Avoid This Popular Exercise - As It Shrinks Your Muscle and Accelerates Aging
By Dr. Mercola
Dr. Doug McGuff, M.D., an emergency room physician, is also an expert in one of my new passions of exercise, namely high-intensity interval training.
One of the primary reasons that drove me into medicine was to apply my interest in exercise to optimize health.
Of course, it morphed into other things like nutrition, but exercise has remained a longstanding passion.
I've been exercising since 1968, but it was only recently – in the last two years – that I started to fully appreciate the benefits of high-intensity exercise.
After 42 years of long-distance running, I switched over to what I refer to as Peak Fitness, which includes Peak 8 exercises, and it was one of the best changes I've ever made in my exercise.
I ditched the conventional cardio completely, and I'm experiencing the benefits of that decision.
Dr. McGuff's passion for exercise began at the age of 14, and over the years, he's developed and refined his own techniques to reach optimal fitness. While I've been recommending high-intensity anaerobic training (Peak 8) using an elliptical machine or a recumbent bike, Dr. McGuff is a proponent of high-intensity interval training using weights. In this interview, he discusses both high-intensity anaerobic-type training, and high-intensity super-slow weight training, which can achieve many of the same results using weights instead of a recumbent bike or elliptical.
You've likely heard the terms: anaerobic-, aerobic- and cardiovascular training.
"… [T]hose are all kind of false constructs created by the fitness industry," Dr. McGuff says. "The first thing you have to realize is that to do cardiovascular exercise, the only way that you can access the cardiovascular system is by performing mechanical work with muscle.
Now, you can do that on an elliptical; you can do it on a Schwinn Airdyne, or you can do it on quality weight training equipment, or with a barbell. As long as you're doing mechanical work with muscle, you're accessing the cardiovascular system…
If you look at cellular metabolism, that sort of work, whether you're doing aerobic low-intensity work or high-intensity work, proceeds to a certain shuttle. You take glucose into the cell and you go through glycolysis… [which turns it] into pyruvate. That pyruvate is then moved into the mitochondria, where it goes through a cycle of chemical reactions in the presence of oxygen. What occurs from glucose to pyruvate is—in the absence of oxygen—the the anaerobic metabolism… Then the pyruvate gets moved into the mitochondria, that becomes your aerobic metabolism.
But you cannot carry out any aerobic work without doing anaerobic work first. The aerobic cycle cannot even run unless it has the substrate delivered from the anaerobic cycle. The anaerobic cycle can deliver that substrate faster than the mitochondria can use it. So if you want an aerobic workout, the best way to do it is by delivering that substrate as fast as possible, and that requires high-intensity exercise."
Achieve Greater Health Benefits in Less Time
This is why high-intensity interval training cuts down on your exercise time so dramatically. You're actually getting MORE benefits from high-intensity training than you do from aerobic/cardio, in a fraction of the time—all because you're utilizing your body as it was designed to be used. You can literally be done in about 20 minutes, compared to spending an hour running on the treadmill.
"… [T]he exercise physiology world has created an inextricable link between the aerobic metabolic system and the cardiovascular. But that's not true at all. There's no way that your heart and blood vessels are hooked up only to the mitochondria. The heart and blood vessels support the entire cellular metabolism," Dr. McGuff says. "The best way to get that benefit is with high-intensity intermittent exercise."
If you give it some thought, it's actually easy to see that your body was designed for high-intensity, short-interval exercise. As Dr. McGuff says:
"… the issue isn't necessarily the running for hours and hours and hours. It's the modality itself. You will never, in nature, see an animal jogging… What the steady-state activity does is it trains the plasticity out of your physiologic system—that ability to handle widely varying levels of exertion within a short span of time gets trained away. You actually make yourself less plastic and less adaptable to physical stress in general."
High-Intensity Exercise Effectively Normalizes Insulin Levels
High-intensity exercises sequentially recruit all the different types of muscle fibers in your body, starting with the smaller motor units made up of slow-twitch fibers—which are primarily aerobic in metabolism, have a lot of endurance, and recover quickly—to the intermediate fibers; followed by the fast-twitch fibers. The key to activating your fast-twitch muscle fibers is speed. (I've explained how to properly perform high-intensity interval exercises in great detail, so for a refresher, please see this previous article.)
Your fast-twitch fibers are largely glycolytic and store a lot of glucose. When these muscles are recruited, it creates the stimulus needed to grow muscle. At the same time, it enlarges the glucose storage reservoir in the muscle, which in turn enhances your insulin sensitivity. I've often stated that normalizing your insulin is one of the primary health benefits of exercise, and this is particularly true in the case of high-intensity exercise.
Conventional aerobics does not do this as efficiently.
"If you're doing long, slow, distance-type of exercise; what you're doing is you're very gradually recruiting the slow-twitch motor units. If you remember those will recover quickly," Dr. McGuff explains. "So rather than moving to the next set of motor units, you're just recruiting that one group over and over again."
As a result, your intermediate and fast-twitch fibers actually begin to atrophy! Aside from losing muscle mass, you'll also experience earlier onset of loss of insulin sensitivity, leaving yourself open to a cascade of health ramifications, such as metabolic syndrome.
You can prevent some of this by optimizing your diet, i.e. avoiding sugars and processed foods, and making sure you consume high-quality healthy fat, but you can't negate it entirely. Unfortunately, most people simply eat far too many carbs—including many athletes. Your body's need for sugar is, biologically, very small. And when you consume more than you need, your body turns it into fat. As I've stated before, you do not get fat from eating fat—you get fat from eating too many carbs (sugar).
Dr. McGuff explains:
"Your skeletal muscle – if you're lucky – can hold maybe 250 grams of glucose, and your liver holds about 70. If you take 320 grams of glucose as what your storage capacity is, you can kill that with a single trip to Starbucks. Once you go beyond that, your body is going to find some sort of way to deal with those excess carbohydrates.
If your glycogen storage is full, your body has nowhere else to put it. So instead of going all the way through this metabolic pathway, it… produces body fat. That's called the novel glycogenosis. We are in the midst of a very bizarre, evil-scientist type experiment in the Western world, because we are dumping into our bodies an amount of carbohydrate and, in particular, refined sugars, that are way above the capacity of our metabolism to handle normally."
The result of our modern diet, which is loaded with grains and sugars (especially fructose), is a large percentage of obesity, and people that are overweight. This can be turned around, however, using a wise combination-approach of a high-fat, low-carb diet and high-intensity interval training.
"Through an amplification cascade, when you're doing a high-intensity exercise, you very aggressively empty sugar out of your muscle cells. By doing that and combining over the low-carbohydrate diet, you start to heal the metabolism," Dr. McGuff explains. "They are able to access their energy source finally. That's how they can turn things around."
It's crucial to remember that you cannot exercise your way out of a bad diet, and the first step toward improving your diet is to cut out as much sugar/fructose and grain-carbs as possible. (For more of Dr. McGuff's dietary insights, please listen to the interview in its entirety, or read through the transcript.) Your diet actually accounts for about 80 percent of the health benefits derived from a healthy lifestyle, with the remaining 20 percent coming from exercise. That benefit ratio could lean even higher toward diet, according to Dr. McGuff:
"The standard American diet is highly inflammatory. It produces systemic inflammation of an order that is almost beyond belief. In that state, if you do exercise of any significant stress, you're just adding inflammation on top of the inflammation, and you're actually putting yourself at a bit of a risk. I advise people to get their diet straight and then exercise. Because I think a highly inflammatory diet, in combination with the acute systemic inflammation that occurs as a part of the exercise stimulus, can actually be a negative thing."
High-Intensity Burst-Type Exercise Promotes Human Growth Hormone
As you reach your 30s and beyond, you enter what's called "somatopause," when your levels of human growth hormone (HGH) begin to drop off quite dramatically. This is part of what drives your aging process. According to Dr. McGuff, there's also a strong correlation between somatopause and age-related sarcopenia (muscle loss). HGH is needed to sustain your fast-twitch muscle fibers, which produce a lot of power. It's also needed to stimulate those muscles.
"What seems to be evident is that a high-intensity exercise stimulus is what triggers the body to make an adaptive response to hold on to muscle," Dr. McGuff says. "We have to remember that muscle is a very metabolically expensive tissue… If you become sedentary and send your body a signal that this tissue is not being used, then that tissue is metabolically expensive. The adaptation is to deconstruct that tissue…"
High-intensity exercise promotes muscle building, but just how much muscle mass you gain is highly variable, and depends on your individual expression of certain genes. According to Dr. McGuff, there are about eight different genes relating to muscle mass, but probably the biggest determinant is a gene called myostatin.
"We discussed that muscle is a very metabolically expensive tissue. Your genome has evolved a governor on how large your muscles can become, and how highly expressed that governor is will determine what your muscle mass response to exercise will be. Regardless of that, your body will shuffle around these different genetic alterations, and everyone gets stronger. Some people get enormously stronger without a lot of change in muscle mass. Other people become modestly stronger with very large increases in muscle mass.
But regardless of whether the masses increased or not, what is for certain is their glucose storage capability – irrespective of how impressive the size increases – does increase significantly. That's the more important thing from a metabolic standpoint."
Repetitions and Frequency of Exercise—What's the Ideal Amount?
I've been recommending doing Peak 8 exercises three times a week, but after doing that myself for about a year, I gradually felt that it was too much for me. I cut down to once a week, which seemed to work out well. But after discussing it with Phil Campbell, he made a compelling argument to increase it back to three times a week. Having your body produce growth hormone three times instead of just once a week can have profound health benefits, so I bumped it backed up.
However, I did reduce the intensity by about five percent. Otherwise I just felt too fatigued between sessions. Dr. McGuff has also convinced me to make some additional changes to my routine, and I am experimenting with that. He believes you only need 12 minutes of Super Slow type strength training once a week to achieve the same growth hormone production as you would with Peak 8. Intensity is key for making it work.
"The intensity of the exercise needs to be high enough, so that you can't stand anymore; that you're giving up," Dr. McGuff says. "With that particular modality being used, somewhere in the realm are seven or eight repetitions – that's maybe about all that you can stand, which determines the dose of the exercise… [But] I found that the results in terms of response do not diminish at all when you cut back from eight down to five rounds. That begs you to say, "What are the other three rounds for, other than taxing my recovery ability unnecessarily?"
Dr. McGuff points out that if the intensity is really high, the frequency may need to be reduced.
"For any interval increase in intensity, there has to be a very disproportionate decrease in frequency for it to continue to be productive," he explains.
For example, as a weak beginner, you can exercise three times a week and not put much stress on your system. But once your strength and endurance improves, each exercise session is placing an increasingly greater amount of stress on your body (as long as you keep pushing yourself to the max). At that point, Dr. McGuff recommends reducing the frequency of your sessions to give your body enough time to recover in between.
"The whole notion of the growth hormone spurt becomes very important for a person who's deconditioned and has lost their fastest-twitch motor units in their skeletal muscle that demand it. But just the presence of having an improved metabolic condition and more fast-twitch muscle cells – just having that there – will augment the normal diurnal secretion of growth hormone that occurs and that should be occurring on a natural basis, but is after-feed in most people.
Because you needed it three times a week to get that spurt [when you were] deconditioned does not mean you need it when you're in excellent condition. By the time you're in excellent condition, you already have the muscle tissue that drives the very large diurnal spike of growth hormone anyway. You only need that extra kick after you have fully recovered, which will be much less frequently."
Why Less is More, When it Comes to High-Intensity Exercise
So essentially, McGuff suggests that once you're fit, you really don't need frequent spurts of growth hormone production. Rather recovery takes precedence as being more important, and your recovery period could be anywhere from three to seven days. In fact, he strongly recommends NOT exercising too frequently once you are in fit condition, and here's why:
"[Y]our adrenal gland… sits right above your kidneys, and it's arranged in layers. On the outermost layers, you have mineral corticoids that control your sodium and your electrolyte levels. In the middle layer, you have your corticosteroids that control sugar and generate stress hormones. And in the innermost layer is where you generate growth hormones and the sex steroids, or that's involved in the axis, in the feedback loop that generates that.
The old saying in medical school to memorize the three layers is "salt, sugar, sex" – the deeper you go, the better it gets. But you got to remember, your adrenal gland is an integrated organ. Those three layers are not perfectly divided.
If through high-intensity exercise you're trying to hammer that adrenal gland three times per week, but now you're much stronger and your body hasn't fully recovered from your Monday session and you come back and hit it again on Wednesday… you're going to tap down into that deeper level.Instead of growth hormones spurt, you're going to get in a cortisol spurt. You're going to completely undermine what is it that you're after."
The Importance of Recovery
I have known the importance of "Listening to Your Body," and always advocate this when it comes to selecting foods. But this also applies to exercise and recovery. The epiphany I had with Dr. McGuff was that I wasn't applying the 'listen to your body' principle with respect to my exercise program. When asked about the parameters of how to know if you are recovered from your exercise, he says:
"You would have a restless energy and feel like you have to engage in some type of physical activity. You will spontaneously just want to work out."
Well that had not happened to me for some time, and I believe I was pushing myself too hard and had not allowed myself enough recovery time. This is probably not a problem for most people who exercise, as they are more than likely not pushing themselveshard enough, but when you go to extremes like in Peak Fitness, this is a serious risk you need to pay careful attention to.
So, as a result of this fantastic interview, I'm now in a massive experimentation phase, and I'm having fun playing around with my exercise program. I can't tell you what a profound realization it was to hear this as it really resonated truth with me, and as a result I doubled the number of recovery days in my exercise program.
So, I will likely be exercising the same length of time, just breaking it up differently. I suspect that will be more ideal for me and I intend to report on my results so you can learn from it. Dr. McGuff goes into far more detail with regards to his exercise recommendations than I have covered in this summary, so I highly recommend taking the time to listen to this interview in its entirety.
Principles of High-Intensity Interval Weight Training
As mentioned earlier, Dr. McGuff recommends using weights rather than a recumbent bike or elliptical machine. Metabolically speaking, both forms are very similar to each other.
"Because what you're doing is that you're producing metabolic byproducts of that fatigue, in particular lactic acid," he explains. "You're moving quickly from one movement to the next, or through cycles of a particular movement in the case of interval training. That lactate begins to stack up in the system, and that generates the whole cascade of metabolic adaptations and improvements that make you more capable.
The difference is that in the type of training I advocate, that metabolic stacking of these byproducts (that fatigue) occurs as a consequence of something even more important to the active genotype. In interval training, this is occurring as a side effect of the activity, whereas in the type of training I'm doing, it's occurring as a deliberate goal of what we're doing. That goal is to momentarily and deeply fatigue the starting level of strength of a given muscle group.
What we're trying to do is we are trying to pick up the movement that will involve several large muscle groups, and then rapidly and systematically deeply fatigue all the fibers of those muscle groups in a span of 60 to 120 seconds."
How to Perform Super-Slow Weight Lifting
Essentially, by aggressively working your muscle to fatigue, you're stimulating the muscular adaptation that will improve the metabolic capability of the muscle and cause it to grow. McGuff recommends using four or five basic compound movements for your exercise set. These exercises can be done using either free weights or machines. The benefit of using a quality machine is that it will allow you to focus your mind on the effort, as opposed on the movement.
Dr. McGuff recommends the following five movements:
- Pull-down (or alternatively chin-up)
- Chest press
- Compound row (A pulling motion in the horizontal plane)
- Overhead press
- Leg press
Here's a summary of how to perform each exercise:
- Begin by lifting the weight as slowly and gradually as you can. The first inch should take about two seconds. Since you’re depriving yourself of all the momentum of snatching the weight upward, it will be very difficult to complete the full movement in less than 7-10 seconds. (When pushing, stop about 10 to 15 degrees before your limb is fully straightened; smoothly reverse direction)
- Slowly lower the weight back down
Repeat until exhaustion. (Once you reach exhaustion, don't try to heave or jerk the weight to get one last repetition in. Instead, just keep trying to produce the movement, even if it's not 'going' anywhere, for another five seconds or so. If you're using the appropriate amount of weight or resistance, you'll be able to perform four to eight repetitions) Immediately switch to the next exercise for the next target muscle group, and repeat the first three steps done in this fashion, your workout will take no more than 12 or 15 minutes. While this may sound ridiculouly short, once you've tried it, you'll likely realize that it's really all you can muster. This super-slow movement allows your muscle, at the microscopic level, to access the maximum number of cross-bridges between the protein filaments that produce movement in the muscle.
"It's sort of like a caterpillar or a centipede that's crawling along a surface. If you start off moving very, very slowly, you're going to engage more legs or more movement arms at the microscopic level. What you have in terms of movement is the difference between a centipede and a millipede, and that also produces very gradual movement.
What the slow movement does is it keeps the muscle under a continuous load. It can never escape being under the stress of the weight, so the fatigue accumulates very quickly.
We'll just have you lift and lower the weight until your fatigue accumulates to the point where you no longer have enough strength to continue to move the weight, at which point we will have you continue to attempt to produce movement even though it is not occurring for several more seconds, which drives your level of fatigue more deeply."
More Effective AND Safer Too!
This type of super-slow weight training has another benefit that makes it ideal for virtually everyone, regardless of age or fitness level, and that is safety, as it actively prevents you from accidentally harming your joints or suffering repetitive use injury.
"Force is mass times acceleration. If you deprive yourself of the acceleration, you're delivering almost no punishment to your joints. There's no repetitive use injury," Dr. McGuff says. "The forces are extremely low, and as you become more fatigued, you're becoming much weaker. So you're actually delivering a smaller and smaller force to your body as you fatigue."
I'm very excited about this information and have already begun implementing it into my fitness program. I hope you'll give it a try too!
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