Let's put cardiovascular endurance development in its appropriate context. The development of cardiovascular endurance is important, but overrated in its importance in distance running. For purposes of this discussion, I will define distance running to include events from one mile to ultramarathon distances. Physiologists especially tend to overemphasize the importance of cardiovascular endurance because that is what they know; they tend to not write about biomechanical efficiency or sport psychology because those are not their areas of expertise. Jack Daniels, Roy Benson, and David Costill are all excellent coaches who place a heavy emphasis on cardiovascular endurance development and have achieved excellent results. Athletes can do better. Let's see where cardiovascular endurance fits in with the kinds of fitness required to perform well in distance running.

There are two main components to successful training for endurance sports: psychological preparation and physical preparation. One Russian study of weight lifters showed that athletes who spent 75 percent of their training time preparing their minds, and 25 percent of their training time preparing their bodies, performed better than any other group with other percentage mixes of physical and psychological training. Psychological training consisted of preparing the mind by learning and practicing mental skills. This included learning: the rules of the sport, how to train, become healthier, appropriate rest & nutrition, relaxation and visualization techniques. These areas are often paid little attention to, yet they are far more important than how many miles per week someone runs.

For physical preparation, physiological and biomechanical (technique) development are both required. Of the two, the longer the distance run, the more important physiological development becomes.

Biomechanical development is absolutely critical in sprinting, more important at faster distance running speeds than at slower speeds, but still important enough that one would not expect to run one's best marathon sideways. Mechanical efficiency of movement is important for the distance runner. Correct technique is essential for optimum application of power at faster speeds.

It takes time to physically change the makeup of the body so that it can meet the demands of long distance running competitions or workouts. Physiological adaptations are numerous. Of the various physiological adaptations which take place with appropriate training, rest and care of one's health, cardiovascular endurance becomes progressively more important the longer the distance run. But what is cardiovascular endurance?

(Having biked 202 miles in 24 hours, run/walked 62 miles in 15 hours and hiked 32 miles of mountains in 17 hours, I understand the role of cardiovascular endurance preparation for long events. I have coached an individual who broke 23 hours for 100 miles of running and walking and another who completed the Ironman Triathlon as the oldest female competitor.)

Cardiovascular endurance is the sustained occurrence of a chain of events in the body in which the nervous and endocrine systems direct the use of oxygen and nutrients to keep muscle cells contracting and relaxing in a coordinated manner without undue fatigue. (Cramps are when muscles fail to relax.) The following is a summary of the chain of events that constitute "cardiovascular endurance".

Long distance running requires that energy be supplied on an ongoing basis by the heart pumping blood with oxygen and nutrients to working muscles. Working muscles use oxygen to burn carbohydrates (in the form of glycogen) and other fuels from liver, blood and muscle fibers. The breathing muscles, mainly the diaphram, but secondarily the external intercostal muscles, cause air to flow into the lungs. Oxygen diffuses from the airspace of the lungs into the bloodstream at a rate sufficent to allow carbohydrate-burning during long distance running at slower speeds. Fats and proteins can also be used as fuel sources, though not preferentially, as they require more oxygen and are thus less efficient to burn. The labored breathing of the tired athlete in a workout is typically symptomatic of fat burning, meaning that glycogen stores are running low. With this comes a heavy feeling in the legs, a slower pace and more psychological effort to maintain pace. This is often the case in the later miles of a marathon. Burning fats is only 72 percent as efficient as burning carbohydrates.

The internal intercostal muscles help to compress the ribcage at high levels of breathing effort and force air out at a faster rate than if forced exhalations were not practiced. This "clears" the lungs of carbon dioxide and allows more  oxygen-rich air to come in. As in the forced exhalations of the Lamaze childbirth methods, there is a systemic relaxation effect that results from concentrating on the rhythmic forced exhalations during high levels of breathing effort required during faster running. Higher levels of breathing effort can also be triggered by running further, not just faster.

(to be continued) - 11/30/03 Brian Cavanagh