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Ultra-endurance exercise pushes the body to the limits. Running extreme distances in extreme conditions like the heat, cold and altitude presents us with the opportunity to learn about how the body changes to handle the physical exertion and environmental conditions. During this expedition, we will focus on how the heart, lungs, blood, muscles, and the nervous system change and adapt. Each day we will present data from runners Ray Zahab and Kevin Vallely, which will show the condition of each of their body's systems. We will also have fun tests that people can do at home to learn about their own bodies!

Expedition Overview

Well we have completed another amazing expedition. Ray Zahab ran across South America and traversed the Andes Mountains. Kevin Valleley and Bob Cox – 2 highly experienced ultra endurance athletes - joined him. Originally my plan as the scientist for the expedition was to measure Ray's physiology and to track how his body adapted to the altitude, heat, and constant ultra-endurance running. We got some great data on this, but we made some incredible discoveries along the way that were totally unexpected. We were all totally surprised at what happened. Some things we could explain, and other discoveries were so surprising that I'm sure they will be dismissed by many people as impossible.

But that is what science is all about! My upcoming blog posts will deal with all the science we learned on the expedition. I hope you enjoy following along as we analyze the data and learn from this incredible experience. Ultimately I hope we all learn more about how our bodies work and that the discoveries inspire everyone to be more physically active and healthy because our bodies and minds are so incredible and if we push them to new limits – you never know what might happen.

Exercise in the Heat

The first few days on the road have been pretty smoking hot. Air temperatures in the shade are about 30 degrees C and it's hotter out on the road. Not crazy temps but still pretty hot when you consider that we left North America in the middle of winter. So the transition has been challenging. I ran 10 k yesterday with the team after lunch and it felt like I was running with 10 lb weights around my ankles. Ray did 65 km in the same conditions. Pretty epic start to the expedition. Check out this video that shows some of our experiences on the road in the heat:

In this blog I'm going to explore some of the physiological science behind the run. And the most important physical challenge so far has been the heat. Normally, the body regulates its temperature by pumping blood from the internal organs and the brain out to the skin, where it can evaporate through sweat. With longer-term exposure to the heat, the body also adapts by:

  1. developing more reactive capillaries in the skin so the blood can circulate better;
  2. sweating more to pull heat out of the body through evaporation;
  3. retaining electrolytes when we sweat; and
  4. increasing the total blood volume.

We have clearly not adapted yet. By the end of this expedition the bodies of the runners will have changed - allowing them to perform in these conditions no problem! In the meantime hydration is the key to make sure that the body has enough water to keep sweating and drawing heat out of the body. The other problem is that when we first arrive at altitude the body tends to lose a lot of electrolytes (like sodium and potassium) in the sweat. Check out this picture of Ray's shirt after today's run. It's covered in salt. Once again by the end of the run that should not be a problem - the body learns to retain electrolytes and sweat water. Pretty amazing.

We are also doing some blood testing each morning and afternoon. Near the end of the morning run Ray was cramping badly. At lunch we found that Ray's potassium levels had spiked 20%. We worked at lunch to get fluids back into his system and then adjusted his Gatordade concentration for the afternoon to lower the potassium and sodium levels a bit to try to keep him close to his normal values. That seemed to work well and he managed another 25 km after the lunch break. But it was a tough start to the expedition. To give you another window into how tough this really was – check out this short interview with Kevin Valleley. Remember that Kevin is one of the best ultra-endurance athletes on the planet.

The Immune System

As we climbed up into the Andes mountains the team was pushing really hard. Long days of running and climbing constantly wears you down. This constant load of exercise and lower and lower oxygen levels presents a specific challenge to our immune systems. The immune system consists of a number of organs like the spleen, lymph nodes and the bone marrow. Our immune system is a complicated - it works to fight off viruses, bacteria and other pathogens. White blood cells are a critical component of the system. It's pretty amazing - like chemical and biological warfare inside the body. When the system works well we are able to fight off invaders and stay healthy. When the system is overwhelmed or is not working effectively we get sick.

With the crazy amount of exercise as well as heat exposure and now altitude it is no surprise that first Bob Cox and then Ray Zahab got respiratory tract infections. Check out Ray's comments in this video about how he is feeling.

A fascinating paradox in human physiology is the concept of a J-shaped relationship between exercise training and health.

The "J-shaped hypothesis" suggests that, in general, people who exercise regularly experience fewer illnesses and infections than those who do not. The relationship is based on research that measured the number of upper respiratory tract infections (URTIs), such as the common cold, that people experience every year. Although this relationship was developed based on the incidence of URTIs, more recent studies have explored the relationship between exercise and other diseases. They have found that exercise affords protection against many diseases, even cancer. Increasing the amount of exercise beyond moderate levels does not improve immunity further. Quite the opposite happens. When athletes train at volumes and intensities excessively higher than normal for extended periods, they experience a significant increase in the number of illnesses.

When we consider the J shaped relationship it's easy to understand why the runners are getting sick early on. The high volume of running, and the environment are very stressful. The immune system is compromised and it's easy to get sick. We've been increasing their vitamins like vitamin C as well as minerals like zinc to help their immune system and speed the recovery of the runners. It's a testament to just how fast ultra endurance athletes adapt because this morning on day 4 everyone is already feeling much better, despite waking up at 12,000 ft elevation.

So, in general, regular physical activity helps to strengthen the immune system and results in fewer infections than would be expected if a person did not exercise. But extreme exercise can cause the immune system to be compromised for a short period of time. For all the people who are participating in the physical activity challenge - not only will you have a higher level of fitness, but your immune system will be stronger. Keep it up! Sometimes when you exercise you even get to see scenes like this one…