Author: alex

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The incredible shrinking hippocampus (and how to stop it)

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Over the last few years, a bunch of studies have built the case that aerobic exercise does something to keep your brain in good working order as you age — or perhaps more accurately, it does several good things for your brain. Last week, I blogged about a study showing that exercise stimulates the growth of new mitochondria in the brain. In the comments of that post, Seth Leon pointed out another new study — this one in the September issue of Neuropsychology — that links exercise to greater volume of the hippocampus, which in turn improves memory.

I’ve been particularly interested in the hippocampus ever since I wrote this article in The Walrus back in 2009, looking at suggestions that increased use of GPS navigation would lead to decreased volume of the hippocampus, where our direction-finding skills reside. And smaller hippocampi are associated with increased risk of age-related cognitive impairment. One of the researchers I spoke to worried that this is part of larger shift:

But Bohbot sees the decline in spatial thinking as part of a broader shift toward stimulus-response, reward-linked behaviour. The demand for instant gratification, for efficiency at all costs and productivity as the only measure of value — these sound like the laments of the nostalgist in the Age of the Caudate Nucleus. But here, they’re based on neuroscience. “Society is geared in many ways toward shrinking the hippocampus,” she says. “In the next twenty years, I think we’re going to see dementia occurring earlier and earlier.”

I can’t count the number of times I’ve taken wrong turns since writing that article because of my stubborn refusal to use GPS unless absolutely necessary! But I digress…

Anyway, this new study, by researchers at the University of Illinois, looked at a group of 158 sedentary adults between 60 and 80 years old, to look for evidence for the following model:

The basic gist is straightforward: they hypothesize that fitness (as measured by a graded exercise test to exhaustion) predicts hippocampus size, which in turn predicts working memory, which in turn predicts how frequently you forget things. What’s new about this study is that they separately consider age, BMI, sex, physical activity, and education to see if any of them are skewing the results. Here’s what they find:

By and large, the data supports their hypothesis. There are a few wrinkles: for example, age, in addition to affecting fitness, also has a direct effect on hippocampus size. That means no matter how fit you are, your hippocampus is still getting smaller. Also, physical activity (that’s the PASE box) didn’t directly contribute to fitness — but that’s not surprising, because the volunteers had to be sedentary in order to be admitted to the study, so they all had roughly the same (lack of) physical activity.

Bottom line: aerobic fitness is good for the brain — and in particular, it’s good for the hippocampus. So maybe if I get enough exercise, I’ll start letting myself use that GPS navigation system.

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Asker Jeukendrup on beets, hydration, train low, etc.

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Amby Burfoot has an interesting interview with Asker Jeukendrup on his Peak Performance blog. Jeukendrup has long been associated with PowerBar, but apparently moved over to the Gatorade Sports Science Institute as “global senior director” a few months ago.

I’ll be interested to see whether this signals a shift in direction for Gatorade: a couple of years ago, Gatorade relaunched its product line to feature a lot of mumbo-jumbo like “theanine to improve focus” and “B vitamins to help you metabolize energy” and so on. At the same time, it also disbanded its U.S. scientific advisory panel, which was composed of external scientists. One of the advisory scientists I spoke to at the time felt that it signalled an unfortunate change in direction away from high-quality, science-based product claims. Hopefully Jeukendrup’s hiring indicates a renewed commitment to science over marketing.

Anyway, the real point of this post is to recommend that you read the interview. Burfoot takes Jeukendrup through half-a-dozen topics of interest to readers of this blog, from beet juice to training on an empty stomach to whether thirst is a reliable mechanism to determine how much to drink. Somewhat surprising to me was Jeukendrup’s response when Burfoot asked if he could explain why beet juice seems to offer such a boost to endurance:

No I can’t explain them. I don’t know the mechanism that would cause them, and that bothers me. It also bothers the scientist who has done much of the work, Andy Jones, who is very good as you say. But he also can’t figure out why the beet juice is enhancing endurance.

I had thought some of the results from the Karolinska Institute in Sweden were shedding some light on how beet juice works — but then again, the explanation was complicated enough that I had trouble following it. So maybe it’s not as clear-cut as I thought. Still, the results have been repeated multiple times under different conditions, so in a sense the “why” is not essential.

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Do you need a bit of extra fat to stay healthy as you age?

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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This week’s Jockology column in the Globe and Mail tries to untangle conflicting data about whether being moderately overweight increases or decreases your lifespan:

It’s a surprising, subversive and very, very popular idea.

Over the past few years, several studies – including a 2009 analysis of Statistics Canada data – have suggested that being a bit chubby as you get older, far from being a health risk, may actually help you live longer. The extra weight, the thinking goes, could help cushion you from the inevitable slings, arrows and hip fractures of old age.

But the newly published results of a three-decade-long study of clean-living Seventh-Day Adventists in California suggest that you might want to go easy on those early-bird specials after all. When confounding factors such as skinny smokers were removed, the effects of extra weight were clear – and bad – even for those older than 75… [READ THE WHOLE ARTICLE]

The article is accompanied by a graphic by Trish McAlaster, which includes a bit of info on the recent study showing aerobic exercise targets visceral fat more effectively than strength training, which targets subcutaneous fat:

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Ice baths: “lab fatigue” vs. “real fatigue”

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Ice baths after a hard workout are very popular, but the evidence for them has always been a little shaky. A group of British researchers (including a pair from the English Institute of Sport) have just published a major meta-analysis in the British Journal of Sports Medicine that adds a couple of interesting insights. The analysis covers 14 different studies with a total of 239 athletes.

What I found most interesting is the following distinction they decided to make:

For the purpose of this review, exercise will be subdivided into two categories: ‘eccentric exercise’ that refers to the stress caused from exercise incorporating high mechanical stress (eg, eccentric contractions) and ‘high-intensity exercise’ that refers to stress caused from exercise with a high metabolic cost as well as some elements of eccentric muscle contractions (eg, repeat sprint sports).

It’s well known that the best way to induce muscle soreness is with eccentric muscle contractions, particularly unfamiliar ones. So most lab experiments on muscle soreness involve simple things like lowering a dumbbell or stepping off a box over and over — it may not be exhausting, but it sure leaves you sore. The problem is, this isn’t the kind of damage that most athletes are interested in recovering from — they’re interested in recovering from training sessions that feature familiar but intense exercise.

So is there a difference between the two? Yes: the meta-analysis found dramatically stronger effect on recovery from “high intensity exercise” than from “eccentric exercise.” It’s worth noting that only two studies looked at the former, while 12 looked at the latter. Still, it offers a possible explanation for why so many athletes believe ice baths help them in training, while lab studies of eccentric exercise continue to find ambiguous results.

Speaking of results, what were the overall conclusions? I quite like the use of forest plots to give a quick visual sense of the overall data. Here are the results for perceived recovery from muscle soreness, with each dot representing a study result (some studies appear more than once for results at 24, 48, and 72 hours after exercise, which is why there are more than 14 dots). Dots to the right of the thick line mean that the ice bath group recovered more quickly; dots to the left of the line indicate that the control group recovered more quickly:

Looks pretty convincing, eh? Unfortunately, the picture is a bit muddier if you look at an objective measure like creatine kinase in the blood (a marker of muscle damage), though there’s still a statistically significant effect in favour of ice baths:

Same goes for recovery of strength:

In the end, we’re still plagued by the fact that it’s impossible to placebo-control an ice bath study. The perceived soreness results do look encouraging, but it’s hard to rule out the effects of the fact that most of the subjects probably expected to feel better when they had the ice bath. By no means is the science settled here yet.

Which brings us to another point that’s currently being hotly debated in scientific and athlete circles (as commenter Rich pointed out last time I blogged about ice baths): If inflammation is part of the body’s adaption response to stress, and ice baths reduce inflammation, does that mean ice baths reduce your adaption to hard training? Interestingly, the lead author of the current study, Jonathan Leeder of the English Institute of Sport, commented on this question in an EIS press release last year:

“There’s evidence to suggest that if you constantly decrease the stress in training that the body won’t adapt, so long term use of a recovery technique, such as an ice bath, should be reviewed to avoid any detrimental effects on performance and to ensure that these techniques have their biggest impact when needed during competition” [Leeder] adds.

But is there really evidence to back this hypothesis up? Here’s what Leeder and his co-authors say in the peer-reviewed BJSM:

It has, however, been suggested that the inflammatory response is critical for optimal repair of damaged tissue. Although the mechanisms of training adaptation are not fully understood, it may be detrimental to reduce the commonly accepted damage-repair-adaptation model by diminishing the inflammatory response; however, there is a lack of evidence to support this. This raises the question of whether frequent or habitual use of strategies designed to reduce inflammatory responses can be detrimental for elite athlete adaptation to training.

So that’s where we’re at: no one really knows whether repeated ice baths have a practically significant effect on reducing adaption to training. From what I understand, the English Institute of Sport has been advising its athletes to avoid ice baths after routine sessions during heavy training phases, but to incorporate them during tapering and competition. In other words, periodize your recovery protocols so that you maximize adaption during training periods and maximize recovery during competition periods. Does this work? Maybe we’ll find out at next year’s Olympics!

 

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Cardio showdown: Strongmen vs. marathoners

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Who has a bigger heart: a 150-lb marathoner, or a 300-lb World’s Strongest Man competitor? And more importantly, whose heart is healthier? Believe it or not, this is an actual study just published in the Journal of Strength & Conditioning Research by scientists in Lithuania. They studied 8 Strongmen, 10 marathoners (nationally or internationally competitive in both cases), plus 9 controls.

In general, you wouldn’t expect strength training to do much for the heart — but these competitors are so extreme that you might expect to see some differences, the researchers argue:

Strongmen with their Herculean strength conduct extremely arduous exercises such as lifting, holding, carrying (hundreds of kilograms), pulling, and pushing (tons) during training and competitions, and such tasks trigger a pronounced cardiac pressure overload and, when conducted over an extended period of time, might be expected to impact cardiac size and function to a greater extent than participation in other types of resistance sport.

The results shows that the Strongmen do have big hearts, but pretty much exactly in proportion to their bodies, whereas marathoners have big hearts but small bodies. For example, the thickness of the posterior wall of the heart was, on average, 11.81, 11.82 and 10.99 mm in the Strongmen, marathoners and controls; but when adjusted relative to body surface area, the values were 7.50, 8.56 and 7.50. More to the point, the hearts of the Strongmen don’t appear to function quite as well (the “E/A” column is a measure of diastolic function):

The Strongmen also fared worse on measures of plasma lipids. What does this all mean? None of the results are particularly surprising. But I suppose if you’re a skinny little marathoner, it’s kind of cool to know that your heart is just as big as the dude twice your size single-handedly hauling an 18-wheeler up a hill on TV.