Sunday, December 18, 2011

Should you think about running in college?

As high school cross country finishes up, many juniors and seniors are turning their attention to college applications.  Some of the more serious runners are probably thinking about running competitively in college.  In talking to high schoolers and their parents, I find there are often a lot of misconceptions about what college distance running is like in the NCAA.  I just finished four years of competing in cross country and track at a Division III school, and I have several friends who are Division I and Division II athletes, so I'm in a good position to comment on college athletics as they are right now.  In this post, I'll try to key you in on what running in college is all about, the differences between the various divisions, and whether you ought to think about running in college yourself.

This time, we don't need a crash course in any kind of -ology, so we'll jump right in.  First off, there's a few things you should know.  College running is different in many respects to high school running, mostly because the bar is set higher.  In college, running is a year-round sport.  Long distance specialists compete in cross country in the fall, indoor track in the winter, and outdoor track in the spring.  Summer is the only real break from competition, and it's devoted to building base strength for cross country.  And even 800m specialists are usually expected to train for and compete in cross country in the fall.   The race distances are also further—most men's races are 8km (5mi) and most women's races are 6km (3.5mi).  At the Division I and Division II level, the regional and national championship races for men are 10km.  So when I say "running in college" I mean cross country and track.   Relatively few programs allow distance runner to compete exclusively in track or cross country, and rightfully so—those who do tend not to improve very much, if at all.

The Divisions
College athletics is dominated by the NCAA, which is itself divided up into three divisions (aptly named Division I, Division II, and Division III—or DI, DII, and DIII for short).  I'll go over the defining characteristics of each division and give you a "snapshot" of a few "typical" runners in that division.  Please note that these "snapshots" are not meant to stereotype the division, nor are they based on real people.  I'm writing them simply to give you a picture of the range of what is typical for each division—your own experience may be totally different.

Wednesday, November 9, 2011

Ferritin, hemoglobin, and iron deficiency in distance runners

Attention readers! This article is officially outdated! I've released a new and updated article on iron deficiency in runners that is much more complete.  

When a distance runner begins to struggle early on in workouts and races, suffers from excessive fatigue, and often feels there's no "gas in the tank" in the final half of hard efforts, iron deficiency anemia should be one of the first problems to rule out.  Having adequate iron stores is essential to any endurance sport, as your ability to run (or swim, or row, or ski, etc.) is predicated by your ability to get oxygen to your muscles, which is accomplished by your red blood cells.  Iron deficiency anemia impedes the body's ability to manufacture red blood cells, and causes a marked decrease in performance.  Red blood cells are comprised almost entirely of a protein called hemoglobin, and at the core of that protein is an iron atom.  Oxygen binds to hemoglobin by binding with the iron atom at its center.  And hence, if there isn't enough iron available to make red blood cells, there aren't enough red blood cells to carry oxygen to the muscles.  And no oxygen means no high-level performance.  Today I'm going to go in-depth on the issue of iron and iron-deficiency anemia, because it is often misunderstood, even within the medical profession.  Technically, anemia only refers to low hemoglobin, but as we'll soon see, it's possible (and very common) to have low iron stores but not have low hemoglobin.  There is mounting evidence that even iron deficiency without anemia is harmful to endurance performance.  We're about to cover all of this in depth.

Introduction: the biology of red blood cells

As usual, though, we need a crash-course instructional first.  This time, in blood physiology.  As mentioned above, red blood cells are the oxygen-carriers of the bloodstream and are comprised mostly of hemoglobin, which in turn contains iron.  Any old red blood cell circulating in the blood stream "lives" about three or four months before it's resorbed or destroyed.  Your body always tries to keep enough red blood cells in reserve to meet the demands you put on it.  So, when you go for several sessions of hard training, your body responds in turn by synthesizing more red blood cells.  They are made in bone marrow, and their synthesis is stimulated by the hormone EPO.  More red blood cells (generally) means better performance.  Illegal dopers boost their red blood cell levels by injecting recombinant EPO; Alberto Salazar's runners boost their red blood cell levels by sleeping in altitude tents, and the Kenyans (unwittingly) boost their red blood cell levels by living and training at high altitude.

Saturday, October 15, 2011

When threshold training isn't threshold training

Most runners are familiar with threshold training.  It's been the chief contribution to real-world training from the field of exercise physiology.  In principle, it's simple: there is a "tipping point," physiologically speaking, when incremental increases in speed become progressively more difficult.  Training right at this sweet spot should raise the threshold, moving that "tipping point" to a faster pace.  But there is not a unanimous understanding of what exactly "threshold training" is, or about how to properly apply it to training.  Threshold training is one of the topics du jour in any number of running magazines and websites, so I don't mean to unnecessarily repeat here what's been done to death elsewhere.  No, today's post is about my own peculiar interpretation of threshold training, and the consequences thereof.  In short, I think the real value of threshold training is that it involves practicing running fast and efficiently in a state of low metabolic stress.  I'll cover exactly what all that means shortly, but the consequences of this are surprising: "threshold" does not always have to correspond to one specific pace.  This opens up a lot of possibilities in training.


First, though, a crash course in exercise physiology and a thought experiment to illustrate: In any athletic endeavor, almost all of your energy is derived from aerobic and anaerobic respiration.  You're probably familiar with these processes: both turn sugars into energy, either by burning them with oxygen (aerobic respiration) or without oxygen (anaerobic respiration).  There are no problems with sustaining aerobic respiration for a long time, but anaerobic respiration is a different story.  Metabolic byproducts like lactate and protons (H+) build up during anaerobic respiration, and eventually cause fatigue.  "Lactic acid buildup" is commonly blamed for the fatigue associated with anaerobic respiration, but this is technically a misnomer.  During an anaerobic effort, blood pH drops (indicating rising acidity) and blood lactate levels climb, but it turns out that these two are mostly independent processes, not the result of "lactic acid."  It seems that the acidity is the chief cause of fatigue, not the lactate. Regardless, except for a narrow window of time where the body's buffering system dampens the buildup of acidity but lactate levels rise (this is called the isocapnic buffering zone), lactate levels and blood pH mirror each other very closely.  In general, it's easier to measure blood lactate, so lactate levels are used as a proxy for how heavily an athlete is relying on anaerobic respiration.  In any case, the body only increases its baseline rate of anaerobic respiration when the energetic demands of an athletic effort exceed the body's aerobic capacity. 

Now, our thought experiment: let's say we take Sam, a hypothetical runner, and put him on a treadmill.  Sam is a reasonably fit runner who has recently set a 3200m PR of 10:00 and a (track) 5k PR of 16:05.  To measure his blood lactate levels, we insert a probe into a blood vessel.  The first thing we'll notice is that before we even start the treadmill, our lactate probe will show that there is a small amount of lactate circulating in Sam's blood, even at rest: about 1.0 millimoles of lactate per liter of blood, or mM for short (mM is just a measure of concentration).  This is because there's always some anaerobic respiration in your body, even at rest.  But there's more than enough oxygen circulating to "mop up" the metabolic byproducts, so the lactate level is stable.  So, we start up the treadmill.  Very slowly at first, say at 10min per mile pace.  Sam's lactate level will jump up a bit right away, perhaps to 1.5 mM, but it won't budge after that.  Even if we speed up the treadmill to 9min/mi, 8min/mi, or 7min/mi, his blood lactate level will move by 0.1 or 0.2 mM.  Furthermore, even if Sam runs on the treadmill for over an hour, his lactate level won't change.  That's because he's running at a steady state effort.  His body is getting all of the energy it needs from aerobic respiration.  

So we keep cranking up the speed on the treadmill, to 6:30 pace, then to 6:00 pace.  Sam's lactate level is probably 1.7 or 1.8 by now.  Just under 6min/mi, we'll see Sam's lactate level start to move up a bit more, reaching 2.0 mM for the first time.  If we stop changing the treadmill's speed, we won't see a change in lactate over time.  Sam is still at a steady state effort.  But if we increase the pace a little more, down to 5:50 or 5:45 pace, Sam will not be at a steady state anymore.  His blood lactate level will rise over time, even if we don't change the speed of the treadmill.  But at this pace, the increase in lactate concentration will be very slow.  Sam can probably sustain 5:50 or 5:45 pace for 80-90 minutes before having to stop due to exhaustion.  So we keep increasing the pace on the treadmill.  Sam's blood lactate will change a bit after each increase in pace.  Once we hit about 5:35, his blood lactate will be at about 4.0 mM.  If we continue to increase the pace, Sam's blood lactate level will start to jump more quickly with each change in pace.  Furthermore, the duration he could sustain a given pace before becoming exhausted will also drop sharply with each increase in pace.  Sam could maintain 5:35 pace for 50-60 minutes with a race-level effort.  But he could only maintain 5:25 pace for about half an hour.  And he could only maintain 5:15 pace for 17 or 18 minutes.  5:05 pace; perhaps 11 minutes.

So clearly there is something going on between 6:00 and 5:35 pace.  Whereas Sam could maintain 6:00 pace for well over two hours in a race situation, his ability to sustain paces for a long duration drops off significantly after 5:35 pace or so.  As you might guess, in this range is where Sam's aerobic system becomes insufficient to meet his energetic requirements.  As such, his anaerobic system needs to pitch in to help, resulting in higher blood lactate levels and an unstable metabolic situation.  Numerous physiological events occur in Sam's body between 6:00 and 5:35 pace, all of which have garnered a name and all of which vie for being called the "real" threshold.  At about 5:55 pace, Sam ceases to be at a metabolic steady state.  Any speed above this point will result in the gradual accumulation of lactate.  So some physiologists call this point the aerobic threshold.  Others think the most important event is when Sam's blood lactate levels cease to rise linearly and instead rise exponentially.  This happens at about 5:35 pace, and is often termed the anaerobic threshold.  Some physiologists are uncomfortable with the term "anaerobic" (since it implies that less oxygen is getting to muscles), so they term it the lactate threshold.  For others, even this isn't good enough: it has to be the onset of blood lactate accumulation (OBLA).  Even others prefer to measure the increase in ventilation, or breathing, and term the sharp increase the ventilatory threshold.  You can see how this has quickly gotten out of hand.

Wednesday, September 28, 2011

Preparing for championship races with Renato Canova

One of the wonders of the internet is its ability to connect people of very different backgrounds and geographic locations.  Because of the web, everybody can have access to information that would be otherwise unobtainable.  Today we're going to see a prime example of this.

Renato Canova is an Italian coach of considerable fame.  He worked with the Italian national team during the '90s and helped propel them to success on the world stage, and more recently, he has worked with elite Kenyan and Ethiopian runners.  His training has propelled his athletes to become some of the most successful in the world, and athletes under Canova's guidance have won multiple medals at many international track and road running championships.  Most recently, his athletes won four medals at the 2011 World Championships in Daegu, which concluded a few weeks ago.  Unlike many other coaches, Renato Canova's faith in his training methods is so strong that he willingly shares the training of his elite athletes with the general public.  The main avenue through which he does so is the infamous message boards.  Typically, he will post a month or two's worth of training for one athlete, for example in this thread on the training of Moses Mosop before the Boston Marathon, where Mosop finished second (and ran the second-fastest marathon of all time).  But after the 2011 World Championships, Renato Canova posted the schedules for the last month of training for all four of his track runners (as well as Abel Kirui, the marathoner who won the World Championship marathon).  In the following post, we'll examine and discuss the training in the last month or so of Canova's track athletes.  We'll take a look at Abel Kirui's marathon training at a future date. 

The athletes

The training schedules that follow were prepared by Renato Canova for Sylvia Kibet, Silas Kiplagat, Imane Merga, and Thomas Longosiwa, who all competed at the 2011 World Championships in Daegu, South Korea.  Sylvia Kibet is a Kenyan with a 14:31 5k PR; she won a silver medal in the 5000m at the world championships.  Silas Kiplagat of Kenya is one of the top 1500m runners in the world, with a PR of 3:29.  He won a silver medal as well.  Imane Merga is an Ethiopian with a 5k PR of 12:53 and a 10k PR of 26:48.  He competed in both events at Daegu, winning a bronze medal in the 10k and finishing 3rd in the 5k, though he was later disqualified for stepping on the infield.  Finally, Thomas Longosiwa is a Kenyan 5k runner with a PR of 12:51.  In the 5000m final in Daegu, he was running comfortably in the lead pack with less than two laps to go, but was tripped by another runner and fell.  He got up, worked his way back into the pack, but finished 7th (and was later moved up to 6th when Imane Merga was disqualified).  Despite his fall, he finished less than four seconds behind the winner, and many believe he would have contended for a medal had he not fallen.

The training philosophy

I have written about Renato Canova's training philosophy in the past.  You can read a 9-page pdf, titled Something New in Training, detailing the basic principles of his training program here.  Theory is very nice, but it is good to see what the training schedules actually look like in real life.  Further, when presented with the training schedule for only one athlete, it's hard to tell the reason for a particular workout.  The schedule might be adapted to the preferences or situation of the athlete in question.  But when you can examine schedules for multiple athletes all preparing for the same or similar events at the same competition, you really have the power to connect theory with practice.

Saturday, September 17, 2011

A guide to anatomical terms of location and movement for the runner


Don't you hate it when you can't find your "distal process on the medial tibial surface"? Or when your doctor tells you that a problem with your posterior tibial tendon is causing excessive foot inversion and possibly decreased knee flexion? Do you ever find you can't tell the difference between the anterior inferior iliac spine and the posterior superior iliac spine? Or just find yourself stumped when your coach tells you you're dorsiflexing your ankle too much? Well have no fear.  Today we're going to decode the mysterious language of anatomical terms of location.  It's a set of vocabulary that describes the orientation and movement of different parts of the human body.  You might wonder, "Why don't we just use 'front,' 'back,' 'inside,' 'outside,' 'up,' 'down,' etc.?" I used to wonder that too.  But I quickly found out that these everyday terms of location are too ambiguous and vague for precise medical use.  For example, do shin splints hurt on the "front" of the shin, or on the "inside"? Is the kneecap in "front" of the femur, fibula and tibia, or on "top" of them? Does turning your foot "in" involve rotating the whole foot or just rolling the ankle? Anatomical terms of location dispel these ambiguities.  Doctors, trainers, and others need to be able to clearly communicate exactly what area of the body they are talking about.

While doctors, trainers, and physical therapists are already well-versed in translating from "normal" speak to medical terms, it is also in your interest to learn them as well.  If your physical therapist mentions that you have some tightness in the medial head of your gastrocnemius, it'd do you well to know what he's talking about.  Additionally, when doing your own research on injuries, rehab, training drills, or biomechanics, you won't make it very far without a good understanding of these anatomical terms of location. Even in this blog, I try to do my best to translate medical mumbo-jumbo whenever possible, but often it's unavoidable.

So, without further introduction, we'll cover most of the terms that a runner will need to know.  I've omitted pretty much all terms having to do with the upper body, as they are mostly irrelevant to the runner, and as such, even I haven't bothered to learn them yet.  The upper spine, shoulders, and hands in particular can move in very complicated ways, making describing their anatomy a difficult feat.  If you've learned anatomical terms of location for other animals, do your best to forget them! For some strange reason, the terms used for a human do not mean the same thing for a fish, for example.  A shark has a "dorsal fin," but on a human, we'd probably call a similar structure in the same location a "posterior fin"!

Terms of location

Anatomical terms of location are relative to the center of the body.  It's best we introduce the planes of the body now, as most the other terms are relative to the centerlines of each of these three planes.  As illustrated in the picture to the left, the body can be bisected by three different planes (in the xy, yz, and xz directions).  The sagittal plane divides the left and right halves of the body.  The frontal or coronal plane divides the front and the back of the body.  The intersection of the sagittal and frontal planes creates the centerline of the body—it runs from the top of the head through the bottom of the pelvis and between the legs.  Finally, the transverse plane divides the upper and lower halves of the body.

Because the body is almost exactly symmetrical in the sagittal plane, the centerline of the body is used as a reference when describing the location and orientation of various parts of the body.  When learning these terms, it makes sense work from the center of the body out.

Sunday, September 11, 2011

Injury Series: Flat eccentric heel drops for insertional Achilles tendonitis


Back in August, we saw how a rehab program consisting of eccentric heel drops with a bent and straight knee reversed damage to the Achilles tendon by inducing collagen remodeling.  One thing I didn't make clear enough is that Alfredson's eccentric heel drop protocol, developed in 1998, was designed for midpoint Achilles tendonitis.  In most cases of Achilles injury, the tendon is damaged between 2 and 6 cm from the insertion point at the calcaneus (heel) bone.  But in a minority of cases, the tendon is damaged at the insertion point—right at the heel bone.  While it might seem like a trivial difference, these are actually parsed into two separate injuries.  While both are the result of damage to the collagen fibers, the surrounding tissue at the insertion of the Achilles tendon is very different from the tissue near the midpoint of the Achilles.

Insertional Achilles tendonitis is fairly easily differentiated from midpoint Achilles tendonitis based on where the pain is localized.  In the latter case, it is a point (as the name suggests) around the middle of the tendon, whereas in insertional Achilles tendonitis, the pain is, of course, at the insertion of the tendon.  But it can also radiate around the heel bone in general and even onto the sole of the foot.  In the early stages, it often feels like a throbbing bruise to the back of the heel.  The area where pain usually localizes after the initial inflammation dies down is highlighted above in red. There are a lot going on near the insertion of the Achilles—there's the retrocalcaneal bursa (a small sac of fluid that reduces friction on the Achilles), the plantar fascia, the Achilles itself, and the fat pad underneath the heel.  All of these can become irritated, and this contributes to the intractability common in chronic insertional Achilles tendonitis.

Though insertional Achilles tendonitis occurs in runners, it also occurs quite a bit in the general population, too.  This complicates studying it, because it's not clear whether you have insertional Achilles tendon issues from running.  Maybe you went too hard at the rec basketball league tournament, maybe you went on a hike with the wrong hiking pole, or maybe you're just getting old!

Treatment with eccentric exercise

Understandably, people first assumed that the eccentric heel drop protocol devised for the midpoint Achilles tendonitis would work just as well on insertional Achilles tendonitis; however, once researchers got around to investigating this, they found that, in contrast to the >80% return-to-activity rate seen in multiple studies for subjects with midpoint Achilles tendonitis, subjects with insertional Achilles tendonitis had a paltry 32% return-to-activity rate.  This problematic result probably stumped researchers for some time—the original study linking eccentric heel drops to good recovery prospects in midpoint Achilles tendonitis was published in 1998, but productive results for insertional Achilles tendonitis did not make it into the literature until 2008.  In the interim period, Alfredson and his coworkers discovered how very minute differences in exercise protocol can make a world of difference in injury rehab. As we covered last week, a 2004 pilot study showed that eccentric decline squats are a highly effective rehab exercise for patients with patellar tendonitis. The results, confirmed by a more thorough clinical trial a year later, showed that just a small change in protocol—doing an eccentric squat on a decline instead of on flat ground—had a significant effect on the patients' outcome.

Friday, September 9, 2011

Behind-the-scenes work

My apologies for not getting around to posting yet this week.  This is always a busy time of year.  If you've checked around though, you'll see that I've been doing some behind-the-scenes work.  There's an "about me" section if you're wondering who the heck I am, and a "contact me" form if you want to get in touch with me directly.  I've also added a page with a variety of possibly-useful links I've collected over the years.  That page is very much a work in progress, and I'm sorry about the mess!  I've also truncated each post that appears on the front page, so I don't overload your browser with dozens of images from all the posts in the past month.  There's a small "read more" link at the end of each article preview.

Finally, I've added tags to the bottom of each post.  This will get useful when the posts start piling up.  So you can search for all articles about injury, or the NCAA, or tendonitis.  Still haven't gotten around to proper citations...that might be a project for next week!  So that's all for now, but expect a (shorter) post in the next few days continuing the injury series.

Saturday, September 3, 2011

Eccentric decline squats, tendon remodeling, and patellar tendonitis

Note: Patellar tendonitis should not be confused with patellofemoral pain syndrome, or "runner's knee," a different injury in the kneecap area with a different ideal treatment protocol

Last time, we saw how an injury rehab protocol consisting of eccentric heel drops can remodel collagen in an injured Achilles tendon.    The intervention was impressive for two reasons: 1) its very high success rate (>80% in most studies) and 2) the fact that it worked even in runners who had been suffering from chronic Achilles tendonitis for several years.  Today we'll be looking at a similar program for another large and commonly-injured tendon in the body: the patellar tendon.

Many of the same caveats we saw with Achilles tendonitis apply to patellar tendonitis as well—it may not technically be an -itis in the classic sense of being an inflammatory problem, I'll still refer to the problem as "tendonitis," even though "tendonosis" or "tendinopathy" would be more proper.

Introduction and background

Like the Achilles, the patellar tendon is one of the largest and thickest tendons in the body.  It is essential in any movement involving the quadriceps and the knee, so practically all sports put significant strain on the tendon during the course of training and competition.  Injuries to the patellar tendon are sometimes inadvertently conflated with other knee injuries, especially patellofemoral pain syndrome (runner's knee).  The knee, although a simple joint compared to the ankle and hip, is nonetheless far more than a basic hinge.  Many different knee-related injuries can have similar symptoms, resulting in a diagnostic nightmare for sports orthopedists.  Often, knee injuries in runners are chalked up to the utterly-useless diagnosis of "knee pain."  In truth, many factors play into knee overuse injuries: muscle strength, biomechanics, scar tissue from previous injuries, and of course training habits.  The rehab protocol we're going to discuss here is designed specifically for injuries to the patellar tendon, not knee dysfunction in general.

Injuries to the patellar tendon, while common among runners, are most often seen in jumping sports.  Basketball and volleyball players, as well as high, long, and triple-jumpers, are the usual victims of patellar tendonitis because of the frequent high-impact landings inherent in those sports.  As such, most studies on patellar tendonitis use volleyball or basketball players, not runners.  The injury itself is characterized by a sharp or dull pain in the tendon below the kneecap, and the area will often be tender to the touch.  It gets worse during activity, including running (especially downhill), jumping, or even simply ascending and descending stairs.  It is often a stubborn injury, and can affect daily life outside of sport.

Given the success and wide adoption of Alfredson's eccentric heel drop protocol for chronic Achilles tendonitis, many researchers (Alfredson included) were eager to extend the same idea to other chronically injured tendons.  The patellar tendon, given its similarities to the Achilles, was the most logical next step.


The patellar tendon, illustrated at left, technically isn't even a tendon in the purest sense.  It's a ligament.  Tendons, by definition, connect muscle to bone, and ligaments connect bone to bone.  The patellar tendon connects the patella (kneecap) to a bump on the shin called the tibial tuberosity.  The patella itself is connected to the quadriceps muscles via the quadriceps tendon.  In most respects the patellar tendon can be pictured as a continuation of the quadriceps tendon, which is why it's still referred to as a tendon, despite technically being a ligament.

Why the patella exists at all is an interesting side-story. The elbow, after all, is quite similar to the knee in anatomy and function, except for the fact that the triceps (the upper body equivalent of the quadriceps) connect directly to the forearm.  Why don't you have an 'elbow cap'? Or why do you have a knee cap? 

 The patella is actually the largest and most well-known example of a sesamoid bone-a roundish bone that develops in a tendon crossing a joint to increase the mechanical advantage and decrease wear on the joint. They are usually quite small (the word derives its root from the Greek word for "sesame seed").  Sesamoid bones are usually found in the smaller joints of the hand and foot, and are always present in another high-load hinge joint: the ball of the foot.  A pair of sesamoids aids the flexor hallucis longus tendon as it crosses the big toe joint (first metatarsal-phalangal joint for the medically-minded). Like all sesamoids, the patella "increases the mechanical advantage of extensor muscles by transmitting forces across knee at greater distance (moment) from axis of rotation," in the words of Duke University's Wheeless' Textbook of Orthopaedics.  So the patella enables the knee to produce and absorb very high loads.  The tradeoff is the high stress on the patellar tendon.

Monday, August 22, 2011

Injury Series: Eccentric exercise and tendon remodeling, part I: Achilles tendonitis

Attention readers: I have published a significantly revised and updated article on midpoint Achilles tendonitis.  I strongly recommend you read that instead! The information below is incomplete and out of date! Click here to go to the updated Achilles tendonitis article.

Note: if you are looking for information on insertional Achilles tendonitis, see this article

We're shifting gears a bit today.  As high school and college cross country seasons approach, lots of runners are hitting their peak mileage right about now.  At the same time, there's a lot of runners who wish they could be out there hitting the road every day, but are sidelined by injury.  This will the the first post in a series on injuries: their cause, prevention, and treatment.  In the past 10-20 years, there have been some very important changes in the way the medical community approaches and treats many common running injuries.  In a few cases, highly effective treatments have been discovered that were not known even a decade or two ago.  Unfortunately, many physicians and physical therapists don't stay on top of the injury research that's being published in several of the major medical journals, so the clinical implementation of these scientifically proven treatments is lagging.  At the same time, many treatments that enjoy wide acceptance have not withstood a scientifically rigorous examination.  While few are harmful, wasting time on ineffective treatments is something neither the patient nor the doctor wants.  At the same time, I realize that treatment based solely on scientifically proven methods is often limited.  I've also amassed a fairly large bag of "tricks" either through experimentation or advice from fellow runners.  In truth, it's usually a combination of "tricks" and "treatment" that get you healthy and running again.  I'll do my best to keep it clear what is scientifically rigorous and what is hocus-pocus-magic.  This is quite a large undertaking, so (much to your delight, I'm sure) I'm going to break with my usual long-winded posts and break this series up in to smaller and more numerous posts, each on a specific injury and its causes, prevention, and treatment.  Today's topic: Achilles tendonitis.

Introduction and Background

Injuries to the Achilles tendon are often cited as one of the "big five" most common running injuries (the others being plantar fasciitis, patellofemoral pain syndrome (runner's knee), medial tibial stress syndrome (shin splints), and iliotibial band syndrome).  Whether to label Achilles injuries as "tendonitis" is controversial.  The suffix -itis implies the main problem is inflammation, as is the case in conditions like appendicitis, gingavitis, etc.  But Achilles tendon issues often present without any signs of cellular inflammation, especially in chronic cases.  Some podiatrists prefer the label "tendonosis," which implies a more general dysfunction in the Achilles.   Some even differentiate between tendonitis and tendonosis when diagnosing Achilles tendon injuries.  Regardless, "tendonitis" is the most common term, and it's the term I'll be using in this post.  However, it is important to remember that the root problem behind Achilles injuries is not inflammation--it is real, physical damage to the fibers of the tendon.


Before we delve into Achilles tendonitis, I need to give a quick primer on concentric and eccentric muscle contractions.  Concentric contractions are simple.  It's when the joint movement is in the same direction as the muscle's contraction.  Using your biceps to curl a dumbbell up towards your shoulders is a concentric contraction.  In contrast, an eccentric contraction is when a muscle is working to oppose the motion of a joint.  Slowly lowering the dumbbell you've curled up to your shoulder is an eccentric motion.  If you were to completely relax your biceps, the weight would quickly slam down.  Your biceps work eccentrically to slow down the motion.  Most "down" motions are eccentric contractions working to oppose gravity: the down phase of a pushup, lowering a barbell down while doing a bench press, and the down phase of a squat all involve eccentric muscle contractions.  These contractions are stressful on muscles and are responsible for most injuries and muscle soreness--it's why running down a long hill several times will often make your quads more sore than if you'd ran up it. 


The Achilles tendon is the biggest and strongest of all the tendons in the body.  It connects the gastrocnemius and soleus muscles to the calcaneus, or heel bone, and allows them to perform their main task: plantar flexing the foot. Its role in running is essential--it allows the calf muscles (the gastrocnemius and soleus) to elastically store energy via the stretch-shortening cycle, which is released upon toe-off.  The tendon itself also stores energy by functioning as a very stiff spring.  And I do mean very stiff--upon loading with 120 pounds of force, it only lengthens by a few millimeters.  In fact, its stiffness tops that of suspension springs in high-end sports cars--it would take over 900 pounds of force to stretch your Achilles an inch!

The Achilles tendon connects the calf muscles--both the gastrocnemius and the soleus--to the heel.  Some doctors and researchers refer to both muscles as one unit: the triceps surae

Monday, August 15, 2011

Caffeine and running: effectiveness, ethics, and the NCAA

In my previous post, I mentioned how caffeine can boost athletic performance by stimulating the central nervous system, which in turn makes a given effort seem easier–the rated perceived exertion (RPE) drops.  I was leading you on a bit: the drop in RPE isn't the whole story with caffeine.  In fact, it only accounts for about 30% of the performance boost that comes from using caffeine.  I've received recieved a few questions specifically about caffeine since then, so today I'm going to go in-depth on the ins and outs of caffeine as an ergogenic (perfomance-boosting) aid.  This article is fairly thorough, since you can encounter a lot of myths about caffeine and sport on the web.  One site will claim "to fail the NCAA's drug test, you'd have to drink twelve cups of coffee in two hours" (page 10, I'm not making this up) while another will claim "just a cup or two of coffee or one energy drink can cause you to fail your drug test!"  I'd like to clear up some of that confusion.  To do so, there's a bit of math ahead–if you find yourself over your head, skip ahead to the next bolded sentence–that's the important stuff. 


Caffeine might just be the "world's greatest drug."  It's certainly the world's most popular.  In the United States alone, 90% of the population consumes caffeine in some form every day.  Worldwide, billions of people consume caffeine on a regular basis.  By all definitions, caffeine is a psychoactive substance, and like all drugs, it has several effects (good and bad) that occur with different doses.

 The negative effects of caffeine at high doses include headaches, difficulty sleeping, tremors, and irritability.  It increases urine production, although regular caffeine users rapidly become immune to this effect.  The "caffeine causes dehydration" myth has persisted for a long time, but it is simply not true.  In massive doses, caffeine can cause seizures and death. Additionally, withdrawal in heavy users can cause headaches, drowsiness, and insomnia, and may persist for up to five days. 

However, it has a very large therapeutic index–the ratio of the toxic dose to the effective dose.  And its benefits are manifold at doses far below those that cause negative effects.  Caffeine boosts mood, alertness, vigilance, and cognitive function.  In an excellent 2008 review of double-blind, placebo-controlled trials, C.H.S. Ruxton concluded:

"From a review of double-blind, placebo-controlled studies published over the past 15 years, it would appear that the range of caffeine intake that could maximise benefit and minimise risk in relation to mood, cognitive function, performance and hydration is 38 to 400 mg per day, equating to 1 to 8 cups of tea, or 0.3 to 4 cups of brewed coffee per day. Current levels of caffeine intake in the UK fall well within this range, suggesting that risk, for example from dehydration, is likely to be minimal."
In a different review, A. Smith concluded that "Regular caffeine usage appears to be beneficial, with higher users having better mental functioning. [...] The evidence clearly shows that levels of caffeine consumed by most people have largely positive effects on behavior."

So even fairly heavy users of caffeine are safe from its negative effects and will reap the benefits of its boost to cognitive performance.  But caffeine also has an effect on athletic performance–a very pronounced one in the case of endurance events.  In a 2005 meta-analysis, M. Doherty and P. M. Smith wrote,

"In comparison to placebo, caffeine also improved performance by approximately 11%, a finding that concurs with another recent meta-analysis of the effects of caffeine on exercise test outcome (Doherty & Smith, 2004). As RPE was lower during exercise but unchanged at the end of exhausting exercise, it may be that part of the explanation for the improvement in performance has to do with a dampening of the perceptual response during exercise. Indeed, our regression analysis revealed that RPE during exercise could explain nearly one-third of the variation in the subsequent improvement in performance." [emphasis added]
Eleven percent is a whole heck of a lot.  And Doherty and Smith's review is only one in a litany of papers that report the benefits of caffeine on endurance exercise.  Away from the lab, for a recreational athlete, the boost will be more like 5%, according to Dr. Mark Tarnopolsky of McMaster University in Canada.  But even then–five percent is the difference between 16:00 and 15:12 in the 5k.  Often, ergogenic aids boost the performance of recreational athletes much more than elites, so perhaps a top-flight athlete wouldn't benefit as much.  But according to Matt Fitzgerald (who didn't cite it, tsk tsk) a treadmill study of elite runners still found a 1.9% increase in time to exhaustion.  Putting that in perspective, 1.9% is the difference between a 4:30 and 4:25 mile.  How does this happen? Is it legal? Is it right?

Thursday, August 11, 2011

The different types of fatigue

In my last post, I discussed how a preponderance of studies show that your running mechanics change when you are fatigued.  The specifics of what changes occur are difficult to discern, as they likely vary from person to person.  Before moving on, I noted a problem with conflating all of these studies, a problem that I'd like to elaborate on today:  "fatigue" is not a monolith! Feeling tired after a 1500m race is not the same kind of fatigue you feel after a 12-mile run on a hilly trail, and that is not the same fatigue you feel 22 miles into a marathon.  This post is more of a grab-bag than usual, and there's a good bit of tangential material, so buckle up!

Overall fatigue can be thought of as the sum of four distinct specific fatigues--muscular fatigue, metabolic fatigue, energy depletion, and central nervous system fatigue.

Muscular fatigue

Muscular fatigue results from microtrauma to muscles--the soreness and weakness in your legs 30 minutes after a hilly run are an example of this.  It is thought that the microtrauma that causes muscular fatigue is also what causes delayed-onset muscle soreness (DOMS).  This damage to the muscles directly impacts performance by reducing strength and power output.  Interestingly, it seems that DOMS is brought on exclusively by eccentric movements, which is why a middle-distance runner gets sore calves and hamstrings after a race, but usually not sore shin muscles or quadriceps.  The quadriceps do work eccentrically when running downhill or over very soft terrain, which is why hilly or mushy runs seem to beat up your quads.

 Doing lots of push-ups will give you muscular fatigue, although the tiredness you feel immediately after each individual set of push-ups is mostly the result of metabolic fatigue in your upper-body muscles.  Doing push-ups will also make you more like Chris Solinsky, which is never a bad thing.

There is little you can do during a workout or race to reduce the eccentric activities that damage muscles.  Running on a softer surface may reduce microtrauma to muscles by reducing the peak impact loading rate and spreading out the impact that must be absorbed over a longer period, but there's nothing more than anecdotal evidence for this.  Most strategies for decreasing muscular fatigue involve limiting the damage after a workout ends.  Icebaths, compression socks, putting your legs up against a wall, and Alberto Salazar's much-mocked cryosauna all attempt to decrease inflammation in the legs and increase the efflux of fluids from the muscles back into the blood and the rest of the body.  Inflammation occurs for two reasons: 1) the damaged muscles leak their contents out into their surroundings and 2) the body rushes blood and lymph fluid to the damaged areas to repair them.  Repair may seem like a good thing, but the combination of the cellular fluids leaking out from the damaged muscles and the fluids rushing in from elsewhere in the body can increase pressure to the point where further damage and internal fluid leakage occurs.  In cases of major internal damage, such as surgery or bodily trauma, the swelling in response to the injury can cause life-threatening complications, and compression, elevation, and ice effectively combat this swelling. There's no reason to worry, however--if internal bleeding and swelling from surgery is a fire hose, post-workout microtrauma is a faucet drip.  But anyone who's had his or her feet swell up after a long hike knows that long workouts do cause inflammation.

There is some evidence that moderate-temperature "ice" baths will reduce soreness and increase performance in the days following a hard workout.  Interestingly, most studies use 12-15°C (54-59°F) water baths--rather puny compared with training-room tough guys who like to crank it down to 50°F or colder.  But there's no evidence colder is better! In fact, some people speculate that very cold temperatures can actually increase damage.  I like to think that the hydrostatic pressure from the weight of the water itself is a significant contributor to the recovery boost.  Standing in an ice bath with 24" of water provides a pressure differential of 45 mmHg between your feet and your knees--that's more than compression socks would provide!  

Likewise, compression wear also has a body of evidence supporting its use.  Compression wear was actually invented to control swelling and reduce the possibility of deep-vein thrombosis in hospital patients after surgery.  Veins have a series of one-way valves that are supposed to allow blood to flow only one direction (back towards the heart).  But the veins in your legs are susceptible to pooling, where blood stagnates because gravity is preventing the blood from achieving a high enough pressure differential for the valves to operate properly.  Compression counters the hydrostatic pressure inside your body due to gravity, allowing better bloodflow.  Compression wear has been getting a lot of attention recently because it might also increase performance during exercise via better bloodflow, increased proprioception, or decreased muscle vibration.

Fortunately for the impoverished runner, the evidence for these approaches is equivocal--some studies find no difference in recovery betwen groups who use compression or ice-bathing and those who do not.  If there are benefits, they are relatively small.  Further, leg elevation is a low-tech approach that likely has many of the same effects as compression and ice-bathing (namely, increasing fluid efflux from and reducing fluid influx to the lower body).  My entire high school team used to put our legs up against a wall for 5 minutes or so following our cool-downs.

Thursday, August 4, 2011

The cumulative damage theory of injuries

I've had injuries on the brain lately.  Why do they happen? My high school's training room had a sign outside that said "Running injury? TOO MUCH, TOO FAR, TOO SOON."  Needless to say, the trainer wasn't very helpful.  But the medical/scientific consensus isn't much more helpful than that.  Overuse injuries are "tissue damage that results from repetitive demand over the course of time" according to emedicine, which is a slightly less harsh wording of the same idea my high school trainer had.  But things are more complicated than that (this is going to become a theme on this blog).  It seems like the rules are always changing--mileage or workouts that were okay last year are problematic this year, or the other way around.  The topic of "why injuries happen" is way too broad to over all at once, but today I'd like to look at one small piece: the process by which damage accumulates.

Each of the various tissues in your body has its own injury threshold.  This is the amount of stress it can take before becoming injured, and it varies from person to person and from time to time.  Healthy training will increase the injury threshold of most tissue.  So a runner who has been running 50 miles a week will be able to handle a given stress (say, a 10 mile easy run) better than a runner who has only been doing 25 miles a week.  However, the higher-mileage runner is also incurring a greater stress on a day-to-day basis.  Statistically, higher-mileage runners get injured more often.  The problem is that, in most studies, "high mileage" is typically defined as 20+ or 25+ miles a week.  Most competitive runners don't consider anything under 30 miles a week to even be "training."  I wish I had the resources to do a large-scale study on factors that can predict running injuries.  There have been some very interesting studies, though they tend to either use a large number of serious runners and find very few conclusive results (these studies are often done via surveys) or they use a small number of recreational runners and get good results, but their applicability to serious athletes is questionable.

Here's an example: Let's say a study finds that recreational runners who weigh over 200 pounds have a greater risk of injury.  We might conclude "lighter is better, since it puts less stress on the body."  But in competitive runners (particularly females), a low body mass index is associated with an increased risk of injury.

Injuries occur when internal factors coincide with external factors.  I might have a biomechanically defective elbow (an internal factor), but since I don't play tennis (an external factor), I don't get lateral epicondylitis--tennis elbow.  I've started to put some things together for a post on the various possible internal causes of injury (e.g. weak hip stabilizers, low bone density), but today I'm going to look at external factors. 

For a given runner, how does stress on the body scale? That's what I want to answer.  What is the relative increase in injury risk for a 4, 6, 8, 10, or 12 mile run? There are three possibilities: the injury risk has a linear increase, a compounding increase, or a compounding recovery.

Saturday, July 23, 2011

Shoes and inserts: how the broken model works

One of the first things we blame whenever we get injured is our shoes.  Most runners are keenly aware of all the minute details of their footwear, and they are easy to pin the blame on.  Whether it's the shoddy upper of the updated model, a too-stiff midsole, shoes that are too run-down, or an abrupt change in brands, we are quick to link our shoes with our maladies.  And for good reason, many podiatrists and doctors would state--shoes can be the cause of a new injury, especially if it occurs within a week or two after a change in footwear.  Problem is, no one can agree on exactly what about running shoes makes them good or bad.

If you try to buy shoes at a chain store, you're probably on your own, unless the salespeople are trying to earn a few extra bucks.  At a specialty running store, you'll probably be exposed to some arcane witchcraft to divine the perfect shoe--the wet foot test, meant to measure arch height, and the standing pronation test, intended to measure rearfoot motion, are the two most common.  Inspecting wear patterns on an old shoe and a pronation examination while running are sometimes also done.  The general idea is as follows: people who underpronate/supinate (the terms are used interchangably) and have high arches can't absorb shock effectively, so they need a "cushioning" shoe.  People who have mild pronation and medium arches need support from a "supportive" shoe.  Finally, people with low arches who pronate severely need very supportive "motion control" shoes.  The driving principle is that pronation is bad and arches need support.

There are several problems with this approach.  The biggest one is that it doesn't work.  As we'll soon see, pronation does not reliably predict injuries, and attempting to correct it does not avoid them either.  Furthermore, the standard tools for correcting pronation, namely, shoe changes and custom orthotics, don't reliably reduce pronation! But perplexingly, switching to a more supportive shoe or getting a custom orthotic from a podiatrist works a good amount of the time! 

Before we tackle that, I'll briefly go over how pronation works, since there's a lot of misinformation about exactly what it is.  Biomechanicists (or is it "biomechanics"?) and podiatrists scoff at the word "pronation"--they prefer "rearfoot eversion," since this more accurately describes what is going on.  Here is an excerpt from a RunnersWorld video that illustrates a runner pronating:

I've skipped ahead to the interesting part. Also, stop watching after about 1:00, since pretty much nothing the narrator says is true.

In principle, pronation during running is fairly simple: after the foot strikes the ground and flattens (whether it is flattening from a forefoot strike or a heelstrike), the foot rotates inward about the subtalar joint.  In my previous post, I mentioned that studies have shown that no matter the stiffness of the surface, peak impact forces are the same.  In a 1998 paper, Wright et al. showed that this phenomena can be explained by a passive mechanism.  That is, the muscles do not interfere in a dynamic way to absorb impact shock.  Rather, the muscles, bones, and joints act like a system of springs, rods, and hinges during the impact phase. 
Wright's model of the leg was significantly more sophisticated than the simple "three hinge leg" model used in some other studies.

The role of pronation in this process is to translate vertical impact force into rotational force, which attenuates the impact by spreading it out over a longer period of time.  Everybody pronates; some do it more than others. Pronating was probably originally suspected of causing injury because it looks odd and out of place.

Running shoes and inserts attempt to correct pronation by supporting the medial arch of the foot.  Remember, pronation is when the foot rolls inwards, so putting a wedge on the inside of the foot should (theoretically) prevent that inward rolling.  This correction is easily visible in a static position; images like this one are common on shoe and insert websites:

 The difference is fairly obvious.  However standing is not running, and as we'll soon see, the difference in degree of pronation while actually running is not nearly as drastic or straightforward as the image above.

So why doesn't the "pronation paradigm" work? First, there is little evidence that the degree of rearfoot eversion/pronation is related to injury.  The biggest study I'm aware of that has found excessive pronation to predict injury is this one by Williams et al.  The study examined 400 subjects over three years.  Some 46 developed "exercise related lower leg pain" (shin splints), 29 of which developed it in both legs.  This gave the researchers 75 injured legs, which they compared with 167 uninjured legs from the students who stayed healthy.  Why they chose 167 is beyond me, but their statistics showed a significant difference in several parameters related to pronation.  The injured group displayed pronation that was faster, greater in magnitude, and occurred later in the stance phase than the uninjured group.  Unfortunately, some experimental oversights make these results untrustworthy.  First, the subjects were recreational athletes who competed in a variety of sports; the study did not use runners exclusively, even though the biomechanical evaluation was a running test.  Second, this biomechanical evaluation was done barefoot.  Running barefoot has a variable effect on rearfoot kinematics (including pronation), so there is no way to know whether someone who pronates barefoot pronates to the same degree in a shoe!

To be sure, there are some other studies that have found a weak relationship between pronation and injury.  But there have been just as many that have found no relationship (like this one, which concluded that "lower-extremity alignment is not a major risk factor for running injuries in [a] relatively low mileage cohort").

Additionally, the two tools used to alter pronation--shoe support and orthotics--don't reliably alter pronation! Benno Nigg, whose work I've cited several times in this post and the previous one, concisely summarizes in a seminal 2000 paper:

"Results from studies with bone pins in the calcaneus, the tibia, and the femur showed only small, nonsystematic effects of shoes or inserts on the kinematics of these bones during running. Even more surprising, the differences in the skeletal movement between barefoot, shoes, and shoes with inserts were small and nonsystematic.The results of this study suggest that the locomotor system does not react to interventions with shoes, inserts, or orthotics by changing the skeletal movement pattern. These experimental results do not provide any evidence for the claim that shoes, inserts, or orthotics align the skeleton."

If shoes don't have the ability to reliably alter pronation, we would expect large-scale studies using familiar tests like the pronator/supinator or wet foot tests to show little or no difference between people assigned the "right" shoe for their foot type and people assigned the "wrong" one.  In fact, this is exactly what we see.  This study by Ryan et al. divided up 81 women training for a half marathon into three groups: neutral, pronators, and severe pronators.  Each group was divided into three subgroups which were each assigned either a cushioning, stability, or motion control shoe to wear for all of their training.  So, for the 30 women who were deemed to be "pronators," 10 received a stability shoe (the "right" one), 10 received a cushioning shoe, and 10 received a motion control shoe. Surprisingly, runners who got the "wrong" shoe got injured slightly less than runners who got the "right" shoe, and everyone who got a motion control shoe was more likely to become injured than those who did not.  A similar study by Knapik et al. with over 1300 Air Force recruits which assigned shoes based on the "arch height" strategy saw no difference between groups.

All I've told you up until now is somewhat old-hat.  The failure of pronation control in preventing injuries has been covered in more detail by others, and the results of the aforementioned studies have been declared as proof of an enormous conspiracy wrought by an unholy alliance of money-hungry shoe companies and doctors.  The problem is that the conclusion is not as simple as it seems, and few people seem to bother with exploring why.  The evidence in the Ryan and Knapik studies, combined with Benno Nigg's review article, seems to lead to a simple conclusion: running shoes and running inserts can't prevent injuries because they don't change pronation, and pronation doesn't cause injuries (which is quickly misconstrued into "running shoes cause injury").  However, this is not the conclusion the data support!  As usual, the details are more nuanced. 

Why?  Because shoe inserts (and probably the right shoe) can prevent injury.  Several studies have found that inserts can relieve or prevent injury; here is one example by M√ľndermann et al. So, even though the inserts are not significantly altering pronation, they are preventing injury.  This points to a different mechanism for injury, which brings us back to Benno Nigg's article. Nigg spends the first half describing why impact forces and pronation have little or no relation to injury risk.  The second half proposes a new model for skeletal movement and its relation to injury.

According to Nigg, the body has a "preferred movement path."  Regardless of the footwear condition or presence or absence of inserts, the body activates the muscles to stay as close as possible to the preferred path.  This is why adding a thick medial wedge on the inside of the foot to oppose pronation does not significantly change the amount of pronation while running.  To overcome a medial wedge attempting to divert the foot from its preferred path, the body simply activates the eversion muscles of the leg more strongly.  Apparently, the muscles controlling the foot are easily strong enough to overcome a small foam wedge.  In contrast, if a shoe or shoe insert encourages the foot to move along its preferred path, the foot control muscles will not have to be as highly activated.  In his own words:

" If an intervention counteracts the preferred movement path, muscle activity must be increased. An optimal shoe, insert, or orthotic reduces muscle activity. Thus, shoes, inserts, and orthotics affect general muscle activity and, therefore, fatigue, comfort, work, and performance."

There is concern that "interventions" (shoes and inserts) that increase muscle activity may cause injury, but no evidence of this yet.  There is evidence that shoes which decrease muscle activity decrease the energetic cost of running, increasing efficiency.  Muscle activity is connected very closely with muscle vibration on impact--muscles act like springs on impact, and just like a real spring, they vibrate.  Much of Nigg's current work is looking at the effects of these muscular vibrations and whether they are related to injuries. 

Benno Nigg uses electromyography machines to prove the changes in muscle activity.  Fortunately, you don't need an EMG machine to tell whether shoes or inserts are encouraging or discouraging your preferred path of motion.  Your body communicates this in a fairly clear way: comfort. Nigg (and other researchers) have published studies indicating that the shoe and insert choices which prevent injury and reduce muscle activity are also the ones which subjects report to be the most comfortable.  In the M√ľndermann study above, the military recruits in the experimental group (which recieved shoe inserts and experienced a lower injury rate) rated their inserts as more comfortable than the control group, which had a simple flat insole.

The factors that affect comfort are not the same from person to person; this is why stability shoes are the right choice for some, and the wrong one for others (and this seems to have nothing to do with degree of pronation).  So, in a long and circuitous way, we have shown that in this case, common sense is right: wear the shoe that feels most comfortable!

Things are, from a scientific perspective, a bit more complicated than that, and I've been itching to do some more reading on how changes in muscle activity and vibration affect injury, as well as how various other changes (texturing for example) affects the way the foot interacts with the shoe and the ground.  Further, there are several factors that aren't taken into account in many of these studies that do come into play in real life.  Most studies use small variations of the same shoe, testing different arch heights, medial wedges, midsole hardness, etc.  But in the real world, much more changes from shoe to shoe.  Flexibility, the fit of the upper, the elevation of the heel, and the lacing system are just a few examples.  So even though one of the new "minimalist" shoes with a low-profile, flexible midsole may feel very comfortable, you may not be ready to run in it.  For exaomple, abruptly switching to a shoe with a lower heel height could induce Achilles tendonitis, or wearing a more or less-flexible shoe could cause foot problems.  Of course, it could prevent them as well! These are all topics for another time, though.  In the next week or two, look for another post on the anatomy of a running shoe and some analysis on the usefulness of some of these things.

Tuesday, July 19, 2011

New York Times article on running surface stiffness

The New York Times has a nasty habit of writing poorly-researched exercise science articles. They go something like this: A new study by professor so-and-so at such-and-such university upends some widely-accepted fact about exercise, and we're darn luck to have these scientists (and the clever journalist) telling us that common sense is wrong.  You have to realize, of course, that the New York Times is a business, and no one's interested in an article titled "Exercise is still the best treatment for a variety of health conditions."  That's old news.  What does sell is controversy: you should run when you are sick, cool-downs are completely unnecessary, exercise is bad for you, abs are bad for you.  I don't disagree with the message in all of these articles; what I disagree with is the methodology.  The articles never put the new findings into context.  It seems like they seek out an exercise-related muck-raker, then report on his or her controversial idea, then include some vague comments like "the full impact of this study remains to be seen."  This most recent New York Times article is a perfect example: posted yesterday, it claims that soft surfaces don't prevent injury, and moreover, that soft surfaces can themselves be injurious.  This happens to be an area of research that I have done quite a bit of reading on, so I'll go through this article piece-by-piece.

The very first picture is anathema to the trained eye: some overstriding, uncouth runner romping his way though the countryside, slamming his heels into the ground, straight-kneed as his legs stretch several feet in front of him.  Now, this is probably just a stock photo from the archives, but it raises a good point: regardless of what we talk about regarding surfaces, running form is a big factor in injury prevention, and ignoring that is unwise.  No matter what surface or shoe you wear, if you run like the man in the stock photo, you're going to have problems.

Moving on, the facts in the first part are more or less correct: there have not been any controlled studies linking soft surfaces to lower injury rates.  This is a bit misleading because there have not been any controlled studies that link much of anything to lower injury rates.  In survey-studies, such as this famous one, no link has been found between injury and shoe type, foot type, running surface, overall fitness, or weight.  The only reliable predictors of  injury are mileage and previous injuries.  Some factors (like hip muscle imbalances) are related to injury risk, but have not been proven (yet) to have a causal relationship.  Still other factors have evidence linking them to injury risk, but have not (yet) been shown to be related.  This is where running surfaces belongs.

The NYT article moves on, touching on the surface-stiffness paradox: surprisingly, the impact force does not differ from surface to surface.  For a given runner at a given speed, the foot will hit the ground with the same force no matter the hardness of the surface.  Therefore, the article concludes, soft surfaces are no better than hard ones since the impact force is the same.  Furthermore, the author concludes that soft surfaces are worse because they tend to be uneven, risking turned ankles and the like.

However, the surface-stiffness paradox is not the end of the story.  Concluding that the injury risk is no different because the impact risk is no different presumes that injury is related to impact, which is not at all clear.  Understanding how the body modulates impact on different surfaces is essential to understand the implications on injury risk, and this is not covered in the NYT article.

During impact with the ground, the leg muscles act like springs.  Before impact, the muscles tense up to absorb the shock.  Unlike mechanical springs, however, the body's muscles can have their stiffness altered.  When you are running, the brain does this automatically.  In order to optimize performance, the brain tenses the muscles to minimize the vertical motion of your center of gravity upon impact.  Using feedback from the skin and muscles, the brain  tenses the muscles so that the stiffness of the overall system remains the same.  What is the overall system? It's the combined stiffness of the surface you are running on, the stiffness of the shoes you are wearing (if any), and the stiffness of your leg muscles.  If the overall system stiffness is to remain constant, the body must modify the stiffness of the leg muscles in order to change it, since surface stiffness and shoe stiffness are out of your body's immediate control.  So, when running on a soft surface, the leg muscles are tighter, and when running on a hard surface, the leg muscles are looser. And unlike the New York Times article suggests, the adjustment is not slow or gradual--it is instant.  In a brilliant 1999 study, Daniel Ferris showed that runners adjust muscle stiffness before the first step onto a different surface.  This is pretty cool.  When you move from pavement to grass, your eyes see that you will land on the grass, your brain interprets that information, and relays it to the legs in the form of increased muscle stiffness.  All this happens on auto-pilot. 

 The muscles and bones of the leg can be modeled as a system of levers and springs.  A realistic model is illustrated on the left, and a more simple one is illustrated on the right.  Unlike real springs, the muscles can be changed dynamically to have a different stiffness--imagine the effect of swapping out a loose spring in the model on the right for a stiffer one.  This is the effect that different muscle pre-tension has on impact.

But impact force is not the whole story when it comes to collision with the ground.  Daniel Lieberman, an anthropologist at Harvard University, has come into the spotlight recently for his work on barefoot running and footstrike style.  More relevant to the current topic, however, is this important illustration of the effect of cushioning: in the graph below, the force at various times in a footstrike are plotted.  The black line represents a barefoot heelstrike, while the red line represents a shod heelstrike.  This is effectively a test of the effect of surface stiffness on the impact parameters (the surface just happens to be attached to the foot).
It's easy to see that a less-cushioned impact (barefoot, black line) has the same impact force (about 2.4x body weight) as a more-cushioned impact (shod, red line).  However, it is also easy to see that the total duration of the less-cushioned impact is shorter.  This means that the loading rate, or the change in force over time, was higher.  This is mostly because the foam in the shoe takes time to deform, spreading out the load both in time and area.  Whether the loading rate affects injury risk is highly controversial: Irene Davis, a highly respected researcher, claims they do (and has data to back it up).  But Benno Nigg (who is also highly respected) claims they don't, and also has data to back it up.

Impact loading rate is the most obvious difference between hard and soft surfaces, and I'll probably deal with the nuances of it in a separate post.  But there are other differences too--the pressure distribution on the foot is one, and the evenness of the surface is another.

Plantar pressure distribution has been overlooked for a long time, since biomechanics researchers assumed impact control was passive for a long time.  We now know that it is active--it involves dynamic feedback between your legs and your brain.  The body senses what type of surface you are in contact with, and modifies muscle activity accordingly.  There are some very interesting results from this: for example, it is easier to balance on a textured surface than on a smooth one. In running we know that the body attempts to minimize pressure on the sole of the foot.  Sensory organs called mechanoreceptors detect the local pressure on the sole of the foot.  If it is too high, the body modifies gait in an attempt to reduce it.  When running barefoot, especially on a hard surface, your body forces you to take choppy, quick steps.  A quicker stride frequency means less impact force per footstrike, so the pressures drop.

In a study published in 2008, Vitor Tessutti and coworkers measured the pressure at different points on the sole of the foot during running on natural grass and asphalt.  Predictably, running on grass resulted in longer contact time with the ground and lower peak pressure.

So if the body can adjust to any surface/shoe stiffness by modifying muscle stiffness, and high plantar pressures should be avoided, why not run with pillows strapped to your feet? Well it turns out that the body can't adapt to any surface/shoe stiffness, and that some plantar pressure is a good thing.

One emerging idea regarding muscle and surface stiffness holds that the body has a Zone of Optimal Leg Stiffness.  Impacts that occur when the muscles are forced to operate outside this zone are definitely uncomfortable and probably injurious.  The zone of optimal leg stiffness is easy to demonstrate using extremes: First, imagine sprinting as fast as you can, barefoot on asphalt.  Of course, this would be a painful and regrettable experiment.  Second, imagine trying to sprint in a high-jump pit.  Not as painful, but nearly as uncomfortable.  In the first case, the leg muscles can't be loose enough, so the legs are forced to absorb too much impact too fast.  In the second case, the leg muscles can't be tight enough and cannot act as effective springs to return the energy from the impact.

I suspect that the zone of optimal leg stiffness changes as muscles become more fatigued--so at the end of a 90 minute run, your body is less tolerant of various surface stiffnesses than it was at the beginning.  This is purely speculative, but from good old-fashioned experience, I (and most other serious runners) can tell you that 13 miles on pavement feels less comfortable than 13 miles on dirt and grass.  I also suspect that most runners encounter the lower end of their zone of optimal leg stiffness more often than the upper end--that is, I suspect that the surface/shoe combination is too hard more often than too soft.  Again, only a suspicion supported by experience. But if I'm correct, a soft surface is a much safer bet, as you will be in less danger of being outside that zone of optimal stiffness.  Fortunately, there are some very smart folks over at the podiatry arena who are on the same page as me.  Too bad the New York Times didn't interview them.

With regard to plantar pressure, emerging research is showing that, although the body tries to avoid high peak pressures, it is also used for feedback.  "Proprioception" is the $5 word for the dynamic feedback between the plantar mechanoreceptor cells and the brain.  As I mentioned earlier about the ease of balance on a textured surface, better feedback about the surface from the soles of your feet is a good thing.  There is some evidence (though not by any means GOOD evidence) that part of the benefit in taping sprained ankles is not from the support, but from the increased proprioceptive feedback.  A 2003 study found that soccer players with a textured insole had much better sensory feedback versus a smooth insole. Unfortunately, thicker cushioning means less proprioceptive feedback.  Alas, this is a topic for another day--shoes, insoles, bare feet, etc.

Getting back to the topic at hand, one final advantage soft surfaces have is their unevenness--this is why I brought up proprioception in the first place.  An uneven surface puts different stresses on the body, and the proprioceptive feedback from the varied surface will result in muscles being tensed slightly differently.  Uphill, downhill, bumpy, and smooth surfaces all stress the body slightly differently.  One step might stress the medial side of the foot more, while the next stresses the lateral side more.  Accordingly, the muscles of the leg are stressed slightly differently.  Sports orthopedists often blame hip and knee injuries on running on the same side of a cambered road, inferring that the same stresses over and over are a bad thing.  So why not switch up the stresses on your body? Repetitive stress is a bad thing in many fields--if I keep typing up this article much longer, I'll get a repetitive stress injury.  To my knowledge there are no studies looking at how slightly uneven surfaces affect injury or running gait.  Most biomechanical studies are done in a lab on a smooth concrete surface, so the dearth of studies is completely understandable. It's hard enough in a lab, imagine doing it on a trail.  This last paragraph is by far the least supported in this whole article, so toss it out if you must--but plantar pressure, impact loading rates, and leg stiffness are the more meaty arguments anyways. 

So in closing: why is the New York Times article wrong? Because all surfaces are NOT the same.  Hard surfaces may can push the body outside of its zone of optimal leg stiffness.  They also increase the peak pressure on the sole of the foot, which we know is a bad thing because the body does all it can to avoid high peak plantar pressures.  Finally, uneven surfaces stress the body in a more varied manner, lessening the risk of repetitive stress/overuse injuries.  Saying there is "no evidence" that soft surfaces are better is a gross mischaracterization.

Monday, July 18, 2011

Something New in Training: The Methods of Renato Canova

This is a piece I finished a few months ago after spending considerable time going over Renato Canova's training methods.  Renato Canova is a world-famous coach who instructs many of the best athletes in the world.  He has worked with the Italian national team in the past, but today, he works mainly with athletes in Kenya.  His athletes have won Olympic and World Championship medals, as well as setting national and world records.  As of 2015, Renato Canova's athletes have set 6 world records, won 42 medals in the World Championships, and 8 medals in the Olympic Games.  He has coached 9 athletes under 2:05:04 in the marathon, and 9 men athletes under 26:55 in the 10,000m.

More importantly, his training philosophy is significantly different than that of any other coach I am familiar with.  I wrote the following article in an attempt to understand the mechanics of his philosophy so it could be applied to any training program, not just one for an Olympian.

>> Click here to download the PDF <<

I recommend actually downloading the PDF from Google Drive, since the in-browser viewer does not always render text in an easily-readable way.

Hello world

Glad you're reading my blog.  I'm a recent Carleton College graduate with a penchant for running and an inclination towards writing.  My high school coach encouraged his athletes to become "students of the sport," and I quickly took to it.  I've spent a lot of time reading and studying running-related topics in the past six years or so, and this blog is a way for me to start synthesizing thoughts and making comments about different aspects of running.  My main area of focus is high-level training and racing: training methodologies, injury treatment and prevention, and the like.  I'm not sure what this blog will eventually turn into; for now, you can expect a mixture of science, common sense, and coaching know-how that has rubbed off on me from many of the brilliant individuals I've met in the running world.  While my training right now isn't going to impress even the lowliest of hobby-joggers, I've trained at a fairly high level in the past.  Even if nobody reads this, it'll be a way to sharpen and develop my writing skills and possibly pass on some knowledge about the sport and lifestyle I love.  Hope you enjoy it.