I did three exciting things today.

1. I learned about the muscular system.

2. I bought the books Born to Run and Chi Running to help with my barefoot running.

3. I got my customized nutrition plan for the week leading up to my race in May (more on that next week).

After my test today I had some time to kill before my appointment with my nutritionist, so I was reading Essentials of Human Anatomy & Physiology by Elaine M. Marieb. Marieb makes a point of saying that although “true” muscle fatigue is very rare, it happens commonly among marathon runners.

“True” muscle fatigue is when your muscles quit entirely. Not many people get to this point because they will feel fatigued first and simply slow down or stop. But marathon runners have been known to literally collapse in exhaustion. These are the stories that scare people away from running. However, I have found that a solid understanding of our muscular system helps ward off a lot of this fear.

Muscle fatigue is believed to be a result from something called oxygen deficit. This is essentially when a person cannot take in oxygen fast enough to keep the muscles supplied with what they need during strenuous activity. Eventually the muscles stop working altogether.

However, this directly depends on your body’s ability to transport oxygen-filled blood to your muscles. There are two ways this can be improved:

1. Decrease your resting heart rate through training. A lower resting heart rate means that your heart is more efficient. In less beats, it can pump enough blood to sustain your muscles over a longer period of time.

2. Increase the amount of oxygen your blood carries. We can do this by increasing our number of red blood cells. We can increase the protein hemoglobin (necessary to bind with red blood cells) and also increase the dilating capacity of our blood vessels. This allows our blood to flow faster and in greater abundance, with many more oxygen molecules.

Also when we train, the mitochondria in our individual muscle cells adapt to store more oxygen. The word hypertrophies is used to describe the literal act of our heart enlarging so that more blood is pumped out with each beat. This could explain why runners tend to be such nice people. Our hearts are bigger.

Besides helping our heart and blood quality, aerobic exercises like running also make our metabolism more efficient. It improves our digestion (and elimination). It makes our bones stronger and our lungs more efficient.

I once said that anyone who could be talked out of running out a marathon shouldn’t run one. I still don’t think marathoning is for everyone. But I know it’s for me. When I hear that people have collapsed in marathons, it doesn’t make me want to stop running. It makes me want to train properly.

Our body is something that we either use or lose. If we refrained from all the physical activities that might make us fall down, we would actually fall a lot more often.

There is one more thing that running does that I found fascinating today: It enhances neuromuscular coordination. I think this is worth describing, but in order for it to make sense I must first briefly explain how muscle contractions work.

To contract a muscle, our brain sends an electrical signal through a nerve cell. One end of this nerve cell contains a neurotransmitter (chemical messenger) called acetylcholine. It is the release of acetylcholine that triggers a more complex chain of events that eventually leads to a muscle contraction.

One of the reasons we experience muscle fatigue is because we don’t have enough acetylcholine keeping up with these transmissions. Research led by Jeff W. Lichtman, M.D., Ph.D., at Washington University School of Medicine in St. Louis, indicates that inactivity will cause a loss of acetylcholine receptors (and in turn contributes to muscle fatigue). However, once that muscle becomes active again, our nerve signals return. Use it or lose it.

Another interesting study at The Salk Institute shows that running can boost brain cell survival in mice that have a neurodegenerative disease with properties similar to Alzheimer’s. Carrolee Barlow, Salk assistant professor and the lead author of the study said that the miles logged correlated directly with the numbers of increased cells. “Running appears to ‘rescue’ many of these cells that would otherwise die. It’s almost as if they were wearing pedometers, and those that ran more grew more cells.”

By contrast, below are some quotes from the skeptics that Born to Run author Christopher McDougall shares.

From the Sports Injury Bulletin:

Just as repeated hammering on an apparently impenetrable rock will eventually reduce the stone to dust, the impact loads associated with running can ultimately break down your bones, cartilage, muscles, tendons, and ligaments.

From the American Association of Orthopedic Surgeons:

Long distance running is “an outrageous threat to the integrity of the knee.”

Wow. It’s a good thing runners are stubborn.