Muscle building exercises usually focus on either fast-twitch muscles or slow-twitch muscles. The most efficient workouts build both types at the same time, if you know how to do them correctly. You can even include intermediate-twitch muscles, too. Here is what you must know.
Which Muscles Are Which?
Skeletal muscles have been classified since the 1970s into main types, fast-twitch and slow-twitch. Refinements of the original classification now divide skeletal muscles into four subtypes.
This classification comes from the book, Body by Science (here on Amazon), by Dr. Doug McGuff and John Little. Please note that their discussion (p. 44-46) conflicts with the classic, and misleading, public understanding of what fast-twitch and slow-twitch muscles are.
Type I (‘slow-twitch’): These are endurance muscles that drive distance and endurance activities such as long-distance running. They are loaded with aerobic enzymes, blood vessels, mitochondria, and myoglobin (an oxygen-storing protein). These ingredients make Type I/Slow Twitch muscles very powerful aerobically – i.e., highly oxidative. They do not, however, create much force. The term ‘slow twitch’ means that these muscles are slow to fatigue (and fast to recover from fatigue). It has nothing to do with twitch velocity!
In fact, the twitch velocity of slow twitch muscles is faster than that of fast twitch muscles.
Type IIA (‘fast-twitch, fatigue resistant’): This muscle type is also oxidative, although poor for endurance compared with slow-twitch muscles.
Type IIAB (‘fast-twitch, intermediate fatigability’): This intermediate fast-twitch muscle type can be oxidative or glycolytic. ‘Glycolytic’ is a fancy term for the type of metabolism that breaks down glucose in the absence of oxygen – i.e., anaerobic.
Type IIB (‘fast-twitch, fatigable’): This type is fully glycolytic (anaerobic), yielding lactic acid upon fatigue. They have less myoglobin and fewer mitochondria than the other fiber types. Type IIB muscle fibers are the slowest to contract (twitch), the fastest to fatigue, and take the longest to recover. They require the highest amount of energy to engage, and they provide the most power when they are engaged.
One More Thing: The Motor Unit
A single muscle is infused with all muscle types, distributed homogeneously throughout the tissue. Each type of muscle, however, is stimulated by a system of main nerves that branch out to individual fibers. A motor unit is a group of same-type muscle fibers that is controlled by a single main nerve. A typical slow-twitch motor unit includes 100 individual fibers, whereas a typical fast-twitch motor unit is comprised of 10,000 separate fibers.
This just means that, engaging all of the fiber types in one muscle requires activating 1,000 slow-twitch motor units in conjunction with 50-100 fast-twitch motor units.
The Big Challenge
When you work out by lifting light weights, the slow-twitch motor units will be fatiguing slowly, recovering fast, and recycling back into the contraction process before you can even engage the fast-twitch motor units. On the other hand, when you lift heavy weights that allow only one or two repetitions, you can recruit all of the available motor units at once. However, by the time your fast-twitch (high power) muscles fail after only two reps, you will not have fully stimulated the majority of your slow-twitch and intermediate-twitch fibers.
The ‘Big Challenge’, therefore, is to choose the appropriate weight that you can lift for the right amount of time. This is a concept that McGuff and Little call ‘Time Under Load’ (TUL). A good example TUL with the right weight would be 90-120 seconds. The ‘right weight’ would ideally be an amount that takes you to muscle failure within that time period.
Additional Keys
Activating all fiber types simultaneously, given the right weight and TUL, depends on ultra-slow movement. This method was originally described as the ‘Nautilus Method’, after the equipment company, and more recently the ‘Super Slow’ method. Combining recent research with all of these key points, into an individual workout plan, is the basis for the Body by Science book.
The nice thing about this information is that it is available almost in its entirety in video form at no charge. I have put up links to all of the pertinent videos on a separate page at this blog here:
Take a look and see what you think. There is a lot of great information in these videos.
WARNING! You’ve Got to Know This Above All Else!
If I made that sound scary, then I meant to. One key component of ALL workout protocols is recovery. Unfortunately, almost all workout programs fail to understand just how much you need for full recovery from a workout and the consequences if you do not get it.
Here is the surprise:
Full recovery from any comprehensive muscle-building or strength-building workout that engages fast-twitch and slow-twitch muscles takes at least 7 days!
Yes, that’s right. All the enzyme indicators, inflammation indicators, rebuilding indicators, whatever can be measured, say the same thing. In fact, if you do not wait at least 7 days between workouts, then you can undermine your progress. Yup, all those workout programs that your fitness trainer assigned you, 3 or more times in the gym each week, are counterproductive.
Can I say it any more clearly: You do more harm than you can imagine when you don’t allow for a recovery period of at least 7 days! Got it?
Personal Experience
I posted some comments early in my training with the Body by Science approach, regarding how it is supposed to work and how it worked for me very quickly. You can get a good idea of how it went for me in this post: How to Build Muscle Quickly and Easily.
That ought to be enough food for thought for now. Enjoy!
Let me know what your experiences have been on this topic, when you get a chance, by adding your comments (or by asking questions) at the bottom of this post.
By the way…
The best books that I know of for showing you how to stay fit with quick, simple, at-home workouts are the Lightning Speed Fitness Program by Roger Haeske and the Fit Over 40 for Women by Brett Yokley. Roger and Brett also throw in lots of bonus books on diet, exercise, and lifestyle when you purchase their books. Click on images below for details.
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All the best in natural health,
Dr. D
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