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 simplest to describe. They are powerful aerobically, meaning good at using oxygen. They are called slow twitch because they are slow to fatigue, not because they are slow to contract. Being slow to fatigue makes this type of muscle fiber important for endurance. These fibers recover fast after being fatigued. Slow twitch muscle fibers are useful to long distance runners and other 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 simplified descriptions of how muscle fibers are classified based on their ability to use oxygen and on the speed at which they fatigue and recover from fatigue. Slow twitch muscles actually twitch faster and recover faster from exercise than do fast twitch muscles.
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.
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 simplest to describe. They are powerful aerobically, meaning good at using oxygen. They are called slow twitch because they are slow to fatigue, not because they are slow to contract. Being slow to fatigue makes this type of muscle fiber important for endurance. These fibers recover fast after being fatigued. Slow twitch muscle fibers are useful to long distance runners and other 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 simplified descriptions of how muscle fibers are classified based on their ability to use oxygen and on the speed at which they fatigue and recover from fatigue. Slow twitch muscles actually twitch faster and recover faster from exercise than do fast twitch muscles.
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.
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.
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