HIIT High Intensity Interval Training

Ask Arivale: Is High-Intensity Interval Training the Best Kind of Exercise?

By Jennifer Lovejoy, PhD, Arivale Chief Translational Science Officer

This past month, I had an opportunity to hear a well-known physician, an expert in prevention and lifestyle medicine, speak about optimizing health.

Much of what he said was right on target, but I was struck a few times by the difference between how wellness and prevention are conventionally discussed and the scientific wellness approach.

Scientific Wellness is grounded in the idea that wellness recommendations should be unique to each individual, based on all the knowledge available to them. Our bodies are incredibly complex, and what works for some simply won’t work for others.

At one point the physician was talking about the health benefits of exercise and made the statement, “High-intensity interval training is the best exercise to do.”

While there is no doubt that HIIT is the best exercise for some people to do, the scientific wellness approach finds that it is not the best exercise for everyone to do.  

Unique advantages of HIIT include an increase in anaerobic fitness, which is important for sports requiring short bursts of speed, as well as increased EPOC (excess post-exercise oxygen consumption). Increased EPOC means more calories are burned in the hours after the workout ends compared with continuous exercise. And, while HIIT doesn’t have an overall unique benefit on weight loss, it does seem to favor abdominal fat loss, which is important for overall wellness.

However, for many aspects of health, the benefits of HIIT and sustained moderate exercise come out about even.

For example, studies show that HIIT and sustained moderate exercise have similar benefits when it comes to increasing aerobic capacity and managing insulin resistance and lipids.

So, individuals who are primarily focused on increasing aerobic fitness or improving cardiometabolic health could choose to implement either a HIIT workout plan or a moderate-intensity plan depending on their personal preference, lifestyle, and time.

In contrast, there are individuals for whom a HIIT workout strategy would not be recommended.  

One example is people with adrenal dysfunction—cortisol levels that are either too high or too low. Vigorous exercise, including HIIT, is a physical stressor and causes significant short-term increases in cortisol. For people who are already showing biological evidence of stress-related challenges based on their cortisol profile, regular moderate exercise may be both physiologically and psychologically better for optimizing wellness than an intense exercise regimen like HIIT.

Of course, the above examples are simply based on blood and saliva biomarkers. Scientific wellness also takes into account your genetics.

For example, if an individual has a high genetic predisposition for tendon and ligament injury, that may impact the type and intensity of workout that is optimal for their health. High-intensity workouts come with higher risk for injury, so HIIT may not be the best choice for someone with a history of chronic sport-related soft tissue injuries or a genetic predisposition for them.

Furthermore, a person’s current lifestyle factors into the decision about whether a HIIT workout is going to be “the best exercise” or not. It will also help determine the timing of when it might be appropriate to add to a workout plan.

One of the main advantages of HIIT workouts is that you can get similar exercise-related benefits on health and fitness in a shorter period of time.  For many people, this means that HIIT fits better into their lifestyle, and they are more likely to consistently fit exercise in. And, of course, for competitive athletes in certain sports, HIIT is recommended for performance outcomes.

But, the truth is many people find high-intensity exercise unpleasant and are more likely to stick to a moderate workout plan that makes them feel better in the moment.

From a behavioral perspective, this fact has led experts like Dr. Michelle Segar to advocate for regular moderate exercise rather than HIIT for most people—especially those who are working on weight loss. It’s more feasible to sustain a moderate exercise plan long-term.  

As Dr. Segar notes, “Science shows that what works most consistently is what feels good now—not something that feels like hard work or punishment, even if you’re doing it for a great reason.”

Optimizing wellness is ultimately a matter of understanding which types of lifestyle changes are right for you—based on your unique body, preferences, and aspirations. 

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