It finally happened

Ever since I went barefoot over three years ago, I’ve scoffed at the “Aren’t you afraid you’ll catch a disease or infection?” comments. Ridiculous, I thought. I don’t walk around with open foot wounds, and my feet aren’t a bacterial highway to my orifices. After this past week, however, I’m realizing that maybe a little fear would have served me well.

Here’s an abbreviated version of my real-life horror-story to scare a little caution into the barefooting community.

Saturday: Post-dinner stomach rumbles evolved into suspected food poisoning. I’ll spare you the details, but any food sent me an immediate angry message that kept me miserable and sleep-deprived for three days.

Tuesday morning: Stomach turned a corner for the better, so despite my fatigue and weakness, I attempted a run. Managed 8 miles but noticed a mild heel ache. Did I bruise it without noticing? Was it a hint of plantar fasciitis? I had sustained a minuscule cut on that heel a week ago, but that had healed. Not overly concerned, I did some gentle self-massage and slathered some DMSO – a controversial chemical thought to promote soft-tissue healing – over the heel and ankle. I then went about my day, walking barefoot and pleased that I was back up and running again.

Tuesday evening: Foot had gotten progressively worse and I’m feeling notably drained. Must have overdone it with the run. Right before bed, my groin region begins to hurt and I’m feeling chilled and achy. 101.5° fever. A little internet research educates me that swollen lymph nodes in the groin indicate injury to the foot or leg. The pieces of the puzzle are starting to fit together.

Infected foot. The doctor's outline shows the extent of the infection.

Infected foot. The doctor’s outline shows the extent of the infection.

Wednesday: I awaken to some rapidly spreading and intensifying foot pain, leading to a trip to the ER. It’s an infection, the doc confirms, and gently suggests I run in shoes. I respectfully tell him I’ll opt for this over chronic fractures and tendonitis. He accepts my decision, prescribes an antibiotic and tells me I’ll be feeling better by the morning.

Drip. Drip. Two hours of antibiotics directly into the bloodstream.

Drip. Drip. Two hours of antibiotics directly into the bloodstream.

Thursday: I awaken to a throbbing foot and the terrifying sight of deep red streaks climbing up my ankle. Back to the ER it is, hopping on one foot most of the way. They give me an IV of vancomycin (an antibiotic) and release me six hours later with prescriptions for two more antibiotics. So. Many. Drugs.

Fast forward two days later, and I can almost walk normally. The infection’s under control and the swelling has mostly subsided, though there’s an ugly patch of broken blood vessels and bruising that’s tight and tender to the touch. Thank god for modern medicine. The alternative of losing a limb (or worse) to a simple infection – a reality that our ancestors and many less fortunate populations around the world today still deal with – is humbling and sobering. That’s a topic for another day.

So what caused the infection? The docs didn’t really care to look into it, but assumed it was the old cut on my heel. I suspect otherwise, as the infection never actually extended to the cut itself. The other possibility, that admittedly creeps me out, is that the DMSO – a “universal solvent” – absorbed some nastiness from the outside world directly into my skin and bloodstream. The chemical is not approved for medical use on humans, apparently for good reason. I’ll never know the exact cause, but my DMSO is enjoying its new home in the trash.

“I told you so!” I can hear you all crying in anti-barefoot triumph. Not so fast. Incidentally, I sustained a similarly serious foot infection a decade ago from a blister caused by … poorly fitting shoes. Life happens, unpredictably and uncontrollably, shod or barefoot. As abandoning my shoes and rediscovering the power of my feet has introduced so much strength, health and joy into my running and everyday life, re-embracing shoes is nowhere on the horizon. Sure, barefoot running carries its unique set of risks. But I’ll take the occasional bruise and fluke infection over repeated broken bones and torn tendons any day.

Stay safe and run happy!

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Global similarity signals of recognition strength

The below article was recently rejected from the Journal of Neuroscience as a ‘Journal Club’ commentary on Davis et al., 2014, ‘Global neural pattern similarity as a common basis for categorization and recognition memory’. Hoping that my efforts will not go to waste, I’d like to give the piece an alternate home here. Please read, comment and share, all free of paywalls!

Theories of long-term memory have linked an item’s memory strength to its “global similarity” (Clark and Gronlund, 1996). The greater the conceptual overlap between a target item and other items stored in memory, the more familiar the item will seem. While psychological models have consistently supported the theory that across-item similarity contributes to recognition memory, it is unclear how neural computations give rise to this relationship between representational similarity and memory strength. Neuroimaging studies have shown that activity in the brain’s medial temporal lobe tracks memory strength as well as the representational overlap between stimuli in memory, establishing this region as a likely host for a global similarity signal that confers accuracy and confidence to recognition judgments.

Model of the multivoxel pattern similarity analysis. A) The multivoxel activation pattern within a region is extracted for each stimulus (S1, S2, etc.). B) The correlation between the activation pattern for each stimulus and that of all other stimuli is computed. Across-item correlations are expected to be higher for stimuli that are strongly remembered than those that are poorly remembered. Adapted from Xue et al., 2010.

Model of the multivoxel pattern similarity analysis. A) The multivoxel activation pattern within a region is extracted for each stimulus (S1, S2, etc.). B) The correlation between the activation pattern for each stimulus and that of all other stimuli is computed. Across-item correlations are expected to be higher for stimuli that are strongly remembered than those that are poorly remembered. Adapted from Xue et al., 2010.

In their study recently published in the Journal of Neuroscience, Davis and colleagues (2014) tested whether the similarity between blood oxygen level dependent (BOLD) activation patterns elicited by an item and other encoded items predicted how confidently the item would later be recognized (see figure). Participants underwent functional magnetic resonance imaging while performing an incidental encoding task of repeated Chinese words. They were later administered a surprise recall task, in which they freely reported any recalled words from the encoding task, as well as a surprise recognition task, in which they reported their confidence in having previously seen a word. The authors then computed a neural similarity score for each word, which measured the correlation between the multivoxel activity pattern for that word and the activity pattern for all other words (Davis et al., Figure 1). This global similarity metric was compared to recognition confidence ratings to assess the relationship between neural representational overlap and memory strength.

Consistent with their prediction, the extent of global similarity between the multivoxel activation pattern of a word and that of all other words correlated with the word’s subsequent recognition confidence ratings (Davis et al., Figure 3A). Within their medial temporal lobe region of interest, the effect was localized to clusters in both the parahippocampal gyrus and hippocampus. This link between neural global similarity and recognition strength held even after controlling for within-item similarity, which the authors previously showed to correlate with memory strength (Xue et al., 2010). Furthermore, medial temporal lobe pattern similarity also correlated with the semantic relatedness between words (Davis et al., Figure 6). This demonstrated, for the first time, that medial temporal lobe substrates of between-item similarity mirror psychological metrics of memory strength and semantic relatedness. The stronger an item is represented in memory, the more highly its semantic content, and its representation in the medial temporal lobe, overlaps with that of other stimuli.

While these initial results speak to the mechanisms by which an item is perceived as familiar, considerable debate exists over whether recognition is mediated by a single neural system. For instance, some neuroimaging and lesion studies have reported functional segregation of familiarity and recollection signals within the medial temporal lobe (Eichenbaum et al., 2007), while others indicate that the medial temporal lobe collectively supports all forms of recognition memory (Squire et al., 2007). Furthermore, there is evidence that successful recall can be mediated by global similarity (Gillund and Shiffrin, 1984), but also by pattern separation of an item from other items (O’Reilly and Norman, 2002). Thus, to dissociate between effects of global similarity on recognition strength and on recall, pattern similarity analyses were additionally performed on non-recalled words alone, and also on recalled versus non-recalled words. Global similarity of medial temporal lobe activation patterns both correlated with the memory strength of non-recalled words and predicted recall success. Thus, both recognition and recall may rely on the degree of neural representational overlap across items in memory.

Finally, the authors investigated whether the association between memory strength and neural similarity extends beyond long-term memory. Given prior evidence that learning categorical rules increases the psychological similarity of learned items and activates the medial temporal lobe, they tested whether global similarity of medial temporal lobe representations reflected category learning. Indeed, global similarity of medial temporal lobe activity patterns correlated with the psychological similarity between an item and others in its category (Davis et al., Figure 3B, C). Notably, these regions overlapped considerably with those from the long-term memory pattern similarity analysis (Davis et al., Figure 4). Thus, global similarity computations in the medial temporal lobe may not selectively subserve episodic memory formation, but might support a range of learning processes.
These findings suggest a universal mechanism of coding memory strength within the medial temporal lobe that generalizes across domains, beyond just recognition memory. This bridge across cognitive domains aligns well with our understanding that acquiring both episodic memories and categorization rules involves learning new information, a process fundamentally supported by memory encoding. However, the breadth of such a medial temporal lobe code, which extends beyond recognition to encompass recall and categorization, raises important considerations regarding the heterogeneity versus homogeneity of medial temporal lobe memory functions.

Some theories of medial temporal lobe function propose distinct roles for the hippocampus and parahippocampal gyrus in long-term memory. A recent study examined whether these regions also functionally dissociate according to memory-related global similarity computations. LaRocque et al. (2013) reported a correlation between across-item neural similarity and recognition strength in the parahippocampal gyrus, but an inverse correlation in the hippocampus. This dissociation contrasts with the parallel representations in the hippocampus and parahippocampal gyrus observed by Davis et al. (2014). Thus, hippocampal representations of global similarity and distinctiveness may both contribute to recognition memory. These seemingly contradictory findings in fact align with computational models of hippocampal function suggesting that the structure performs both pattern completion and separation in the service of long-term memory (Yassa and Stark, 2011). These operations are likely computed by separate hippocampal subregions and support distinct memory functions. Specifically, pattern separation may be mediated by the dentate gyrus and promote discriminative processes that aid encoding and recollection, whereas pattern completion may be mediated by CA3 and generalize across inputs to signal familiarity. It is therefore possible that hippocampal signals of representational overlap and distinctiveness coexist in complex tasks like those employed in these studies (LaRocque et al., 2013; Davis et al., 2014), which may dynamically engage concurrent memory encoding and retrieval processes. Follow-up studies will help to resolve why a pattern completion or separation signal would dominate depending on the task condition or memory manipulation.

Furthermore, given the inherent ambiguity of multivoxel signal content, it is unclear what particular information is carried in overlapping activation patters. Here, BOLD patterns correlated with both memory strength and semantic content; yet, multiple additional variables may covary with these cognitive measures and hence contribute to the similarity across multivoxel space. As the authors acknowledge, an infinite number of factors, which can be challenging to detect or control, may increase the similarity between BOLD activation patterns (Todd et al., 2013). Further research will be important to more completely characterize how variance in factors such as stimulus features, cognitive sub-processes, BOLD dynamics, or analysis procedures, may additionally drive the overlap in BOLD patterns of neural representations.

The findings of Davis and colleagues provide novel insight into medial temporal lobe coding mechanisms of memory strength, linking computational models that implicate psychological similarity in recognition strength with representational similarity of memory-related brain activation patterns. Together, these results solidify a base upon which to more thoroughly examine the breadth of this medial temporal lobe similarity signal across cognitive processes. Such findings will serve as critical steps towards clarifying the extent to which overlapping neural representations in the hippocampus and parahippocampal gyrus contribute to a range of learning processes – including both those within and beyond the domain of episodic memory.

References

1. Clark SE, Gronlund SD. 1996. Global matching models of recognition memory: How the models match the data. Psychon Bull Rev 3:37-60.
2. Davis T, Xue G, Love BC, Preston AR, Poldrack RA. 2014. Global neural pattern similarity as a common basis for categorization and recognition memory. J Neurosci 34:7472-84.
3. Eichenbaum H, Yonelinas AP, Ranganath C. 2007. The medial temporal lobe and recognition memory. Annu Rev Neurosci 30:123-52.
4. Gillund G, Shiffrin RM. 1984. A retrieval model for both recognition and recall. Psychol Rev 91:1-67.
5. LaRocque KF, Smith ME, Carr VA, Witthoft N, Grill-Spector K, Wagner AD. 2013. Global similarity and pattern separation in the human medial temporal lobe predict subsequent memory. J Neurosci 33:5466-74.
6. O’Reilly RC, Norman KA. 2002. Hippocampal and neocortical contributions to memory: advances in the complementary learning systems framework. Trends Cogn Sci 6:505-10.
7. Squire LR, Wixted JT, Clark RE. 2007. Recognition memory and the medial temporal lobe: a new perspective. Nat Rev Neurosci 8:872-83.
8. Todd MT, Nystrom LE, Cohen JD. 2013. Confounds in multivariate pattern analysis: Theory and rule representation case study. Neuroimage 77:157-65.
9. Xue G, Dong Q, Chen C, Lu Z, Mumford JA, Poldrack RA. 2010. Greater neural pattern similarity across repetitions is associated with better memory. Science 330:97-101.
10. Yassa MA, Stark CE. 2011. Pattern separation in the hippocampus. Trends Neurosci. 34:515-25.

ResearchBlogging.org
Davis T, Xue G, Love BC, Preston AR, & Poldrack RA (2014). Global neural pattern similarity as a common basis for categorization and recognition memory. The Journal of neuroscience : the official journal of the Society for Neuroscience, 34 (22), 7472-84 PMID: 24872552

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Feet in shining armor: Paleo Barefoots review

CHAINMAIL. Quick … what comes to mind? Medieval warriors? Knights in shining armor? Running shoes? (Okay, maybe not so much shoes.) Given traditional recommendations for cushioned, supportive running shoes, the thought of metal chains against naked feet might not elicit a strong sense of comfort or safety.

THE CONCEPT

Indeed, even I – a barefoot runner – was skeptical when I first heard of the Paleo Barefoots, a minimalist footwear constructed entirely of chainmail. Being a sucker for functionally and aesthetically innovative advances in minimalist running, I became immediately intrigued. Like most minimalist shoes on the market, the Paleos are designed to allow the foot move as freely and naturally as possible, with just enough protection against the elements. But what sets the Paleos apart is their unique design that, theoretically, will let them last a lifetime. Even the most minimal shoes – including the more popular “toe” shoes or huaraches – require a rubber-like sole at least several millimeters thick to confer durability and protection. In contrast, the Paleos’ construction from metal – yes, literally minuscule steel links – eliminates the need for a thicker sole. This design yields a sock-like slipper, only 1.4 mm thick, with ultimate flexibility and ground feel.

My Paleos@Ultra with green paws

However, while chainmail will win the battle against dirt, sand, twigs and grass, the victor of a metal-versus-concrete war is anyone’s call. Thus, Paleos are intended only for use on ‘natural’ surfaces, and aren’t recommended for running through the concrete jungle. Such a product sounds like a dream come true for any barefoot runner looking to venture into more challenging terrain. But the unfortunate reality is, dreams aren’t fulfilled for free. In fact, the Paleos carry perhaps the heftiest price tag on the minimalist shoe market – on the order of two- to three-hundred U.S. dollars, depending on the style and options.

THE PRODUCT

After reading several glowing reviews, I became curious – okay, no … obsessed – with trying the Paleos. I rationalized the sacrifice to my bank account with the reassurance that it would be a one-time cost, as the Paleos should last forever if cared for. After much deliberation, I bit the bullet and purchased my very own Paleos@Ultra. Considering the high price tag and the shipping time from Germany, I was nervous about their fit and my chosen options. To my relief, their customer service promptly evaluated my foot tracing and confidently offered a size recommendation.

My Paleos fit perfectly right out of the box.

When they arrived, I was first struck by the quality of not only the shoe, but also the thoughtful packaging, informative care guide and personal touches. My Paleos arrived packaged carefully in an exquisite metal box, along with instructions and a complementary chainmail key chain. My personalized Paleos were equipped with engraved metal plates, black elastic laces, mesh lining socks and ankle wraps, and green “paws”, designed for extra grip on rough rocky or urban terrain. Right out of the box, this was clearly a quality product.

PERFORMANCE

In all honesty, it took me three attempts to fully appreciate the Paleo experience. As they’re unlike any other footwear I’ve tried, it took me some time to refine my fit and preferences. When I first put them on, they felt loose and heavy on my foot as I walked around my apartment. I couldn’t imagine them performing well while running. My first test run was a brief trot on a sandy trail cut short by skin irritation at the back of my ankle. Feeling that my Paleos were too loose, I had tightened the laces too snuggly, to the point where they dug into my achilles. Discouraged but not defeated, I tried another day, loosening the fit and wearing the sock liners. This first mini test-mile was a success and I was ready for a real trial run.

Paleos with sock liners

As I am far from an experienced trail runner, I sought out a gentle trail for my test run. The terrain was mostly packed sand, but also included several unavoidable rocky patches and stretches of rough gravel. I had only previously attempted this trail in full shoes or Luna sandals, and would never consider tackling it barefoot. In fact, convinced the Paleos would not hold up against the gravel and rocks, I stashed my Lunas as back-up. To my great surprise, the Paleos handled even the roughest segments with ease. The fine gravel and stones, which would typically abrade my bare feet, didn’t phase me. Although I could feel the larger rocks, not once did I get a foot bruise, which I’ve become notorious for sustaining. About two miles in, I did feel some irritation around my achilles (and later discovered a small blister as a result), which was easily remedied after a quick adjustment to loosen the laces. As the run progressed, the experience became almost surreal, as I soon forgot I was even wearing footwear, yet still felt well protected from the rough earth under foot. I found myself sprinting the end of my five-mile test run, carefree and thrilled with the Paleos’ exceptional performance.

THE SERVICE

This review wouldn’t be complete without mentioning the great folks behind the product. From start to finish, the owner himself made it a priority to respond to my questions and concerns via email and social media. They shipped my Paleos faster than promised, and they arrived in the U.S. remarkably quick. When they got stuck in customs, the owner looked into the issue and sent me shipping updates along with his apologies for the delay.

Sure, it may take some time for the mainstream running community and shoe market to embrace a metal sock as an acceptable option for running footwear. I don’t predict the PaleoBarefoots will soon be ranked among Runner’s World’s most popular shoes for comfort, style or affordability. But based on my initial impressions, I suspect there’s a niche of selective athletes who would be thrilled to discover this treasure. What barefoot runner isn’t looking for foot protection that not only embodies minimalism and functionality, but also the bonus perks of quality, creativity and beauty?

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Navigating the niggles

You’re midway through an otherwise phenomenal run. You’re feeling strong, just tackled that dreaded hill and have fully entered the zone. Suddenly, your heart sinks a bit as you feel a niggle coming on. Whether it’s an ache in your foot, a twinge in your knee, or tightness in your hip, these minor discomforts can be majorly disconcerting. Maybe it will dissipate in a minute … or maybe it will evolve into a serious injury. Sure, a smart runner will listen to their body. That’s easy enough when your body is screaming adamantly “Your foot is broken, dummy!” But how do you respond when your body mumbles incoherently “Yeah, I’m not feeling so hot. The ankle feels kinda blah … you might want to check it out … or not … I don’t care”. In these situations, neither intense trepidation nor denial of the warning signs are ideal approaches. But don’t fret, runner. There is in fact a middle ground on which you can cautiously and safely test the injury waters.

1. SLOW DOWN, SWITCH IT UP, SHAKE IT OUT

Sometimes a simple correction is all you need. If that niggle arose from pushing too hard, just slowing your pace could reset you back to normal.

We often think of over-use injuries as emerging after many days or weeks of too much running. But sometimes monotonous motion – even over the course of several minutes – can trigger over-use symptoms. If you’ve been running on the road, find some grass or trail. If the terrain’s been rough or uneven – for instance, a rocky path or canted road – switch to something more stable. The slight change in muscle engagement might be all you need.

If these quick fixes don’t fix, stop and shake it out for just a moment. Sadly, many of us have been taught that running breaks are a sign of weakness. Believe me, running yourself into a broken bone or torn tendon will leave you much weaker than had you taken a brief pause. Even a 30-second rest might allow an overworked muscle to recuperate, leaving you refreshed for the rest of your run.

2. FOCUS ON FORM

The onset of a niggle is the perfect time to check back in with your body. Often, a slight form correction can nip the problem in the bud. It’s not always obvious where the imbalance is coming from, so scanning the body – from tip to toe – will cover your bases.

Good running form, courtesy of the Mark Cucuzzella and the Natural Running Center.

Good running form, courtesy of the Mark Cucuzzella and the Natural Running Center.

Head. Starting with your head, assess your posture. Imagine a string pulling your head up from your shoulders, elongating your neck and spine into a tall, straight line. Keep the shoulders relaxed but don’t forget to keep the arms bent and active. The rhythm of your arm swing can have a powerful impact on your running cadence – which we all know is a critical element to strong, healthy running.

Core. Moving down, evaluate your hips and core. Stability in these regions are perhaps the most essential component of good running form, and – as the term implies – comprise the core of a runner’s stride. Imagine your hips on an even horizontal plane, the right and left hip bones perfectly aligned, neither dipping nor rotating with your stride. Keep a slight lean in the upper body, visualizing a straight planE from head to toe angled forward, being mindful not to bend at the hips.

Legs. Next come the legs. Bend the knees, and keep the gluts and hamstrings active. Check where your feet are landing. They should contact the ground directly under the hip, not in front (this is ovestriding – an all-too-common source of many problems!), nor at the midline (this is a cross-over gait, which can be the source of many lateral injuries). Sometimes mentally exaggerating these features can help achieve them – for instance, aim to make foot contact behind and to the outside (laterally) of your hips. You’ll likely end up striking right under the hips.

Feet. Lastly, check in with your feet. Keep them relaxed – your foot muscles are not “power muscles” as are your quads, gluts and abs, and thus should not be relied on to propel you through your stride. Especially if you are running barefoot or minimalist, there can be a tendency to unnecessarily over-engage the feet. Imagine landing as lightly as possible, lifting the foot at the moment it touches the ground, rather than pounding or slapping. And of course, keep your cadence high. Aim for a balanced foot strike that’s neither excessively fore-foot nor rear-foot. I find that focusing on a “pancake-flat” foot-strike (forefoot and heel striking simultaneously) works best for me, but play with this to find your comfort zone.

3. UNEARTH THE ROOT OF THE PROBLEM

Modifying your speed, terrain or form are great quick fixes for mid-run niggles. But the critical question for preventing a recurrent, or long-term injury, is what caused the problem in the first place? This is some great food for thought for the remainder of your run … reflect on what you were doing leading up to the onset of the problem. Revisit not only the moments before, but also the days and weeks before. Did you just summit a monster hill? Maybe you’ve incorporated more speed work than normal this week, or have been pushing your mileage recently. Subtle changes, even those unrelated to your training, can impact your running health. Sleep deprivation, poor diet or stress can all work against a runner, impeding recovery, promoting inflammation or increasing fatigue. Chances are, you might be battling several of these aggravators, making it challenging to pinpoint one root cause. So go ahead, take an extra rest day, treat yourself to a deep-tissue massage and indulge in an extra hour of sleep.

And remember, a niggle’s nothing more, unless you let it be. Embrace these moments as learning tools and you’ll only grow stronger and healthier!

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Skora Core: A sh*e review?!

Fare warning, barefoot runners … the following post contains sensitive content. It is, indeed, a SHOE review.
“Has she turned to the dark side?” you might ask.
“Hypocrite!” you may holler.
Don’t fret, barefooters. I still run exclusively barefoot, strongly advocate free feet, and don’t foresee changing my ways any time soon.

That said, I am not anti-shoe, but rather, view shoes as tools that can be immensely beneficial when used in the right context. I’m writing this review not because I’m swapping my feet for SKORAs, nor do I suggest you do, if you’ve already discovered the joys of naked soles. Instead, I’m writing this as a former shod runner who understands the value (and rarity) of a quality running shoe and believes that SKORA is about as good as a shoe gets. During my roughly two year transition to minimalist – and later barefoot – running, I experimented with shoe after shoe after shoe. Many failed miserably while others were unimpressively acceptable. Through these many trials and errors I vowed to never become a brand evangelist. That is, until I put on my SKORA Cores.

When I bought my pair of SKORAs last year I took a huge gamble. I had never purchased a running shoe without first trying it on, but was so intrigued by others’ glowing reviews that I just had to try them. With a hefty price tag of $110-195 depending on the model (as of Winter 2014), this isn’t a cheap gamble to make. But when I took them out for their first spin, I had no regrets.

STRUCTURE

Skora_CoresThe Core is constructed of a Goatskin leather upper and an injection blown rubber sole. Because of this composition, and its lack of cushioning, the shoe can allegedly sustain 1000+ miles, compared to the measly 300-500 mile lifespan of typical running shoes. It is zero-drop (no heel-toe differential) and has an 11-mm stack height, making for a truly minimalist ride. Like all of SKORA’s aesthetically pleasing models, the Core comes in a range of color options, including my chosen charcoal / cyan / purple combo. You can find all of the other juicy details in SKORA’s product description.

FIT

When SKORA says they fit true to size, believe them. I didn’t, and it took three orders (which they gladly exchanged) to finally find my correct size. For reference, I usually wear an 8-8.5 (Women’s US) in everyday shoes, and a 9 in running shoes, and my SKORA size was an unambiguous 8. Once I finally settled on the right size, I discovered just how comfortable they are. Out of the box (which, by the way, is nearly as beautiful as the shoe) they almost molded to my feet. After a few more runs, they further softened and fit the foot like a glove. The toe box was comfortably roomy, although my feet are admittedly on the narrow side, so I can’t speak for those with a wider forefoot. The Core weighs in at a mere 6.7 ounces, but I might have guessed even less. Unlike many of the minimalist shoes I’ve tried, they make it easy to forget you’re in a shoe.

RIDE

The Core may be light and comfortable, but how does it perform? As a diehard barefooter, nothing will ever compare to my own two feet. But if you’re looking for a bit of protection from the elements while minimizing the bulk and interference from a standard shoe, the Core’s a great choice. When I first tried the Core I immediately noticed how engaged my feet were compared to the other minimalist shoes in which I had been running. I could feel my foot landing, rolling through the arch and toes, and could detect variations in ground surface that were blocked by other shoes. That said, they performed well on a range of surfaces, including some pretty rough trails.

Back when I was a shod runner, I so loved my Cores that I applied to be a SKORA ambassador. Since going full bare, I have only rarely worn my SKORAs, but this does not discredit my accolades for their shoes. From their philosophy of “running real” to their exceptional product quality to their fun social media, the company is one even a barefoot runner can stand behind. So, for those of you who do enjoy wearing a shoe, this one’s worth checking out.

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Blisters, bruises and other bumps along the barefoot road

Your average runner has much to consider before heading out for a run. Do you try to stay cool and dry in your moisture-wicking tank, or bundle up in a hat and gloves? What socks are best for preventing blisters? Have your shoes surpassed their mileage limit? How much water and fuel should you tote during your long run?

Running barefoot eliminates many of these concerns, as the fit, cost and lifespan of socks and shoes become irrelevant. But barefoot running carries its own unique set of considerations that the typically shod runner may not anticipate. Since ditching my shoes I’ve encountered several new challenges, some of which are easily addressed, while others I have yet to conquer. Below I discuss the issues with which I’ve most frequently struggled, along with whatever solutions (if any!) that I’ve discovered.

Terrain

The beauty of going bare lies in the rainbow of sensory input from the earth to the feet. But sometimes these sensations can verge on intense, especially to the novice runner. With time, the trained barefooter should be able to run lightly enough that even the roughest gravel doesn’t phase them … or so I’ve heard. But for the rest of us who are still growing, challenging terrain can be the greatest limiting factor to enjoyable running. When I first began running barefoot, I restricted myself to the smoothest concrete and paved surfaces, still my favorite terrain. As I’ve become more adventurous, I’ve discovered the pleasures and benefits of diverse surfaces, and now incorporate as many different types as possible into my runs.

Smooth, flat, hard surfaces permit greater stability in the ankles and other joints, and can be an excellent way to reinforce proper form. However, miles of concrete can rapidly tire the feet. Veteran barefooters will attest that rough gravel is ideal for learning how to run lightly and softly. Even the slightest friction between foot and ground will tear up the feet, encouraging you to “place” and “lift” the foot, rather than skid, shuffle or push off. Even if you despise gravel running as much as myself, there is absolutely truth behind these claims, and it can be highly beneficial to incorporate brief rough stretches into your runs. Perhaps the most fun terrain, as any child will readily tell you, is grass or soft dirt. Besides just feeling magnificent on the soles, the natural variability of the surface is a great tool to strengthen the feet and ankles, and train the body to rapidly adapt to uncertain terrain. However, all that instability can also fatigue the legs if you’re not well adapted. And while that soft green grass may look inviting, it’s also a great hiding spot for twigs, stones and bugs! I’ve had one too many carefree grassy sprints abruptly disrupted by bruises, thorns and bee stings.

Blisters, abrasions and callouses

I lump these issues together as they often share both common causes and common fixes. The first discovery a new barefooter will likely make is the pain of blisters on the soles of the feet. Over my first couple weeks of running barefoot, my feet developed multiple small blisters on my toes and balls of my feet. As blisters are a direct result of friction, their location can inform about what you’re doing wrong, and help to easily correct your form. Blisters on your big toe? You might be gripping or pushing off aggressively during foot lift. As you self-correct, the blisters will quickly disappear. In fact, I can’t even recall my last blister. That said, I do still struggle with mild abrasions and callouses, both on the ball of my left foot, which too reflect improper form. Gait analysis confirmed that reduced mobility in this foot causes mild sheering at foot contact. Clearly, I still have work to do.

First Aid

photo credit @reasra

The best treatment for these form-related skin problems is, of course, to identify the problem and correct it! In fact, this is the only sustainable solution. That said, there are a few tricks to help you deal with – and dare I say, keep running through – these issues. Obviously, keep any open blisters or abrasions clean and protected. I’ve also found that applying vitamin E oil, or using finger and toe blister Bandaids, can expedite skin healing. For callouses, moisten the skin and then carefully file down the callous (don’t break the skin!) using a nail file. If you need to run with such an “injury”, a bandaid won’t last a quarter mile. However, covering the bandaid with a layer or two of strong athletic tape works wonders (I love leucotape). Be sure to to include the bandaid over the wound, to avoid irritation from direct contact with the tape adhesive. Using this application, the tape has remained intact for me over distances up to half marathons. I’ve had limited success with liquid bandages and super glue for short runs, but find that they wear off much faster than tape.

Bruises

Unless you run exclusively on treadmills or tracks, bruises – from rocks, acorns, uneven sidewalk, you name it – will be unavoidable. Usually, these are pretty benign. I often get them on my metatarsal heads or heel, and can easily run through them without pain. Gentle massage can help initially, and mild bruises typically clear up within 24 hours. However, in rare situations, a severe bruise can lead to more debilitating trauma. Just a few weeks ago, I trod on a rock at mile 2 of a 14-miler. I finished the run, only to notice the dull bruise after finishing (endorphins are both miraculous and dangerous!). I’ve been suffering intermittent burning, aching and numbness in that heel ever since, which I only just recently connected to that bone bruise sustained weeks ago. Oddly, I’ve been able to continue easy running, as it’s most aggravated by walking or downhill running. There’s not much one can do to treat a bone bruise, besides wait the natural course of healing, although I’ve found some mild relief from taping and cold/hot contrast water therapy to flush out the inflammation.

Cuts

“Don’t you cut yourself on broken glass?” asks everyone, all the time. I have yet to discover this planet laden with broken glass which shod runners apparently inhabit. However, if you’re running through a rough part town, a construction zone, or the Las Vegas strip (as I just recently attempted!), you just might encounter some glass. While this may be the greatest fear of many new barefooters, it actually poses much less risk than imagined. The skin rapidly adapts to barefooting by thickening, becoming remarkably resilient. I have indeed stepped on broken glass – probably way more often than I’m even aware – but have only been cut once. This, due to my own stupidity. I jumped full force into a deep puddle, only to discover a shattered bottle lurking within. The sole of my foot was covered in shards of glass, but only one managed a tiny puncture. I removed it, cleaned it, and was out running the next day. So runner, fear not the broken glass.

As I’m still admittedly a barefoot noob, there’s certainly much more I have yet to learn. So please, share your thoughts! What are your favorite ways of dealing with rough terrain, blisters, bruises and cuts? What other challenges have you encountered in your barefoot journey that I may soon discover?

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A BOLD signal in the hippocampus ambiguous

When you see a red blob on an fMRI activity map, what do you think? We all know fMRI doesn’t directly measure neural activity, yet an increased BOLD (blood oxygen level dependent) response is commonly used as a proxy for elevated “brain activity”. This interpretation is, in fact, strongly supported by studies identifying a relationship between the BOLD response and underlying neural activity. In particular, this signal correlates most strongly with the LFP (local field potential), suggesting that synaptic potentials – rather than spiking – primarily drive the BOLD signal 1.

But what about those blue blobs on that brain map? What exactly does a negative BOLD response represent? Do BOLD signal increases and decreases respectively represent neural activation and deactivation, as we often presume? Neuroscientists know the story isn’t that simple, yet still, we often construct our interpretations according to such idyllic principles.

fMRI 101

BOLD

In fMRI 101 we learned that the BOLD response results from changes in the relative amounts of oxygenated and deoxygenated hemoglobin, which – because of their distinct magnetic properties – are respectively associated with BOLD signal increases and decreases. When a brain region becomes active and requires energy, oxygen metabolism (CMRO2) increases, reducing blood oxygenation levels. A coincident increase in cerebral blood flow (CBF) partially counteracts this by delivering more oxygenated blood to the area. Since the BOLD signal increases with higher blood oxygenation, the direction of the BOLD response depends on the relative change in CBF and CMRO2. Since the increase in oxygenated blood flow typically exceeds that of oxygen metabolism, elevated neural activity (usually) leads to a positive BOLD response. So if a positive fMRI activation reflects increased blood blow and metabolism, negative activity should reflect the opposite … right?

Hippocampus ambiguous

One oft-overlooked feature of this mechanism is that the coupling between blood flow and metabolism varies across brain regions. Across the cortex, the coupling ratio between CBF and CMRO2 is heterogeneous but generally high, on the order of 2 to 4.5 2,3, generating a reliably positive BOLD signal with activation. But recent studies have shown that other regions have lower coupling ratios. Of particular concern is the hippocampus, with an estimated coupling ratio of 1.7 4. One possible reason for this discrepancy is the remarkably poor vascular supply to the hippocampus compared to the surrounding cortex 5. Thus, hippocampal activation would result in a notably reduced BOLD response compared to a cortical activation. As this CBF:CMRO2 coupling ratio flirts dangerously with unity, it raises concern that in certain situations it might dip to or below one, resulting in no change, or even a negative BOLD response, following neural activation. Indeed, upon stimulating neural activity (by inducing seizures) in rats, researchers observed a positive BOLD signal in the cortex, but a negative signal in the hippocampus 6.

What’s a hippocampal imager to do?

So what does all this mean for us foolish – I mean, unfortunate – cognitive neuroscientists using fMRI to study the hippocampus? For one, we face vastly greater challenges to interpreting our data than our lucky cortical colleagues. When the hippocampus activates, we can be relatively confident that blood flow and metabolism (and presumably, underlying neural activity) are concurrently elevated. But a deactivated hippocampus is an ambiguous hippocampus. A negative BOLD response could theoretically indicate an underlying decrease or increase in both or either parameters. Let’s explore three alternative scenarios which could theoretically engender a negative hippocampal BOLD signal.

1. ↓ CBF, ↓ CMRO2. The most intuitive explanation is that neural activity declines, reducing both blood flow and oxygen metabolism within the region. This scenario is certainly feasible if the hippocampus maintains a certain level of tonic activity and a given condition actively suppresses it below baseline.

2.  CBF, = CMRO2. Since the ratio of CBF to CMRO2 is the key determinant of the BOLD response, a change in oxygen metabolism is not requisite for a negative BOLD signal if blood flow alone declines. Such is the premise for the “vascular steal” hypothesis, which posits that blood is diverted from less critical regions to those directly involved in the task at hand, regardless of any change in oxygen consumption.

3.  CBF,  CMRO2. While the former two scenarios imply reduced hippocampal recruitment, either metabolic or vascular, a final scenario entails the opposite: elevated blood flow and metabolism drive the negative BOLD. Because of the hippocampus’ problematic coupling ratio, if the metabolic increase exceeds the blood flow increase, this manifests as a negative response.

Alternative interpretations

To disambiguate these alternatives, we must think outside the blob and interpret our effects in light of integrated electrophysiology, lesion and cognitive psychology findings. Two examples from recent fMRI studies illustrate the aforementioned challenges as well as how alternative explanations best account for a task-induced hippocampal deactivation.

First (shameless self-promotion alert!), during effortful memory retrieval, we consistently observe a negative hippocampal response 7-9. What might this signal represent? Given that the hippocampus is critically involved in encoding new memories 10, it’s possible that it remains continuously “online”, storing features of our ongoing experience into memory. Now, when one engages in a difficult mental task, such as trying to recall a weak memory, attention is diverted away from encoding irrelevant background information towards the target task. Scenario one would nicely account for this observation, as hippocampal neural activity dips below its baseline level and generates a negative BOLD. Considering that this negative response correlates with task difficulty (indexed by either response times or memory strength) and impaired encoding of the background environment, this seems like the most logical scenario. For now, that’s our story and we’re sticking with it (but please get in touch if you have other ideas!)

Yet in other situations, negative hippocampal responses have been observed during conditions in which, based on lesion and electrophysiological studies, one might expect the hippocampus to activate. For instance, a recent study observed hippocampal deactivation during landmark-based spatial memory retrieval 11. In this case, as the authors propose, the task-induced deactivation just might reflect neural activation.

Of course, we can’t simply choose a preferred explanation at whim that best supports our hypothesis. Au contraire, carefully considering the complicated nature of the hippocampal BOLD response might help expand our too-often blob-centric minds, and set a framework from some pretty awesome multi-modal hypothesis testing. Science isn’t supposed to be easy, but it can still be fun. Now, who else is eager to go crazy with some hippocampal calibrated fMRI and depth recordings?

References

1. Logothetis NK & Wandell BA. 2004. Interpreting the BOLD signal. Annu Rev Physiol 66:735-69.
2. Hoge RD et al. 1999. Linear coupling between cerebral blood flow and oxygen consumption in activated human cortex. Proc Natl Acad Sci U S A 96:9403-8.
3. Leontiev O et al. 2007. CBF/CMRO2 coupling measured with calibrated BOLD fMRI: sources of bias. Neuroimage. 36:1110-22.
4. Restom K et al. 2008. Calibrated fMRI in the medial temporal lobe during a memory-encoding task. Neuroimage. 40:1495-1502.
5. Borowsky IW & Collins RC. 1989. Metabolic anatomy of brain: a comparison of regional capillary density, glucose metabolism, and enzyme activities. J Comp Neurol. 288:401-13.
6. Schridde U et al. 2008. Negative BOLD with large increases in neuronal activity. Cereb Cortex. 18:1814-27.
7. Reas ET & Brewer JB. 2013a. Effortful retrieval reduces hippocampal activity and impairs incidental encoding. Hippocampus. 23:367-79.
8. Reas ET & Brewer JB. 2013b. Imbalance of incidental encoding across tasks: An explanation for non-memory-related hippocampal activations? J Exp Psych-Gen. 142:1171-9.
9. Reas ET et al. 2011. Search-related suppression of hippocampus and default network activity during associative memory retrieval. Front Hum Neurosci. 5:112.
10. Squire LR et al. 2004. The medial temporal lobe. Annu Rev Neurosci. 27:279-306.
11. Nilsson J et al. 2013. Negative BOLD response in the hippocampus during short-term spatial memory retrieval. J Cogn Neurosci. 25:1358-71.

ResearchBlogging.org
Reas ET, & Brewer JB (2013). Imbalance of incidental encoding across tasks: An explanation for non-memory-related hippocampal activations? Journal of experimental psychology. General, 142 (4), 1171-9 PMID: 23773160

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When barefoot novelty becomes a bare necessity

When I began running barefoot over a year ago, each barefoot run was a thrill. My feet experienced a world of exciting new sensations, I was running smoother and lighter than ever before, and running was simply fun! Over the ensuing several months, some of novelty, but none of the pleasure, wore off. My strength increased and I was able to run about half of my mileage barefoot. After following this system for some time, a distinct trend appeared. I deeply looked forward to those barefoot runs and approached them fearlessly, confident – no, certain – I would feel great. Coincidentally, a subtle dread for my shod runs began to grow. When I laced up my shoes, I could sometimes squeak out a good run, but just as often would slog through, tired, sloppy and achy. I hesitated to give up my shoes for fear of reducing my mileage, but began to resent those miserable junk miles. Finally, I became fed up with the frustration and – just over two months ago – took off my shoes for good. I had reached a turning point where I was no longer running barefoot just for fun, but because I found myself unable to run shod without significant discomfort. Bare feet had become a bare necessity.

The switch did not come without its sacrifices, however. Given that I was still adjusting to the unique demands of barefoot running, I had to cut my weekly mileage in half. This is no easy feat for a running junkie. Yet the patience required to start from scratch, in essence relearning to run, has proven beyond worth the challenge. I’ve learned more about proper biomechanics, my body’s strengths and weaknesses, and the delicate relationship between form and function, over the past ten weeks than over my entire 17 years of running.

Shod running forces one to perceive their form as if through a frosted window. In contrast, barefoot running allows you to perceive it in high resolution, as if through a microscope. Any structural imbalance or mechanical error is immediately apparent, as your feet afford the most exquisite and accurate sensory feedback. This feature builds the framework for a foolproof system to rapidly correct and optimize one’s running form. A few examples from my own training adaptations illustrate these benefits.

Overstriding > ankle pain

Slight overstriding on my right leg contributed to ankle pain. (Gait analysis courtesy Jennifer Reiner, DC)

Slight overstriding on my right leg contributed to ankle pain. (Gait analysis courtesy Jennifer Reiner, DC)

A major impetus for going bare was perpetual instability and strain in my ankles. I felt chronic fatigue in my posterior tibialis, Achilles and peroneal tendon, before and during the first few weeks of my switch. Playing with my form, I noted that the strain was alleviated when I landed with my feet under – not in front of – my center of mass. I had been … (gasp!) overstriding. It’s quite likely I’ve been doing so for many years, probably contributing to prior injuries, but it only became apparent barefoot. It’s not only visibly obvious, but also audibly detectable, as I hear a distinct slapping sound when my form gets sloppy and I return to my overstriding tendencies.

Heel-striking > shin stress

As my ankle issues resolved, the stress moved up my lateral shins and I acquired mild symptoms of anterior compartment syndrome. A bit of research suggested that shin pain can result from heel-striking, which can easily be resolved by adopting a forefoot strike. Within just a few days of consciously landing forward on the ball of my foot, my shin pain had cleared up. Intriguingly, though I was running barefoot and (mostly) avoiding overstriding, which are often associated with forefoot striking, I had still retained a subtle rearfoot strike.

Forefoot striking > forefoot ache

No gait change comes without some cost. With my forefoot shift, I experienced some moderate tightness and bruised sensations under the ball of the foot. Cautious not to overstress my feet with these new changes, I’ve been focusing on modifying my form according to my body’s current needs. If I feel excessive tension in my shins, I’ll emphasize a forefoot strike; when the forefoot acts up, I relax back into a rearfoot strike. When barefoot, these rapid shifts – and their immediate benefits – are easy and effective.

Foot immobility > abrasions

Immobility in my left big toe joint caused ankle rotation and shearing.

Immobility in my left big toe joint caused ankle rotation and shearing.

While I haven’t suffered a blister or cut in many, many months, my left ball of foot (under the base of the big toe) tends to get disproportionately tender compared to the left. With my increasing mileage, this had become increasingly problematic, and recently became coupled with a growing callous under the neighboring second metatarsal. This was a clear sign, that would otherwise have been masked by shoes, that there are still some lingering mechanical issues. My insightful physical therapist, who noted immobility in my big toe, prescribed some exercises to increase flexibility and mobility in the big toe joint. After only a few days, I’ve already noticed much less abrasive shearing. Yet again, another simple fix.

Personally, this recent barefoot journey has been immensely successful, enabling me to retrain myself to run well and consequently resolve chronic injuries, all the while restoring hope that most running problems can be overcome by simple training modifications. Yet despite the fact that I had to take off my shoes to discover this, I’m not convinced that it’s purely an issue of footwear. Rather, successful running fundamentally comes from proper form. Some can achieve this regardless of footwear. Others, such as myself, will need more help from tools that encourage mechanical corrections. For me, one of simplest, not to mention liberating, ways to do so has been to break down the barriers between body and environment and let my feet directly sense and respond to its rich surroundings.

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Why sweeping generalizations aren’t best for most runners

Barefoot is bad!Every movement has a counter-movement. Barefoot running is no exception, having recently been met with its share of backlash from skeptics and naysayers. While open discussion and objective critique are healthy responses to any fad, a recently published article – Why barefoot isn’t best for most runners – went a step too far with its distorted claims, never mind snarky attitude, to leave untouched.

Let’s walk through (shod or bare, I don’t care) some of the article’s most shining moments.

Seasoned members of staff can normally categorise runners at first glance … people looking for Vibrams are usually already wearing Vibrams, which is something of a giveaway. They also tend to look disgusted when you tell them that the shop doesn’t stock them, as though the sale of more traditional running shoes was some sort of conspiracy.

I’d like to start by commending the author for admitting that he and the other shoe store employees outright judge their customers based solely on appearance. I’ll be sure to avoid your store. On the other hand, they’ve sparked my curiosity with their mind-reading powers that enable them to detect paranoia over shoe conspiracy from just a facial expression. Of course, every shop should be free to stock only their chosen products. But if they decide to exclude an entire shoe category, they should be willing to accept that some customers will be disappointed by the limited options.

The problem is that we also didn’t evolve to run on roads. Or if we did, the evolutionary process that built the roads was the same one that designed the cushioned running shoe.

We can argue the evolution argument until we’re blue in the face, but for now there is no clear answer. Yes, it’s true neither modern shoes nor concrete existed until relatively recently. Sure, our bodies haven’t yet perfectly adapted to either. However, we also certainly haven’t evolved to remain sedentary 60% of our waking hours, rely on machines for transportation, stare at electronic screens or consume highly processed, packaged foods. But we’re an innovative and adaptable species and are surviving fine (for now) in the face of these rapid changes. The more immediate question, rather than how our ancestors ran, is what’s best for the modern runner. There’s no evidence (correct me if you can find some!) that 1) roads are worse for runners than dirt or grass, or 2) cushioned running shoes actually protect against the alleged “dangers” of modern running surfaces. Researchers have just begun to study the relationship between footwear and injuries, and the jury is still out. Thus far, there has been a lot of conflicting evidence, depending on the particular study methods and population, suggesting that the answer isn’t as simple as modeling our running after Grok.

When people were following the “Paleo diet” from necessity rather than whimsy, their life expectancy was probably in the 20s, if they were lucky.

How is the paleo diet relevant? The author appears to be critiquing barefoot running by debunking a completely independent lifestyle choice. I’m unaware of any correlation between footwear preference and dietary habits. In fact, I know several barefoot runners (@caitymccardell, @KenBobSaxton, myself) who are vegetarian or vegan, which one could argue is the antithesis of paleo.

For those who are planning to spend £100 or more on barefoot shoes to emulate Bannister, it should be noted that you can buy plimsolls for £4 on eBay.

Agreed. Spending $100+ on shoes is absurd. All the more reason to go barefoot. It’s free.

When I see people out running in barefoot shoes, they never look as if they’re having a particularly good time … Most people who use barefoot shoes admit to having to run less because of the pressure on their joints. For someone who enjoys running long distances and the feeling of having a bit of a spring in their step, the choice of barefoot shoes is therefore a bit baffling.

Sure, maybe those runners are miserable. Sure, maybe it’s because of their shoes, or maybe it’s because of the judgmental grimace on a certain gawker’s face. We’ll never know. But rather than speculate about another runner’s experience, why not just ask them? As one who actually runs barefoot and knows other barefoot runners, I can attest that my barefoot runs are often far more freeing and exhilarating than my shod runs. The spring in our step is precisely why we prefer to go bare. When running barefoot you literally feel that spring, conferred by the awakened, elastic arch and tendons of the foot. As for the relationship between barefoot running and joint pain (or lack thereof), look no further than some actual research.

A recent study published in Medicine and Science in Sports and Exercise, however, supports what I’ve learned from talking to customers who have experimented with barefoot shoes … Half of them (study participants) began running in Vibram FiveFingers shoes gradually, following the guidelines set out on Vibram’s website, while the control group continued to run as normal. After 10 weeks, the control group had remained the same, but 10 out of the 19 runners who had transitioned to Vibram FiveFingers showed raised levels of bone marrow edema (a buildup of fluid similar to bruising) in their feet. The worry is that the barefoot running trend is a fairly recent one, and most of the study’s runners with raised levels of bone marrow edema wouldn’t actually have noticed an injury yet – many of the injuries caused by barefoot shoes may be lurking just around the corner.

This – the only piece of solid evidence presented – is once again misconstrued to support the “barefoot is bad” argument. Just a few of the flaws to this interpretation, which have been thoroughly detailed elsewhere, include:

1. The study used a transition protocol that was far more aggressive than experts recommend (Vibram has since changed their guidelines).

2. Many of the subjects didn’t even follow protocol, increasing their mileage more rapidly than advised.

3. Some edema can be part of a healthy response that leads to bone strengthening, indicating that the bone is appropriately adapting to a new stressor. The MRIs could not distinguish between normal edema and signs of injury.

Most running shops will now offer gait analysis, with the aim of selecting the type of shoes most suitable to the individual’s running style, body type and the surface they are planning to run on.

Note the term “aim”. Regardless of the intention, such recommendations are meaningless if their underlying assumptions are flawed (see herehere and here for why).

One final editorial note: By definition, barefoot running requires bare feet. Any individual’s beef with minimalist shoes bears little weight on the “goodness” or “badness” of barefoot running.

Rather than make a convincing argument for the author’s footwear preference, commentaries like this exemplify the absurdity of the growing barefoot versus shod derision. Get ready to defend yourselves, runners. Next up is the great headband versus hat debate!

A special shout-out to @akiraoc for bringing this article to my attention!

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To the depressed brain, it’s all the same

If you’re among the 8-12% of the population who will suffer from depression during their lifetime 1, you’re painfully aware of its debilitating symptoms – hopelessness, indifference, emptiness. While it’s clear how depression radically affects one’s emotional state, emerging research is showing that the reaches of depression extend far beyond our mood. In fact, depression can disrupt basic cognitive functions, with a particularly devastating impact on memory 2. However, at present we don’t fully understand the brain processes that give rise to depression, never mind how they contribute to the disorder’s associated cognitive impairments. A recent study published by neuroscientists at Brigham Young University suggests that depression is associated with problems with a particular memory operation known as pattern separation.

Can you tell Buddy from Fuzzy? Thank your hippocampus

Yassa & Stark, 2011

Imagine your two neighbors both have black labs, one slightly smaller and fuzzier than the other. A part of your brain called the hippocampus registers the subtle differences between the dogs and creates distinct representations of the two. You recognize Buddy and Fuzzy as unique because your brain effectively pattern separated them, forming distinct memories of each. It is this process that the researchers speculated might go awry in depression.

Earlier studies have shown that depressed individuals have smaller 4 and less active 5 hippocampi during memory formation than non-depressed people. Although pattern separation is not the only memory function mediated by the hippocampus, depression symptoms can manifest as a tendency to overgeneralize, the opposite of pattern separating. The authors therefore wondered whether diminished pattern separation might lie at the heart of depression-related memory problems.

Pattern separation to the test

To test their hypothesis, they had 98 adults perform a memory test that demanded pattern separation, and complete questionnaires evaluating depression, anxiety, sleep and exercise. Participants with higher depression scores performed significantly worse on the memory test than those with low depression scores, consistent with past studies. Critically, the depressed group had particular difficulty distinguishing a new item they had never seen from a similar one they previously encountered, indicating that they were pattern separating poorly. Furthermore, they found that the higher an individual’s depression score, the worse their pattern separation performance. Importantly, there was no correlation between pattern separation and anxiety, sleep or exercise, suggesting that the memory deficit was specifically related to depression, and not confounded by other associated factors.

But why don’t depressed brains pattern separate?

This study goes a step beyond prior work to identify what specific memory function is compromised in depression. Although the study didn’t examine the neurobiological processes underlying the pattern separation deficit, its findings provide a clear direction for further research.

Past studies suggest that newly born neurons in the hippocampus, produced by neurogenesis, contribute to pattern separation 6 and an association between reduced neurogenesis and “depression” in animals 7. If there are links between pattern separation and neurogenesis, neurogenesis and depression, and now depression and pattern separation, might a causal relationship exist among the three? The authors propose that depression could inhibit neurogenesis, thus impairing pattern separation. Alternatively, reduced neurogenesis (which can be regulated by numerous factors such as exercise, drugs or a rich environment) may induce depressive symptoms. Given the invasive nature of currently available methods to study neurogenesis, examining the effect of neurogenesis on human depression and memory is no easy feat (although some innovative folks recently devised a clever way to document human neurogenesis).

Can poor pattern separation make you sad?

But this study raises another, possibly more accessible, question over how pattern separation is involved in emotional regulation. Whereas the average person might readily discriminate between similar objects or experiences, someone suffering from depression would emphasize the similarities. A pathological tendency to excessively generalize could account for an unwarranted negative outlook.

“That last party was so awkward, I should just stop trying to be social.”

“I was bad at my last job, so I’ll certainly fail at any job I try”.

We’ll have to wait on future research to fully understand whether poor pattern separation contributes to a negative outlook, as well as the brain basis of memory impairments in depression. In the meantime, take a moment to notice the subtle differences around you – it just might make you happy.

References

1. Andrade L et al. 2003. The epidemiology of major depressive episodes: results from the International Consortium of Psychiatric Epidemiology (ICPE) Surveys. Int J Methods Psychiatr Res. 12:3-21.
2. Zakzanis KK et al. 1998. On the nature and pattern of neurocognitive function in major depressive disorder. Neuropsychiatry Neuropsychol Behav Neurol. 11:111-9.
3. Shelton DJ & Kirwan CB. 2013. A possible negative influence of depression on the ability to overcome memory interference. Behav Brain Research.
4. Videbech P & Ravnkilde B. 2004. Hippocampal volume and depression: A meta-analysis of MRI studies. Am J Psychiatry. 161:1957-66.
5. Fairhall SL et al. 2010. Memory related dysregulation of hippocampal function in major depressive disorder. Biol Psychol. 85:499-503.
6. Clelland CD et al. 2009. A functional role for adult hippocampal neurogenesis in spatial pattern separation. Science. 325:210-3.
7. Petrik D et al. 2012. The neurogenesis hypothesis of affective and anxiety disorders: are we mistaking the scaffolding for the building? Neuropharmacology. 62:21-34.

ResearchBlogging.org
Shelton DJ & Kirwan CB (2013). A possible negative influence of depression on the ability to overcome memory interference Behavioral Brain Research DOI: 10.1016/j.bbr.2013.08.016

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