Tag Archive for: high-intensity interval training

HIIT Can Be Fun

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After you’ve checked with your doctor to find out any limitations as it relates to exercise intensity, then it’s time to get after it—not to lose a whole bunch of weight, not to win the next 5k, not every day—but to make your heart and body stronger and fitter.

Modes of Exercise for HIIT

The approach remains the same no matter what mode of exercise we choose: increase speed or resistance for a specific amount of time ranging from 15 to 90 seconds, and then actively rest for 3 or 4 minutes, repeating the cycle 4–6 times. Here are some ideas.

Friends
There’s probably no addition to your HIIT exercise routine that’s more fun than getting several people together and doing it as a group. Someone can be the designated timer to keep track of the intervals and rest times. Walking is the logical choice, but group exercise can be done in a pool, indoor bikes, calisthenics, or some other group activity or class. It may bring about a little competition, which can be motivating. It especially helps on those days when you really don’t want to work harder. Obligation to someone else can keep you on track.

Trampoline Rebounder
These are available at moderate cost at big box stores or online. They come with a variety of aerobic workouts. The simplest thing is to increase your foot speed as you bounce. I’d recommend one with a bar to hang onto while working out. You can also bounce higher, but if you do that, you have to remember your ceiling height. Also, hit the rebounder straight down dead center or you could bounce yourself off the equipment onto the floor or whatever else is in the way.

Pool
If you have access to a pool, you can always use pool walking as your mode of exercise. There are a number of ways to increase the intensity: you could walk faster, move from the shallow end to a deeper section, or increase the resistance by using your arms to push the water to propel you faster as you walk. If you want to have some more fun, skip across the pool.

One more thing: you could hang onto the side of the pool and practice your freestyle leg stroke. Same idea, go faster for a specified time and then chill by walking for the rest interval. Be cautious if you have a large hot tub; that adds another stressor: heat. One stress at a time, done in the correct fashion, is a better idea.

Walkers and Wheelchairs

If you have difficulty moving without assistance, you can still do some interval training. Using your walker for balance, depending on how much room you have in your home, your driveway, or in a local park, you can simply walk faster for 15 seconds to start. If you have a wheelchair, the same approach applies. I know from observation that some people like to use their wheelchairs to scoot along using their legs. As long as you’re always under control, that would be acceptable—just not down a hill!

They also have rollers that wheelchairs sit on for people who want to exercise indoors. That’s another way to train your arms as well.

The Bottom Line

If you really want to try HIIT, you might have to be creative. Just remember that the basic time of interval is 30 to 90 seconds. The rest interval is 3 to 4 minutes, and don’t do it more than 2 or 3 times per week with a rest day between each session.

If you’ve found other ways to do HIIT, let me know and I’ll include them in a follow-up Memo in the future.

What are you prepared to do today?

        Dr. Chet

HIIT Fun?

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I have a confession: I married a woman who doesn’t like to exercise. I know—it’s not what you’d expect from guy committed to a career in making people fitter and healthier, but she was and is irresistible. Since we met, I’ve been on the lookout for fun ways to exercise, especially since HIIT (high-intensity interval training) has become popular. One could argue that HIIT shouldn’t be fun, but maybe it could be more interesting?

We’ve worked out that distraction helps, so Paula usually is reading or watching TV while biking or doing other exercises. How can we work HIIT into that formula?

  • The simplest way is just to see whether she can increase the RPMs for 30 seconds by pedaling as fast as possible; maybe she only makes it 15 seconds.
  • Then pedal at an easy pace for three and a half minutes; repeat four to six times.
  • The goal is to last for 30 seconds during all the intervals.

Another approach would be to keep the same pace, but bump up the resistance for 30 seconds, followed by the same approach of easy cycling at reduced resistance.

The same logic could be used for walking, elliptical trainers, and stair climbers. What about other forms of exercise or exercise equipment? What do you do for exercise that’s fun?

One important caution: you should always check with your physician or cardiologist before you do HIIT just to be sure your heart is healthy enough to try it. That doesn’t mean you have to make an appointment; if you see your doctor regularly, you can probably call the office or send a message through the online portal and get an answer. What are you prepared to do today?

        Dr. Chet

HIIT for Everyone

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Before I get into this study on high-intensity interval training or HIIT, I want to be sure you understand that unless you’re under 30 and very fit, you need guidance and advice from your physician before you attempt a HIIT program, especially if you have cardiovascular disease, diabetes, or are on medications for these conditions. I’ve been doing interval training for over 40 years, but the intervals I do today are within the limitations of the body I have today, not the limitations I had in my 30s. With that in mind, let’s proceed.

HIIT After a Heart Attack

Researchers in China recruited over 200 subjects with a specific cardiac profile: the subjects all had myocardial infarctions (commonly known as heart attacks) that were resolved by a percutaneous coronary intervention (treatment used to open blockages in the coronary arteries) such as a stent. This group requires special attention in that they are at serious risk for another event within the next year.

As part of a 12-week cardiac rehabilitation program, researchers divided the subjects into three groups:

  • A moderate-intensity continuous training group (MICT)
  • A HIIT group
  • A group that did a combined MICT and HIIT program.

The advantage is that every exercise session was under the supervision of professionals trained in cardiac rehab who knew how to respond if something went wrong.

All groups improved their fitness levels, but the combined training program of MCIT and HIIT provided better results than either of the approaches done separately. From a fitness perspective, those in the combined group increased the amount of oxygen they could use by more than the other groups and pumped significantly more blood per beat. Most important, there were no differences in major adverse events.

The Bottom Line

I specifically chose this study because these subjects were most at risk. With a doctor’s approval and under the right supervision, they were able to do HIIT safely. For most of the rest of us, those are obstacles and advantages we don’t face.

We should be prudent and check with our physicians first. We should also get some guidance on how to begin a HIIT program; if possible, get an appointment with a physical therapist to plan your workout program, because they’re trained to understand and work around everyone’s physical limitations and avoid injury. The workout plan must be within our fitness level right now, not 20 years ago. It can be as simple as walking faster for 30 seconds at a time during the walk you already take, but the gains can be significant toward improving our healthspan.

What are you prepared to do today?

        Dr. Chet

Reference: Aging and Disease. 2025. http://dx.doi.org/10.14336/AD.2024.0642

HIIT at Any Age

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Last week, I talked about taking inventory of where your body is now, primarily in your ability to move your limbs. The reason was that regardless of age as well as physical limitations, you can improve your fitness level; better yet, you can potentially accelerate the process using high-intensity interval training, also known as HIIT. It may take ingenuity if your physical limitations are significant, and you should be guided by your healthcare professional to get started. Let’s take a look at a recent study.

Researchers in Australia recruited a group of apparently healthy subjects 65 to 85 years old to participate in a HIIT study focusing on changes in body composition. With a mean age of 72, the subjects were randomly assigned to one of three groups: a control group who focused on stretching and balance exercises, a moderate intensity group who walked on a treadmill for 45 minutes at a specified target heart rate range, and a group who walked 40 minutes including a 10-minute warm-up, four 4-minute intervals at a specified heart rate range interspersed with 3 minutes of active recovery, and a cool down.

There were significant changes in body composition between the control group and both the HIIT and the moderate-intensity group with a specific change in the visceral fat. Were they fitter? The HIIT group had a greater use of oxygen than the moderate group, but it was not statistically significant. The important point was that even people over 80 could perform HIIT based on their specific fitness level. What about people who recently had heart attacks? I’ll tell you about another study on Saturday.

Tomorrow night is the Insider Conference Call, and the topic of the night is reducing the risk of dementia by changing the lifestyle factors that are under our control. You can participate if you become an Insider by 8 p.m. Eastern Time tomorrow night.

What are you prepared to do today?

        Dr. Chet

Reference: https://doi.org/10.1016/j.maturitas.2025.108763

HIIT: Specific Fat Loss

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What were the results of HIIT training? The researchers found that there were reductions in overall weight as well as subcutaneous and visceral fat. What’s the difference? The fat just under the skin is subcutaneous fat; visceral fat is behind the abdominal muscles and around the internal organs and is more related to the development of cardiovascular disease and type 2 diabetes. There were no differences in the outcome variables with two exceptions:

  • Those who were in the running group lost a greater percentage of subcutaneous fat than the cycling group at 16.1% vs. 8.3%. The other difference was that positive changes in the microbiome were correlated with the loss of subcutaneous fat. Before you get too excited, the actual loss of subcutaneous fat was close to two pounds in the running group and about one pound in the cycling group. Still, ask your butcher for one pound of fat and see what it looks like. It’s a lot and probably worth the effort doing the HIIT program.
  • The other benefit was an improvement in some positive bacteria in the microbiome. It wasn’t associated with running or cycling; it was correlated with the loss of subcutaneous fat. It seems that visceral fat would show more benefit, but that wasn’t the case. Maybe someday we’ll find out why.

The obvious problem with doing a running HIIT program is that you have to be able to run—at least for 45 seconds. While my running is progressing slowly, I do intervals only while walking or riding the exercise bike. But running for 45 seconds? I can handle that.

Finally, while I was puzzled about the microbiome benefits, I also questioned why there was a difference between cycling and running when it came to the loss of subcutaneous fat. The researchers didn’t have a reason to explain it. I’ll give you my informed opinion: running integrates more of the core during the actual interval than cycling does. My hunch could be tested with sensors that detect the electrical activity of muscles, but that’s fine tuning that might not be necessary. As a scientist, I always want to know why, but that’s not important; it’s just important that it is.

We’ve seen that 30 minutes of moderate walking can prevent the loss of muscle and a HIIT running program can help lose subcutaneous fat in those who are overweight. How about getting fitter faster? Is that possible? Find out next week when we look at SIT training—and sitting does have something to do with it!

What are you prepared to do today?

        Dr. Chet

Reference: Med Sci Sports Exerc 2024 May 1;56(5):839-850.



HIIT and Fat Loss

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One of the “facts” exercise professionals will tell you is that there is no such thing as spot reduction; by that I mean you cannot target a specific area of your body, let’s say your abdominal area, and lose fat by doing a targeted exercise such as sit-ups or leg lifts. You can make the muscles underneath the skin stronger for sure, but there doesn’t seem to be any evidence that you can reduce the amount of fat in that area.

With 35 years of experience in the field, I would say that requires a qualified answer—it needs to be qualified with the word yet. There hasn’t been a study that proves that you can reduce fat in a specific area yet. Is it theoretically possible? Yes, I think it is. The problem is this: who would do the high quantity of exercise focused on one area long enough per workout session to do themselves any good? It may be that we’ve approached it all wrong by focusing on resistance exercise. Let’s take a look at another study that compared high-intensity interval training (HIIT) on a cycle ergometer versus a treadmill.

Researchers began with two questions. Is there any difference in the fat mass in specific areas of the body after training using a cycle ergometer (an exercise bike that measures the energy output of the cyclist) or a treadmill? In addition to that, is there any change in beneficial microbes in the microbiome after training?

Let’s take a look at what they did. Researchers recruited 16 men with a mean age of 54 and initial BMI of 29.9. After assessing initial fitness level, body fat, and body-fat distribution using the DEXA scan, and taking an initial stool sample for analysis of the microbiome, the subjects were randomly assigned to the bike or the treadmill. To make sure that there were no significant changes in diet, the subjects were required to maintain their typical diet and do seven-day diet records periodically during the study.

Think of this as intervals for the everyday exerciser. The HIIT bike program required them to do ten intervals for 45 seconds each at 80–85% of the maximal heart rate (MHR), and then a 90-second active recovery, or a HIIT running program which were nine intervals for 45 seconds at 80–85% of MHR and again with 90 seconds of recovery between intervals. They were to do this exercise under supervision three times per week for 12 weeks. The goal was to have all exercisers use the same number of calories during the workouts, whether cycling or running. The subjects were then retested to examine the differences if there were any. What did they find? I’ll tell you on Saturday.

What are you prepared to do today?

        Dr. Chet

Med Sci Sports Exerc 2024 May 1;56(5):839-850.

Isometric Exercise Lowers Blood Pressure

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This summer has seen several studies about exercise, so we’ll just continue with the flow from last week. The first study caught me by surprise: isometric exercise lowers blood pressure. When you do isometric exercises, you increase tension in a muscle without moving the joint, such as holding your leg still while you clench your thigh muscles; if you’ve got a wall, a chair, and a floor, you’ve got all you need. We don’t think of isometric, also called static exercise, as being effective in changing the dynamic flow of blood in the cardiovascular system. Let’s take a look at the study.

Researchers conducted a literature search of all published studies that examined the impact of any type of exercise on systolic blood pressure (SBP) and diastolic blood pressure (DBP.) They conducted a pairwise and network meta-analysis to see which exercise helped BP the most. The most important finding was that every form of exercise significantly reduced SBP and DBP when performed for two weeks and longer: aerobic exercise, dynamic resistance (weight) training, combined training, high-intensity interval training (HIIT), and isometric exercise.

When they compared the efficacy of the different forms, isometric exercise lowered SBP the most, followed, in order, by combined training, weight training, aerobic training, and HIIT.

To me, isometrics are somewhat easy to perform because it removes obstacles such as orthopedic issues or equipment. But why would it reduce blood pressure more than other modes of exercise? We’ll check that out on Saturday.

What are you prepared to do today?

        Dr. Chet

Reference: British J Sp Med Online July 2023. doi: 10.1136/bjsports-2022-106503

Yes, Intensity Matters

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Can you get away with less time exercising and still protect your cardiovascular system? We know from Tuesday’s Memo that more time spent on physical activity will provide more protection. Can we save some time? Or perhaps better stated, can we do something in short bursts of time that can increase the moderate to intense exercise we get?

Before I answer that, remember that physical activity means everything you do that requires movement: walking to the kitchen, gardening, cooking, and the activity involved in your job. Exercise is also a part of your overall physical activity. In the study, all activity was registered by the accelerometer the subjects wore.

Intensity Matters to Reduce CVD Risk

With that in mind, the answer is yes: exercise intensity matters when it comes to protecting yourself from cardiovascular disease (CVD). I must admit that the charts and graphs published in the study were challenging to understand. They used a percentage of calories used per day as the way to measure outcomes. For the exercise intensity analysis, they considered the percentage of calories at moderate to high intensity. They found that as the percentage of activity at moderate to high intensity increased, the rate of CVD events decreased.

Here’s an example. Let’s take a 180-pound guy who uses a low amount of energy in physical activity such as five calories per kg body weight. The total calories he uses daily would be about 400 calories, including any exercise he did. But let’s say the percentage of moderate to severe intensity exercise rises from 10% of total exercise to 20% of that total. His risk of a CVD event would be reduced from 2% lower to 20% lower. He hasn’t invested any more time, yet he gets a jump in benefit just from increased intensity.

What Does That Mean for You?

Does this mean that everyone should be doing high-intensity interval training? Not in the classic sense; what’s high intensity for you may be impossible for your elderly neighbor and a breeze for your kid’s soccer coach. You don’t have to do special workouts such as high-intensity interval training where you’re going to bust a gut for 60 seconds and then take it easy for five minutes. That is intense, but it takes less time overall and you could do that if you want; there’s more info at drchet.com if you decide to try it.

In physical activity, everything counts from housework to walking the dog to breaking into a run to catch a bus. Those would show up as mild or moderate intensity, or high-intensity exercise for the running. It doesn’t mean that all the exercise you do has to be high intensity, but investing time in higher intensity exercise may provide you with additional benefits. Working a little harder is going to reduce your risk of cardiovascular disease and, while not assessed in this study, your risk of type 2 diabetes, hypertension, and cancer would be reduced as well.

Of course, the question is what’s high intensity for you. The chart above is geared toward weightlifting, but it will give you some ways to think about how hard you’re exercising, no matter what you’re doing. If you’re running for the bus, could you run one more block? If you’re cleaning house, do you have enough juice left to go for a bike ride?

The Bottom Line

You must be fit enough and ambulatory enough to actually do moderate to high-intensity exercise. But you know something? I know of one physical therapist who encourages patients to do jumping jacks while sitting in a wheelchair. Of course they can’t do the actual jumping part of it but for 60 seconds, their arms are going up and down, up and down, up and down at a very high rate, and maybe their legs are moving, too—and that’s high intensity for them. For others of you, it may be doing a two-minute walk up a very steep hill. The intensity of the exercise stresses the heart in ways that a nice easy walk does not. And for that, you get additional benefits, no matter where you’re starting.

So check with your doctor to find out your limitations as it relates to exercise intensity, and then get after it. Not to lose a whole bunch of weight, not to win the next 5K, not every day—but often enough to make your heart stronger and fitter.

What are you prepared to do today?

        Dr. Chet

P.S. Happy Canada Day to our neighbors to the north! We’re taking next week off to enjoy the July 4th holiday and hope you do as well (even if you’re not in the U.S.) We’ll be back with new Memos the week of the 10th. Meanwhile, it’s a great time to try increasing your exercise intensity.

Reference: Eur Heart J (2022) https://doi.org/10.1093/eurheartj/ehac613

Research Update: Exercise in Short Bursts

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High-intensity interval training (HIIT) has become very popular due to the possibility of gaining fitness in a short amount of time, but when done correctly workouts still take 20 to 40 minutes. A group of researchers examined the United Kingdom Biobank data to see if a sub-group of subjects who wore accelerometers might benefit from short bouts (one or two minutes) of intense physical activity independent of a regular exercise program. Researchers termed the exercise bouts “vigorous intermittent lifestyle physical activity” (VILPA) and they were not part of an intentional exercise program. They just happened with people who were going about their daily routines.

They tracked the subjects for almost seven years to see if there was any reduction in their death rate. The data showed that as few as two or three short bouts or approximately three to four minutes of VILPA per day were associated with substantially lower all-cause, cardiovascular, and cancer mortality risk. More VILPA sessions per day resulted in a greater reduction, but the greatest reduction occurred in three to four minutes per day. The reduction was a 38% to 40% reduction in all-cause and cancer mortality risk and a 48% to 49% reduction in CVD mortality risk. One more thing: the average age of the over 25,000 subjects was 61.8 years.

The facts that struck me was whether a person exercised or not, or ate a high amount of vegetables and fruit or not, they had a reduction in mortality. To be safe, you and your doctor should discuss whether you can try a minute or two of intense physical activity a few times per day. Maybe it will happen organically as part of your day, like sprinting up a flight of stairs to get to a meeting, or running to catch a bus, or chasing a toddler. Or maybe that exercise bike you’ve been using as a clothing rack can be put to use as it was intended. Find your spots and do what you can. You may have years to gain.

What are you prepared to do today?

        Dr. Chet

Reference: Nature Medicine. 2022; 28 (12):2521–2529

Getting to the Exercise Sweet Spot

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Do you realize that five minutes is only 0.3% of a day? Can you really say you can’t at least begin to exercise? “Five minutes isn’t the issue—it’s the 45 minutes a day!” Yes, although 45 minutes is only a whopping 3% of your day, I know it can be hard to work it into your schedule. How about if you could cut the time spent in aerobic exercise in half, from 45 minutes to just over 20 minutes? Interested? Just remember there will be a price to pay.

High-Intensity Interval Training (HIIT)

HIIT as is currently practiced began about 2008 and has been the focus of a lot of research since 2017. The current version alternates very intense intervals from 30 seconds to four minutes with rest periods of at least four minutes; most common is one minute of high intensity and four minutes of rest. Understand that the intensity is an all-out effort, something most sedentary people cannot and should not do—yet.

Remember the price? It’s getting in good enough aerobic condition to be able to handle the increased intensity. When you’re fit enough, four 20-minute HIIT sessions per week can provide you with the exercise sweet spot. Just remember this is only aerobic fitness. Lifting weights, yoga, stretching—that’s all separate.

Intensity

Here’s the real reason I’m getting a knee replacement done: I can’t work hard enough on the exercise bike to reach my target heart rate. Thigh pain above my bad knee hinders me from getting there. I’ve been on the cycle for at least six months, and I’m tired of not getting the workouts I’m used to getting through running.

Although running is not in my future after the knee is replaced, walking will be as well as using the elliptical again. I can replace running with walking uphill in order to achieve the fitness effect I want. It’s not as good but it will give me some variety. I can handle the pain of high-intensity training once I no longer have this level of knee pain. And that’s why I’m doing the knee replacement now.

The Bottom Line

The exercise sweet spot isn’t as precise as I would like, but it does follow a logical progression. Some exercise is better than none; if you’re not exercising at all, start with five minutes. Aspire to at least 30 minutes per day at least four days a week, then work up to 45 minutes.

When you can handle that and your physician says it’s okay, then you can start HIIT training to increase your fitness in less time and still have time to get stronger and more flexible. Even at 45 minutes a day, that’s just 3% of your day committed to exercise. That commitment of time will reduce your risk of just about every degenerative disease, which will help you really live more days of your life and not just struggle through them. Isn’t that worth the investment?

What are you prepared to do today?

        Dr. Chet