Tuesday, May 19, 2015

Twin Cities 1 Mile in retrospect: How slow was it? A statistical analysis

2015 TC 1 Mile Champions Garrett Heath and Heather Kampf

The Medtronic Twin Cities 1 Mile is one of the premier road miles in the United States.  It has hosted Olympic medalists and has borne witness to several sub-four-minute miles.  In addition to a top-flight pro race, the TC 1 Mile features several "open" waves, which usually total over two thousand finishers.  The traditional course was flat and very fast.  This year, the installation of a new light-rail transit line forced the course through downtown Minneapolis to be changed, likely permanently. 

This course change was announced a few months ago, and after researching the elevation profile of the new course, which gains about 30 feet of elevation in the first half mile before flattening out, I published an article in which I predicted the new course would be five to eight seconds slower. 

The race itself, which happened last Thursday, was held on a cool, rainy evening with slight winds.  Weather data pegs the exact conditions at 54 degrees F, light rain, and 9 mph winds at race time—certainly not conducive to the very fastest times, but not terrible.  The winner, Garrett Heath (a Minnesota native), took the win in 4:08, which was a sharp contrast to Nick Willis' blistering 3:56 course record the last time the race was held.  Heath himself was runner-up in that race with a 3:57. 

By looking just at the pro results, the new course looks substantially slower than the old one, but you could chalk this up to cautious tactics early in the race, or just a fluke from a small sample size.  To get a real answer on how much slower the new course was, and how accurate my prediction was, we'll have to do some statistical analysis.

The rest of this article will go in detail on the methods I used to compute how slow the course actually was, but if you're just looking for a quick conversion, here it is: For competitive runners, the 2015 TC 1 Mile was 13 ± 3 seconds slower than the 2013 course. A more accurate conversion is to multiply your 2015 race time by 0.9581 to get the equivalent 2013 time and multiply your time by 0.009 for the uncertainty. 

Saturday, April 25, 2015

The bone stress injury model: a new way to deal with stress fractures and stress reactions in runners

An MRI reveals a tibial stress fracture
Traditionally, overuse injuries to the bone in distance runners are divided into two distinct categories: stress reactions and stress fractures.  Runners who develop pain along one of their bones hope desperately that they have the former and not the latter, since the usual prescription for stress fracture recovery is six to eight weeks of no running whatsoever.  The usual restrictions for stress reactions depend on the doctor, but typically involve two to four weeks away from running.  Some doctors, coaches, and runners eschew the term "stress reaction" entirely because, in their view, you either have a stress fracture, or you don't—that's all there is to it.

Normally, the story unfolds something like this: a high school runner develops a sharp, aching, localized pain somewhere along a bone in his lower body.  It doesn't improve much with icing and lowered training volume, so his coach or trainer refers him to a doctor.  The doctor orders an X-ray, examines it, but sees no evidence of calcification, so he orders the runner to ease back into training, but return if pain continues.  The high schooler gives running a shot, but continues to have pain.  The doctor then orders a bone scan or an MRI, which shows bone marrow edema or increased metabolic activity at the location of pain.  This is deemed to be a stress fracture, and the runner is put in a boot, forbidden from running for six to eight weeks, and his season is effectively over.  Sound familiar?

The reason for caution with stress fractures is well-known.  If you have a stress fracture and continue to run recklessly on it, it can worsen and eventually lead to the bone splitting in two—a true fracture.  This can lead to heaps of complications and could end your running career.  There is also a category of "high risk" stress fractures that occur in particular areas like the femoral neck, the navicular, and the sesamoid bones, which are known to have a significant risk for poor healing or nonunion.1 These require even more time off and a much slower return to running.

Problems with the old model

However, doctors and physical therapists are starting to learn what coaches have already picked up on: the traditional approach to low risk stress fractures (as the vast majority are) is inadequate on a number of points.

The case for a new approach to bone injuries in runners was laid out in an exhaustive review article published in October of last year by Stuart Warden, Irene Davis, and Michael Fredericson, three extremely prolific running injury researchers.2 They propose using the term "bone stress injury" or BSI, which is intended to encompass all overuse injuries to bone that runners sustain. 

Under Warden, Davis, and Fredericson's model, bone stress injuries exist on a continuum.  On the most severe end of this spectrum are true stress fractures: a fracture line is observable on an MRI or CT scan, and there is edema (swelling) in the bone marrow and periosteum, the membrane that covers the surface of the bones.  A stress fracture is accompanied by a sharp pain or ache during weight-bearing activity that sometimes persists even when you're resting. 

The next step down the continuum of bone stress injury is the stress reaction: pain and aching during or after weight-bearing that is associated with bone marrow edema (on an MRI) or increased bone remodeling (as imaged by a bone scan), but lacks a visible fracture line. 

Further down the bone stress injury spectrum lies asymptomatic areas of bone remodeling.  As it turns out, if you were to schedule weekly MRIs for a group of high-level runners in heavy training—say, a college cross country team—you would quite often find runners developing transient areas of bone marrow or periosteal edema that would be indicative of a stress reaction, except that they have no pain associated with them, and never develop problems in the area.3 

The biology of bone remodeling

One of the core paradoxes of stress fractures and stress reactions is why they occur in fairly experienced runners.  All medical students can recite Wolff's law—bone responds to stress by becoming stronger.  So, theoretically, running more should lead to stronger bones, not stress fractures.

Thursday, April 9, 2015

Using the Tempo Trainer for pacing interval workouts on the track

The Tempo Trainer
As a high school coach, one of the toughest things to teach young runners is proper pacing.  Everyone has seen a high schooler who takes off far too fast in a mile or two-mile race, only to stagger home disappointed and out of energy at the end.  Pacing in races is obviously important, but so is pacing in workouts.  An improperly-paced interval session can ruin the intended purpose of the workout.

Take, for example, a staple high-end aerobic session: "cruise interval" kilometer repeats done at the anaerobic threshold.  A high school runner who is currently in 9:55 3200m shape might be looking to run 6x1km at around 3:30 per kilometer with a minute's rest between each.  When done properly, running each repeat at an even pace, this is a fairly relaxed workout.  However, if poorly paced, it quickly becomes a lot more challenging. 

For an experienced runner or a coach, it can seem baffling when a new runner is incapable of pacing.  Younger runners haven't developed their own internal sense of pacing yet, so they struggle to hit prescribed workout paces, even if the workout isn't inherently difficult. 

Can't you just check your watch every 200 meters? Frequent watch-checking is the most obvious solution, but this brings along a host of problems.  First, you're relying on all of the runners you are coaching to remember to bring a watch, which can be its own struggle.  Second, a watch only allows you to check cumulative times; adding up splits in your head can be a little tricky if you aren't running a mathematically convenient pace.

The proper pace for a 3:30 kilometer is 42.0 seconds per 200 meters.  What I'll often see when a group of high school runners attempts to run this pace is wild variation in the per-200m split, alternating between too fast and too slow.  So, a group might run the assigned pace of 3:30, but will do it with intermediate splits of 39 - 41 - 44 - 44 - 42.  Hardly ideal! You can take a split each 200 on your watch, but then you can't report your overall time to your coach.  Using the watch to gauge pacing can also lead to overcorrection: running a 40-second 200 to "get back on pace" by 400 meters, following a first 200m split of 44 seconds, for example. 

Discovering the Tempo Trainer

Through a combination of luck and resourcefulness, I stumbled across a more robust solution.  In the fall, I suffered a case of Achilles tendonitis which led to a few weeks of aqua-jogging in the pool to maintain my fitness.  I shared pool space with a club swimming team which occasionally used a small pacing device called the Tempo Trainer to help them set their stroke rate (much like some runners use a portable metronome to assist with setting their stride rate).  The waterproof unit was meant to be tucked inside a swimmer's swimcap and was loud enough to be heard underwater. 

It wasn't until I mentioned the Tempo Trainer to a swimmer friend of mine that I realized that it could be used for pacing interval workouts as well.  My friend remarked that she often used its pacing function so she could hear a "beep" at a prescribed interval during long repeats in the pool.  So, for example, if she wanted to swim a 100 yard repeat in 66 seconds, she'd set the Tempo Trainer to beep every 16.5 seconds, so she'd hear it each time she pushed off each wall in a 25 yard pool.  By judging whether the beep was early or late, she'd be able to tell whether she was ahead, behind, or on pace.

Hearing this reminded me of a special workout called the "Faraggiana-Gigliotti Test" that Italian running coach Renato Canova conducts on his top marathon runners.  The test involves taking blood lactate samples after a series of 2km repeats at a range of potential marathon paces to get a reasonable estimate of an athlete's current marathon fitness.  To ensure his athletes pace each two-kilometer repeat as efficiently as possible, the coach sets out cones every 25m and uses a loud beeper set to beep at the proper interval for the required pace.  As John Kellogg has pointed out, doing so requires the beeper to be placed in the center of the infield, so you don't get pacing variations due to the speed of sound as you round the track.  One central beeper also has to be loud enough to be heard from the other side of the track, and you can only use it for one workout group at a time.  Finally, unless a coach manually resets it or changes the beep interval, the athlete has no control over it. 

The Tempo Trainer circumvents all of these limitations.  It's small enough to easily be carried in your hand during a workout, and it is loud enough to be heard even while running in a group, but not so loud that everyone within a quarter-mile can hear. A large track or cross country team could use one Tempo Trainer for each workout group.  Finally, if you get sick of it, you can turn it off and toss it on the infield.  It also comes with a clip that you could use to attach it to your shorts, but I found it easier to just carry it in your hand.  After doing some research, I bought one and tested it out. 

Thursday, February 12, 2015

Is the new course for the 2015 Twin Cities 1 Mile going to be slower?

Nick Willis leads the 2013 TC 1mi

This week, Twin Cities in Motion announced that the 2015 edition of the Twin Cities 1 Mile will be run on a new course heading north on Hennepin Avenue through downtown Minneapolis, instead of the historic course down Nicollet Mall.  The motivation for this change was construction of a new light rail line that crosses the Mall, with trains that run every few minutes—far too frequent to be able to get a full wave of runners across quickly.
The old course was flat and very fast, and with its very generous prize purse, the elite wave attracted several extremely fast milers.  Because of stormy weather, the race was canceled at the last minute in 2014, but in 2013, Nick Willis set a course record of 3:56.1 in 2013 for a cool $10,000 bonus, and five other runners broke four minutes. 

A new course, but the same record

In a recent interview with Minnesota running blog Down the Backstretch, TC 1 Mile race director Jeff Decker clarified that, even though the course has changed, Willis' 3:56 (and Sara Hall's 4:30.8, run in 2011) are still considered the "event records," so to earn the $10,000 record bonus, these are still the marks a runner would need to hit. 

Which brings us to the new course.  The new route up Hennepin Avenue has no turns to mention, but it does have a noticeable uphill in the first half mile or so.  Down the Backstretch provided a handy chart comparing the elevation profile of the old and the new course.  Can we use this to predict whether the course will be faster or slower, and what kind of performance would be necessary to break a course record?

In fact, we can, as long as we make a few simplifications.  If we can make an idealized model of each course, we can compare their relative "fastness."  As you can see in the chart above, the old course fluctuates a bit, but never gains nor loses more than ten feet.  Because of this, I'm comfortable treating the old course as if it were perfectly flat, i.e. no significant differences from an idealized "fast as possible" course.

Tuesday, February 3, 2015

Is less running better for you? An in-depth look at "Dose of jogging and long-term mortality"

About once a year or so, a new scientific study comes out which makes bold claims about the harmful effects of too much exercise.  These get a lot of media attention and feed a strange sort of schadenfreude among the sedentary populace.  Meanwhile, other research that doesn't carry such contrarian views is quickly brushed aside.

It's about that time again—this week, a study published in the Journal of the American College of Cardiology made the case that infrequent, slow jogging is best for health: too much jogging, or jogging too fast, are detrimental to the point of being just as bad as sedentary life.  The news media, eager to grab onto a more attention-grabbing storyline, highlighted the article's claim that too much jogging is as bad as being sedentary.  Cue the satisfactory back-patting from the couch potatoes. 

The scientific paper in question was published by Peter Schnohr and other researchers at a number of hospitals in Denmark, as well as the University of Missouri-Kansas City.  Some other online commentators have brought up the authorship issue—one of the coauthors, James O'Keefe, is a cardiologist who strongly believes that endurance training is bad for your cardiovascular system and has authored or co-authored many of the attention-grabbing scientific papers in the past few years that argue high-volume endurance training is harmful—but here, we'll concern ourselves only with the data and its interpretation, not any accusations of bias.  If we're bringing up author bias, certainly you must include me (a proponent of and participant in high volume and high intensity training) in the discussion.  But instead of fretting about all of this, let's jump right in to looking at this article. 

The statistics of study design

By following a very large group of Danish citizens for a twelve-year period, the authors sought to investigate the effects of jogging (let's leave the "running vs. jogging" terminology debate for another day) on your risk of death from any cause.  Because it picked out a large group of healthy subjects, then followed them to observe who ended up dying before the study's conclusion, this study was a prospective study.  This design gives the study a lot more predictive power to discover associations between lifestyle and mortality (i.e. death rate), but at the cost of making the statistics harder.

The best analogy for us to understand a prospective study versus the alternative, a retrospective study, is to imagine trying to figure out what causes a running injury like IT band syndrome.  The most obvious way to investigate the causes of IT band syndrome would be to gather up a large group of runners who already have IT band syndrome, then make some measurements (like impact forces during running, or hip strength, for example) and compare these measurements to an equally-sized sample of healthy runners.  This design is retrospective, and though it's easier to find a large number of people with the condition we are interested in, you can probably see some of the problems with this.  Maybe we discover that the runners with IT band syndrome have a "hitch" in their stride when compared to the healthy runners.  Is this asymmetric stride the cause of their IT band syndrome, or is it a result of trying to avoid putting weight on the injured area? The retrospective study design is fraught with these types of problems.

A prospective study designed to investigate IT band syndrome would have to gather a large group of healthy runners, measure all of them, and then wait and see who goes on to develop IT band syndrome in a year (or any timeframe, really).  We can gather some very powerful information from this type of research, because the data grant us predictive power.  After doing our analysis, we might be able to say "runners with poor hip strength are twice as likely to get IT band syndrome," for example.  The only problem is that it's very hard to get good data in prospective studies because often, the condition you are trying to study is just not very common.  Let's say we follow 200 runners for a year, and half of them suffer an injury at some point during our study.  From other research on the frequency of running injuries, we would only expect about eight cases of IT band syndrome from our initial sample.  So, to draw useful information from prospective studies, you need to do at least one of three things:

1) Have a very large sample size
2)  Follow your study population for a very long time
3) Be comfortable inferring conclusions from small sample sizes

The same issues hold true for the Danish longevity study.  While it's measurably harder to do a retrospective study on mortality (good luck asking a dead man about his exercise habits), the prospective design is still the right choice.  To achieve usable results, however, the authors of this study had to take all three of the above steps.

Friday, January 30, 2015

52 more things I learned from a third year of weekly writing

This month marked three years since I started writing articles for RunnersConnect.net investigating what the scientific literature has to say about a wide range of running-related topics, from injuries to training to peak performance on race day.  At the end of each year, I've made a list of one useful tip or interesting fact that I learned from each week's research.  Here are fifty-two more things I learned from reading scientific research this past year, one from each article.  If you want to see all of the material I've written, head on over to the blog section of RunnersConnect! Also feel free to check out the yearly lists from 2013 and from 2012.

1.  Celiac disease, which affects around one percent of the population, can cause a wide range of vague, non-specific symptoms that can interfere with your training, like joint pain, extreme fatigue, weight loss, gastrointestinal problems, and anemia.  Further, even once you've adopted a gluten-free diet, it can take a while for your body to return to normal.

2.  If you choose to eat a vegetarian or vegan diet, you're more likely to have iron-deficiency anemia, amenorrhea (if you are a woman), and insufficiently vitamin B12 levels.  Though it's very possible to have a complete diet as a vegetarian or vegan, you need to take extra care to ensure you get enough protein, vitamin D, and iron, and you should probably take a vitamin B12 supplement or eat foods that are fortified with it.

3.  Scientific findings can run contrary to your own experiences.  The research says it's okay to run when you have a cold, that the speed of your daily runs does not affect your injury risk, and that it's okay to do some running on an injured area, as long as you monitor your pain and stop before it's over 5/10 on the pain scale.  In my own training, I can't get away with any of this! There might be subtle reasons why the findings from one study don't apply to your own experiences.

4.  The faster you run, the greater the proportion of your energy that comes from carbohydrates.  This has some major implications when it comes to running out of fuel in the marathon.  The people most at-risk for "hitting the wall" before the finish of a marathon are very fit runners who can run at a high percentage of their VO2 max, and heavier, overweight runners—especially if their extra weight is not in their legs.

5.  When planning out a fueling strategy for a marathon, you should generally shoot for taking in 60 grams of carbs per hour of running.  If you have had major problems with hitting the wall, you may consider increasing your carb intake to 90 grams per hour.  However, if you've had gastrointestinal problems from trying to refuel, you might want to cut this down to 45 or 30 grams per hour. 

6.  Gels, sports drinks, and energy chews are all equally valid choices for refueling during a long race.  None of them offer a distinct physiological advantage, so feel free to choose whichever suits you best. 

7.  Electrolytes aren't all that important for endurance events.  There's no good evidence that you need to replace the salt you lose in your sweat—it appears that your body intentionally modulates the amount of salt you lose in your sweat to keep the concentration of electrolytes in your blood constant, so there's no need for salt tablets or super-salty sports drinks.

8.  There's no magic formula for carbo-loading.  All you need to do is increase your carbohydrate intake by 50-75% over the last few days leading up to a long race (over 90 minutes), and you don't need to do a "depletion period" prior to it to get the benefits of carbo-loading.

9.  In a marathon, elite Canadian runners consume between 16 and 26 fluid ounces of liquids per hour of running and about 50-75 grams of carbs per hour.  Elites use a combination of gels, solids, and sports drinks according to personal preferences.

10.  When runners collapse after finishing a race, it's usually (though not always) from a sudden drop in blood pressure that's triggered when you stop running.  After laying down for a few minutes and elevating their legs, they'll be fine.  When runners collapse during a race, however, it's much more likely that they're having a medical emergency like hyponatremia or sudden cardiac arrest. 

11.  Some research suggests that taking vitamin C before and after completing an ultramarathon can decrease your risk of getting sick.  Over half of the finishers of a 90km ultramarathon in one study came down with a cold in the weeks following the race!

12.  However, try not to load up on antioxidant supplements in general.  They can inhibit your body's adaptation to exercise: oxidative stress is a big part of improvement! Fruits and vegetables are probably okay, though.

Monday, January 19, 2015

Video: Testing the science behind Kenzen's Echo H2 Sensor

A few days ago I came across this Indiegogo crowdfunding campaign for a new wearable device called the Echo H2 Sensor which claims it can detect your glucose levels, hydration status, and lactate levels in real-time during exercise by analyzing your sweat.  I set out to do some research on whether there's any science behind their claims.

If you've got a question that you'd like answered in a future video or blog post, leave a comment here or on the video page, or drop me a line at the Contact Me page!