I find particular interest in the "force plate" experiment.
The Truth About Fast-Twitch
and Slow-Twitch Muscle Fibers:
An Interview with John P. Kalas, M.D.The following excerpts are from 1976 discussions I had with Dr. John Kalas,
who was Chief of the Department of Pathology, West Volusia County
Hospital, DeLand, Florida. A subsequent article was published in Athletic
Journal (January 1977) as a rebuttal against the popular practices of
coaches and athletes to "train fast to be fast." The concepts
explored within these answers are as relevant today
as they were 30 years ago.by Ellington Darden, Ph.D.
Ellington Darden: John, tell us about your interest in strength training and muscle physiology?
John Kalas: I was involved in weight training in high school and played several sports. As a teenager, I had an ongoing curiosity about my muscles, what made them stronger, and how growth occurred at the cellular level.
That interest was carried through college, medical school, a three-year residency in internal medicine, a year research fellowship in physiology, and finally a four-year residency in pathology. During my residency in pathology, I had considerable exposure to muscle physiology at the Armed Forces Institute of Pathology. My background includes a full 10-year period at the Walter Reed Army Medical Center and 50 published research studies.
It's unfortunate that people with my experiences, or similar experiences, cannot have personal associations with coaches, who are attempting to combine the disciplines of muscle physiology and athletics. This is a common situation that exists in most areas.
The laboratory scientists communicate with each other, but rarely with physicians in the field of disease rehabilitation. These physicians have knowledge that is easily interchangeable with coaches. Unfortunately our society keeps most of us (laboratory scientists, physicians, and coaches) so busy that we are unable to communicate in a productive manner with each other.
This massive amount of information, thus, remains disjointedly scattered throughout the literature without the basic information ever reaching the athletes who need it the most.
ED: You're certainly on target with your assessment. Was there a specific topic that repeatedly caught your attention?
JK: One particular aspect of muscle physiology seems to be a recurring subject of discussion in almost every sports or fitness publication that I've recently read. Although this topic is very complex, it's usually referred to as the concept of
fast-twitch, slow-twitch muscle fibers.
As usual, attempts to simplify complicated subject matter frequently lead to misunderstanding. This has certainly been the case in the fast-twitch, slow-twitch area.
Muscular Contraction
ED: Before we get into a discussion of fast and slow fibers, can you briefly describe how a muscle contracts?
JK: The answer is theoretical and complicated. There are however, three areas that can be discussed with relative certainty.
The first way a muscle contracts is through a conscious command from the brain. The second way is through what is called a reflex arc. The third method is through a conditioned reflex, as demonstrated initially by Ivan Pavlov and his dogs. Athletes use all three of these ways constantly in their practices and competitions.
Even more complex is the mode by which the muscle itself contracts. Albert Szent-Gyorgyi, the famous Hungarian biochemist, demonstrated that the chemicals, actin and myosin, contract in the presence of adenosine triphosophate (ATP).
Later it was determined that this contraction is modified by some 70 or more enzymes and/or chemicals. This applies whether the muscle is called slow, fast, red, or white. Furthermore, this underscores the complexity of the problem of muscle contraction when it is considered along with the influences of the nervous system.
Fast and Slow Confusion
ED: How do the concepts of fast-twitch, slow-twitch muscle fibers relate to athletics?
JK: Classically, the fast-twitch fibers are white and the slow-twitch fibers are red. (The colors are determined by muscle samples, appropriate stains, and microscopic examinations.) Many coaches contend that fast-twitch, white fiber development is necessary for fast athletic activity and that slow-twitch, red fibers are necessary of slow athletic activity.
Unfortunately, it's demonstrated in nature that the non-flying domesticated animals, such as chickens, have white breast muscles and red leg muscles. The fast flying wild fowls, such as ducks, have red breast muscles but white leg muscles.
Furthermore, most authorities believe that there are fast and slow red fibers and fast and slow white fibers in animals. In humans, however, these authorities believe that the differences between the two are less than in animals.
In truth, no one knows very much about the various fiber distributions in humans. In addition, it is believed that at least eight (and probably more) fiber types are prevalent in animals.
Humans Are Different
ED: So, you're saying that the muscle fiber types in humans are different from those found in animals, right?
JK: I'll answer that with
probably. The muscle fiber types in humans have not been well defined. It's believed that as one progresses up the phylogenetic scale, the differences in muscle fiber types diminish. Only a few muscle biopsy specimens have supplied the data that have resulted in the sweeping conclusions drawn by many coaches and athletes.
Muscle Biopsy
ED: What exactly is a muscle biopsy?
JK: A muscle biopsy consists of cutting through the skin and taking a small strip of muscle, usually for diagnosis of disease states by chemical and microscopic techniques. It can also be performed with a large bore needle. A biopsy is usually taken from the surface of a muscle.
For accurate determination of muscle types, however, entire cross sections of muscle with corresponding physiological studies would be necessary. This is not practical in humans.
To make some inroads in this area, without securing complete cross sections of muscle, would mean taking at least three levels of biopsies from one muscle. And at each level, several hundreds of biopsies would be necessary for statistically significant muscle counts to be made. Such research has not been attempted.
ED: I guess it should be fairly obvious that NO athlete (or human) is going to allow scientists to take multiple biopsies from the same muscle at three different levels. "Hey Doc, please take three plugs from my biceps and another three plugs from my triceps. And here, do the other arm too." That entire process could injure the involved muscles, right?
JK: (Laughing . . . ) Correct. With animals, it's been done, but it hasn't been accomplished with humans – for obvious reasons (still smiling). As a result, very little is known about white and red muscle distributions in humans – especially among highly skilled athletes.
Note: One of highlights of being friends with Dr. John Kalas was the time
he invited me to his laboratory to watch him perform an autopsy on
a person who had problems with the heart, liver, and upper arms.
John provided me with a close look at the liver and heart, as
well as the fatty deposits surrounding the gut. Plus, he also
collected multiple biopsies from the biceps and triceps.
What a meaningful experience that was to me.
Fast Exercise for Fast Muscles: Be Cautious
ED: Okay, so translate your experience and beliefs concerning muscle fibers to strength training – does doing an exercise fast make you faster?
JK: It is impossible to simplify muscle fibers into white
fast and red
slow. It is equally impossible to simplify muscular contraction into fast exercise for faster movement and slow exercise for slow movement.
Coaches, therefore, should be very cautious about having their athletes perform fast exercise for fast muscles. There is little basis in science for such a recommendation.
Also, coaches need to be aware that performing fast repetitions is dangerous.
The Danger of Training Fast
ED: What's wrong with performing fast repetitions?
JK: So there is no misunderstanding, I want to define what I mean by "fast." When a barbell, dumbbell, or machine repetition exceeds the muscle's ability to contract, or the tool is thrown rather than lifted, then that is too fast.
As an example, let's examine a barbell overhead press being performed by a subject standing on a force plate connected to a recorder. (A force plate is a delicate measuring device that is used to measure changes in force.) If the subject presses and lowers the barbell in a slow, smooth manner, a steady force is recorded throughout the entire movement. On the other hand, a fast movement applies force to only a small portion (usually at the start and at the end) of the repetition.
After the start of a fast repetition, the barbell is actually lifting the subject's arms (due to momentum). The force applied during the start of the fast movement can often amount to several times the weight of the barbell (a 100-pound barbell for an instant could weigh from 200 to 300 pounds).
Yanking muscles, and that is exactly what is happening, does not build strength. Instead, it exposes the joints, muscles, and connective tissues to danger. Force causes injury, and throwing a weight certainly increases the force.
For the best results from strength training, athletes should perform slow, deliberate repetitions. They should raise the weight smoothly (with minimum acceleration) and lower the weight slowly under full control.
Returning to the example of a barbell overhead press, while standing on a force plate, if you move at a faster pace than approximately 3 seconds on the positive and 3 seconds on the negative, then the bleep running across the scope begins to flutter significantly – which is an indication of too much changing force.
Thus, 3-seconds lifting and 3-seconds lowering seems like a reasonable guideline to follow on each repetition, which is relatively
slow when compared to the fast styles that most coaches and athletes utilize.
Skill Training
ED: At Florida State University, I studied extensively about the need for strength training to be general and skill training to be specific. Since most skills are best performed quickly, motor learning experts recommended that skill practice be done at full speed. What has your neuromuscular study and experience shown you about skill learning?
JK: I agree with the motor learning experts. The neuromuscular pathways for the development of various sports skill must be mechanized through repeated, competition-like practices. Strength training needs to be based on the general functions of the major muscle groups. Skill is specific and strength is general.
Perhaps most importantly:
Do not try to simulate in the weight room what happens on the athletic field. Many coaches fail to grasp this principle and instead, jump aboard the misleading philosophy based on power cleans and explosive bench presses.
Once again, coaches who recommend fast lifts are doing a disservice to their athletes. Such lifting so can lead to neuromuscular confusion and possible injuries.
Coaches would do well to remember the following:
Skill train fast; strength train slow.
Five Basic Guidelines
ED: Thanks, John, for your astute answers. Do you have any final thoughts?
JK: Since we've been kicking around this topic (the talks took place over several days), I phoned an old friend from my Walter Reed Hospital days, Dr. Harold M. Price, former Chief of Muscle Branch, Armed Forces Institute of Pathology.
Dr. Price emphatically stated that I should be as strong as possible in my conclusions about fast-twitch and slow-twitch muscle fibers. He said that
absolutely no one can draw conclusions about human muscle fiber distributions, or tell athletes how to train, from the animal experiments and the few biopsies performed in humans to date.
From my personal study and experience, I offer the following guidelines:
- Training fast will not make an athlete faster.
- Fast-speed repetitions are dangerous.
- Strength training should be performed with heavy weights, which should be lifted smoothly for approximately 8 to 12 repetitions, until momentary muscular failure.
- Training slow will not make an athlete slower.
- Moving fast is required in most skill training and practice must be identical to competition for the best learning to occur.
