Intensity and Fiber Recruitment

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Intensity

Without intensity a program is not very productive. As pointed out by Tim Swanger, Mike Bradley, and Steve Murray, Strength and Conditioning Coaches at the United States Military Academy, “You must place your muscles in
a critical situation. The effort level must be maximum. Your brain will only recruit the minimum number of muscle fibers necessary to do the job.”

Intensity has to be learned. Usually after a year of training the athlete will understand what an intense workout really is. A coach can identify it by looking at an athlete after a set of squats. If the athlete has to sit down a few minutes because of muscle exhaustion, they finally understand intensity. There are specific ways to teach intensity if a coach is not satisfied. This brings up the type of exercise performed. In order to train the fast twitch muscle fibers effectively and efficiently, the athlete must use a heavy weight and perform enough reps to trigger the strength process.

Olympic lifts such as the power clean does not effectively train the fast twitch muscle fiber like a slow, controlled movement would. If a lot of momentum is put on the bar that means that the intensity of the exercise is reduced and thus not very effective. Momentum lifts take the stress off the muscle for a brief time during the repetition of an Olympic lift. This is what makes those exercises less intense.

Why is intensity so important? As it will be pointed out below in our Fiber Recruitment comments, intensity triggers the fiber recruitment process. According to Matt Brzycki, Strength Coach Princeton University, “It is only when the intensity of activation is very great or when the Slow Twitch [fibers] are fatigued that the larger, more powerful fast motor units are brought into play.”

 Fiber Recruitment

The time has come for us to revisit some fundamentals of a safe, productive, and efficient training program. As our readership grows we are receiving a lot of e-mails asking us to defend our views against using Olympic lifts to train traditional athletes. This article explains the Principle of Fiber Recruitment, which is a basic element in terms of developing the quick twitch muscle fibers. This article first appeared in December of 2001....

Muscle fiber is recruited in a certain way during a set in any exercise. There are 4 types of muscle:

To illustrate when an athlete trains to failure on the bench and happens to reach failure on the 8th repetition, the first 2 reps have trained the Type I fibers, the 3rd and 4th reps have trained the Type IIA fibers and so on.

Matt Brzycki, Coordinator of Recreational Fitness and Wellness Programs, expresses a concern over the misconception that quick lifts can defy the fiber recruitment pattern. “It is believed that explosive movements [power clean, etc..] will somehow bypass the Slow Twitch fibers and target the Fast Twitch fiber population, which would be a clear violation of the orderly recruitment pattern suggested by Henneman’s Size Principle of Fiber Recruitment.”

In an Olympic movement such as the power clean, Type IIB fibers do not get trained to the fullest extent because failure was not reached in any particular muscle. The momentum of the clean reduces the intensity of the exercise, which takes stress off the muscle never allowing the muscle fibers to get fully exhausted.

Tim Swanger, Strength Coaches at the University of Cincinnati, Mike Bradley, former Strength Coach at Stanford University, and Steve Murray, Strength and Conditioning Coach at the University of Toledo, give a proper analogy of this principle. “As fatigue sets in on the playing field, you are gradually bringing more fibers into play. It could be during a long drive, the fourth quarter, or halfway through practice. If your training consists of a few heavy reps or stopping your exercise short of fatigue, you’ll eventually be using muscle fibers on the field that you didn’t strengthen in the weight room.”