Dr. Phil Maffetone: What is Endurance?

Dr. Phil Maffetone: What is Endurance?

To say the word “endurance” in adventuring circles, one immediately thinks of the ill-fated ship belonging to Sir Edward Shackleton that got stuck in polar ice off the Antarctica coast, thereby  forcing a 900-mile open-water self-rescue mission in small boats that  become the stuff of legend.

Endurance is also something long-distance hikers and mountain climbers also speak of and embrace. But the term also has meaning for the rest of us, whether we are weekend backpackers, century riders,  paddlers, and runners. Endurance doesn’t mean you have just thru-hiked the Appalachian trail. In fact, knowing more about how the body responds to activity over a sustained period of time, even for as short as three hours, will make any hike, paddle, bike ride more enjoyable.

Dr. Phil Maffetone has been a student of endurance for over three decades. He’s also the best-selling author of numerous books on health and fitness, as well as the coach of multisport greats such as six-time Hawaii Ironman champion Mark Allen and ultrarunner Stu Mittleman.

Maffetone offers a unique perspective on what fuels the human body over long distances– and it’s not what you think. The energy burned comes from your body’s fat stores. Moreover, the endurance athlete –hiker, runner, paddler, climber– can only optimally tap into this source by going aerobic. In other words, by not going all out and learning to keep below a certain heart-rate threshold.–Planet Wild


What Is Endurance?

by Dr. Phil Maffetone

To be human is to possess endurance. It’s built into our genes. One of the primary ways we’ve survived as a species is thanks to the role endurance has played in our own evolution. With bipedal and upright posture, feet designed for walking instead of climbing and hanging from tree branches, and the ability to generously sweat, which prevents the body from overheating, early humans were able to travel long distances without fatigue, heat exhaustion, or injury. The search for food or water could lead to newer life-sustaining environments many miles away.

If, over the course of several million years, natural selection has given us the gift of endurance, it is only recently that sports science has begun to fully examine what it means for an athlete to go far at a consistent intensity. But what accounts for the physical differences among us regarding endurance? Why are some of us faster? Why do some of us excel at shorter distances? Or others race better in longer ones?

While genetics may dictate some of these performance differences, we actually control much of our natural athletic expression through the training and lifestyle habits we choose. Making the right decisions brings out the built-in endurance we already have in our bodies. We increase our endurance by being both fit and healthy.

By looking at the whole body and fine-tuning all of its functions, one can automatically improve endurance. To have great endurance is to be holistic. If you want to achieve optimum endurance—the path to achieving your athletic potential—balancing the whole body is key to bringing out the endurance power within. Many factors contribute to and create our endurance, from muscle function and burning fat, to the various nutrients we consume and the intricate workings of our brain. The optimal working of all these factors is important, and if one is deficient, endurance diminishes. As such, endurance in another individual feature we all uniquely posses. Endurance helps make us more than the sum of our parts.

But what is the meaning of endurance for athletes? Endurance can be defined in many ways. The popular college textbook Exercise Physiology, by Ardle, Katch, and Katch, discusses dozens of different aspects of endurance but does not define the term until page 756, and then only in more academic and less practical terms. Other sports researchers and authors define endurance as a form of survival. But you don’t want to just survive a triathlon like the Ironman; you want to embrace it, live it, and enjoy it—otherwise, why are you participating? One unique feature of endurance that differentiates it from true sprinting speed is effort: endurance is performed at sub-maximal exertion while sprinters perform at all-out, maximal effort.










Endurance has  a wide range of physical, chemical, and mental functions.Endurance is our personal human performance; we use it to reach our athletic potential.

We obtain endurance by first developing our slow-moving parts, so to speak. Our aerobic system contains “slow twitch” muscles that burn fat for energy. Training these relatively slow muscles is the first step to building greater endurance. Initially, these muscles will move us at relatively slow paces. But as the body can more readily convert fat to energy, aerobic muscle function improves, enabling our endurance to build.

Another important aspect of endurance, and one that differentiates it from all-out speed, is aging. Endurance can persist for many years. Instead, too many athletes lose endurance with age—not always for lack of training, but for lack of proper training, and lack of health. Many endurance athletes can continually improve well into their forties and fifties. Master athletes often outrace younger athletes, despite having a lower maximum oxygen uptake (VO2max). But improvement over time also means that athletes who begin serious training relatively late, such as in their thirties or forties, can perform their best even in their fifties and sixties. And, athletes beyond age sixty and seventy can still achieve remarkable feats, and sometimes still outrace some twenty- and thirty-year-olds.

The Endurance Triangle: The Big Picture

Although the word “holistic” has been overused, abused, and misunderstood for decades, it remains an appropriate term to use when one is referring to endurance. The true holistic approach to developing more endurance is one in which all aspects of the athlete are considered—these are the triad of structural, chemical, and mental fitness and health.

The holistic approach can be represented as an equilateral triangle. Each equal side represents one important aspect of the athlete: the body’s structural, its chemical, or mental and emotional state. While this concept is a simple illustration, it does not convey the complex interrelationships that exist throughout the body. For example, the muscles—a dominant part of our body’s structure—won’t power us through a workout without significant chemical activity to generate energy. And, our hormones, key aspects of our body’s chemistry that help guide our training development, are produced in the physical glands stimulated by chemical reactions. The mental and emotional components of sport—in fact, all our thoughts—are produced by chemical reactions within the structure of our brain.


This side of the triangle represents all the physical, structural, and mechanical aspects of endurance. The most obvious ones are the muscles, which promote body movement for long periods without fatigue, and support the activities of ligaments, tendons, joints, and bones throughout the body, helping to prevent them from damaging wear and tear. All the muscles are part of a body-wide kinematic chain, with virtually all these structural parts very much dependent upon one another. And, these muscles rely on the bones—in fact, our entire skeleton—for their attachment and to help leverage movement; at the same time, the muscles hold up our skeleton. The bony arches in the foot enable us to run because of the muscles that support these arches. And the physical equilibrium of the bony pelvis, itself dependent upon good muscle balance, has an indirect but significant impact on neck and shoulder movements.

The structure of the brain and all the interconnecting cells (such as neurons) that ultimately tell each muscle fiber when to contract and relax are vital to endurance. Without body chemistry, however, providing fats for use as energy, optimal endurance won’t develop. Moreover, if we try to develop endurance only through training our body structure—working the muscles during training—without considering the importance of body chemistry, we won’t reach our athletic potential.


The body is full of complex biochemical reactions taking place from moment to moment even at rest. These are as important as our structure for optimal endurance. These chemical activities have specific effects on other aspects of our body chemistry and on our structural and mental state. For example, the wide-ranging effects of many of the body’s hormones, including testosterone and growth hormone, influence our training. The reverse is also true, as these hormones are also influenced by our physical training. These actions control physical muscle development, the chemical reactions that supply energy, and the body’s natural anti-inflammatory chemicals, which promote recovery. These changes also influence our mental state.

Consuming different types of foods can also produce various effects on the body, which influences endurance. This takes place in the brain, muscles, intestines, and other areas. For example, a meal of highly refined carbohydrates, such as pasta, pancakes, or cereal, before training or competition can have an adverse effect on the use of fats for energy and endurance. Or, going on a diet to lose weight can result in structural changes in muscles that can cause an injury or a stress fracture in a bone. Caffeine and other popular drugs, such as NSAIDs (non-steroidal anti-inflammatory drugs), affect the body in ways that can help or hurt endurance, too. Even the brain’s delicate chemistry can influence our muscle function, hormones, and our thought processes through the balance of chemical messengers called neurotransmitters.

Mental and Emotional

This side of the triangle incorporates our behavior through the activities of the physical and chemical brain. The mental state is also called cognition, and includes our sensations, perceptions, learning, concept formation, and decision-making. These are all important features of great endurance. We must sense our body and its relationship to the environment—such as feeling the ground with our feet as we run instead of blocking that sense with over-supported training shoes. We also sense the water as we swim, and, if we are sensitive enough, how our muscles, joints, and brain respond to training and competition.

The emotional state includes important factors such as pain, moods of anxiety or depression, and motivation to improve our natural endurance. Both our emotional and mental states can produce significant stress, if we allow it, through improper control of our structural and chemical body; this can contribute to poor performance, physical injury, and even overtraining.

The process of educating ourselves about endurance, and how training, diet, and other key features of fitness and health affect endurance is another important example of the mental- emotional side of the triangle.  Many athletes believe that pushing themselves beyond the limit—the myth of giving 110 percent—is necessary for great endurance. Ad campaigns with unreal and unhealthy images are thrown at us and our children on a daily basis, which only perpetuates attitudes and perceptions that contribute to fit but unhealthy athletes. Without an overall balance of fitness and health, our endurance will be less than adequate.

Fitness and Health

The terms fitness and health are often used interchangeably, but they are actually two different, but mutually dependent states.

 Fitness is defined as the ability to perform physical activity.

 Health is defined as the optimal balance of all the body’s systems.

Good overall health requires proper balancing of the nervous, muscular, skeletal, circulatory, digestive, lymphatic, hormonal, and all other systems. With this balance comes optimal health and the reduction or loss of common signs and symptoms—complaints that many athletes have, which are often considered normal in the course of training and competition but, in fact, are not. Fatigue, injury, allergies and asthma, frequent colds, and other complaints indicate an imbalance of health, often due to neglecting health and pushing fitness. These aspects of health are also the very systems that provide the activities to build fitness. Athletes who are fit but unhealthy not only have problems on various physical, chemical, and mental levels, but are unable to reach their athletic potential.

Both states of fitness and health should be balanced with each other. Injuries, sickness, fatigue, and so on indicate an imbalance between fitness and health. While these problems are common, especially physical injuries, they are not normal in endurance sports the way they are in contact events such as football or hockey. It is unfortunate that most athletes are willing, consciously or not, to sacrifice health for greater fitness.

Aerobic and Anaerobic

Two of the most important terms used in endurance sports are aerobic and anaerobic. These relate not only to training but also how they are affected by diet, stress and other factors.

Take a snapshot of the body’s metabolism, and the most obvious feature is oxygen. As everyone knows, oxygen is essential for energy production. But not all energy is obtained with the help of oxygen. When oxygen is used to generate energy, it is called aerobic, and when the body derives energy without using oxygen it is termed anaerobic. But these common academic definitions are not very practical. Instead, a more relevant way to define aerobic and anaerobic is by the prominent fuels they use to produce energy: fat and sugar, respectively. Let’s define each as follows:

Aerobic: the ability of the body to use more fat and less sugar (glucose) for energy.

Anaerobic: the ability of the body to use more sugar and less fat for energy.

The chemical generation of energy from fat and sugar occurs in the aerobic and anaerobic muscle fibers, which are important components of virtually all skeletal muscles in humans.

Note: Our body contains three kinds of muscles. Skeletal muscles are used for physical activity, seen bulging when contracted; smooth muscle is contained in our intestine and blood vessels, and regulates the size of the passageways; and cardiac muscle is the type found in the heart, used for its “beating.” In this book, most of the time I will simply refer to skeletal muscle fibers as aerobic or anaerobic muscles.

Aerobic and anaerobic muscles perform a variety of activities in addition to generating movement. I will sometimes refer to these collectively as the aerobic system and the anaerobic system.

We are all endurance athletes, whether we workout or not. The question is this: do we choose to satisfy our natural human abilities.

This article has been adapted from Dr. Phil Maffetone’s The Big Book of Endurance Training and Racing.


1 Comment

  1. Hi,

    i’m a beginner middle distance runner (half marathons) i want to get quicker at these and look towards doing a marathon. i want to loose weight and i want to use your method of the heart rate training and train my body to use fat as an energy source. i have been in search of someone in Melbourne Australia that could me with my training and i haven’t been able to find anyone, do you know of anyone?

    thanks Margaret.


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