Sunday, December 2, 2012

How to find a good running doctor or physical therapist

My Injury Series articles detailing the causes and treatments backed by scientific research for the most common running injuries are some of the most popular posts on my blog.  Of the readers who are drawn to these articles, perhaps half of them are newly-injured runners who are looking to read up on what they need to do to recover.  The other half are runners who have suffered through the injury for weeks or months, having already been to and been disappointed by one or more doctors or physical therapists.  The medical community, like all trades, has a distribution of talent: there are some great doctors, a lot of mediocre doctors, and some very bad ones.  While many injuries can be successfully cured without ever seeing a doctor or physical therapist, there are definitely a lot of cases where it’s in your best interest to see a medical professional.  When to seek out a doctor’s help for an injury is mostly up to you; my own general rule is if a few days’ time off and some “self therapy” doesn’t help at all, and I can’t figure out what the problem is, it’s time to see a doctor or physical therapist.

The focus of this article will be fairly narrow: How do you find a good doctor or physical therapist? I won’t really cover the functions of individual specialties like podiatry vs. orthopedics and when to use them, but that’s something you can probably figure out on your own.  And if not, it’s a topic I’ll be covering in my third booklet, which I hope to release sometime in 2013! In any case, I think it’s advantageous for you as a runner or as a coach to build a network of medical practitioners who can help you out if you come down with an injury.  I say “network” because even the best doctors won’t be able to take care of all injuries.  Many top sports orthopedists have a special interest, be it the hip or the knee or a particular type of injury, so the person you’d see for a recalcitrant case of plantar fasciitis is probably not the same one you’d see for a perplexing case of groin pain.  Likewise for physical therapists: some are especially gifted in the function of a particular body part or particular type of injury, so the PT who can help you get over a bad ankle sprain sustained on a hike or during a workout might not be the one best-suited for recovering from a hip flexor strain.

Monday, November 26, 2012

Some thoughts on sexism in athletics and the implications of gender differences

A new research paper recently came out on gender differences in athletics, written by Robert Deaner.  I am not as plugged into the online running community as I’ve been in the past, so I can’t tell how much “buzz” it’s generating, but it’s certainly got a fairly provocative message: women are intrinsically less interested in competitive sports due to evolutionary pressures, which is evidenced by female participation rates in team and competitive sport.  Deaner is the author of another fairly controversial paper published last year which generated quite a bit of buzz on; this one posited that more non-elite men at local road races run “relatively fast” than do women.  As evidence for this, he examines statistics from road races in the Buffalo, NY region and shows that a higher proportion of men run within an arbitrary margin (say, within 25%) of the averaged top-10 all time performers.  Furthermore, Deaner argues that about three times as many men train seriously than do women, again using the statistics done on various competitive and noncompetitive road races.   These differences are also traced to evolutionary pressures.

As I don’t have much of a background in psychology and only passing knowledge of evolutionary psychology in particular, I’m not going to deeply examine the methods and conclusions of Deaner’s work as I might if it were a physiology or biomechanics paper.  Rather, I’d like to go through this paper and use it to launch into a more philosophical discussion of the topic of sexism in sport, which is something I’ve wanted to write about for quite some time.  Before we get too into this latest paper, I want to clear up any confusion from the title of my blog post—I’m not accusing Deaner or anyone else of sexism.  In fact I applaud his openness and willingness to discuss these sensitive topics (especially at a place as infamous as the LetsRun message boards), as it fosters a more even-handed approach to dealing with the issues that inevitably arise when our worldviews clash with new evidence.  But let’s jump into the research before we get to the philosophy, ethics, and real-world implications.

Thoughts on Deaner et al.

First, let’s take a look at Deaner’s paper.  It’s actually a three-pronged study which looks at results from a time-use survey of over 100,000 Americans, field observation studies at local parks, and sports participation rates in intramural athletics from colleges and universities in the United States.  In the first study, a large number of participants were asked to record their daily activities for one day, which were then pooled and analyzed.  In the second, observers were sent to public parks in Michigan and New York to record the number and gender of people participating in various activities (walking, tennis, skateboarding, etc.).  In the third, participation rates from intramural sports leagues at a sampling of colleges and universities were analyzed. 

Sunday, October 21, 2012

Injury Series: Medial tibial stress syndrome ("shin splints") as a bone injury to the tibia

Medial tibial stress syndrome is related to tibial stress reactions and stress fractures, which you can read about here
For an in-depth discussion of returning to running following a bone stress injury like medial tibial stress syndrome, see this article

Medial tibial stress syndrome (MTSS), or shin splints, is perhaps the best-known running injury to the average citizen.  Aching or throbbing shins is an ailment that many new runners and many athletes in all sorts of impact-related sports, like volleyball, basketball, and sprinting, deal with on a regular basis.  Unlike some running injuries, which appear to be non-discriminatory—both Joe Jogger and Ryan Hall suffer from plantar fasciitis, for example—medial tibial stress syndrome seems to be an issue encountered more often by new or seasonal athletes (though not exclusively).  The reasons for this tie in closely with its root causes, which we’ll get to in a moment.  Shin splints also have a complicated and fascinating relationship with tibial stress fractures, which we will also get to later on in the article.  If you’ve read my Injury Series post on tibial stress fractures, you might see some familiar material.  But first, as usual, we need a bit of anatomy.

Anatomy and terminology

The tibia is your “shinbone,” the long, straight bone that forms the front of your leg.  The tibia carries a significant portion of the impact that goes up your leg when you hit the ground, and it also serves as an attachment point for the muscles that control your foot and ankle, all the way from the relatively small ones like the flexor digitorum longus muscle, which flexes your little toes, to the calf muscles, which are the engine below the knee for forward movement.  The medial edge of the tibia runs up the inside of your leg and borders your calf muscles.  The “stress” part of medial tibial stress syndrome just means that the condition is demonstrably associated with weight-bearing stress from exercise.  Other more exotic names for medial tibial stress syndrome have cropped up, like “exercise-related lower leg pain,” but at this point, medial tibial stress syndrome or MTSS seems to be the predominant and most useful term.  In this article, I’ll use these terms interchangeably with “shin splints,” the less-descriptive and colloquial term for this injury, but keep in mind that the medically-correct term is medial tibial stress syndrome.   


The most obvious symptom of MTSS is, of course, shin pain.  The pain usually presents as an aching, burning, or throbbing feeling along the inside edge of the shinbone, usually dispersed over several inches along the shin.  The shin (or often, both shins) gets progressively more painful throughout the duration of a run or workout.  Early cases of shin splints might be nothing more than a bothersome ache near the end of a long run, but can progress to the point where even short jogs cause pain.  There may also be some tenderness along the medial edge of the tibia.  One review study recommends that medial tibial stress syndrome be defined as pain which extends for at least 2 inches along the middle to bottom-third of the shin, which is aggravated by weight-bearing and subsides with rest.1  Cases of shin pain which is localized to a very small area should be examined by a doctor to rule out a stress fracture.  X-rays are insufficiently accurate to rule out a tibial stress fracture, so your doctor should use a bone scan or, preferably, an MRI, to diagnose your injury. 

Monday, October 1, 2012

The use of charts for mileage progression

My previous post got me thinking about mileage charts again.  I haven’t given them much thought in well over a year, since I haven’t actually been using them for about as long, but it’s a topic that I think is very important to runners in training.  I used to be more of a proponent of the “listen to your body” philosophy, but as I found out the hard way, often your body wants more than it can handle.  While the “10%  rule” is of course totally arbitrary, I (and many others) have found that it’s a fairly good guideline to keeping your mileage progression under control to avoid injuries related to sudden jumps in volume.  In general, I found myself and my teammates in college were afflicted by two classes of overuse injuries: ones related to changes in volume over time and ones related to the sustained stress of continuous high mileage (or intensity).  Controlling, overcoming, and avoiding the sustained-volume injuries is the focus of much of what I write about: how to shore up biomechanical defects, stride patterns, and other factors associated with injury.  To a certain extent, a particular level of stress is necessary to becoming a great runner.  You will have a hard time hacking it as a male collegiate cross country runner if you can’t handle at least 70 miles a week. 
Example #1: Mileage chart from my junior year.  Click to enlarge.
But injuries related to changes in volume can likely be avoided, or at least minimized, by following a logical mileage progression.  Some runners can plow right through lower mileages until they approach their previous “peak” mileage with no problem; others will struggle even at modest mileages if they ramp up their mileage too fast.  I belonged in the latter category.  I probably sustained more injuries at 50 miles a week than I did at 100, and it wasn’t for lack of weeks on the high end of things.  As any runner who has made a return to running after a long time off knows, the same adaptive mechanism that allows you to handle progressively larger volumes over time also works in reverse: after a long time off from running, even very low mileage is a large, new stress on your body, which it may not tolerate well. 

So hence, mileage charts.

Friday, September 21, 2012

Does anyone bother to read more than the abstract?

Training plan I made in college that mostly follows the 10% rule.
Scholarship is sometimes a lonely endeavor.  Especially when it feels like everyone else is “doing it wrong.”  Today was one of those days—all the buzz online is about a new study titled “Can GPS be used to detect deleterious progression in training volume among runners?” in the Journal of Strength and Conditioning Research that purportedly shows that the oft-cited (and obviously arbitrary) “10% rule”—that is, you should increase your mileage by no more than 10% per week—is more conservative than necessary, and that novice runners may increase their mileage by 22% per week with no increased risk of injury.  This stat made it onto several Twitter accounts I follow, the front page of, and garnered a brief write-up in Runner’s World.  Seeing all this, I did what I always do when a study comes out and makes some noise: I read the article. 

The abstract, which is freely available, is as follows:

There is a need to ascertain if an association exists between excessive progression in weekly volume and development of running related injuries. The purpose of this study was to investigate if GPS can be used to detect deleterious progression in weekly training volume among 60 novice runners included in a 10 week prospective study. All participants used GPS to quantify training volume while running. In case of injury participants attended a clinical examination. The thirteen runners sustaining injuries during follow-up, had a significantly higher weekly progression in total training volume in the week prior to the injury origin of 86 % [95 % CI: 12.9 to 159.9], p = 0.026 compared with other weeks. Although not significant, participants with injuries had an increase in weekly training volume of 31.6 % compared with a 22.1 % increase among the healthy. [...] Based on the results from current study, increases in weekly training progression may become deleterious at a weekly increase above 30 % which is more than the 10 % rule, currently used as guideline for correct progression in weekly volume by runners and coaches. Still, no clear evidence for safe progression of weekly volume exists. But is seems like some individuals may tolerate weekly progressions around 20 to 25 %, at least for a short period of time.
Now, I could whine about the usual problems—the small number of runners who became injured, the problems of applying studies on complete novices to experienced athletes, and so on.  But I’ll bite my tongue for now, because that’s not what wrecked my day today.  When I said “I read the article,” I did mean the whole thing.  Let’s take a closer look at the protocols of this study as outlined in the all-important methods section.

The study itself was mostly well-done: 60 novice runners from Denmark, none of which had any underlying health issues or injuries, and none of which had run further than 10km, were issued GPS watches and turned loose for 10 weeks of running training. 13 came down with a running injury during the course of the study, which was defined as “any musculoskeletal complaint of the lower extremity or back causing a restriction of running for at least one week,” which in my book is a fairly strict distinction.  The injured runners had been increasing their weekly mileage (or kilometerage, as this was a European study) at approximately 33% per week, while the healthy group had averaged 22%.  Notably, the injured runners had a statistically significantly higher BMI than the healthy runners—27.6 vs. 24.8 (a BMI of 25.0 is considered “overweight”; for a 5’9 person like me, that’s 170 lbs!).  The average weight of the subjects in this study should give us a few clues that we aren’t exactly dealing with world-beaters.  Unfortunately, because of the small sample size, the authors were not able to statistically extract the effects of weight and mileage on injury risk.

The most important detail, however, and the sentence that ruined my day, was this one:

The participants ran a total distance of 4556.5 km in 1172 training sessions during the 10 weeks

Doing the math, we get some troubling numbers.  1172 training sessions ÷ 60 participants ÷ 10 weeks = 1.95 training sessions per participants per week.  And the average weekly mileage? 7.6 kilometers.  That’s 4.75 miles per week.  Incoming freshmen at my high school were asked to run six times as much for the entire 10-week summer!  To picture things a bit more clearly, I created an example chart of the average weekly mileage of a healthy runner in this study (keeping in mind 1.95 training sessions per week):

Miles per week
Miles per run
% increase


Now, I hope I don’t offend any readers of this blog, but even 10 miles a week is more jogger territory than “real running.”  And percent increases at such low mileage are almost meaningless—a one or two minute difference in the duration of a run has a substantial effect on the week’s mileage!

In all, I can only chide the authors of the study for not making it more clear how low the volume of running was in this study.  And for not including all the relevant information in the abstract (which is always a big misstep, in my opinion). Happily, there are some lessons to be learned from the study, too: being overweight is definitely a risk factor for injury.  More impact per footstrike is the likely culprit, but the general lack of athleticism associated with being overweight probably doesn’t help either.  Additionally, mileage increases in such a population should be constrained to around 20% per week.  However, I suspect it would be more helpful to discuss mileage increases at low volumes in terms of absolute distance, not percent.  For competitive runners in training, I have always liked “5mi per week or 10%, whichever is more.”  After all, as my college coach said, if you start from zero, ten percent more than zero is still zero.  Finally, GPS watches are a great research tool.  I would love to lead a study much like this, except giving GPS devices to a cadre of 50 or 100 collegiate cross country runners at the beginning of the summer.  That could be a treasure trove of data, given that GPS watches can collect information about not only distance, but speed too—a benefit not utilized by this study.  Garmin execs, are you reading this?

Anyhow, one more point I should make is that a 21.6% injury rate among runners averaging less than five miles a week is (philosophically speaking) absolutely unacceptable.  To me, that indicates that sedentary people have underlying biomechanical or strength defects that need to be addressed before or while they begin a fitness program.  I don't believe that everyone was "born to run" 100 mile weeks, but nearly everybody ought to be able to jog around the block a few times a week without getting injured.  
I hope that this paper spurs more research into training loads and injury rates, but I certainly hope it doesn’t encourage high school and college runners to jack up their mileage by 15 or 20 miles in a single week.  There is a big, big difference between moving from eight to ten miles a week and jumping from 65 to 80.
Lastly, I have some stern words for the folks who’ve already jumped on this “out-with-the-10%-rule” bandwagon: next time, please read more than the abstract.  Or at least talk to someone who has.  Perhaps LetsRun doesn’t have journal access (though any coach at a University ought to—just saying), but Runner’s World definitely does.  Or should.  Maybe more journals need to be open access.  Or maybe exercise physiology and biomechanics needs an ArXiv equivalent.  But even without, just because you’re out of school doesn’t mean you don’t have to do your homework...

Sunday, September 16, 2012

Blog updates and some exciting news!

Given that it’s been nearly a year since the last “behind the scenes” post on this blog, and seeing as the last month has represented an awfully long break in my posting on this blog, I thought I’d write up a quick post to let you all know what I’ve been up to.  I also have some very exciting news!

The main reason I have been skirting on my blogging duties for the last month or so is because I have been preparing for my new position as Director of Education and Outreach at the Runner’s Health and Performance Institute in Leesburg, Virginia.  RUNHAPI (clever name, no?) aims to be a comprehensive injury and performance center for runners with many different services all under one roof.  Within the traditional medical system, a runner with an injury first has to make an appointment to see an orthopedist, podiatrist, or sports medicine doctor, then will get referred to a physical therapist whom he or she can see several days later, then get referred again by the PT to a chiropractor for ART or Graston, a gait analysis lab, a nutritionist, or a running store for new shoes.  This is an exceptionally inefficient model, as I’ve experienced myself several times.  Often the delay between being able to see each provider is several weeks.  RUNHAPI will provide all of these services—injury diagnostics, podiatry care, physical therapy, chiropractic, nutrition, gait analysis, performance/training advice, and even a running store—under one roof.  So, instead of waiting for a week to see a PT after your doctor’s appointment, you can just walk down the hall. 

I was contacted in July by Dr. George Lane, the founder and CEO of RUNHAPI.  He flew me out for a weekend and I was very impressed with his knowledge about and passion for running.  Moving out here last week was and still is a big jump for me, a Minnesota boy through and through. Anyways, the relevant part for you, the reader, is that while I’m in a different venue and have taken on a “real” job, I’m still committed to my own writing.  I have several projects that are in development and should see the light of day in a few weeks now that I've gotten settled in.  Among them, injury series articles on medial tibial stress syndrome (or “shin splints”), plantar fasciitis, hamstring tears/strains, and groin injuries; some considerations on running shoes or a lack thereof; and running training for team sport athletes.  I’m also hoping to release Modern Training and Physiology, my second booklet, by the end of 2012.

I've also made some behind-the-scenes changes.  The most noticeable is the CAPTCHA required for comments.  While I don't like entering these words any more than you do, it should keep my email inbox from looking like this every morning:

 Which has unfortunately led to a few anonymous comments being missed or labeled as spam.

Thanks for staying patient in my absence! I’m looking forward to this new opportunity and others that may present themselves.  Since I’m a lot closer to many of the major running hubs on the East Coast, there may be more collaborative work on this blog in the upcoming months.  In the mean time, check out the still-very-under-construction RUHAPI website (coded by me!) and the logo/wordmark (above—designed by me!).

And lastly, if you are a doctor, chiropractor, physical therapist, or any other professional who works with runners and are interested in collaborating with or becoming a part of our project, head on over to the RUNHAPI website and send us an email!

Useful predictions from biomechanics: Don't run on uneven surfaces at night

 Biomechanics, as a useful science, is still in its infancy.  This might sound shocking, given that research on human gait and locomotion has been going on for well over a century (one might call Eadweard Muybridge the pioneer of "video" gait analysis), but the power of biomechanics as a useful science is still rather limited.  Science is useful not so much because it explains the world around us, but because it allows us to make predictions about the future.  While knowing how gravity works is jolly interesting (and a process we still don’t yet fully understand!), Newton’s equations changed the world because they allowed us to predict when we can see Venus, where a cannonball flies, and how long the sun will shine.  Likewise, all of this research on biomechanics is only useful if it allows us to make some predictions about the future.  Who is likely to get injured? What will happen if you change X about your running form? Is there an optimal design for footwear? Many of these types of fundamental questions remain unanswered, and because of that, we can’t really call biomechanics a “mature” field.  Fifteen years ago, the prevailing opinion in biomechanics circles was that overpronation was the root cause of many running injuries, and this risk could be mitigated by wearing running shoes which controlled and limited your pronation.  We now know that pronation is only weakly connected to a few (not many, and certainly not all) injuries, that devices intended to control pronation do not function as they ought to,1 and that the various types of shoes recommended for certain arch types or severity of pronation don’t reduce injuries like they are supposed to.2, 3 

With all of this in mind, I have been pondering whether we can make some useful predictions about injuries and performance using current topics in biomechanics.  This will perhaps morph into an occasional, ongoing series of posts, but I believe I’ve developed at least one practical and novel recommendation: don’t run at night on uneven surfaces. 

Why not? Here’s the logic: it’s well-documented now (and a well-covered topic on this blog) that running on surfaces of differing stiffnesses—say, concrete and grass—does NOT result in a significant change in the impact forces going into your body.  The reason for this is that your body alters the stiffness of the muscles in your leg so that the sum of the system of stiffnesses below your center of gravity remains constant.  So, if you run in soft shoes on a soft surface, your legs will be quite stiff, and likewise, if you run in thin shoes (or none at all!) on a hard surface, your legs will be less stiff.4  Much of the recent work of Benno Nigg, who is probably the most prolific and influential biomechanics researcher in the past few decades, focuses on the spring-like behavior of the muscles of the lower leg during running.  It seems that the body “tunes” the leg muscles before impact to dampen the vibrations that are sent up the leg after impact.5  As any engineer will know, to properly dampen a vibrating system, you need to properly tune your dampeners.  Your body does this by tuning the stiffness of your leg muscles before every single footstrike.

Friday, July 20, 2012

Brief Thoughts: The rise, fall, and resurgence of high school distance running

 One of my favorite historical trends that I’ve used to illustrate the importance of high mileage and high quality aerobic work is the yearly count of elite high school boys performances at one and two miles, as measured by the number of miles under 4:10 and two-miles under 9:00.  The graph below, which is based on data put together by (if I recall correctly) former steeplechase American record holder George “Malmo” Malley, illustrates plainly what many coaches and longtime followers of the sport already know: high school running was at a very high level during the 1970s, but plummeted throughout the ‘80s and ‘90s, eventually beginning to recover around the year 2000.  I'd love to look at similar data for girls, but due to the unfortunate history of sexism in sport, high school girls didn't even run the two-mile until relatively recently.

Note that the moving average trendline lags by a few years in the 2000s due to lack of recent data

Wednesday, July 18, 2012

Brief Thoughts: Front running is one second per lap harder!

 I do some freelance writing for a website called RunnersConnect.  Part of my work there is a weekly column that involves writing short reviews of scientific articles on a topic relevant to runners.  This weekly column gives me an opportunity to look into what the science says about some of the less-though about topics in running.  For example, one of my articles was all about the various skin ailments (blisters and so on) that afflict marathon runners.  A few weeks ago, I decided to look into the effects of wind on oxygen expenditure—that is, how much will the wind slow you down?  I found some pretty interesting studies on the subject which involved putting a treadmill inside of a wind tunnel, then measuring the oxygen consumption of a runner when subjected to different wind speeds.  As expected, wind had a significant effect on a runner’s efficiency: for each incremental increase in wind speed, the impact on running effort goes up by a power of two.  So a 10 mph wind is four times as fatiguing as a 5 mph wind.  The same effect applies to running speed in calm air.  The wind resistance that has to be overcome at 5:40 mile pace is twice that at 8:00 mile pace (root-two slower).  This is why wind can be such a nuisance (or aid!) in the sprints.  A large percentage of a sprinter’s energy goes towards overcoming air resistance as he or she powers forwards.  As a general rule of thumb, a wind equal to your running speed will slow you by about 6 seconds per mile (so running 6:00 mile effort with a 10 mph headwind will result in a 6:06 mile).  Running with a tailwind only aids you by about half that amount.

None of this should surprise an experienced runner, however.  We’ve all had plenty of stiff headwinds and generous tailwinds.  But the researchers investigated something I might not have thought of: the drop in air resistance when you “draft” behind another runner.  In a 1971 study by L.G.C.E. Pugh (the initials stand for " Lewis Griffith Cresswell Evans"), oxygen consumption values were first recorded for a single runner on the wind-tunnel treadmill.1  Then another runner was put on the treadmill (presumably this was a fairly large treadmill) and oxygen consumption values were recorded for both.  Trailing about one meter behind another runner reduced air resistance by 80%! To confirm this, Pugh took air pressure measurements at various positions behind a single runner on the treadmill.  As is clear in the image below, air flow drops precipitously in the wake of another runner. 

Air pressure is significantly lower in the wake of a runner.  From Pugh.

Pugh’s measurements were largely confirmed by a similar investigation nine years later by C.T.M. Davies.2  Drafting on another runner virtually eliminates air resistance.  According to Davies, a runner in a middle or long-distance track race in still air can expect to save about 1 second’s worth of effort per lap.  That is, if you draft behind a runner clocking 70-second laps, your energy expenditure would correspond to 71-second laps if you were running alone.  Given the impact of a headwind, it’s only logical to expect this advantage to be magnified on windy days.  Four seconds per mile is a huge advantage from a competitive standpoint, and the physiology behind wind resistance might explain why the runner who takes the lead early on in a race almost never wins unless he or she is significantly more fit than the rest of the field.  Many coaches and athletes try to explain this away with psychology, saying that it is much more difficult to lead a race than to follow.  And this is entirely true! But the physiology of air resistance is a non-negotiable fact.  Mental toughness and a competitive mindset can’t change any of that, which makes front running a tactically poor decision for most high-stakes championships.  How did “Pre” do it? Well, he was just that much more fit than everyone else! Keep in mind that runners behind YOU are only getting a competitive advantage if they are within a few meters of you.  Having a large lead neutralizes the effect of wind resistance, at least for the next runner back.  Of course, to actually establish a large lead might necessitate some poor pacing choices from a physiological perspective, but that’s a topic for another day!

So, if running from the front (or out by yourself) has a consistent and measurable negative effect on performance to the tune of one second per 400m, what are the implications? For one, it emphasizes the importance of getting yourself into highly competitive races.  In my opinion, too many colleges (and probably high schools) short-change their runners by going to low-key meets without strong competition.  A top-flight 5k could boost your time by 10 or 12 seconds vs. running alone at a dual meet.  And that’s in calm air—it could be much more with a wind.  Additionally, it helps explain why taking the lead early on in a distance race is usually a big mistake.  There are plenty of other tactical considerations to factor in, of course.  If you’re a big kicker and want to make sure the race goes out slow, you can get to the front and slow it down for a few laps before tucking back into the pack.  Or you could take the lead to help a teammate hit a time standard or run the kick out of a fast finisher.  But from a completely selfish perspective, the only time to take the lead is when you are sure you can open up a significant gap (several meters or more). 

So, when you are watching the Olympic track action get started at the end of the month, don’t be surprised to see races going out at a woeful pace as the field plays a game of chicken to see who will be the “sacrificial lamb” and take the lead.  And you can bet money that the leader at 1/3 or 1/2 of the way though the race won’t be the winner at the end.  Not necessarily for a mental reason—just plain old fluid dynamics.