.gif "IP Gear")
- Joined
- Oct 20, 2005
- Messages
- 816
Optimal Eccentrics
The research shows that optimal gains in muscle size and
strength require eccentric, or negative, muscle contractions.
by Eric Sternlicht, Ph.D.
Many of us regularly use negatives and forced reps in our training. Forced reps enable us to do a few more reps than we can handle on our own, while negatives let us use more weight during the lowering part of a movement than we can lift at the start - or so most bodybuilders believe. What does science say about the abovementioned intensity techniques? Are they really beneficial? And if so, how much weight should yo use? How many force reps should you perform?
While it's widely accepted in the athletic community that negatives and forced reps work, the scientific community has only recently began looking at training methods that focus on eccentric muscle contractions. The research appears promising, as it shows that optimal gains in muscle size and strength require eccentric, or negative, muscle contractions. Both the United States military and NASA are now funding further research involving eccentric exercise in an effort to develop more effective training programs for the troops and astronauts. You'll benefit form all the research as well, as the knowledge gained will lead us to create more effective and time-efficient programs to meet your training goals. Rather than doing forced reps or negatives because you think they work or because they feel good, you'll actually have the answers to questions like "How much?" and "How many?"
As you probably know, every rep of every weight exercise includes two phases: the concentric, or shortening phase, in which you raise or push the weight, and and eccentric, or lengthening, phase, in which you lower the weight or otherwise return it to its original position. Many people think their muscles only contract during the concentric, or positive, movement; but the fact is, whenever you control the eccentric phase by showing the weight's movement as it returns to the starting position, the muscle continues to contract as it resists the force of gravity acting on the weight. In other words, eccentric contractions involve a lengthening of the muscle as it contracts to resist gravity or momentum. The fact is, anytime you get a spot you're using some form of advanced eccentric training, even if you're not aware of it.
While there's a vast amount of existing research on muscle physiology and bio mechanics, most of it involves concentric muscle contractions and traditional modes of resistance exercise. At present there's a limited amount of research regarding eccentric muscle contractions and only speculation at to the mechanics at work. Several recent studies report significantly greater improvements in muscle strength and size when programs focus on the negative phase of lifting movements as compared with more traditional training - exactly what many people had observed in the gym.
Despite those results, eccentric training has some limitations. The first is muscle soreness: Both eccentric exercise and exercise the body isn't accustomed to can lead to delayed-onset muscle soreness or COMS. There are conflicting reports as to the effect of DOMS and / or prior muscle damage on subsequent muscle functions, with some research is showing to change and some showing a decrease in performance. In terms of rehabilitation, however, eccentric exercise appears to be beneficial for both injury prevention and rehabilitation.
Eccentric muscle contraction also make unique metabolic demands on the body. In one study the addition of negative loads following concentric muscle contractions increased metabolic costs by 14 percent. Another limitation is that you have to have a partner. Not many machines let you vary the resistance between concentric and eccentric phases of an exercise.
There are limits to how much weight a muscle can resist during any eccentric movement. Theoretical and applied research suggests that the optimal load is between 104 and 140 percent of the muscle's maximal isometric contractile force, or MICF: the neuromuscular systems interact to function optimally while protecting themselves from injury. In this case the nervous system not only directs your muscles to contract and lift a weight, but it also receives feedback that limits the force of contraction to protect the tissue form excessive stress, damage and injury.
Looking to rectify at least one of the above-mentioned limitations of eccentric exercise. Flex Equipment Inc. commissioned Stuart Rugg, Ph.D., and me to perform a series of pilot studies to determine the optimal resistance for eccentric movements. Under the auspices of Simply Fit Inc. and Occidental College we designed studies involving traditional resistance-training equipment and electromyography. The EMG recordings allowed us to examine the degree of muscle activity during the entire range of motion.
Five subjects who had weightlifting experience, including one professional bodybuilder, participated in the study. While the subjects preformed numerous exercises, the results for the barbell curl are typical of our findings for the other machines and muscles tested.
Each subject performed multiple sets of barbell curls for four repetitions, each using four different workloads, with the concentric load remaining constant at 80 percent of the subject's one-rep max The eccentric load was increased in increments of 10 percent, producing negative workloads of 100, 110, 120 and 130 percent of the positive load. The subject all took rest periods between sets to minimize fatigue.
With respect to muscle physiology and bio mechanics, it's well documented that when the load is kept constant during an exercise, both the energy expenditure and mean EMG values decrease during the eccentric phase. In other words, when the weight remains constant during the entire movement, there's less muscle activity during the negative phase.
Our data confirm that - at least on the second set of barbell curls; however, on the third set, on which the eccentric load was increased by 20 percent, the muscle activity went back up. It wasn't just the elite bodybuilder either. For all five subjects the mean eccentric EMG values started to maintain or increase when the negative workloads increased to 110 to 120 percent of the positive load. When the subjects used 130 percent ont he eccentric load, though, the mean EMG values once again dropped below those for the corresponding concentric phase. That decline may be due to the fact that the subjects could no longer control the descent of the load; so it represents a decrease in recruitment of the target muscle.
Based on our preliminary data, we believe the eccentric load should not be more than 20 percent greater than the concentric load. Although the theoretical limit for eccentric overload had been reported at as high as 140 percent of a muscle's maximal isometric contractile force, our five subjects were incapable of controlling eccentric overloads of 130 percent. Using a negative load of no more than 120 percent MICF enables you to control the movement and limits your potential for muscle damage. Any more weight would make it difficult for you to perform multiple reps with proper form, would most likely produce a drop in muscle activation and would increase the probability of your sustaining muscle connective tissue and / or joint damage during training.
Forced Reps and Negatives Research Applied
Base on current research, here's how you'd go about selecting a proper weight for forced reps or negatives. First, determine your one-, three-, and eight-rep maxes for the exercise in question. (That's the maximum amount of weight you can handle with proper form for the given number of reps.) For example, say your poundages are a s follows:
1RM: 100
3RM: 90
8RM: 80
Force reps: Take the weight you can handle for eight reps max and add 20 percent. In the above example you'd add 16 pounds to the bar or machine (80x.20=16) for a total of approximately 95. Perform as many correct repetitions on your own with that weight, then have your training partner assist you with forced rep until you reach a total of eight.
Negatives: Take the weight you can handle for three reps maximum and add 20 percent. In the example that would be 18 pounds (90x.20=18), or a total of 108. Note that it's more weight than you can handle with proper form for even one repetition. With negatives, however your partner helps you lift the weight to the top position. Then lower the weight to the starting position in a slow controlled manner. Perform three negative repetitions to complete your set.
The research shows that optimal gains in muscle size and
strength require eccentric, or negative, muscle contractions.
by Eric Sternlicht, Ph.D.
Many of us regularly use negatives and forced reps in our training. Forced reps enable us to do a few more reps than we can handle on our own, while negatives let us use more weight during the lowering part of a movement than we can lift at the start - or so most bodybuilders believe. What does science say about the abovementioned intensity techniques? Are they really beneficial? And if so, how much weight should yo use? How many force reps should you perform?
While it's widely accepted in the athletic community that negatives and forced reps work, the scientific community has only recently began looking at training methods that focus on eccentric muscle contractions. The research appears promising, as it shows that optimal gains in muscle size and strength require eccentric, or negative, muscle contractions. Both the United States military and NASA are now funding further research involving eccentric exercise in an effort to develop more effective training programs for the troops and astronauts. You'll benefit form all the research as well, as the knowledge gained will lead us to create more effective and time-efficient programs to meet your training goals. Rather than doing forced reps or negatives because you think they work or because they feel good, you'll actually have the answers to questions like "How much?" and "How many?"
As you probably know, every rep of every weight exercise includes two phases: the concentric, or shortening phase, in which you raise or push the weight, and and eccentric, or lengthening, phase, in which you lower the weight or otherwise return it to its original position. Many people think their muscles only contract during the concentric, or positive, movement; but the fact is, whenever you control the eccentric phase by showing the weight's movement as it returns to the starting position, the muscle continues to contract as it resists the force of gravity acting on the weight. In other words, eccentric contractions involve a lengthening of the muscle as it contracts to resist gravity or momentum. The fact is, anytime you get a spot you're using some form of advanced eccentric training, even if you're not aware of it.
While there's a vast amount of existing research on muscle physiology and bio mechanics, most of it involves concentric muscle contractions and traditional modes of resistance exercise. At present there's a limited amount of research regarding eccentric muscle contractions and only speculation at to the mechanics at work. Several recent studies report significantly greater improvements in muscle strength and size when programs focus on the negative phase of lifting movements as compared with more traditional training - exactly what many people had observed in the gym.
Despite those results, eccentric training has some limitations. The first is muscle soreness: Both eccentric exercise and exercise the body isn't accustomed to can lead to delayed-onset muscle soreness or COMS. There are conflicting reports as to the effect of DOMS and / or prior muscle damage on subsequent muscle functions, with some research is showing to change and some showing a decrease in performance. In terms of rehabilitation, however, eccentric exercise appears to be beneficial for both injury prevention and rehabilitation.
Eccentric muscle contraction also make unique metabolic demands on the body. In one study the addition of negative loads following concentric muscle contractions increased metabolic costs by 14 percent. Another limitation is that you have to have a partner. Not many machines let you vary the resistance between concentric and eccentric phases of an exercise.
There are limits to how much weight a muscle can resist during any eccentric movement. Theoretical and applied research suggests that the optimal load is between 104 and 140 percent of the muscle's maximal isometric contractile force, or MICF: the neuromuscular systems interact to function optimally while protecting themselves from injury. In this case the nervous system not only directs your muscles to contract and lift a weight, but it also receives feedback that limits the force of contraction to protect the tissue form excessive stress, damage and injury.
Looking to rectify at least one of the above-mentioned limitations of eccentric exercise. Flex Equipment Inc. commissioned Stuart Rugg, Ph.D., and me to perform a series of pilot studies to determine the optimal resistance for eccentric movements. Under the auspices of Simply Fit Inc. and Occidental College we designed studies involving traditional resistance-training equipment and electromyography. The EMG recordings allowed us to examine the degree of muscle activity during the entire range of motion.
Five subjects who had weightlifting experience, including one professional bodybuilder, participated in the study. While the subjects preformed numerous exercises, the results for the barbell curl are typical of our findings for the other machines and muscles tested.
Each subject performed multiple sets of barbell curls for four repetitions, each using four different workloads, with the concentric load remaining constant at 80 percent of the subject's one-rep max The eccentric load was increased in increments of 10 percent, producing negative workloads of 100, 110, 120 and 130 percent of the positive load. The subject all took rest periods between sets to minimize fatigue.
With respect to muscle physiology and bio mechanics, it's well documented that when the load is kept constant during an exercise, both the energy expenditure and mean EMG values decrease during the eccentric phase. In other words, when the weight remains constant during the entire movement, there's less muscle activity during the negative phase.
Our data confirm that - at least on the second set of barbell curls; however, on the third set, on which the eccentric load was increased by 20 percent, the muscle activity went back up. It wasn't just the elite bodybuilder either. For all five subjects the mean eccentric EMG values started to maintain or increase when the negative workloads increased to 110 to 120 percent of the positive load. When the subjects used 130 percent ont he eccentric load, though, the mean EMG values once again dropped below those for the corresponding concentric phase. That decline may be due to the fact that the subjects could no longer control the descent of the load; so it represents a decrease in recruitment of the target muscle.
Based on our preliminary data, we believe the eccentric load should not be more than 20 percent greater than the concentric load. Although the theoretical limit for eccentric overload had been reported at as high as 140 percent of a muscle's maximal isometric contractile force, our five subjects were incapable of controlling eccentric overloads of 130 percent. Using a negative load of no more than 120 percent MICF enables you to control the movement and limits your potential for muscle damage. Any more weight would make it difficult for you to perform multiple reps with proper form, would most likely produce a drop in muscle activation and would increase the probability of your sustaining muscle connective tissue and / or joint damage during training.
Forced Reps and Negatives Research Applied
Base on current research, here's how you'd go about selecting a proper weight for forced reps or negatives. First, determine your one-, three-, and eight-rep maxes for the exercise in question. (That's the maximum amount of weight you can handle with proper form for the given number of reps.) For example, say your poundages are a s follows:
1RM: 100
3RM: 90
8RM: 80
Force reps: Take the weight you can handle for eight reps max and add 20 percent. In the above example you'd add 16 pounds to the bar or machine (80x.20=16) for a total of approximately 95. Perform as many correct repetitions on your own with that weight, then have your training partner assist you with forced rep until you reach a total of eight.
Negatives: Take the weight you can handle for three reps maximum and add 20 percent. In the example that would be 18 pounds (90x.20=18), or a total of 108. Note that it's more weight than you can handle with proper form for even one repetition. With negatives, however your partner helps you lift the weight to the top position. Then lower the weight to the starting position in a slow controlled manner. Perform three negative repetitions to complete your set.
