A typical myth in bodybuilding circles is that you must exercise fast and slow twitch muscles separately for getting the best muscle building workout. This could not be further from the truth. In fact, you can easily exercise both muscle types at the same time and still get excellent results. Here is why and what you should do in your own workouts for optimum results.
Slow twitch muscles are the easiest to describe. They are very powerful aerobically, meaning that they are good at using oxygen. They are called slow twitch because of how slow they are to fatigue, not because of their speed of contraction. Muscles that are slow to fatigue are important for endurance. These types of fibers also recover fast after getting fatigued. That is why slow twitch muscle fibers are so important for long distance runners and similar endurance athletes.
On the other hand, fast twitch muscles are more complicated to describe, because they are categorized into three different subgroups. The Fast Oxidative fibers are powerful aerobically and the most resistant to fatigue. In comparison, Fast Glycolytic fibers, which are more effective anaerobically (i.e., without oxygen transfer), are the easiest to fatigue and the slowest to recover. The third type is in between these two, called the Fast Oxidative Glycolytic fibers. Remember that fast twitch fibers are called fast because they fatigue fast. Then they recover very slowly.
These are rather simple descriptions of muscle fiber types based on how well they use oxygen and on how fast they fatigue and recover. Indeed, so called slow twitch muscles actually contract faster and recover faster from workouts than do any subgroup of fast twitch fibers.
Muscle fibers are recruited by your brain to optimize force and not speed of contraction. Because of this, slow twitch muscles are the first and easiest fiber type to engage. This type also requires the least amount of energy. This means that if you lift weights too quickly, you will engage mostly your slow twitch muscles.
A little more energy is necessary to engage the Fast Oxidative muscle fibers. Even more is necessary to engage the Fast Oxidative Glycolytic fibers. And the largest amount of energy is required for engaging the Fast Glycolytic fibers.
The key to the best workouts, therefore, is to follow the advice of physiologists to take advantage of what they call orderly recruitment of muscle fiber types. Orderly recruitment means to engage each type in sequence, from low energy/fast recovery to high energy/slow recovery. The most important components of such a workout are: 1) sufficient weight to bring on muscle failure (i.e., enough that at some point you can no longer lift); 2) the right speed of lifting for recruiting all fiber types in sequence; and, 3) the total time under load (TUL) for each muscle group.
The best approach for accomplishing orderly recruitment entails a very slow lift rate, with an equally slow return rate. Such super slow movements provide the extra advantage of being easier to keep good form throughout the lifting. Fast lifting would otherwise lead to jerking weights and not really lifting them smoothly. Besides, jerking weights generally recruits mostly slow twitch muscles, leaving the other fiber types underutilized.
All the recommendations in this article are backed by numerous scientific studies over the past few decades. The best summary of this research is now available in a book, 'Body by Science', by Dr. Doug McGuff, M.D., and John Little. It is the best and most recent book on this topic. By the way, the subtitle of this book is, 'A Research-Based Program for Strength Training, Body Building, and Complete Fitness in 12 Minutes a Week'. Based on my experience, 12 minutes a week may even be more than you need. My own muscle building improvements have accrued very effectively on about 10 minutes a week.
Slow twitch muscles are the easiest to describe. They are very powerful aerobically, meaning that they are good at using oxygen. They are called slow twitch because of how slow they are to fatigue, not because of their speed of contraction. Muscles that are slow to fatigue are important for endurance. These types of fibers also recover fast after getting fatigued. That is why slow twitch muscle fibers are so important for long distance runners and similar endurance athletes.
On the other hand, fast twitch muscles are more complicated to describe, because they are categorized into three different subgroups. The Fast Oxidative fibers are powerful aerobically and the most resistant to fatigue. In comparison, Fast Glycolytic fibers, which are more effective anaerobically (i.e., without oxygen transfer), are the easiest to fatigue and the slowest to recover. The third type is in between these two, called the Fast Oxidative Glycolytic fibers. Remember that fast twitch fibers are called fast because they fatigue fast. Then they recover very slowly.
These are rather simple descriptions of muscle fiber types based on how well they use oxygen and on how fast they fatigue and recover. Indeed, so called slow twitch muscles actually contract faster and recover faster from workouts than do any subgroup of fast twitch fibers.
Muscle fibers are recruited by your brain to optimize force and not speed of contraction. Because of this, slow twitch muscles are the first and easiest fiber type to engage. This type also requires the least amount of energy. This means that if you lift weights too quickly, you will engage mostly your slow twitch muscles.
A little more energy is necessary to engage the Fast Oxidative muscle fibers. Even more is necessary to engage the Fast Oxidative Glycolytic fibers. And the largest amount of energy is required for engaging the Fast Glycolytic fibers.
The key to the best workouts, therefore, is to follow the advice of physiologists to take advantage of what they call orderly recruitment of muscle fiber types. Orderly recruitment means to engage each type in sequence, from low energy/fast recovery to high energy/slow recovery. The most important components of such a workout are: 1) sufficient weight to bring on muscle failure (i.e., enough that at some point you can no longer lift); 2) the right speed of lifting for recruiting all fiber types in sequence; and, 3) the total time under load (TUL) for each muscle group.
The best approach for accomplishing orderly recruitment entails a very slow lift rate, with an equally slow return rate. Such super slow movements provide the extra advantage of being easier to keep good form throughout the lifting. Fast lifting would otherwise lead to jerking weights and not really lifting them smoothly. Besides, jerking weights generally recruits mostly slow twitch muscles, leaving the other fiber types underutilized.
All the recommendations in this article are backed by numerous scientific studies over the past few decades. The best summary of this research is now available in a book, 'Body by Science', by Dr. Doug McGuff, M.D., and John Little. It is the best and most recent book on this topic. By the way, the subtitle of this book is, 'A Research-Based Program for Strength Training, Body Building, and Complete Fitness in 12 Minutes a Week'. Based on my experience, 12 minutes a week may even be more than you need. My own muscle building improvements have accrued very effectively on about 10 minutes a week.
About the Author:
Dr. Dennis Clark researches, reviews, and provides science-based advice on bodybuilding foods in his popular free report on the muscle building diet. Dr. Clark also offers tips on where to find the best bodybuilding supplements anywhere.
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