By Dr. Mercola
Many studies support the importance of high-intensity interval training (HIIT) to improve your health. Some of the latest research involves myokines—a class of cell-signaling proteins produced by muscle fibers—and how they can combat cancer and metabolic syndrome.
Dr. Doug McGuff, an emergency room physician, is also an expert in high intensity training as applied to strength training. My previous interview with him was very popular, and we recently sat down again to discuss some of this more recent research.
What Is High Intensity Strength Training?
What distinguishes high intensity strength training from regular weight-lifting is that it's a process where you're trying to generate a stimulus to cause strength and metabolic improvements, as opposed to simply trying to demonstrate strength by lifting the weight by any means possible.
"You're actually using a style of performance that makes the exercise very, very hard," he explains. "It produces a very rapid rate and depth of fatigue, which is the end-goal of what you're doing with that kind of exercise.
You're lifting and lowering the weight very slowly in a way that deprives you of all momentum and in a way that fatigues the muscle deeply and quickly... It is definitely something that triggers all of the desirable outcomes from exercise."
High Intensity Strength Training Promotes Anti-Inflammatory Myokines
Exercise plays an important role in your health, in part by its ability to affect your body composition. Some forms of exercise are more effective than others in this regard, however.
Unfortunately, anywhere from 90 to 98 percent of people who exercise are NOT doing high intensity exercises. By focusing on slow endurance-type exercises, such as running on a treadmill, you actually forgo many of the most profound benefits of exercise.
Conventional thinking has been that the human body is a homeostatic organism that automatically trends toward optimal health. According to Dr. McGuff, this is not really the case... and this is where recent research into myokines comes in.
Once they're factored into the equation, it becomes easier to see how and why each lifestyle choice adds to or takes away from your body's ability to maintain health.
Myokines are a type of a chemical messenger in a class called cytokines. Many of the cytokines we already know about are the kind liberated from adipose tissue, your body fat, particularly the truncal fat mass that gives you that apple-shape. Many of these are inflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha) and interleukin-1 family (IL-1).
"All of these are involved in inflammatory and disease states and are cytokines known to be elevated in people who develop cancer," Dr. McGuff says. "Starting around 2003, they started to realize that muscle was also an active endocrine organ. It produces cytokines of its own, which they ended up terming myokines. ('Myo' is jst a Latin root for muscles.) These myokines are very anti-inflammatory and they produce all of the effects that are the antithesis of the metabolic syndrome. They increase your insulin sensitivity. They increase your glucose utilization inside the muscle.
They increase liberation of fat from adipose cells and the burning of the fat within the skeletal muscle. They also act as chemical messengers that inhibit the release and the effect of the inflammatory cytokines that are produced by body fat. They also significantly, via inhibitory effect, reduce body fat irrespective of calorie intake. It actually has a fat-reducing effect that exists outside of energy balance. They have very profound effects."
New Research Suggests HIIT May Help Combat Cancer
There are a number of different myokines that work by different mechanisms. As far back as the 1980s, and maybe even previous to that, research by Ken Cooper with the Aerobics Institute showed that exercise reduces your risk of cancer. But it's not an intuitive connection. Why would exercise prevent cancer other than making you healthier in general? Still, research showed exercise has profound metabolic effects, and myokines now appear to be an important part of the answer.
"In my book, Body By Science, my co-author and I decided to define health in our own terms. One of the best ways I could describe it is that there's an appropriate balance between the catabolic (breakdown) and anabolic (build-up) state. There has to be a balance in the body.
That's what this interplay between anti-inflammatory myokines produced by muscle and inflammatory cytokines produced by body fat and other tissues comes into play. There is a critical balance there that's important. When that balance gets disrupted by changes in lifestyle that are not congruent with our evolutionary background, that's when disease starts to happen," Dr. McGuff explains.
As Dr. McGuff explains, your diet is one of the major ways in which you can give either the right or wrong tissue the competitive advantage. By eating inflammatory foods, such as sugar/fructose, grains, trans fats, and processed foods in general, your body will generate inflammatory cytokines. And, unfortunately, you simply cannot exercise your way out of a bad diet. No amount of exercise will successfully create enough myokines to out compete the inflammatory cytokines produced by an unhealthy diet.
Your Body Was Built for Brief, High Intensity Workouts
Mankind evolved performing very high-intensity activities, moving intensely for brief periods of time. As Dr. McGuff notes, it's part of our genotype. A frequent question that comes up with regards to high intensity exercise is the differences between the high-intensity cardio that you can do on an exercise bike or elliptical machine, versus high intensity strength training, using weight.
In many ways, they provide similar benefits. Both trigger your body's fight or flight mechanism, which results in the release of adrenaline and epinephrine. These hormones trigger an amplification cascade that empties your muscles of glucose in order for it to be used for fuel.
"As a result, it increases your insulin sensitivity and basically starts to reverse or tilt all the effects of the metabolic syndrome," Dr. McGuff explains. "You get that with high-intensity interval training and you get that with high-intensity strength training, which is something that I advocate.
The primary difference between HIIT and high-intensity strength training is the degree of muscular fatigue. In evolutionary terms, high-intensity interval training is like being on the hunt and intermittently sprinting for your life for a short span of time, whereas high-intensity strength training would be like getting in a life-and-death wrestling match with someone almost perfectly matched to your capabilities. It would be a massive struggle with great fatigue."
So basically, high intensity strength training gives you all the benefits that HIIT provides—including all the cardiovascular benefits—but in addition to that, it also induces a rapid and deep level of muscle fatigue. This triggers the synthesis of more contractile tissue, and all the metabolic components to support it—including more myokines.
"Skeletal muscle is one of the largest glucose reservoirs in your body. It's going to improve your glycogen storage and utilization capabilities, which improves your insulin sensitivity and does everything to kind of flip the metabolic syndrome on its head. In addition to that, it triggers the release of a lot of myokines.
These myokines have very specific effects on body composition, systemic inflammation, and risk for chronic disease that are outside anything to do with energy balance itself. When we really ramp up the intensity so that the muscle is truly challenged and fatigued, we get a lot of extra benefit out of that."
Why High Intensity Strength Training Can Provide Even Better Cardiovascular Benefits Than Aerobic-Style HIIT
In terms of cardiovascular benefits, compared to the aerobic version of HIIT, high intensity strength training is actually a bit superior, even though it will typically not bring your heart rate as high. Dr. McGuff gives an excellent explanation for this somewhat counterintuitive phenomenon. I would encourage you to watch the video to hear him personally explain it, but it is written below.
"Let me explain why you don't see the level of heart rate rise with high-intensity strength training that you do with high-intensity interval training. It is actually a reason why it's a better cardiovascular stimulus. When you're doing hard work, your cardiovascular system needs to supply working muscle with increased cardiac output. Cardiac output equals your heart rate times your stroke volume. The stroke volume is the amount of blood that's ejected from the heart with every beat.
What determines how much blood is ejected out of the heart with every beat is how much blood is brought to the heart before each beat by venous return. Now, when you're doing high-intensity strength training, those intense tonic muscular contractions are milking massive amounts of venous blood back to the heart.
That increased venous return causes a larger volume of blood to be in the heart so that each beat you have a much higher stroke volume. In order to increase cardiac output, when you're doing high-intensity strength training, you're increasing stroke volume to the extent that you don't have to increase heart rate as much… The other thing that's important is, when you're doing high-intensity training on an aerobic piece, you're not getting that much venous return.
Your stroke volume is less, so you have to compensate. In order to produce an equivalent cardiac output, you have to compensate by producing a higher heart rate to generate that. But once the heart rate goes above a certain point, once it goes above 160 generally, it's now beating so fast that there is not enough time for cardiac filling to occur between beats. So stroke volume starts to get compromised."
Recovery Is Also an Important Part of Your Fitness Plan
Ideally, you'd incorporate both versions of high intensity exercises, as they each provide important pieces of the fitness puzzle. For example, you might do conventional HIIT using a stationary bike once or twice a week, and super-slow high intensity weight training once a week—or vice versa, to end up with a total of three high intensity sessions per week.
Remember that, as your fitness increases, the intensity of your exercise goes up, and the frequency that your body can tolerate goes down. As a result, you need to continuously customize your program to your own fitness level and other lifestyle issues. As a general rule however, you do not want to do high intensity interval training exercises more than three times a week. High intensity strength training can be done twice a week initially, but as you get stronger you will need more recovery time and eventually drop down to once every 7-10 days. Any more than that and you'll put your body under too much strain. Your body needs time to fully recover in between sessions.
"Keep in mind that exercise does not directly cause physiologic improvement. Exercise is simply a stimulus, a negative stressor that's delivered to your body, which your body then makes an adaptation to and which causes you to improve. But make no mistake, it's a stimulus that your body has to recover and super compensate from, and that takes time. You can never let your thinking to generate into more is better; sometimes less is better," Dr. McGuff warns.
"I tell people that as a consequence of their exercise, they should feel better. They should feel above baseline more days than they feel below baseline. Because if you do really hard exercise, you're going to feel somewhat fatigued afterwards. But that fatigue should not be long lasting and it should not be cumulative. You're doing this to improve your capability and performance, not to wear yourself down."
Sample High Intensity Strength Training Workout
While you can certainly use gym equipment, you can also get an incredibly high-intensity workout right at home. All you need is a set of dumbbells and a chin-up bar. Here's one sample workout:
- With a rubber ball behind your back, hold a dumbbell in each hand, and do a static contraction; keep your hips flexed at 90 degrees and your knees flexed at 90 degrees. Basically, you're in a sitting position without a chair underneath you and, with a weight in each hand, you simply hold that position statically for as long as you can.
- Follow this with several very slow deep knee bends (squats). By that time, you'll be so fatigued that lifting your own body weight will be quite challenging. Do them to failure.
- Next, use your dumbbells for an overhead shoulder press. Initiate the movement as gradually as you can and then move slowly, pressing the weight upward for 10 seconds or more, and lower it back down over a count of at least 10 seconds. Do not rest at any point. In a short amount of time, you will fatigue your shoulder girdle. Select a weight that you can do 8-10 reps with to failure. If you can do more than 10 reps then you need a heavier weight; if you can't do 8, you need a lighter weight.
- Biceps and triceps curls with one weight in each hand.
- If you have a chin-up bar, do several chin-ups using an underhand grip (palms up), as slowly as you can, until fatigue. If you're not strong enough to do a chin-up, stand on a chair to reach the top of the bar, and simply hold yourself at the top position for as long as you can.
Using an underhand grip puts you in the strongest position for engaging all the muscles of your torso musculature. When your hand is supinated and at shoulder width, you're using your bicep in its strongest position. If you have your hands out or pronated, you're actually using smaller muscles; you're using your brachialis and brachioradialis that are going to be a weak link in that movement and cause you to fatigue prematurely before you've challenged the bigger muscles in your torso.
- Next, do one standard military-style push-up with your body in plank position. Start with arms straight. Go slowly down until your chest almost touches the floor. Then slowly push back up. If you're strong enough, use a very slow cadence of 10 seconds down, 10 seconds up. If you're not strong enough, you can do push-ups from your knee, or you can do them up against the countertop, where your entire plank torso is on an incline to decrease the resistance.
Strength Training Only Becomes More Important with Age
Activities to improve your mobility and balance are also important aspects of fitness. One example is slacklining, which is becoming increasingly popular, in large part because it's more like play than exercise. That said, improving your strength is still among the most important, and it only gets more important with age. Your risk of falling increases with age primarily due to lack of muscle strength—not because the balance organ in your ear deteriorates. So, as Dr. McGuff notes, when an elderly person falls, it's not due to a balance problem; it's a strength problem, and when you're older, falling can be lethal...
"You break a hip. You have to have surgery. You get a deep vein thrombosis (DVT), a clot in your leg. It breaks off and goes to your lungs, pulmonary embolism, and you're dead. I mean, it's a slippery slope once that starts to happen. That's why it's so important for strength as we age," he says.
Yet another key ingredient for optimal health is to avoid sitting for extended periods of time, and this advice applies even to the fittest of athletes. Ideally, you'll want to avoid sitting for more than 15 minutes at a time. In a previous article, I included dozens of videos demonstrating simple exercises you can do throughout the day, right at your desk.
On Dr. McGuff's website, DrMcGuff.com, you will find links to an entire YouTube library of workouts, done in various locations—in gyms around the country, and at home, using little more than body weight, dumbbells, kettlebells, and a rubber ball. He also has a directory listing facilities around the US that offer super-slow weight training classes. You can also find more information on high intensity strength training on BodyByScience.net.
"I think the closing statement is: just get started," Dr. McGuff says. "Go do something of a meaningful intensity because what we're finding is that the sum is much greater than its individual parts, and that you're producing hormonally active substances that do everything that we want to reverse the diseases of modern civilization. It's all in skeletal muscle.
Your body will quickly make adaptations so that the intensity can actually escalate much quicker than you'd realize. If you engage it in a meaningful fashion, you're going to do everything that you possibly can to augment your metabolic health, your cardiovascular health, your general health, bone mineral density, and protect against Alzheimer's or cancer. I mean, it is all there. All of these beneficial myokines released. We're just learning about it. It's very exciting, and it's good, good stuff. Go get yourself some."