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Friday, December 14, 2007

Running Economy Part III

Training techniques to improve economy (or should that be performance?)

Today sees the third and concluding part of our series on Running Economy. It's been a whistle stop tour of a complex subject. We have no doubt that we'll be returning to the topic in time, because it has major implications for how we understand fatigue and performance, but for now, we stuck to the boundaries - there is a lot to be written in the coming week! But hopefully today we'll provide some 'meat' that might help explain economy a little more, as well as provide some practical insights into how it can be improved.

On that note, there's a very valid question about whether you should worry about training specifically to improve your running economy, or whether good, common sense training just happens to improve economy as you do it.

I was out on a training run just yesterday, and have a 10 km loop that I do once in a while. Compared to about a month ago, when I just started running again after a layoff due to illness/injury, I covered the 10km a minute or so faster, running at the same effort level as before. And it occurred to me as I was jogging along that if I were to put on my scientist's hat (or lab coat, if you wish), I would probably find about four or five reasons to explain how I can run faster with the same level of effort - running economy would be one of them, for sure.

So in other words, scientists are sometimes very good at looking at the runner (or sportsman) after the fact and working out that X, Y and Z have changed, and that must explain the faster running, when all along, it's the simple fact that you've been running that explains it! Had I consciously spent the last month trying to improve my economy to help me get faster, chances are I'd only improve by the same amount anyway, or maybe even less!

The point is, sometimes the simplest solution is the best one, and that is the case with running economy. Over-complicating things by trying to target what we've emphasized is only one of many factors contributing to performance is likely to be a bit of a self-defeating task - rather just train, and let it happen!

The best way to improve running economy - just run!

Don't worry, that's not all we have to offer as practical advice for today! But it's the most obvious and truest statement we could make! When it comes to training, practice makes perfect. A great illustration was provided a few months ago when we were discussing Pose Running Technique, and we came across a study that looked at the oxygen cost of running in a group of athletes who had been taught Pose for 12 weeks.

What one would predict is that when learning a new running technique, the oxygen cost would go UP, because you'd be less economical as a result of doing a task that is relatively unfamiliar. And sure enough, that's what they found - running economy was worse when running Pose. A number of people wrote in and said this was expected, and that given more time (than the 12 weeks of training in the study), the Pose Runners would improve their economy. Maybe that's true (the debate about Pose was covered back then, you can link to the posts and read it), but the point is, within 12 weeks, economy was still worse.

Turning that around, it implies that regular running will improve economy. We don't often think of running as a task that requires co-ordination, timing, balance and motor control, but it most certainly is. If you ever want to see that in action, then you need to watch an elite runner training. They move differently from you and me (OK, from me - you may be one of them!). I remember standing track side as SA's Olympic Silver Medallist Mbulaeni Mulaudzi did some 300m repeats once, and being struck by the fact that he just moved differently - the flick of the heel during the swing, the arm carriage, knee drive etc. are all subtly different and I have little doubt that this neuromuscular control, while not exclusively responsible for performance, plays a big part, especially in distance runners. There are some other factors, which we'll touch on in a moment, that also contribute to this, though.

Endurance running - what do the studies show?

A couple of problems exist with the scientific literature on running economy. First, there are surprisingly few studies - remember, running economy was called the "forgotten" variable by one author (Carl Foster). Secondly, the initial level of fitness and ability of the runner plays a huge role, as I'm sure you can appreciate - a good runner needs very different training compared to a novice. So it's a little tricky to tease out the valuable information.

In general,however, research studies support that running economy improves with higher volume, slower running. So longer and slower distance training is more effective as a means to improve economy. The reasons for this include the increase in mitochondria, which means more effective use of oxygen by muscle. Also, it's been found that the longer and slower running eventually leads to a 'learned' neuromuscular response where the vertical oscillation of the runner is reduced. In otherwords, less time going up and down, more energy saved, and this is simply a function of repetition!

Now here's where things get tricky! Many of you are probably thinking "what about speed work?" Surely that will see massive improvements in running economy? There's always confusion about whether faster runners are more or less economical. And here, the general rule is that it follows what one might call The Law of Specificity, which basically says that you'll be good at what you train for! In otherwords, if you are a middle distance runner (800/1500m), then you'll be more economical at higher speeds than a marathon runner at those higher speeds. The interesting thing is that it's been found that this same middle distance runner then becomes less economical at the slower speeds than the marathon runner. So again, economy is good where you train it, which to me really re-inforces the value of training specifically, and how important co-ordination and motor control are!

So the take home message - if you're talking novice runners, with little running behind them, then any running will make a difference (as it did for me in the last month, I'm sure!). This is the point I made earlier - economy improves with fitness, and so any running is beneficial. But if it's performance you're after, and the very small improvements that make a big difference to performance (not just economy), then other forms of training become more critical. This also illustrates the complexity of training, and this is where we get into plyometrics and strength training.

Strength and plyometrics

Let's deal with strength training first. There is evidence that strength training improves running economy, probably because it improves the function of the neuromuscular system. In order to understand this, we first have to run through an admittedly basic introduction to an important concept known as the Stretch Shortening Cycle.

Basically, when you are running, a great deal of muscle activity occurs in the milliseconds BEFORE your foot lands on the ground. Why? Well, the muscle is 'pre-activating' in order to increase stiffness of the leg and joints ahead of landing. The stiffer muscle not only absorbs more shock, but it also helps the muscle-tendon unit to store more energy.

Think of the muscle-tendon as a spring. When you land, the muscle lengthens, in what is called an eccentric muscle contraction. As soon as you then push off, for what is called the concentric part of the running stride, you can 'harness' the energy that was stored when you landed. The concentric contraction is more powerful and more efficient, if it follows the eccentric contraction. It therefore uses less oxygen and energy to do the same job, or can do a better job. This is why if you want to jump up as high as possible (for example, to slam dunk a basketball), you bend down and then 'bounce' back up - you are taking advantage of what is known as the "Stretch-shortening cycle" to improve the performance of your jump.

The same goes for running, where this Stretch shortening cycle is critical to performance. The result of all this pre-activation and concentric-eccentric contraction is that the CONTACT TIME is reduced, and performance is improved. Fatigue during the course of a 5km time-trial has been shown to impair the ability of the muscle to "pre-activate", and the result is that your contact time with the ground goes up. Imagine a ball bouncing off a wall - if it gets softer and softer, it bounces off much more slowly, whereas a very stiff ball returns quickly (golf ball vs squash ball, for example).

How does this relate to running economy and strength?

Well, apart from the obvious theory which is that the muscle is stronger, the theory and evidence is that strength training improves running economy specifically because the contact time and reflexes that control the neuromuscular system are improved.

In particular, there is a type of training, known as PLYOMETRIC training that has been theorized to be very effective as a means for improvement of performance and running economy.

Plyometric training

Plyometric training is an explosive form of strength training, which uses drills like hopping, bounding, jumping, skipping and sprinting. During plyometrics, you are exaggerating the stretch shortening cycle, causing major eccentric and concentric training, and this helps to improve the efficiency of the whole system. The result is that the athlete is better able to store and use energy, and therefore the muscle can produce the same force (and hence running speed) with less energy demand, so VO2 goes down. Also, there is evidence that plyometrics increases the stiffness of joints, and stiffer joints are better able to store and release the energy, again saving the cost of running without sacrificing speed.

There is a very intriguing theory that African runners have a more developed, better functioning stretch shortening cycle that Europeans. Also, a Finnish scientist (Paavoleinen) found that plyometric training improved 5km time-trial performance by 3% (this was in quite good and highly-trained runners, so 3% is no laughing matter), which was associated with reduced contact times and running economy (8% lower).

Having said all this, beware of overdoing plyometrics as the "Secret weapon" for your training! The risk of injury is high, and so this should neither be tried out by novice runners, or done too often. It's a very effective method of training if done properly though. I certainly don't coach athletes without also using this kind of training, though it takes different forms, depending on the athlete - sometimes hill running is sufficient, whereas other times, you can get creative and come up with all sorts of drills, using hurdles, ropes, and your imagination! But again, not something that should be overdone...

Flexibility - you CAN be too flexible

The final component of training we look at is flexibility. There was a time when athletes were being drilled to do as much stretching as possible - failing to do so, we were told, would predispose you to injury. Well, injuries aside, there is evidence the being TOO flexible also negatively affects running economy, and thus possibly performance.

There is confusion about it though (as usual, I guess!). One study, for example, found that improving flexibility of the hip flexors and extensors(to lift the knee) resulted in better running economy. The argument here was that if you are flexible enough, and provided you have balance between left and right, front and back, then you need to do less work to balance and stabilize the body during running.

But then other research has found that being less flexible is better. In fact, more studies show that less flexible runners are more economical than the other way around. For example, from novice runners all the way to elite runners, it's been found that as the flexibility in the trunk (hips, and core muscles) and the legs improves, running economy is lower. Therefore, if you want to be economical, you'd err on the side of being inflexible!

The theory behind this option is far more believable to me. We've discussed how the stiffness and ability of the muscle to store and then release energy helps with running and reduces oxygen cost above. Now, the same goes for flexibility. If you are very flexible in the legs (especially the calf and ankle), then you need to do far more to stablize and store energy, and so it pays to be stiffer, less flexible.

As far as the core muscles and trunk go, the less flexible you are, the more stable the pelvis is, and the less muscle work is required to limit the motion as you run - you're a more 'compact unit' so to speak. To sum it up then - less flexibility means less work required for stability and also more elastic energy return from stiffer muscles and joints. I therefore tend to believe the theory that being less flexible is better for running.

Having said that, it doesn't mean that flexbility is not important. I hope it's quite clear that it's all about BALANCE. In other words, right vs. left, front vs. back balance (in both strength and flexibility) is what determines stability and thus possibly economy. The take home message is therefore to avoid random, indiscriminate stretching, because for all you know, you're messing up your natural balance, increasing injury risk and becoming less economical. But also, don't avoid stretching altogether, because then you might go the other way and get too tight in one important area! Everything in moderation!

Conclusion

So that's it for Part III, and the series. It's been a very interesting one, confirming the words of Carl Foster that running economy is a forgotten aspect of performance! It certainly seems that we have much to learn. The future of running research may be along the lines of the Tadese study that kicked off this series, and perhaps in a year or two, we'll understand much more what causes such remarkable running economy.

My personal feeling is that biomechanics, small calves and long legs aside, there is something critical that we can't quite measure. I am a big believer in the neuromuscular factors affecting performance. I believe that running economy is in fact a symptom of some underlying neuromuscular process or system that confers an advantage of certain runners. When you train, your neuromuscular system improves, you become more co-ordinated and your running economy improves, along with performance. But quite what this neuromuscular adaptation is (apart from the ones we've discussed) is not clear just yet. I feel it will go a long way to explaining the East African dominance in running and will also explain fatigue more comprehensively than any other theory.

So it's quite clear that we're not done with Running Economy! It will be back! We hope that this particular series has been interesting - we certainly haven't had the same debate, but it's a far less controversial topic than the muscle cramps and fluid ones!

Join us over the next few days as we scratch the surface of Baseball's Mitchell report and the report on Pistorius (which we hope is out soon)!

Ross

13 Comments:

Oliver said...

Great stuff again.

Running Economy may be the 'forgotten' variable to the sports scientists, but its something that is always discussed amongst seasoned marathoners or on forums.

Some of the stuff that I have been saying is confirmed, i.e. if you ask me for advice on a sub 3hr, the first thing (amongst others in a limited time for training) is to run a good % of training at that pace. race pace training is specific and will ensure best economy at that pace.

Another thing that I have related back to RE is the stride and footstrike- again something, as you mention may be neuromuscular, which comes with enough running at that pace.

When the argument about heel strike/midfoot/forefoot comes up, I just point people to elite race videos- my favourite is 2002 London which had a big pack to 30+ km. All bar one strike mid/heel and the argument about 'braking' 'overstriding' is not supported. The reason ,a s observed is that the stride is due to a high backlift aided in part by 'free' energy from the spring effect of the stored tendon/muscle energy. This enables the carriage to be such that there is a lot of 'air time' to create a long stride (without 'over' striding) with the leading leg landing with almost verticle lower leg at contact, as torso comes right over it (i.e. under centree of gravity).

this is an important aspect (one aspect) of why these guys are economical beacause they achieve high backlift without high knee lift (or verticle oscillation) and the carriage of the knee is then propelled forward by the pendulum of lower leg, thus repeating swing again.

Keep it up, all the stuff so far is music to my ears.. the salt debate, hydration, now RE, possibly, possibly because we hail from the same neck of woods-- which of course is the danger of our bias and paradigms one has to guard against.

cheers

Ross Tucker and Jonathan Dugas said...

Hey Oliver

Thanks a lot! INteresting addition to the argument.

There was a study from a group in Japan recently, looking at footstrike patterns in a group of 21 km runners.

They found that in a group of runners taking part in a high level 21 km race (where competition was invitation only - so the field was incredibly strong), 75% landed on the heel, 24% landed mid-foot and only 1% were fore-foot strikers.

In the top 50 runners (guys who ran under 63 minutes for the race), 62% were heel strikers, 24% midfoot and 2% forefoot.

So the perception that the faster, elite runners are forefoot strikers, which is a perception largely created and driven by Pose/Chi running, though they'd argue otherwise, seems not to be supported by this study. This is a study I'll probably tackle in a "filler" post some time in the future!

I also observed Haile Gebrselassie running in Berlin for the WR and he's definitely not a forefoot striker in the marathon. On the track he probably was, but he's now midfoot, some times heel.

So I agree with you on that. The other thing that has always struck me about the elite is that 'heel flick' at the top of the swing phase for the trail leg, as mentioned regarding Mulaudzi. That action means that the leg is in the fully flexed position as it is swung through, which is the most economical (see Part II) because the "lever arm" is as short as possible. So the velocity of the swinging leg is maximized with minimal effort, also contributing to the stride length they achieve.

Great comments, thanks for the continued support!

Ross

Ryan said...

Hi Ross and Jonathan-
Have you guys heard of the Newton shoe? It is designed for forefoot runners, its pretty interesting. Go to this page: http://www.newtonrunning.com/run_better.php

It seems like a gimmick to me, but I would still like to test them out! But the price doesn't warrant the investment ($155)
Maybe once they distribute in regular stores.

Anyway, I agree with almost everything you guys have talked about in your Endurance series, Kudos!

I have an interesting perspective on heel-striking and Pose/Chi Running. Last spring I tried Chi-running because I ended up with severe cramps in both of my hamstrings in the LA marathon. They turned black and blue 2 days later. I have been running for 10 years and my hamstrings have always been tight and suspect. When I switched to Chi running, my hamstrings finally loosened up and haven't bothered me since. I don't follow any of the wacky Chi stuff though, the things I got out of it are that I just lean forward slightly, run with a faster cadence, try not to overstride and focus more on relaxing. It works for me, and avoiding heel striking has helped me get faster with less injury.

St. Kevin said...

I have read some of your posts. There was one you mentioned the stress put on the knee is moved to the ankle when you land on the forefoot or midfoot vs landing on heel.

I agree with you about theres no 'one style fit us all'.

Someone may be able to handle more stress on the ankle, while some can handle more stress on their knees.

So some may be better with heel, while some may be better with midfoot or forefoot. Since they will come up with less injury and down time.

Just my 2 cents.

Keep the great posts up!

Ron said...

Your theories about stretching seem slightly humbug to me

The human body is so complex that all these theorizing is not going to help. Some things work for people, some don't. I ask whether you're theories are observed in reality and whether they are repeatable.

I suggest you bring something up specifically about how this runner trained in the next part. Thats what I'm interested in knowing. Because all other factors aside, we all know its maybe a 1 in 100 or 1000 chance that we'll have the genetic characteristics of this particular runner. I hope the study says something about his training schemes so comment on that.

Ross Tucker and Jonathan Dugas said...

Hi Ron

Not sure I follow exactly what you're talking about, to be honest?

When you say "this runner", are you referring to Tadese? Also, if you read the posts, particularly the previous parts to this series, you'll see how we repeatedly emphasize the point that the human body is complex and probably too complex to understand fully.

So I feel that perhaps you are expecting a magic bullet, one-stop shop where someone tells you EXACTLY what needs to be done to improve running economy - unfortunately, you'll be looking for a long time, because no one knows!

So the section on the flexibility is a summarize on the available literature, as well as the THEORIES surrounding it - there is no way to study or to summarize this any better, so I'm sorry it's "humbug"!

Truth is, it's the most that's known about it.

So yes, perhaps you think that all this "theorizing is not going to help", but then you've missed the point - the site was never intended to be the Book of Answers, just an interesting site on what available knowledge there is, and this is it as far as running economy goes - See Parts 1 and 2 for more on that!

Thanks for the comments!
Ross

Anonymous said...

great post and great blog guys! keep it up

Anonymous said...

Hi Guys:

I'm really enjoying the work you're doing... keep it up!

One comment on the role of flexibility and performance/running economy: Agreed that too much flexibility may compromise the stability about the joints of the pelvis and lower limb. As you mention, I think individual flexibility needs will no doubt guide a runner in his/her training, however I feel it should be reinforced that strong yet flexible muscles will yield the highest performance/injury resistance benefits. In other words, flexible muscles are really only a risk if they are also not strengthened appropriately.
I also believe that the important distinctions be made regarding the various types of flexibility training available to runners. I'm sure you will agree that static stretching methods produce rather different results as compared to more dynamic flexibility techniques. I could elaborate more on the different types of flexibility training, but perhaps you might consider running a series of posts addressing this?

In closing, let me say that while you guys discuss sometimes "controversial" topics, you always seem to do so in a very professional, objective manner, and you respond to blogger comments in a very courteous manner. Much appreciated, and certainly refreshing!

Happy trails,

Ironpat

John said...

I've been doing 90 min. uphill runs on a treadmill twice a week at a slow pace but at 6 degrees incline. I'm thinking of that as a form of strength training and that uphill running for that long will improve my running economy. What do you think?
(I've read that Moses Tanui used to do these kinds of run except on a real hill in Kenya.)

Anonymous said...

Hi

Thanks for all the commentary.

Just wondering about something i heard (no idea of source any more) that running hills wont build speed for sprinters because your leg turnover is slower on the hill...
Hills only ok for more endurance events, which begs the question, at what distance?

Thanks

Ross Tucker and Jonathan Dugas said...

Hi there John and Anonymous

Thanks for the comments, I do apologize for the delay in replying to your post, John. I will blame it in Festive season disorganization!

My own personal take on hills is that everyone can use them, even sprinters, but you have to be very clear about the objectives or goals from the session.

If you are a sprinter, then the benefits you develop from running a hill is very very different to what you need as a marathon runner. A sprinter wants power and explosive strength, an endurance runner is after fatigue resistance, endurance and stamina. So it stands to reason that aspects of the session should be very different too.

For example, if you are a sprinter, then my advice is to choose a very steep hill (10 to 15%), but make sure it's very short, and that you get long recoveries between runs. You might do a session of 8 x 60m sprints up this steep hill, with a 3 minute rest. Because the repeat is so short (10 seconds) and the rest so long, the pace must be high. In this case, you overcome that problem of slow leg turnover and derive the main benefit, which is power.

For a sprinter, I would not do a long hill, because yes, the relatively slow loading rate doesn't contribute all that much to the running ability. Of course, there is no 'cut-off' point, and any hill running still develops all the 'ingredients'. But my personal coaching philosophy is to put all your eggs in one basket PER SESSION. In otherwords, don't mix and match from training - pick a goal, and then go for it in each session. The right mix of goals adds up to a faster runner.

You can apply the same logic to endurance runners. As an endurance runner, you have a choice of how to put a hill session together. I personally would go for one of two extremes:

1. If your goal is stamina, strength, and strength-endurance, then pick a long hill, but make sure it's gradual - it doesn't need to be steeper than about 5%. In fact, if it is to steep, the session becomes counter-productive, because it becomes too "static" and you lose out on the neural and muscular adaptations. So rather stick to a gradual slope. The length would be anything that takes 3 to 4 minutes - so between 500 and 800 m for most people, on A GRADUAL hill. As for number of repeats, 5 to 8 will do. Recovery will be a 1:1 ratio, so if you run 3 minutes, rest 3 minutes.

2. The second option you have is to improve your own power (for finishing kicks, sprinting ability, which all endurance runners need). Here, you do the same as a sprinter - a steep hill (10%), short repeats (80 to 100m), and focus on keeping the leg turnover high. Recoveries would be between 2 and 3 minutes.

That's my take on hills. The mistake I feel people make, even endurance runners, is to pick a hill that is too steep to run LONG repeats, the result of which is that they become laboured and ultimately compromise other important aspects of performance. You may slog up a hill feeling like you're training incredibly hard, but you drift away from the specific training that you should be focused on.

Happy New Year, by the way!
Ross

Srdan said...

Hi, for those who are interessted in further studies about the influence of plyometrics on running economy check SPURRS et al. (2003) and SAUNDERS et al. (2006).
Right now I´m doing some research on the effect of plyometrics on the running economy through optimizing the "stiffness" of the leg and thus using the elastic energy more efficently. So, I totaly agree with your post and the comparison of the human leg with a spring.If you can sustain a high pre-activation of the leg throughout a long part of the race, you use more of the elastic energy (which is passive), "bounce along" and thus can save more of your (active) muscle energy production i.e. for the last lap. But to store or use the elastic energy, you must run on your mid-foot because only then you get the achilles-tendon and the triceps surae muscle group to stretch and store the elastic energy. This does not happen if you run on your heel. Perhaps those to things are a part of the mistery of the Etiopians incredible last lap and the remarkable running economy of the East Africans.

Lem said...

To srdan,

I used to think like you that a heel strike is uneconomical, but I now qualify that belief. I now believe that the heel strike predisposes one to an inefficient running gait (i.e., not maximizing the preactivate-stretch-recoil cycle) but does not absolutely condemn one to it. I will have to agree with the ideas in the book by Frans and Bosch that utilizing "reactivity" (their term) depends on where the foot is in relation to the body's projection of center of gravity on the ground once the weight of the runner is fully supported by the stance leg.

I am doing similar research as you (plyo and RE) and we could exchange notes and ideas if you like.

Lem