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.”