the later miles of the race. At this point, the body becomes less efficient at using energy, thus producing excess heat and raising the body temperature.

So, to avoid hyperthermia, experts recommend trying to take in 8-10 ounces of fluids every 10 to 20 minutes during a marathon, and shedding clothing according to body temperature.

Hyponatremia

So, staying hydrated is the key, right? Apparently, there is such a thing as water intoxication, or in technical terms, hyponatremia. Women are more prone to cases of hyponatremia, since we have smaller bodies and tend to run slower.

Less water can cause more dilution in smaller bodies and the longer you run, the more you are at risk of taking in too many fluids. Hyponatremia can cause swelling of the brain, which estrogen can in turn exacerbate once the swelling begins.

Hypothermia

Not only can your body temperature rise, but it can also fall to dangerous levels. Usually, environmental factors such as wind, rain and snow can contribute to hypothermia during marathons. Running the last half of the marathon slower than the first half can also result in not enough body heat being produced to maintain proper body temperature. Additionally, when salt is lost through sweat, it can build up in clothing and pull away necessary heat from the body.

The experts recommend wearing enough layers to keep a normal body temperature and to replace wet clothing when possible.

Glycogen Depletion

During a marathon, muscles are fueled by glycogen in the muscles cells and from blood glucose. As blood glucose gets used up during prolonged running, the liver converts its stores of glycogen into glucose, which gets released into the bloodstream to fuel the muscles. When glycogen runs low, muscles are forced to use slow-burning fats to operate. This results in the dreaded wall.

Thus, marathoners are encouraged to carb-load in the days leading up to the marathon by eating meals with around 50% carbohydrates. Originally, I thought I could have a meal that consisted only of Olive Garden endless breadsticks and Mrs. Field's Cookie Cake.

However, eating only carbs could lead to a feeling of heaviness and bloat, which could result in slower times. Additionally, experts recommend taking in carbohydrates during the race, to avoid complete glycogen depletion. The recommended dose is 120-180 calories per hour and 30-40 minutes prior to fatigue.

Weakened Immune System

Running a marathon results in muscle damage, which requires immune cells for repair. The flood of immune cells to the muscles can also weaken other cells, compromising the immune system as a whole and leaving it less able to protect the body. Apparently, this could make marathoners more susceptible to upper respiratory tract infections. The experts recommend the usual things to avoid illness, but my favorite are the following:

Keep other life stresses to a minimum.
Avoid sick people and large crowds.
Avoid overtraining and rapid weight loss.

Have these experts ever seen a marathon?

You are hoping that all of your out-of town guests make it to their spectator spot while streets are closed and subways packed.
You are running with thousands of similarly immune suppressed people in usually chilly conditions. Since cabs are impossible to get, you have to get on the subway to head home, full of germy tourists.
Clearly, they have never seen a marathon training plan, which consists of running half-marathons or more each weekend for 3 months.

Conclusion

Now that I have concluded my research, I now know that I must do the following things to avoid certain death on Marathon Sunday:

1. Somehow, find the illusive line between keeping hydrated and brain-swelling-inducing water intoxication.

2. Find a fanny pack big enough to carry extra clothing for all possible weather conditions.

3. Hire chef/nutritionist to make all my meals during Marathon Sunday to ensure I carb-load properly.

4. Since my fanny pack will be full of clothes, guilt-trip friends and family to post-up at exactly each 30-40 minute interval on the marathon course to feed me carbs.