In a recent episode, we reviewed a recent study that examined the benefits of High Intensity Interval Training on brain health and cognitive function. In this episode, we field a question from Jennifer, who wonders how necessary it is to follow the protocol outlined in the study to reap the benefits. Some related questions we answer in the episode include:
What's the minimum effective dose of high-intensity training for cognitive benefits?
What's the true relationship between exercise duration and intensity? Is there an optimal balance for brain health?
Could lactate - traditionally viewed as a metabolic waste product - be a key mediator of exercise's cognitive benefits?
How much do laboratory exercise protocols need to be modified for real-world application while preserving their core benefits?
What can the stress adaptation patterns of elite athletes tell us about preventing cognitive decline in aging populations?
Why does the 150-minute weekly exercise threshold appear so consistently in cognitive research?
At what point do additional hours of exercise stop providing proportional cognitive benefits?
How can building physical resilience serve as a model for building cognitive resilience? What are the shared mechanisms?
To listen to the episode, click below. To read the edited transcript, then keep on scrolling…
EDITED TRANSCRIPT
Josh: Before we get to our question, I know you were recently traveling to Austin for some Formula One performance consulting. Could you tell us a little bit about your trip there?
Cognitive Enhancement in Formula One Requires Multiple Performance Optimization Strategies
Tommy: Yeah, we’ve talked about this a little bit before, but I’ve been working in Formula One for seven years. Facebook recently reminded me of the first time I posted photos from Austin. I normally go to the U.S. Grand Prix in Austin every year and spend the week meeting with drivers, coaches, managers, various team principals, people involved in the teams, mechanics, and engineers.
That work is generally focused on human cognitive and physical performance, and I try to assist wherever I can. Different drivers and individuals have different needs. Sometimes it’s talking about cognitive stuff, sometimes physical, and sometimes it’s nutrition and sleep.
This year’s theme was cognitive enhancement in a number of different ways—how you can measure and improve cognitive function, particularly under significant physical and cognitive stress, which is especially prevalent towards the end of races.
When we previously talked about my F1 work, we discussed an article I was interviewed for in The Times (UK) about whether there could ever be a Formula One world champion in their forties. This time, I was interviewed for TV, which will air in all Scandinavian countries, the Netherlands, and maybe a few others. Specifically, we discussed cognitive enhancement, which was kind of fun.
We also talked about ideas for maintaining performance under stress. I thought about it in terms of three different approaches.
One approach is to improve your tolerance to stress. For example, if it’s a physical stressor, you could increase your physical capacity by becoming fitter. If it’s a cognitive or psychological stressor, mindfulness meditation is known to improve stress tolerance.
Another approach is to improve the function itself. We know that if you have a higher total capacity in a given cognitive function, then even when you’re stressed and lose some of that function, you’ll still be able to maintain a higher level of performance.
A third approach is to train under stress. You create either a physical stress, cognitive stress, or cognitive fatigue, and then challenge these functions. This framework has proven useful for some people.
We also touched on preventing physical and cognitive decline as people age. The interviewer didn’t know it, but she set herself up when she mentioned she was in her fifties and felt like there was no point in going to the gym because she wasn’t as fit or strong as she had been in the past. That allowed me to bring up an idea we talk about often: the first thing you need to realize is that if you continue to engage and challenge the body or the brain, it can adapt and improve.
But the first step is believing that it can and will. The second step is engaging in the activities that make that happen. It was nice to tie these concepts together during the conversation.
Josh: Yeah, that’s great. I like that framework. I think people listening might assume that the strategies you use with a Formula One driver or other high-level athletes wouldn’t apply to them. But I think these scenarios are excellent for helping us understand how to build resilience.
These athletes are trying to maximize their physical and cognitive capacity, and that’s essentially what we’re trying to do to maintain cognitive performance, prevent cognitive decline, and avoid Alzheimer’s—build as much resilience as possible.
These drivers serve as great test populations to learn about these principles. On the opposite end of the spectrum, in the medical sphere, you often work with people who have lost resilience. There’s a different set of lessons to be learned there, but both ends of the spectrum are valuable.
High-Intensity Exercise Benefits May Not Require Strict Adherence to Research Protocols
Josh: All right, enough of that detour. There’s a whole episode in there, though—probably one we’ll come back to, or maybe even more than one.
Today’s question—and by the way, you can find the episode we did where Tommy talked about whether a driver over 40 could win a Formula One championship—that’s in a prior episode available in our feed.
Today’s question is actually a follow-up to a topic we covered just a few weeks ago. It comes from Jennifer in Fort Collins, Colorado, who asked:
"Does your heart rate have to stay in the high zone for the entire four minutes in order for it to be beneficial, or is it about touching the zone? I find it very challenging to stay in the high zone for that long. Is it about working your way up to staying in the zone for the full four minutes?"
Jennifer is referring to the episode about a study on high-intensity interval training, where one group followed a protocol that involved maintaining their heart rate in the high-intensity zone for four-minute intervals, followed by rest. They completed four of these intervals, and that particular group showed impressive benefits, including improvements in cognitive function, protection against cognitive decline, and notable benefits observed in their brain imaging.
Physical Activity Benefits Follow a Linear Relationship with Time and Intensity
Josh: So Jennifer’s question is whether you have to adhere to that exact same protocol—which she finds challenging—and it definitely is challenging. Or can we extrapolate and think that we might get some of the same benefits by doing something similar, even if it’s a modification of that protocol?
So, Tommy, what do you say to that?
Tommy: Yeah, this is a great question and an important one to think about, especially when people listen to individuals like you and me on a podcast, giving advice about ways to improve physical health, cognitive performance, and related areas.
Some of the issues stem from the kinds of studies we have available to discuss and how we might extrapolate those findings to other individuals. I’ve encountered several people who’ve heard advice like, “You need to do X amount of X to see *X benefit.” The immediate response for many—especially if the advice involves several hours of a given physical activity—is, “I just don’t have time,” or “I can’t do that. Either I don’t have the physical capacity or the time to do it.”
If they believe that’s the only way to see a benefit and they can’t meet those requirements, they may decide not to do anything at all. It’s a perfectly reasonable response, right?
For example, if Jennifer thinks—understandably, based on the study—that she needs to spend four minutes within 85–95% of her maximum heart rate three times a week for several months, and she can’t maintain that, she might ask herself, “Why bother doing it?” It’s hard and not fun, so what’s the point?
But we know that any physical activity you start doing, as long as it increases time, intensity, or capacity compared to what you were already doing, tends to translate into improvements in both physical and cognitive health.
So, the quick answer to Jennifer’s question is: No, you don’t need to spend all four minutes at that intensity to see benefits. Across a wide range of physical activities, there’s generally a dose-response relationship, particularly for non-professional or non-competitive athletes engaging in a few hours of activity per week.
When you look at large meta-analyses and meta-regressions of the amount of physical activity people do, the data suggests a linear relationship in terms of cognitive function benefits. Statistically significant benefits start to appear at around 150 minutes of activity per week, and those benefits continue to increase as you do more—up to a limit of probably five or six hours per week.
After that point, you start to see diminishing returns. You can still gain additional benefits, but the improvement per additional hour of exercise becomes smaller.
Exercise Volume Can Be Achieved Through Various Combinations of Duration and Intensity
Tommy: I think a useful framework is that most benefits seem to come from the total product of intensity multiplied by time—what we might call "volume." This concept is relevant for both aerobic and resistance training.
If something is less intense, you probably need to spend more time doing it. If something is more intense, you may need to spend less time. This brings up one of my potential criticisms of the study we discussed, which is that they didn’t match volume.
They had lower-intensity groups, but the question is: if you did lower-intensity exercise for a longer period, would you see benefits similar to those of the high-intensity group? I think we would have seen more benefits in those groups if they had matched volume, even if the benefits weren’t as significant as in the high-intensity group.
The more you're able to do—and the more you improve—the greater the benefits. For example, there was a previous study that looked at hippocampal volume in older adults. They were put on a walking program that involved 40 minutes of walking three times a week for a year.
The first part of that program focused on building them up to the desired level of intensity. If you were to jump straight into something like four minutes at 90% max heart rate, repeated four times, it would be extremely hard. These protocols in research studies are often difficult to follow in real-world settings, as they typically involve a scientist with a clipboard watching you. People are more likely to comply when there’s someone monitoring them.
Maximum Intensity Protocols Generate Beneficial Lactate but May Be Impractical for Most People
For the average person, starting at that intensity is less realistic. Building up gradually is a great approach—you'll slowly improve your capacity, and it gives you a reasonable target to aim for. Some protocols, however, are nearly impossible to do at home because they’re so demanding.
Take, for instance, the Tabata workout: eight sets of 20 seconds of effort with 10 seconds of rest, performed on an exercise bike. The wattage they expected participants to produce was incredibly high—beyond what most people could replicate at home. The benefit they observed in VO₂ max was impressive, but the protocol itself is almost prohibitively difficult.
That said, you can still see benefits if you’re working hard but can’t quite sustain four minutes at high intensity. If you need slightly longer rest periods and build up gradually, that’s perfectly fine. Similarly, you can also see benefits from lower-intensity activity done for longer periods because of the "volume effect."
One key difference between high-intensity and lower-intensity exercise is the physiology involved—particularly lactate production. If you follow something like the Norwegian 4x4 protocol, you’ll generate a lot of lactate, which is beneficial. Lactate has fascinating effects on both the brain and the body.
Interestingly, you don’t need to follow a 4x4 protocol at 90% max heart rate to generate lactate. Shorter, harder sprints can also produce it. For example, you could do 30 seconds of all-out effort, rest for a few minutes, and repeat. Studies show that such protocols generate significant amounts of lactate, which is associated with acute improvements in cognitive function.
This illustrates that there are many ways to approach the goal. Just because a study used one specific protocol doesn’t mean you have to follow it exactly to see similar benefits. For example, you might spend more time at lower intensities, jogging on a treadmill, and occasionally include very short, hard sprints. You’re still challenging the same biochemical and physiological systems, stimulating similar adaptations, and generating metabolites like lactate.
So, if you’re trying the Norwegian protocol, great! It’s hard work, but if you can work up to it, enjoy it, and fit it into your routine, that’s excellent. However, the key is spending time across a range of intensities to drive those adaptations, without worrying too much about sticking rigidly to the exact protocol.
Josh: Great answer. This highlights the challenge we all face when translating scientific studies into real-world, actionable advice. If you’re being a strict scientist, you can only say that a specific protocol caused a specific effect. But the real world is messy—you can’t test every scenario people might encounter, so you often have to make educated guesses about how to apply the findings.
This is true in medicine as well, which is why people often call it an art rather than a science. You’re almost never making decisions based on a definitive study because individual patients often differ in significant ways from the study population.
Studies give us general direction and ideas about what matters, but we still have to figure out how to best apply them. For this topic, as you said, the benefits of exercise volume—and potentially additional benefits from high-intensity metabolites like lactate—suggest that almost any reasonable protocol is likely to provide benefits.
While we can’t say with 100% certainty that a modified protocol will deliver the exact same results, we can say it’s highly likely. Even if you do less than what the protocol specifies, spending some time in that range will confer benefits. Starting where you are and building from there is far better than doing nothing.
Whatever you can do is a good starting point, and you can ramp up from there.
That was a great follow-up question. I thought we might get something like that after putting this topic out there, and I was glad to see it. If anyone has more questions about this or other topics related to brain health and fitness, just send them our way at brainjo.academy/questions.
Key Points from the Episode:
High-intensity exercise protocols shown in research studies don't need to be followed exactly to gain benefits. There's typically a dose-response relationship between exercise and cognitive benefits.
Physical activity benefits appear to come from the total "volume" of exercise, which is a product of intensity and time. If intensity is lower, you may need to exercise longer to get similar benefits.
Regular physical activity shows a linear benefit for cognitive function, with statistically significant benefits appearing around 150+ minutes per week. Benefits continue increasing up to about 5-6 hours weekly, after which there are diminishing returns.
High-intensity exercise produces specific metabolites like lactate that may be beneficial for brain health. These can be generated through various protocols, not just the specific 4-minute intervals discussed in the study.
When studies show benefits from very demanding protocols (like Tabata intervals), it's important to recognize these were done under controlled conditions with researchers present. Home implementation may need modification.
Alternative approaches to high-intensity training can include shorter sprints (like 30 seconds) followed by rest periods, which still produce beneficial metabolites like lactate.
Starting where you are and progressively building up intensity is more important than trying to immediately match research protocols. Some activity is always better than none.
The principles of building resilience and performance capacity seen in Formula One drivers can be applied to cognitive health - the goal is to build physical and cognitive reserve to maintain function under stress and prevent decline.
Exercise adaptation requires both belief that improvement is possible and engagement in challenging activities, regardless of age or current fitness level.
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