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The Three Muscle Energy Systems and How to Train Them

August 16, 2004 11:12 AM

Our muscles have different biochemical requirements according to our chosen activities. The energy we get to jerk a couple of 2 poods, wrestle, or XC ski comes from entirely different biochemical reactions.

First, an extremely short and simplistic lesson:

Our body uses energy that is given off from the breakdown of a molecule called ATP. The timely availability of ATP determines whether our muscles will be able to meet our demands. This is accomplished by three systems: the phosphagen, glycolytic and oxidative. These three systems metabolize and recover ATP in different degrees all the time. The ratio in which they are active is a continuum that fluctuates with the intensity of the activity.

In brief:

typical activities that use this system to metabolize ATP are explosive, require maximal effort and are very short in duration. A barbell snatch is a good example.

Glycolytic: a typical activity is wrestling, which requires a sustained, intense effort, but not maximal. Use of this pathway causes lactic acid build up, which must be addressed in training.

Oxidative: if enough oxygen is available, the glycolytic pathway is diverted to the oxidative system. The most familiar activities that use this system are low intensity, long distance activities like marathon running and XC skiing. ATP recovery is very high in the oxidative system.

In the course of four articles, we will look at each of these systems and how to train them -- with the fourth article addressing the integration of two or more systems into your training, such as strength-endurance activities or how to train all three.

A final note before we move on to the phosphagen system. The oxygen component of the oxidative pathway has led to a convention of calling the training "aerobic." By default, the other two pathways are said to be, "anaerobic." This is merely a convention and keep in mind that you have to breathe oxygen in order to perform any of these activities!

Phosphagen system:

The phosphagen system is primarily used for high intensity activities. Training in this environment enhances fast and powerful movements.

Training that concentrates on the phosphagen system is typically under 10s in duration. In addition, the rest periods provide almost complete recovery (e.g., 5 ? 7 min). This prevents any significant accumulation of lactic acid and allows athletes to perform at maximal intensities.

Maximal effort requires a well-rested muscle, hence the long rest periods. These skills must be practiced in the beginning of a training session when the athlete is fresh, and not in any way fatigued. Maximal motivation, maximum neural recruitment and adequate rest are essential for a quality workout.

Sports of very short duration, with requirements for immediate energy availability are the obvious beneficiaries of the phosphagen system: shot put, high jump and sprints, or burst-like sports, such as football, basketball, and volleyball. Less obvious are the final kick to the finish line in a marathon and the takedown at the end of a long wrestling match when lactic acid levels are high.

In these cases, the athletes spent most of the time in an oxidative and glycolytic environment, respectively, but phosphagen provided the extra burst that can make the difference between first and second place.

Training programs that utilize this system increase the amount of available ATP (and creatine phosphate) in the muscles that are being trained. Training activities requiring higher power output produce larger gains in the muscle's "phosphagen department." (Without going into too much detail, the phosphagen system accesses ATP molecules in the muscle in a location that makes them immediately available for muscle contraction.) With this type of training, the athlete will be able to recover more of these well-placed ATP molecules when they are needed most.

Training in the phosphagen environment:

In "Science and Practice of Strength Training," Vladimir Zatsiorsky gives an elegant training protocol for training for higher power output, or what he calls, the rate of force development (RFD). Exercises with maximally fast bursts of muscle action against high loads are used. With very heavy loads, the resistant object may not move very far, but speed of the muscle action must be extreme. The bursts of muscle action should be performed as fast as possible with maximum effort and maximum recruitment. These exercises are done in a rested state, usually right after a warm-up.

Typical routine:
  • 3 sets of 3 reps at 90% 1RM
  • 5 minutes rest between sets
  • For improving performance: train 4 times a week
  • For maintenance: train 2 times a week
Benefits what types of activities:

ALMOST EVERYTHING. A glance down Table 8.1 in the Essentials text shows the primary metabolic demand from the phosphagen system is listed as "high" for 21 of the 25 activities listed. Therefore, it is easier to state what activities do NOT have the phosphagen pathway as the primary metabolic demand: marathon, XC skiing, long distance track, and ultraendurance events.
Next installment: The Glycolytic Pathway. If want to build your tolerance for lactic acid build-up, this is the pathway to train. Stay tuned...

Self-reverence, self-knowledge, self-control ?
These three alone lead life to sovereign power
? Alfred, Lord Tennyson

  1. "Essentials of Strength and Conditioning," 2nd Edition; Baechle, Earle; NSCA, Human Kinetics
  2. "What is Fitness?" CrossFit Journal, October 2002
  3. "Metabolic Conditioning," CrossFit Journal, June 2003,
  4. Lecture, "Responses and Adaptations to Training, " Jeff Falkel, PhD, PT, CSCS
  5. Lecture, "Metabolic and Nutritional Aspects of Exercises and Training," Mike Conley, MD, PhD, CSCS
  6. Zatsiorsky, Vladimir M., "Science and Practice of Strength Training,"