Newsletter #306: Acute Effects of Strength Training on Learning & Memory 🧠
Previously in this newsletter, we have discussed how exercise can enhance learning and memory.
This is, in part, mediated by hippocampal neurogenesis — meaning, the generation of new brain cells in the hippocampus, a structure of the brain that plays a key role in the formation and storage of memories. Physical activity nurtures this process, perhaps better than anything else.
For instance, rodents that live in cages with running wheels (and thus are able to exercise) wind up producing far more hippocampal neurons than counterparts in cages without wheels. Remarkably, even old mice exhibit this effect. Similarly, older humans who undertook an exercise regimen showed an increase in hippocampal volume of 2%, which effectively turned back the clock of typical age-related loss of volume by a couple years.
Of course, these studies are capturing the long-term impact of exercise on the brain, usually occurring over the course of years. But does exercise exert acute effects on the hippocampus? Can even a single bout of activity affect your capacity to learn and remember new information?
A new study suggests the answer to that question might be yes.
This Week’s Research Highlight
A single strength-training session can improve learning and memory.
Japanese researchers recruited 60 students at Tohuku University. These were healthy young adults, aged 19-27, who weren’t currently involved in strength training. Participants were randomly divided into a training group and a control group. Both groups visited the lab on two different occasions: an intervention session, and then a post-intervention session two days after.
During the intervention session, the training group underwent verbal memory testing (free-recall and cued-recall tests, using lists of words), followed by brain MRIs.
Then, they performed a very short resistance training session, using a contraption that is pretty similar to the leg curl and leg extension machines that you see at commercial gyms. They did three sets of 8 reps at 80% of their one rep maximum, with a 1-min rest interval between sets. The total duration of this workout was less than seven minutes. Two days later, the exercisers returned to the lab and redid the memory tests, as well as the brain MRIs.
Meanwhile, the control group underwent just memory tests at both sessions.
Sure enough, the training group was able to recall more words from the lists they had studied, compared to the control group.
But this could not be explained by neurogenesis in the hippocampus, like we described earlier — that process operates on much longer timescales. When the researchers looked at the brain imaging, they determined that this difference could be explained by changes in hippocampal connectivity.
Previously, we talked about how physical activity can influence brain volume. But just as important as the size of the brain is how different regions of the brain are linked to one another. For example, several different regions of the brain are actively engaged when you are reading – one area that helps perceive letters, one that maps sounds to letters, and others involved with word meanings and grammar rules. These regions are connected through nerve fibers known as white matter, and they have to work together super fast. The strength of this signaling has been shown to be crucial for reading ability (it has been suggested that dyslexia is due to issues with this internal highway system).
Similarly, in order to form memories, your hippocampus needs to be wired to many other areas that are involved with taking in and processing new information. In these participants, verbal recall scores in the two days following resistance training were associated with changes in connectivity between the left posterior hippocampus and the cuneus, a structure involved in visual processing. Prior research has suggested that this connection may be associated with verbal fluency, so this makes sense.
It’s encouraging to see that such a bite-sized dose of exercise can have a beneficial impact on memory, and that it can happen so quickly!
However, one thing that jumps out at me in this study is that this exercise seems to have been a novel stressor for these participants. That’s important because over time, we adapt to whatever training that we undertake. Generally, that’s a good thing (otherwise we wouldn’t get faster, stronger, etc), but it also suggests that performing the same exercise at the same duration/intensity/frequency is likely to be less effective over time, since some level of physiological arousal appears to be key for eliciting this effect on connectivity.
As one review of this subject noted: "If a person becomes overly accustomed to the exercises, then those exercises will not be as physically taxing, which will decrease the physical benefits and could lead to decreased neurobiological and cognitive demands, hindering any potential cognitive and neural benefits."
In other words, you need to make sure you’re continuing to challenge yourself with your training program, in order to see ongoing physical and mental gains.
Random Trivia & Weird News
When Henry VIII was on his deathbed, medical staff refused to tell him how serious his condition was for fear of being executed.
One of the great limitations of authoritarian regimes is that it becomes perilous to tell the truth.
At the age of 55, King Henry VIII was in failing health, due to an array of serious maladies (his actual cause of death remains a source of ongoing debate among historians). But due to a statute that rendered it treasonous “to compass or imagine the death of the king,” physicians were too afraid to be honest with him about his deteriorating state.
Finally, Archbishop Thomas Cranmer gently informed the king that his days were numbered.
Podcasts We Loved This Week
- Venki Ramakrishnan: Nobel laureate alarmed by over-hyped longevity research. Via the LLAMA Podcast.
- Daryl Van Tongeren: A personal tale of intellectual humility – and the rewards of being open-minded. Via The Conversation Weekly.
Products We Like
Competition Kettlebells
Competition kettlebells offer several major advantages over the typical lumpy cast iron kettlebells that you usually see in commercial gyms. For one thing, the handle is smaller and much smoother, which reduces grip fatigue and friction for the kinds of dynamic activities that you typically do with kettlebells. They’re also uniform in size regardless of mass, which helps a lot when practicing said movements and when you transition between different weights. Finally, they have a wide flat base, so they’re less likely to fall over, which is especially good if you are bracing yourself on them. I’ve got a couple of these, and I am a huge fan. Definitely worth it if you train with kettlebells regularly.
humanOS Catalog Feature of the Week
Daily Performance and Physical Activity
In this course, we review:
🧠 Effects of exercise on the brain
💡 How physical activity within the day can improve your thinking
🏋️ Strategies to integrate more movement into your day
Wishing you the best,
