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Thursday, June 19, 2008

Running injuries expanded

Expanding on running injuries (and some admin)

Yesterday, Jonathan did a post looking at running injuries and specifically the common training error made by runners who tend to move from one injury to the next in their training! He raised the the guideline that a 10% increase in distance from one week to the next is probably about the limit of what most people can aim for before they start running (literally) into injury territory.

And the post got some pretty good comments and discussion going, and it struck me that the whole concept of injuries in runners (and in other sports, cycling and swimming especially, since our focus is on endurance) is a topic that we have never really tackled here.

And since it's so prevalent - studies suggest that about 2 in 3 runners will be injured every year - it seems like a topic worth delving into in a bit more detail in the coming months!

Of course, it's a vast, enormous topic, and much like our Fatigue Series, it's probably too big to be discussed adequately in a nice, packaged series of three or four posts. So rather than introduce it as a series, I think I'll put forward that we will start giving a lot more thought to some posts that follow on from yesterday's post and the resultant suggestions, and then roll those posts out a little less frequently than we would in a dedicated series. But just be assured, it's on the radar screen!

So just a couple of ideas around injuries in running:

1) Running technique and injury

First, a couple of people raised the issue of running technique and injuries, which is a pretty common thought these days. I honestly don't believe that running technique, at least in the form that it's been "packaged" and then sold to runners, has a great deal of importance for injuries. I'd go with the theory that if a runner is injured, look first at training, second at training, third at training, fourth at strength and flexibility imbalances, and fifth at training. Maybe at number six, you can consider running technique.

All this is obviously within reason, and as one reader (Cassio) pointed out, there are obvious technique related things that can easily be addressed, like very obvious overstriding. So sure, in that case. But the case that is made for subtle changes is really overdone and overmarketed, in our opinion.

The issue of technique is however one that we have covered in great detail, and so this is not a debate we need to have right now - it's been had! You can read our series on running technique here for all the discussion of those ideas.

2. The inter-relatedness of it all

Of course, at this point, we must make a very very (very) important point. Nothing in your running (or cycling or any sport) can ever be looked at in perfect isolation. In otherwords, training may well be the cause of most injuries, as we've said, but there is a substantial interaction between the training you do and other variables which act externally to affect your unique response to that training. A 55 kg Kenyan might go from no running to 120 km in a matter of months, and be racing competitively in less time than that. Another person will be bed-ridden in weeks with stress fractures! Why? Because their unique physiology, anatomy and response to training means that "not all training is created equal".

So I am firmly of the belief that if correct training principles are adhered to, then any athlete can train without injury - the level they reach and their success as a runner is of course dependent on numerous other factors. But the problem that we land ourselves in is that we "train by numbers", and try to fit all athletes into the same mould. So the concept that training is simply run from a template doesn't work, precisely because we are not all average.

So the truth is, training might make up the first three areas of concern for an injured athlete (in my opinion), but you can't look at the athlete's training without considering things like flexibility and strength balance (as Sean has pointed out) because they MODERATE the athlete's response to training. That's why I'm in agreement that the athlete must address strength, flexibility and balance.

Now, if we want things to get really tricky, then we start talking about flexibility - can you be TOO flexible? I think when asked in that way, the answer is quite obviously "Yes". But what if it's asked a little differently: Should runners be stretching? Because now all of a sudden, the answer is "Maybe". And once again, we have a case where "one size does NOT fit all". There is, in other words, evidence that stretching can CAUSE injury, not prevent it. And excessive strength too. The key then is balance, and that's a topic worth getting into in the future as well

3. The influence of intensity - critical

Then lastly, the other variable in your training programme is the intensity. Yesterday, Jonathan touched primarily on VOLUME, and raised that guideline (not a rule, remember) that 10% increases are usually the limit. What that doesn't deal with is intensity, so we have to discuss the impact of increasing intensity.

What often happens is that a runner will very patiently and methodically build up VOLUME, because it's much easier to measure - time or distance. What they neglect, and it's more difficult to quantify, is intensity. Because my experience, and theory, suggests that a 5% increase in intensity is NOT the same as a 5% increase in volume.

In other words, if you increase the intensity very slightly, the volume has to drop quite a lot more in order to keep the OVERALL load the same. And so what often catches runners out is that they ramp up the volume by 5 to 10%, but the intensity goes up by 5% too, as they get fitter, or push a little harder. The net result is that the overall training quality increases too much, and they break down.

This is also why the biggest danger period for any runner is that moment when they start to add in the high intensity training to the programme. They finish base training, and suddenly start to do the odd track workout, some fartleks, or the like. But if they don't manage a reduction in volume, the combined effect can be damaging.

So that's another topic worth discussing

One final point - no research available

One thing that we must make clear right up front, is that as we tackle this topic on and off over the coming months, there is very little scientific evidence on this, and so we rely instead on theoretical insights, experience and "bald assertions". Studies often look backwards at injury, and work out after the fact that X, Y and Z are the likely predictors for injury. For example, we know that if you've had a previous hamstring injury, then you have a many-fold greater chance of a hamstring injury! (hardly rocket science...)

But scientific studies that look at the long term effects of different volumes and intensities of training are, for many reasons, just about impossible to do effectively, so it's looking backwards that reveals the evidence.

But, that's no reason not to discuss it, and we'll welcome any comment or feedback. So keep an eye out for those injury posts!

Ross

14 Comments:

Ashish M said...

Okay, maybe I'm beating a dead horse here, but if (1) technique is "what you do," and (2) training is "how much you do," can you really say that "how much you do" is more important than "what you do"?

How can that possibly be true?

Ashish M said...

I went back and read your responses yesterday. True, I am a student of the Pose Method, and maybe you're not sold on Dr. R. Maybe you feel that no one -yet- has discovered the proper technique to running. (I respectfully disagree.)

But how can you argue that running technique does not exist - essentially, that training quantity is more important than quality? In what other sport or human activity would that be true?

Ross Tucker and Jonathan Dugas said...

HI Ashish

No worries, beat away!!

I think if you read the entire series on Running technique, you'll see the argument develop.

I'm actually not against running technique, and the notion that there is a "better" way to run.

But to suggest that there is a "RIGHT" way to run is one of the more arrogant claims made - that's like saying there is a RIGHT hair colour, and it ignores the fact that individuals cannot be squeezed into a mould that doesn't fit them. But then of course, if you want to sell a product, you cannot customize it.

So in fact, if you read that series in its entirety, you'll see that I'm not at all against the idea of teaching technique. But it's the "packaging" of the technique into a product that bothers me. I won't repeat the arguments here, they've been made in our technique series.

But certainly, Pose and Chi both have elements of common sense to them, both are correct in many fundamental respects. But both make claims (driven by marketing and dollars) that cannot be proven. If anything they have been disproven. But of course, their creators conveniently throw the blame back onto the poor runner who picked up the injury - "you didn't do the technique properly", is the response. Well, that's hardly a viable product, when one in four people can even do it.

So technique, yes, very good to teach. But not the cause of injuries, unless established other wise, and nor should it be a priority for most recreational runners, who should be looking at dozens of things ahead of it.

But, ultimately, it's common sense that should prevail - ever considered why, if you look at 100 runners, you'll see 100 different techniques? Or, perhaps one should say, you'll see an innumerable number of technical elements. So who decides which are important? The footstrike? The activation of muscle? has anyone even measured the activation of muscle on Pose? No, they haven't, and so it's all conjecture. ANd more people get injured on it, in my experience, than anything else.

ANyway, that's a long ramble - the series is even longer! But the opinion is all in there!

REgards
Ross

Gráinne said...

I'm forced to agree with you again! I attended a Chi running course a couple of weeks before I got my initial stress fracture. As part of it we were videoed running by the instructor (Catherina McKiernan actually-former winner of London marathon) prior to being taught the technique. She went through the videos after teaching us some of the basic principles. I was actually not far off the Chi style naturally. Wasn't particularly heel-striking, had good posture, high cadence... But 3 weeks later I had a pelvic stress fracture. Despite decent "technique". The thing she commented on? My mileage. She thought it was too high for a beginner. And in my case she was right. I agree with you guys that it's a combination of things. My biomechanics aren't ideal. There are questions about my bone density. But, like my podiatrist friend remarked, people with osteoporosis can run ultras. If they build up to them properly! I'm not anti-Chi or Pose. Think they have some good points. But they're not the be-all and end-all.

Meanwhile, I'll be avoiding the f words...that is, running too far, too fast or too frequently!

Jen said...

You make a lot of valid points and I agree with you that when the intensity increases, the volume you needs to decrease at first. In my experience runners injure themselves doing too much, too fast and too soon- especially when it comes to intensity. For the majority of people, the 10% rule applies but for the injury prone- a 5% cap in volume is often helpful. As far as speedwork is concerned, there are many people out there that equate running faster with having to completely blow themselves up. Intensity training should be based on the current fitness level. I have worked with several athletes that have made the mistake in the past of pushing themselves beyond their limits. For example: 24 minute 5k fitness does not equate to running having the ability to run 1:30's for 440's on the track and yet the thinking was to go as hard as possible and frequently to see a performance improvement quickly. In some cases there will be an improvement but it usually comes at a cost and thus the injury cycle begins!

Mike LaChapelle said...

I think you may have overlooked equipment as a potential cause of injuries, specifically shoes. Shoes that don't fit, are the wrong type for the type of foot/footstrike that you have, or that are too worn can cause injuries.

I also think that overstriding is a very common flaw in running technique among non-elite runners. In my experience, overstriding often leads to shin splints.

Colenso said...

G’day Ross and Jonathan. Along with the exercise physiology of overheating in hot, humid and sunny climates, with almost five decades of competitive running under my feet this topic is another of my favourites. As you have both rightly pointed out, there is not a lot of empirical evidence here, so I would like to give my two pennies worth about some of the concepts of the underlying mechanics from the perspective of an ex-physics teacher.

1. Over the years, I have observed that there’s a lot of misunderstanding in this area, some of it propagated by quite well known and well regarded athletic coaches, including one very famous coach with an engineering background. Typical of the misunderstanding propagated here, is the misconception of force: specifically, that with every foot strike the cumulative force “absorbed” by the human body increases so that by the end of a long run the body has absorbed a force many thousands of times one’s body weight! Of course, if that were so, then at some point within the first few minutes of a run, one’s legs or pelvis ought to snap because the breaking strength (measured in newtons) of the weakest point of one’s bony, cartilaginous or fibrous structures has been exceeded. This doesn’t happen (usually) because such a model is based on the erroneous assumption that force is a scalar quantity like energy, when of course force is not a scalar quantity - it is a vector quantity like displacement, velocity, momentum and acceleration. So, if one looks at a typical graph of the (average) force plotted up the vertical axis versus time plotted along the horizontal axis for a given runner’s foot strike, typically it’s approximately an inverted U-shape, with the maximum force exerted by the ground on the sole of the foot during the strike (the time the foot is in contact with the ground) being the value of the force at the top of the curve. It is the average force because typically the evaluated runner is running on a treadmill with a pair of pressure plates of some sort in place. One type of pressure plate might consist of a plate-sandwich. As each foot lands on the plate sandwich, the plate sandwich is bent slightly under the impact – it changes shape. This small change in shape creates a small change in the capacitance of the plate-sandwich which leads to a small change in the potential difference (Pd) between the two plates that comprise the sandwich. By calibrating before (and afterwards) the measured Pd against known loading forces, one can translate Pds measured in millivolts into forces measured in newtons. This does not of course tell you what the actual forces are at any moment on particular parts of the foot being compressed, only the force acting on the area of sole in contact with the pressure plate. (And if one knows the area of sole in contact, then one easily calculate the contact pressure in pascals by dividing the measured force by the area). It follows that one particular part of the foot, say part of the arch, could be experiencing a much higher external or internal force than the average force across the sole would indicate.

2. Having wittered on about forces above, the truth of the matter however is that in the real world it is not net forces that dictate change in shape or change in motion: it is net torques – that is the sum of each of the vector products of each of the forces acting around a point in space and the displacement of that force from that point. This latter point is rarely recognised even in biomechanics courses taught at university level. The problem here is fundamental because it goes right back to the way that mechanics has traditionally been taught at school and university in physics courses – start with linear mechanics: linear displacement, inertia, velocity, acceleration, momentum and force; then proceed, often as an afterthought, to spend a bit of time on rotational or angular mechanics: angular displacement, moment of inertia, angular velocity, angular acceleration, angular momentum and torque. It’s Newton’s fault actually – he left successive generations of school teachers and curriculum developers with the notion that force is fundamental, whereas in fact it is torque, not force, moment of inertia not inertia, angular momentum not linear momentum that is fundamental to an understanding of (classical) dynamics in the real world of everyday happenings like runners injuring themselves.

3. Clearly then, a proper understanding of the rotational mechanics involved here is essential to an understanding of the forces and torques generated during each foot strike that might eventually lead to the damaging of an essential structure in a runner’s toes, arch, heel, ankle, lower leg, knee, upper leg, pelvis or lower back. And without that proper understanding many misconceptions will inevitably arise. Let me suggest however that the runner’s mass, his or her structural cross-sectional areas, tissue type, thickness and density and the resultant strength and stiffness of his or her moving structures are all critical to whether injury takes place or not. We know that muscle strength increases quite quickly, typically after as little as six weeks, in novices undergoing a introductory weight training program. The strength of one’s ligaments and tendons develops much more slowly, typically taking a year or more to increase significantly in strength; cartilage is even slower to respond, taking two years or more to thicken and strengthen measurably. Bone density and the orientation of one’s bone grain structure seems to be somewhere in between and varies widely from individual to individual and from males to females

4. The mass of the beginning runner is particularly important. Many beginning runners injure themselves because they are quite simply far too heavy for the strength of their connective tissues and bones, for the speed and duration they run at and the hard surfaces on which they run. (Generally, the faster one runs the greater the maximal forces on one’s organic structures.)

5. Is there a simple way to prevent injury? In my experience, gained over almost fifty years, the answer is yes. If your BMI exceeds 25, and you haven’t run before, then walk, cycle or swim and modify your diet to get your BMI below 25 before you start running. Run off road wherever possible: soft sand, muddy ploughed fields are much better for your structures than concrete or tarmac. On soft sand run in bare feet; otherwise wear purpose designed off-road or trail shoes. If you want a hard workout, run uphill reps, walk don’t jog back down and shuffle slowly with little steps on the flat sections for recovery. After a minimum of two years of being injury free and gradually progressing from walking to slow running for short distances on the flat (harder only uphill), maximum increase of 10% per week in duration, the runner can then start to think about some serious training: long distance runs of two to three hours or more; hard intervals on the track several times a week; training twice a day etc.

Above all seek to improve thyself. After all, if you never measure or evaluate your performance, never compete, even against yourself, then you will never discover that of which you are truly capable.

Jean-François said...

read the follow up of first divison female volley ball season in Holland

Jot said...

I've always had an issue with the 10% rule. I guess because generalizations often break down.

If I'm running 18 miles a week by doing 3x6 miles and I increase 20% by adding a 3 mile run on an off day I think the chances of injury are slim.

If I increase that same 20% by doing 3x7 I think the chances are higher. This is, regrettably, not backed up by any study I've ever seen. :)

My instinct says that injury is likely to happen as a result of too much stress while fatigued, which will happen at the end of long runs. I'm curious as to your thoughts.

The other point I haven't seen discussed is the anatomical things that make injury more likely. Are there anatomical features that can be predictive for injuries? Things that come to mind include bowleggedness (no idea what the technical term is) leading to knee injuries.

Thanks for the articles.

-Jot

Ross Tucker and Jonathan Dugas said...

HI Jot

Great points, you're absolutely right. If you want to take it even more to the extremes, your 20% increase could come from going from 3 x 6 to suddenly doing 2 x 10 miles, and then you'd break down, precisely because you would be stressing the body to fatigue and the maintaining that stress beyond it.

So you're 100% right.

As for the anatomical differences and structures, spot on again. I kind of alluded to that in the post when I spoke of anatomical factors that determine how an athlete responds to training. That includes leg length imbalances (even a small difference can have a large effect), foot structure (which determines pronation/supination) and then the various anatomical angles (q-angles and so forth). We'll certianly have to cover these factors.

The key there is that they impact on the athlete's ability to adapt to training injury free. THat's why the "lucky ones" can get away with hard training, and get right up to 50 miles a week, whereas others spend months building up in tiny increments! So they're certainly related in this "web" of factors. Again, however, the training is the one you can control. So when an athlete breaks down injured, you can't say "the anatomy CAUSED the injury". The training did. The anatomy simply contributed to the failure to adapt, and so the controllable factor, training, is still the key to address!

Thanks for the comments, and hopefully when you tackle the issue in coming months, we'll eventually cover your comments in much more detail, because they're spot on!

Cheers
Ross

amby said...

Guys: I've been reading a lot of exercise epidemiology recently, and in the 2007 ACSM/AHA position paper on recommended exercise prescription, I came across an injury observation I had never considered before. Namely: It means nothing to say that XYZ percent of runners get injuries unless we also know what percent of non runners get injuries. And there's good reason to think that non exercisers are more susceptible to certain accidental slip-and-trip types of injuries than exercisers, because they haven't built the same muscles and stabilizers. Plus, the obese non exercisers have additional problems. I don't think anyone would argue that runners get fewer injuries than non-runners. But the differential is surely less than those scary "60 percent of runners get injuries" statements we read all the time. Amby Burfoot

Stan Silvert said...

Good point Amby.

And when you put it all in that context, the whole idea of a "runner's injury" seems kind of silly. An injury suffered by a runner usually just means he has to rest a few days with an ice pack. When you talk about the injuries of non-runners you are usually talking about something more serious.

So the word "injury" is a very overloaded term that non-runners rarely understand in the same way we use it. When a non-runner hears about running injuries he is thinking of something more dreadful.

Stan

vikram said...

So when an athlete breaks down injured, you can't say "the anatomy CAUSED the injury". The training did. The anatomy simply contributed to the failure to adapt, and so the controllable factor, training, is still the key to address!

Hi Ross, when you get some time, could you expand on this ? What exactly does failure to adapt mean, and what does constitute an anatomical reason for failure to adapt ?

You mention that some athletes can get upto 50 miles a week without injuring themselves, while others have to incrementally build miles. So, the rate at which an individual can increase training stress (volume or intensity) is largely individual - depending on all the inter related factors that you have mentioned.

But how does one go about finding out what that rate is ? How do I know the rate at which I can increase volume and intensity ? 10% is just a number - going from 10 to 11 miles a week is very different from going from 50 to 55, right ?

Jonathan had mentioned in one of his comments that "Listen to your body". For me at least, I know that by the time my body has given an appropriate signal, it is usually too late - I need to back off for weeks. Also, it is hard to decipher whether the body is saying "slow down, you are increasing volume too fast" from "keep going, this is the right pace of increasing training strss, I'm adapting with appropriate rest". How does one identify the line which differentiates the two ?

Jesse's Cycling Addiction said...

Once again these Science of Sports articles have been timely based on my current status as I have expressed on the following blog entry.

http://thecyclingaddiction.blogspot.com/2008/06/managing-load.html

Thanks