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 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!
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)!
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Friday, December 14, 2007
Training techniques to improve economy (or should that be performance?)