To sustain movement over time, we utilize energy. In our bodies, the basic currency of energy comes in the form of a high-energy compound called adenosine triphosphate (ATP). Our muscles store ATP in limited amounts which can be quickly tapped for energy. The amounts are so limited that any type of activity over a few seconds in duration requires the creation of additional ATP. One way the body can immediately manufacture additional ATP is by utilizing creatine phosphate (CP) to produce a few more seconds of energy. Like ATP, only a limited amount of CP is stored in the muscles so it’s only useful for short bursts of activity. Fortunately, the body is equipped with additional (although slower) manufacturing processes to supply that needed ATP.
For more pressing energy needs, the next pathway involves a process that breaks down carbohydrate stored in the muscles (glycogen) or carried in the bloodstream (glucose). As with the immediate pathways that use stored ATP and stored CP, this process occurs without the presence of oxygen. It is termed anaerobic glycolysis. The prefix an- derives from the Greek “without” while aero- refers to “oxygen” and bic- “pertaining to life.” So the term anaerobic means life without oxygen. Since there is no oxygen present, the metabolic reaction creates an end-product called lactate in addition to the ATP it produces. As this energy pathway continues to produce small amounts of ATP, lactate continues to accumulate in the cells along with positively charged hydrogen atoms that make the blood acidic. If your bloodstream begins to accumulate more lactate than it can clear; then a decline in muscular performance occurs within a few minutes. Keep in mind that it’s not the presence of lactate per se that causes the performance decline, but rather the acidic environment that accompanies the lactate. As anyone who has tried sprinting for a few minutes knows, sustaining that high intensity level becomes nearly impossible as your muscles start to feel like they are burning.
To continue supplying energy, the body needs a more efficient energy pathway. If oxygen is present, then that oxygen can be mixed into the metabolic reaction to form much larger quantities of ATP. In addition, this process—aerobic oxidation (aerobic meaning “life with oxygen”)—can metabolize not only carbohydrate, but also fat and protein. The drawback, however, is that it takes much longer to produce the ATP than do the anaerobic pathways. As a result, your body must slow down a bit to accommodate the energy production process.
So the major energy pathways the body uses to produce energy can be characterized as either anaerobic (without oxygen) or aerobic (in the presence of oxygen). It is important to emphasize that these are not mutually exclusive pathways. Anytime you head out the door for a run, you utilize all of the available energy pathways. But you use those pathways to differing degrees depending upon the intensity at which you’re exercising. The faster you run (and hence the higher the energy demands placed on the body), the more you rely upon anaerobic pathways to supply quick energy. The slower you run, the more you are able to rely upon the more efficient aerobic pathway to supply your energy needs.
As endurance athletes, we want to go as fast as possible over long distances. The better you can tap into the aerobic energy pathway while maintaining higher intensity speeds, the more successful you will be. Remember, this is because a higher reliance on the aerobic pathway provides energy while limiting the buildup of lactic acid in the blood (which can only be tolerated for so long before performance declines).
TRAINING GUIDE CONTENTS
– Train with a Purpose
– The ABCs of Systematic Training
– The R&R of Training
– Begin with the End in Mind
2. Exercise Science Concepts
– Overreaching and Overtraining
– Energy Systems
– Aerobic Capacity
– Lactate Threshold
– Aerobic Threshold
– Muscle Fiber Types
3. Monitor Your Training Intensity
– What is Training Intensity?
– Key Indicators of Intensity
– Using Training Zones
– Training by Feel, or Perceived Exertion
– Training with Pace
– Training with Heart Rate
– Running with Power
4. Create Your Training Plan
– Prioritizing Your Events
– Overview of the Training Phases
– Choosing Your Periodization Schedule
– Filling in the Details of the Overall Plan
5. Create Your Weekly Workouts
– Creating Weekly Schedules
– Establishing and Developing Your Base
– Building Upon Your Base
– Peaking for Your Target Event
– Race Week and Race Day Warmup
6. Functional Strength
7. Recovery and Nutrition
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