6 Lessons From Physiology and How They Make You a Better Runner


When done correctly, it is a scientific endeavor to maximize running performance. Unfortunately, nearly all scientists spend their careers in academia without venturing out into the arena that got many of them interested in physiology in the first place—competitive sport. As a result, few scientists are coaches. The opposite is also true—few coaches are scientists. Being both, I have learned that each can learn from the other, as my experience has given me a unique view of the sport and of the training process. Here are 6 lessons I have learned from physiology and how they can make you a faster runner. 

Lesson 1: Lactate threshold and running economy are more important than VOmax.

While VO₂max (the maximum volume of oxygen your muscles can consume per minute) has received most of the attention among runners and coaches, a high VO₂max alone is not enough to be a good runner; it simply gives you access into the club, since a runner cannot be good without a high VO₂max. I have tested many athletes in the laboratory with an elite-level VO₂max, but few of them were capable of running at the elite or even sub-elite level because they did not have a high lactate threshold or were not very economical. Running economy is the volume of oxygen consumed at submaximal speeds; the less oxygen you use to run at a given pace, the better.   

For longer races (half marathon and marathon), your running economy and the speed (pace) at lactate threshold are the most important factors. For shorter races (1,500 meters/mile, 5K, 10K), the speed at VO₂max is the most important factor. So that is what you have to train.   

Lesson 2: There are different muscle fiber types.

Humans have 3 types of muscle fibers, with gradations between them: slow-twitch, fast-twitch A, and fast-twitch B. The exact percentage of each that you have in your muscles is genetically determined and dictates your strengths and weaknesses as a runner. Skew your training to your strengths determined by your dominant muscle fiber type.

Lesson 3: A larger, stronger heart can pump more blood and oxygen to your muscles.

Your left ventricle is responsible for pumping blood to every inch of your body except your lungs. Your maximum stroke volume (the maximum volume of blood your heart pumps each beat) and your maximum cardiac output (the maximum volume of blood your heart pumps each minute) dictates your body’s ability to deliver oxygen to your muscles and determines your running performance. The bigger your left ventricle, the more blood it can hold; the more blood it can hold, the more blood it can pump with each beat. Make a bigger heart, and you deliver more oxygen to your muscles.  

Lesson 4: Metabolism is tightly regulated by enzymes and oxygen.

Enzymes are biological catalysts that speed up chemical reactions. The faster chemical reactions occur, the faster you produce energy (ATP) for muscle contraction. Make more enzymes involved in the aerobic and anaerobic metabolic pathways, and you make ATP faster, which enables you to run faster.

Metabolism is also regulated by the availability of oxygen, which determines the metabolic pathway used. If there is adequate oxygen to meet the muscle’s needs, your muscles will rely on aerobic metabolism. Conversely, if there is not adequate oxygen to meet your muscle’s needs, your muscles will rely on anaerobic metabolism, which causes the development of acidosis, causing you to fatigue and slow down.

Lesson 5: Carbohydrates are extremely important.

People think carbs are bad. If you are one of those people, stop it. Research since the 1960s has shown that endurance performance is strongly influenced by the amount of stored muscle glycogen, with intense endurance exercise decreasing muscle glycogen content. Carbohydrates are so important that ingesting them during prolonged exercise delays fatigue. That muscles prefer carbohydrate as a fuel is so fundamental to exercise metabolism, when your carbohydrate fuel tank gets very low, your liver makes glucose from amino acids and lactate to assuage the threat of a low carb fuel tank. (That’s why a ketogenic diet doesn’t really keep you in ketosis—because your liver is smarter than you and will break down protein into amino acids to make more glucose to assuage the threat presented by not eating carbs.) You need carbs to run fast.

Lesson 6: Most female distance runners get better the longer the race.

Estrogen shifts metabolism to a greater reliance on fat and less on carbohydrate when running at the same pace as a man. The longer the race, the more important this shift in metabolism becomes, since the conservation of carbohydrate is very important given that we have only a limited store of it. The faster the pace you can run while still using mostly fat, the better long-distance runner you will be. Most women, therefore, get better the longer the race. The performance difference between men and women is much smaller for ultramarathons than it is for races shorter than a marathon because the longer the race, fuel use starts to outweigh the importance of cardiac performance and oxygen transport in the blood, characteristics that favor men. Because of women’s estrogen-induced predisposition toward endurance, women should embrace aerobic training and run a lot to maximize their running performance. (Get my book, Running for Women, for a lot more detail, including how to train around the menstrual cycle, pregnancy, and menopause.) 

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