leonidas1977
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something i read online and thought it would be nice to share your views on the matter.
“The bottom line seems to be that in the many studies that have compared training with heavy versus moderate resistance as long as sets end with a high degree of effort there are no differences in strength outcome.” Richard A. Winett, PhD
“Some people may have a fear of injury—that need not exist.” Ralph N. Carpinelli, PhD
Forget Heavy, Think Effort
Muscle Fiber Activation and Rep Range
The health establishment struggles mightily to persuade people to exercise regularly with mixed results at best. The latest scientific findings and government guidelines say that strength training should be part of the mix at least twice a week Many people, including those that need it most, are turned off by weight training. They imagine themselves having to lift heavy weights, and that turns them away.
Is that true? Do they have to lift very heavy weights? An eye-opening new study says "NO." The study has the potential to change how strength training is perceived--and get many more people, perhaps millions more, pumping iron.
The study could revolutionize strength training for everyone, from pencil necks to muscle heads.
I'm eager to tell you about it. Pour yourself a cup of coffee and pull up a chair.
We have been told that heavier resistance produces greater gains in size and strength. “Only the heaviest possible weight will bring the maximum number of muscle fibers into action,” I wrote in Ripped 2. The underlying idea is correct—but there's more to the story. It turns out that many experts in the field have made the same error.
Dr Ralph N. Carpinelli, Human Performance Laboratory at Adelphi University in Garden City, New York, has made an exhaustive review of the scientific literature on this issue and reported his findings in the Journal of Exercise Science and Fitness, volume 6, number 2, 2008. His report is important, exciting, and complicated. I’m going to summarize and, where necessary, explain the results. Please bear with me. You’ll be glad you did.
Carpinelli’s analysis turns on the size principle, which governs how muscle fibers are recruited. Carpinelli says the size principle is “perhaps the most supported principle in neurophysiology.” So let’s start there. What is it?
The Size Principle
The size principle is a law that explains the order in which muscle fibers contract. In a nut shell, it says small fibers contract before large fibers.
The small fibers are slow-twitch, and the large fibers are fast-twitch. The slow-twitch fibers are the endurance fibers, which predominate in marathon runners and other endurance athletes. Like the Energizer Bunny, they don’t give out, they keep on contracting. They don’t generate much force, however. Fast-twitch fibers are the strength fibers, which rule the roost in sprinters, weight lifters, and other strength athletes. They are strong, but fatigue rapidly. Most of us are born with a roughly equal balance of slow/small and fast/large fibers. (Some fast fibers, which we’ll come to later, are intermediate in strength and endurance.)
Muscle fiber activation begins with a signal from the brain to motor units, which include a nerve and a companion group of muscle fibers. Fast-twitch and slow-twitch motor units operate separately; motor units are either slow or fast. Identical-twitch fibers are serviced by a single motor nerve that comes down into the muscle like an electrical wire. Slow-twitch units have approximately 100 fibers. Fast-twitch units may have as many as 10,000 fibers. Slow-twitch units, therefore, take up less space and have many more connecting wires or nerve branches than do fast-twitch units. Consequentially, many more slow-twitch motor units are likely to be triggered than larger fast-twitch units. You might have 1,000 slow units activated compared to only 50 to 100 fast units.
Importantly, motor units operate on an all-or-none basis. For a unit to be recruited, the nerve impulse must be strong enough to activate all of the muscle fibers in the unit maximally. If that threshold is not met, no fibers in the unit contract. Motor units contract for all they’re worth or not at all.
The bottom line is that it’s much harder to trigger fast motor units than it is slow units; it takes a lot more current or stimulus, more intensity.
With that background, we’re ready to sum up the size principle, which Carpinelli expresses as follows: “The size principle states that when the central nervous system recruits motor units for a specific activity, it begins with the smallest, more easily excited, least powerful motor units and progresses to the larger, more difficult to excite, more powerful motor units to maintain or increase force.”
In summarizing orderly motor unit recruitment, Jack Wilmore and David Costill drop the reference to size and say it more directly in the third edition of their highly regarded textbook Physiology of Sports and Exercise: “In low-intensity activity, most muscle force is generated by slow-twitch fibers. As the intensity increases, fast-twitch fibers are recruited, and at the higher intensities, the fast-twitch fibers are activated.”
Strange as it may seem, speed makes no difference. Motor units are recruited in an orderly sequence, slow to fast, no matter what the speed of the movement. Speed of action does, however, affect the amount of force developed. Slow movements generate more force. “The closer you get to zero velocity, the more force can be generated,” say Wilmore and Costill. Slow motion dampens momentum; at zero speed force is maximized.
Force, however, is not the variable that triggers muscle fiber contractions. I'll say that again, because it's very important. Force is not the kick off factor.
As Carpinelli writes in his report, “Force [is] not the prerequisite for recruitment; force [is] the result of a more intense stimulus.” He continues, “The level of effort…determines the degree of motor unit activity.” Effort, of course, begins in the brain.
Keep the distinction between force and effort in mind, because we’ll be coming back to it over and over. Effort generates force, not the reverse.
That brings us to the big question that every weight trainer wants answered: What’s the best and safest way to stimulate and build the maximum number of muscle fibers?
Is heavier better?
The studies that Dr. Carpinelli reviewed attempt to answer that question. But do they succeed? Do the findings support the conclusions? Where do the well designed studies come down? Read on and find out.
Some studies have misapplied the size principle, according to Carpinelli. We’ll look at those studies first.
Misunderstanding the Size Principle
Dr. Carpinelli analyzes more than 30 specific studies and, in some cases, books in this section of his report. I will summarize representative studies and explain how Carpinelli says the size principle was misapplied or bypassed.
Here’s the problem, as Carpinelli sees it: “Although the size principle is described reasonably accurately, it is often followed by a misunderstanding of the underlying neurophysiological concept and its practical application.” For example, many authors conclude that maximum or near maximum force—very heavy resistance—is necessary in order to recruit the large motor units and maximize strength gains. In other words, they decide that heavier is better.
“[That] is an invalid reverse inference of the size principle,” says Carpinelli. As noted above, force or resistance is not the controlling factor.
For example, the authors claim, citing the size principle, that heavier resistance (3 to 5 rep max) recruits higher-threshold motor units than lighter resistance (12 to15 rep max). Force or resistance, they assert, is the factor that determines whether high- or low-threshold motor units are recruited.
That’s demonstrably wrong, according to Carpinelli. Resistance (poundage) makes little difference, says Carpinelli, as long as the last few reps are at or near maximum. Effort, not force, is the controlling factor.
The simplest example, says Carpinelli, is an isometric muscle action. “If a person is holding a 20 kg [about 45 lbs] dumbbell at an elbow angle of 90 degrees…the first 10 seconds may feel relatively easy. After about 60 seconds [however] the person will no longer be able to hold the 20 kg mass.”
What changed? The force, the weight, remained the same, so force was not the controlling factor. It was the effort that changed, the required effort, wasn’t it? The weight felt heavier and heavier as time passed, until the person was no longer able to hold it at a right angle.
“Despite the increasing effort throughout the 60 seconds duration, the muscular force remained constant until it decreased at 60 seconds when the individual was no longer capable of producing [the] muscular force [necessary to hold the weight],” Carpinelli explained. “At the point of maximal effort (~60 seconds), all the motor units in the pool were recruited [including the large/fast motor units] for that specific isometric muscle action.”
He’s right, isn’t he?
Other studies claim that heavier resistance produces greater strength gains, but provide no credible supporting evidence. Often citations are provided which offer no actual support. Some references allude to the size principle and others make claims or recommendations without supporting evidence.
Carpinelli methodically dissects study after study showing specifically how each author’s citations failed to support their claims or recommendations. This is “important,” he maintains. “It is not sufficient simply to cite the reference without noting exactly what the authors of those studies and reviews report.”
Several studies claim that advanced weightlifters may be able to override the orderly recruitment of the size principle because they “can inhibit the lower-threshold motor units and preferentially activate the higher-threshold motor units.” In other words, they are somehow able to recruit the large motor units first. No citation or other evidence is offered in support of the assertion that the size principle can be violated. This is unsubstantiated opinion.
One author claimed that a 10 RM (repetition maximum) builds strength slower than a 5 RM. The reference cited, however, was a training study which compared 6-8 RM, 30-40 RM, and 100-150 RM. The study did not include 5 or 10 RM protocols. (We’ll discuss the drawbacks of very high reps below.)
Other authors claimed that “high-velocity movements” skip over the smaller motor units so that the larger units can be recruited first. Again, no supporting evidence was offered. By the same token, another author claimed that slow movements cannot generate enough force to trigger the larger motor units. As before, no training studies or other evidence was offered in support.
“The bottom line seems to be that in the many studies that have compared training with heavy versus moderate resistance as long as sets end with a high degree of effort there are no differences in strength outcome.” Richard A. Winett, PhD
“Some people may have a fear of injury—that need not exist.” Ralph N. Carpinelli, PhD
Forget Heavy, Think Effort
Muscle Fiber Activation and Rep Range
The health establishment struggles mightily to persuade people to exercise regularly with mixed results at best. The latest scientific findings and government guidelines say that strength training should be part of the mix at least twice a week Many people, including those that need it most, are turned off by weight training. They imagine themselves having to lift heavy weights, and that turns them away.
Is that true? Do they have to lift very heavy weights? An eye-opening new study says "NO." The study has the potential to change how strength training is perceived--and get many more people, perhaps millions more, pumping iron.
The study could revolutionize strength training for everyone, from pencil necks to muscle heads.
I'm eager to tell you about it. Pour yourself a cup of coffee and pull up a chair.
We have been told that heavier resistance produces greater gains in size and strength. “Only the heaviest possible weight will bring the maximum number of muscle fibers into action,” I wrote in Ripped 2. The underlying idea is correct—but there's more to the story. It turns out that many experts in the field have made the same error.
Dr Ralph N. Carpinelli, Human Performance Laboratory at Adelphi University in Garden City, New York, has made an exhaustive review of the scientific literature on this issue and reported his findings in the Journal of Exercise Science and Fitness, volume 6, number 2, 2008. His report is important, exciting, and complicated. I’m going to summarize and, where necessary, explain the results. Please bear with me. You’ll be glad you did.
Carpinelli’s analysis turns on the size principle, which governs how muscle fibers are recruited. Carpinelli says the size principle is “perhaps the most supported principle in neurophysiology.” So let’s start there. What is it?
The Size Principle
The size principle is a law that explains the order in which muscle fibers contract. In a nut shell, it says small fibers contract before large fibers.
The small fibers are slow-twitch, and the large fibers are fast-twitch. The slow-twitch fibers are the endurance fibers, which predominate in marathon runners and other endurance athletes. Like the Energizer Bunny, they don’t give out, they keep on contracting. They don’t generate much force, however. Fast-twitch fibers are the strength fibers, which rule the roost in sprinters, weight lifters, and other strength athletes. They are strong, but fatigue rapidly. Most of us are born with a roughly equal balance of slow/small and fast/large fibers. (Some fast fibers, which we’ll come to later, are intermediate in strength and endurance.)
Muscle fiber activation begins with a signal from the brain to motor units, which include a nerve and a companion group of muscle fibers. Fast-twitch and slow-twitch motor units operate separately; motor units are either slow or fast. Identical-twitch fibers are serviced by a single motor nerve that comes down into the muscle like an electrical wire. Slow-twitch units have approximately 100 fibers. Fast-twitch units may have as many as 10,000 fibers. Slow-twitch units, therefore, take up less space and have many more connecting wires or nerve branches than do fast-twitch units. Consequentially, many more slow-twitch motor units are likely to be triggered than larger fast-twitch units. You might have 1,000 slow units activated compared to only 50 to 100 fast units.
Importantly, motor units operate on an all-or-none basis. For a unit to be recruited, the nerve impulse must be strong enough to activate all of the muscle fibers in the unit maximally. If that threshold is not met, no fibers in the unit contract. Motor units contract for all they’re worth or not at all.
The bottom line is that it’s much harder to trigger fast motor units than it is slow units; it takes a lot more current or stimulus, more intensity.
With that background, we’re ready to sum up the size principle, which Carpinelli expresses as follows: “The size principle states that when the central nervous system recruits motor units for a specific activity, it begins with the smallest, more easily excited, least powerful motor units and progresses to the larger, more difficult to excite, more powerful motor units to maintain or increase force.”
In summarizing orderly motor unit recruitment, Jack Wilmore and David Costill drop the reference to size and say it more directly in the third edition of their highly regarded textbook Physiology of Sports and Exercise: “In low-intensity activity, most muscle force is generated by slow-twitch fibers. As the intensity increases, fast-twitch fibers are recruited, and at the higher intensities, the fast-twitch fibers are activated.”
Strange as it may seem, speed makes no difference. Motor units are recruited in an orderly sequence, slow to fast, no matter what the speed of the movement. Speed of action does, however, affect the amount of force developed. Slow movements generate more force. “The closer you get to zero velocity, the more force can be generated,” say Wilmore and Costill. Slow motion dampens momentum; at zero speed force is maximized.
Force, however, is not the variable that triggers muscle fiber contractions. I'll say that again, because it's very important. Force is not the kick off factor.
As Carpinelli writes in his report, “Force [is] not the prerequisite for recruitment; force [is] the result of a more intense stimulus.” He continues, “The level of effort…determines the degree of motor unit activity.” Effort, of course, begins in the brain.
Keep the distinction between force and effort in mind, because we’ll be coming back to it over and over. Effort generates force, not the reverse.
That brings us to the big question that every weight trainer wants answered: What’s the best and safest way to stimulate and build the maximum number of muscle fibers?
Is heavier better?
The studies that Dr. Carpinelli reviewed attempt to answer that question. But do they succeed? Do the findings support the conclusions? Where do the well designed studies come down? Read on and find out.
Some studies have misapplied the size principle, according to Carpinelli. We’ll look at those studies first.
Misunderstanding the Size Principle
Dr. Carpinelli analyzes more than 30 specific studies and, in some cases, books in this section of his report. I will summarize representative studies and explain how Carpinelli says the size principle was misapplied or bypassed.
Here’s the problem, as Carpinelli sees it: “Although the size principle is described reasonably accurately, it is often followed by a misunderstanding of the underlying neurophysiological concept and its practical application.” For example, many authors conclude that maximum or near maximum force—very heavy resistance—is necessary in order to recruit the large motor units and maximize strength gains. In other words, they decide that heavier is better.
“[That] is an invalid reverse inference of the size principle,” says Carpinelli. As noted above, force or resistance is not the controlling factor.
For example, the authors claim, citing the size principle, that heavier resistance (3 to 5 rep max) recruits higher-threshold motor units than lighter resistance (12 to15 rep max). Force or resistance, they assert, is the factor that determines whether high- or low-threshold motor units are recruited.
That’s demonstrably wrong, according to Carpinelli. Resistance (poundage) makes little difference, says Carpinelli, as long as the last few reps are at or near maximum. Effort, not force, is the controlling factor.
The simplest example, says Carpinelli, is an isometric muscle action. “If a person is holding a 20 kg [about 45 lbs] dumbbell at an elbow angle of 90 degrees…the first 10 seconds may feel relatively easy. After about 60 seconds [however] the person will no longer be able to hold the 20 kg mass.”
What changed? The force, the weight, remained the same, so force was not the controlling factor. It was the effort that changed, the required effort, wasn’t it? The weight felt heavier and heavier as time passed, until the person was no longer able to hold it at a right angle.
“Despite the increasing effort throughout the 60 seconds duration, the muscular force remained constant until it decreased at 60 seconds when the individual was no longer capable of producing [the] muscular force [necessary to hold the weight],” Carpinelli explained. “At the point of maximal effort (~60 seconds), all the motor units in the pool were recruited [including the large/fast motor units] for that specific isometric muscle action.”
He’s right, isn’t he?
Other studies claim that heavier resistance produces greater strength gains, but provide no credible supporting evidence. Often citations are provided which offer no actual support. Some references allude to the size principle and others make claims or recommendations without supporting evidence.
Carpinelli methodically dissects study after study showing specifically how each author’s citations failed to support their claims or recommendations. This is “important,” he maintains. “It is not sufficient simply to cite the reference without noting exactly what the authors of those studies and reviews report.”
Several studies claim that advanced weightlifters may be able to override the orderly recruitment of the size principle because they “can inhibit the lower-threshold motor units and preferentially activate the higher-threshold motor units.” In other words, they are somehow able to recruit the large motor units first. No citation or other evidence is offered in support of the assertion that the size principle can be violated. This is unsubstantiated opinion.
One author claimed that a 10 RM (repetition maximum) builds strength slower than a 5 RM. The reference cited, however, was a training study which compared 6-8 RM, 30-40 RM, and 100-150 RM. The study did not include 5 or 10 RM protocols. (We’ll discuss the drawbacks of very high reps below.)
Other authors claimed that “high-velocity movements” skip over the smaller motor units so that the larger units can be recruited first. Again, no supporting evidence was offered. By the same token, another author claimed that slow movements cannot generate enough force to trigger the larger motor units. As before, no training studies or other evidence was offered in support.
