One of the most common myths of bodybuilding is that fast and slow twitch muscles have to be exercised separately to achieve the best muscle building workout. This is simply not true. You can, indeed, exercise both muscle types simultaneously and get good results. Here is the explanation behind what you should know and what to do in your own workouts.
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.
Fast twitch muscles are more complicated, because they are classified into three subgroups. One is the Fast Oxidative fibers, which are good aerobically and are resistant to fatigue. Another type is Fast Glycolytic, which includes fibers that are more effective anaerobically (without oxygen transfer). They are the easiest to fatigue and the slowest to recover. The third type is intermediate, referred to as Fast Oxidative Glycolytic. The fast twitch muscles are so called because they fatigue fast. However, they recover slowly after being fatigued.
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.
Your brain recruits muscle fibers for force rather than speed of contraction. For this reason, slow twitch muscles are the easiest fiber type to engage. They also require the least amount of energy. In fact, if you lift weights too quickly, you primarily engage your slow twitch muscles.
Slightly more energy is required to engage the Fast Oxidative muscle fibers, and still more for the Fast Oxidative Glycolytic fibers. The highest amount of energy is required to engage 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.
The approach recommended here is backed up by many scientific research studies over the past few decades. The best summary of these studies is provided in a book, 'Body by Science', by Dr. Doug McGuff, M.D., and John Little. It is the best and most thorough book on this topic. Interestingly, the subtitle of this book is, 'A Research-Based Program for Strength Training, Body Building, and Complete Fitness in 12 Minutes a Week'. In fact, based on my experience, 12 minutes a week is more than enough. My personal muscle building workouts have yielded tremendous results in just under 10 minutes per week on average.
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.
Fast twitch muscles are more complicated, because they are classified into three subgroups. One is the Fast Oxidative fibers, which are good aerobically and are resistant to fatigue. Another type is Fast Glycolytic, which includes fibers that are more effective anaerobically (without oxygen transfer). They are the easiest to fatigue and the slowest to recover. The third type is intermediate, referred to as Fast Oxidative Glycolytic. The fast twitch muscles are so called because they fatigue fast. However, they recover slowly after being fatigued.
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.
Your brain recruits muscle fibers for force rather than speed of contraction. For this reason, slow twitch muscles are the easiest fiber type to engage. They also require the least amount of energy. In fact, if you lift weights too quickly, you primarily engage your slow twitch muscles.
Slightly more energy is required to engage the Fast Oxidative muscle fibers, and still more for the Fast Oxidative Glycolytic fibers. The highest amount of energy is required to engage 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.
The approach recommended here is backed up by many scientific research studies over the past few decades. The best summary of these studies is provided in a book, 'Body by Science', by Dr. Doug McGuff, M.D., and John Little. It is the best and most thorough book on this topic. Interestingly, the subtitle of this book is, 'A Research-Based Program for Strength Training, Body Building, and Complete Fitness in 12 Minutes a Week'. In fact, based on my experience, 12 minutes a week is more than enough. My personal muscle building workouts have yielded tremendous results in just under 10 minutes per week on average.
About the Author:
Dr. Dennis Clark shares his expertise on how to eat for bodybuilding in his popular free report on the muscle building diet. Also see what Dr. Clark has to say about where to find the best bodybuilding supplements anywhere.
