How Much Physical Activity Is Required to Boost Cognition, For How Long?

I’m well aware that physical activity measurably increases cognition and focus. But, what I’m less clear on is how much activity is required to get this effect and for how long.

So, yes, I’m looking for the minimum effective dose. But, it would also be helpful to know at what point the law of diminishing returns kicks in and further exercise — for the purpose of temporarily increasing cognition — becomes wasted effort.

Any takers?


There might be something useful in the link here: "30 Minutes of Aerobic Exercise Supercharges Semantic Memory"

There’s also a page that lists posts about exercise and memory that might have links to studies.


Depends a bit on the school of thought, because none of those studies are conclusive. If you assume that a dominant influencer is the central nervous system and oxygenation, then do 30 seconds of squats, deadlifts, and push ups. Add 30 seconds rest for a total of 2 minutes. Repeat once or twice more for either 4 or 6 minutes. That way you got a bunch of compound movements hitting pretty much every muscle.

Not gonna call it a placebo effect, but you wanna test out yourself what (you think) works for you. You can do the above aerobic or anaerobic. The former will have a better oxygenation effect whereas the latter will have more of an impact on your CNS.

If you wanna go the completely aerobic route by going running, have a look at studies comparing running outdoors to running on a treadmill. It seems the effort of navigating outdoors have a bigger impact than just the physical aspect when compared to running on a treadmill.

Either way, jogging won’t have much of an impact after 4-6 minutes, so play with the routine outlined above… and figure out if it’s CNS, ATP, Oxygen, etc. that influences you personally.

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I’ve recommend the book Spark by John Raty elsewhere on this forum and I’ll do so again here. It’s a fantastic book length treatment of this very complex topic.

In general, a “minimal effective dose” would vary greatly according to each person’s mental, physical, and emotional circumstances–it’s all connected in surprising ways. More generically, the daily recommendation for general physical and mental health is weekly aerobic activity minutes burning calories equal to eight times your body weight. So, based on typical body weight/heart rate/calorie metrics, if you weight 150 lbs, that is six 200 calorie 30 minute sessions.

This is the minimum recommended. This is less than half of the amount of energy usage that our genes are encoded for. Paleolitic ancestors would need to walk 5-10 miles each day just to gather enough food to eat.

Keep in mind also that mental health broadly and memory specifically is influenced by factors such as nutrition and social relationships as well. If you get the “minimum effective dose” of exercise and eat poorly and are unhappy, lonely, and depressed, you’re still cognitively well below peak performance.

On the exercise only aspect, the best, research, based on when that book was written in 2008, however, would be to do some form of aerobic activity six days a week, for forty-five minutes to an hour. Four of those days should be on the longer side, at moderate intensity, and two on the shorter side, at high intensity.

If you google around for Brain-Derived Neurotrophic Factor or BDNF, you’ll find the research on how BDNF is like “miracle-gro” for the brain, if you’re interested in specific neurological benefits.

Based on current research, there doesn’t seem to be a clear upper limit of where exercise becomes wasted effort. From a practical point of view, it’s more about time management and less about optimal exercise. There are only 1440 minutes in each day, and it’s up to you to decide how you’d like to spend them!



Just saying, but you do know that the link you’ve posted there goes to an article that clearly states:

The studies Ratey covers are mostly small in scale or were conducted with animals, leading one to wonder whether he is always justified in making generalizations from such data.

…and Ethiopia does have some of the best long distance runner in the world; but how come that doesn’t translate as far as academia?

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Yes, I am aware. Good reviews do point out the shortcomings of books as well as their benefits. I’ve also read the entire book, and I encourage you to do so as well.

Unfortunately, the best science in many areas are limited to correlative studies based on animals and not gold-standard double blind randomized control trials with human subjects. The field has certainly advanced since the book was written and changes rapidly as studies build on early work.

I’ll just leave your comment about Ethiopia alone because it is a hugely problematic can of worms. Correlative stereotypes like that are statistically deficient in the same way as you point out in the review of Ratey’s book.

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A 10 year old book with references to even older studies? No thanks! These days you could google “CRISPR Bdnf” and find stuff like this:

But let’s not get carries away… how about this one first as a case against aerobic exercise:

Thirty HIIT sessions significantly increased BDNF levels (protein) in the brain compared with continuous training protocol and a control group (Afzalpour et al., 2015). The authors discussed that HIIT increased hydrogen peroxide (H2O2) and Tumor Necrosis Factor Alpha (TNF-α) concentration in brain; and these molecules could activate the BDNF synthesis (Wang et al., 2006; Bałkowiec-Iskra et al., 2011) or CREB (Pugazhenthi et al., 2003), a transcription factor positively regulating BDNF synthesis.

By those standards and considering the obesity epidemic in the states, half the population would be a good couple of σ left of μ as far as IQ… unless walking from the couch to the fridge is now considered “exercise”!?!

I don’t see the issue here… famous runners like Haile Gebrselassie have pointed out on numerous occasions how they walked to school 5 miles in the morning and 5 miles back in the afternoon… that’s not a “correlative stereotypes”.

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My experience, and I think this is the recommendation, is that about 20 mins a day or 120 mins a week of aerobic exercise will keep the brain sharp. If you are in average shape, that shouldn’t feel like much work. I’d start with that and adjust to suit.

I hike regularly but I have periods where I train fairly intensively and when I do there’s a definite cognitive hit the following day or days while my body recovers. So there’s a balance which probably depends a lot on the individual. I’m 69 and recovery is noticeably slower than when I was 40.

While I’m exercising, I like to try and do arithmetic problems in my head as a test. When I can no longer complete a 2x2 multiplication I know I’m working hard enough.


So only off by 100 to 200 percent… personal opinion and 10 year old book. You guys are aware though that @8bit was not asking for the healthiest or most recommended but rather the minimum effective dose.

2x2… what kind of exercise to you do?

That GIF is funny…

What kind of exercise to you do?

Right now… I go to the gym and see a personal trainer 1× weekly.

In addition to that…

  • 3× 50 push ups, most days.
  • Planks every so often, most days.

I work in IT. I spend most of my waking hours in front of a computer dealing with Linux related issues and/or writing gobs of Python/Bash/Perl code to “make things go.”

That’s about it… I’ve been working to get into better shape and drive down my ADHD-driven dependency on soda as a ready source of caffeine. My soda intake was ridiculous at one point, now it’s merely “too high for my liking.” The exercise is helping my base energy level and my mental focus. I just wish I could ditch the soda faster.

My entire interest in mnemonics is driven by a desire to get my brain in its optimum state and side-step or nullify my ADHD, Dyslexia, and Dyscalculia. The latter being Dyslexia’s lesser known math related evil twin that is sometimes considered the same as dyslexia and sometimes treated as a separate disorder.

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Had this saved in my notes, a personal interest of mine.
“Respecting study limitations, we suggest based on our results and available evidence, the following FITT-based exercise recommendation to improve BDNF level: Frequency: 2-3 times per week; Intensity: at least 65% of VO 2 max; Type: moderate-intensity continuous training; Time: at least 40 minutes. Also, exercise is more effective and improves the BDNF level in linear intervention, and exercise intensity is linearly associated with BDNF changes.”

Full text here:

Of course, there are too many factors in play to give a clear cut minimum or optimum amount. I think it’s fairly safe to say that more is better in almost every respect. An hour of brisk walking a day would be a great starting point / baseline minimum. I feel a significant difference in my mental clarity as well as mood and sense of well-being when I include constitutionals in my daily routine.

Obviously there is more to optimizing cognitive function than just increasing BDNF, and there is probably far too much interpersonal variation to give an accurate minimum. Someone with an ideal BMI and no metabolic syndrome may not need as much exercise to achieve “mental clarity” as someone that has a relatively high degree of insulin resistance accompanied with prolonged states of elevated blood glucose that may cause cognitive sluggishness.

Can’t go wrong with self experimentation and (attempting) mindfulness of one’s physical and mental states.

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I think Jack Lalanne is probably a pretty good role model :wink:

Rather Father Jack Hackett than Jack Lalanne myself. Only time in my life when i have achieved my supposed ‘optimal for health’ body weight was when I was drinking a litre and a half of cheap scotch every day and totally unable to keep any food down at all. Fortunately alcoholic drinks have loads of lovely calories otherwise I would have starved to death.

Does this apply to you @Tea, age-wise I mean?
Their conclusion basically ONLY applies to teenagers. Under the link it says:


[…] Also the subjects of most of these previous experimental studies were adults. The purpose of this study was thus to examine the effects of varying intensities of aerobic exercise on resting serum BDNF, IGF-1 concentrations, cortisol, and memory of adolescents.



Forty male middle school students […] with no history of physical illness volunteered to participate in the study.



[…] In the present study, the subjects were adolescents whose bodies are still growing and developing. Aside from exercise intensity, this factor could have also influenced the result involving IGF-1.


We conclude that adolescents whose brains are still developing, […]

According to the study you are citing, brisk walking will in fact have no notable effect:


[…] One of the most interesting findings of the present study was that the exercise-induced changes in BDNF were dependent on the intensity of exercise. This supports findings of Rojas-Vega et al. [23], who reported that when athletes performed 10 min of warm-up exercises, there was no notable change in the serum BDNF concentration level. However, after subjects performed ramp tests, the level of serum BDNF significantly increased. Also, Ferris et al. [24] reported that when subjects performed 30 min of cycling at below 20% of threshold concentration level of ventilation (55% VO2max), there was no notable difference in their serum BDNF level; however, when they performed 30 min of cycling at higher than 10% of threshold concentration level of ventilation (75% VO2max), their serum BDNF level significantly increased.

Here is another study, this time with healthy adults, aged 18-25. “Vigorous intensity (80% heart rate reserve), long duration (40 min) exercise offered the greatest probability of a significant BDNF elevation.”[r]

So at there very least, there seems some consistency that higher intensity exercise is better for increasing BDNF.

As for why I notice mood elevation and cognitive benefits from simply long walks, hard to say. I am not a stroke patient, but this may still apply. “A single session of moderate intensity walking increases brain-derived neurotrophic factor (BDNF) in the chronic post-stroke patients
The Effect of Walking and Consuming Boswellia serrata on the Levels of BDNF and TNFα in Older Men

There are plenty of confounding factors. I also consume a bunch of things purported to increase BDNF, such as EGCG, curcumin, anthocyanins, astaxanthin, fish oil, etc. So maybe I’m getting some synergistic effect from long fast walks. Or maybe if you walk long enough at an appropriate intensity you can break through the threshold needed to increase BDNF. Or maybe I’m getting the mood elevation through a different means when walking. But I certainly don’t notice the same mood elevating effects from other forms of exercise, such as resistance training, regardless of the intensity.


Even twice daily short walks (1/2 mile) seem to help my wife immensely and have kept her, along with a regiment of medication of course, from being detained in an asylum . She’s a paranoid psychotic btw. Infact if she says she doesn’t want to go for a stroll its rarely just ‘nothing’.

Wouldn’t that require having a look at the interaction between BDNF and serotonin though? I mean, I’m happy for your elevated mood, but what does that have to with BDNF directly. Along the same lines… the original question was:

I’m sorry, but we’re getting way off topic here… next we talk about prolonged fasting and how ketone bodies are better fuel for the brain.

BDNF plays key roles in mood regulation, depression, memory, and so on. Consciousness and changes in mental states can’t simply be pared down to single neurotransmitters, but you’re right, my walker’s euphoria or another’s runner’s high would probably be more the interplay of dopamine, serotonin, noradrenaline, and endocannabinoid signaling.

But then again, what are we looking for? Means of increasing cognition and focus. Does increased focus accompany improvements in mood? Seems pretty likely. Does a “cleared head” count as an increase in cognitive function? For me it does, particularly if I’ve been dealing with some amount of brain fog. This is why I emphasized self experimentation.

I recommended an hour brisk walk as a baseline because I notice real cognitive benefits from it, and there are many accompanying improvements to physical health that I believe will translate to better brain health, regardless of whether a study says walking increases BDNF or not. Not to mention, not everyone is looking to dive into 40 minutes of 80% heart rate reserve. On the other hand, I’ve tried literally dozens of substances that increase BDNF and NGF and noticed subtle to no effects from them.

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