What does ‘flexibility impairs economy of running’ actually mean?

The researchers since the mid 90s have decided that flexibility impairs economy of performance in running. They have tested it. And that’s what they have found. Or that is what I read according to sports scientists I respect. I am not an expert of the metabolic aspects of economy but I believe it means that being more flexible leads to having to use more effort and so burn more oxygen which is used as an indicator for economy. Well not every piece of research has come out that way but quite a bit and none has come out positively in favour of ‘flexibility’. And it interested me because while Feldenkrais certainly doesn’t seek flexibiity as the answer to everything (rather improved use of self to do whatever it is you want to do – which we could call integrated functional organisation perhaps) I do spend a lot of time enabling runners to be able to find more possibilities in places where they need it to be able to, well, run better and while I don’t have this kind of research I am quite sure it doesn’t impair their economy. Quite the opposite. Maybe that doesn’t count as flexibility? I understand the need for a certain kind of ‘stiffness’ in the sense of a stiff spring that rebounds rather than a soggy spring that doesn’t but I wouldn’t call that INflexibility. Indeed, inflexiblity and stiffness don’t have to be the same thing. If you wish to be able to make an effective kick to someone’s head in karate you will need astonishing flexibility in the hip joints and back (and even a whip-like compliance in a round kick) but also stiffness on contact to transmit force. And it is my experience in running that compliance in the right places and to the right degree enables you to use the possibilities of inherent elastic rebound as well as a certain stiffness in the tissues. We are after all talking about a spring. Not a plank. But does that count as flexibility?

the researchers’ favourite test

So I was puzzled. What did they mean by flexibility or inflexibility and where? So I went looking for the research itself. Some of it is pretty interesting – eg the introduction to nelson et al (available in full on the net) but It turns out that the test for flexibility in every piece of research I could find the details for was a seated stretch and reach test. Ie sit on the floor with your legs out in front and reach for your toes. That’s it. There may be 5-15 exercises to improve ‘flexibility’ (mostly different versions of stretch and reach with  a couple of stretches for the front of the hip (passive) and a calf stretch) and then they are all tested by stretch and reach. The first question I have is in what way does this test represent the kind of flexibility you need for running? Leaving aside the arguments over what kind of stretch it is (static and passive rather than dynamic) and what this kind of stretching actually achieves, and when you do it in relation to running or for how long (all of which are interesting and very valid questions) just ask yourself how many people run by lengthening the backs of their legs and bending forward? If this is flexibility I can well imagine that learning to do this doesn’t help runners! At the best being able to do this might not impede them which is the best any of the research can come up with. It is not a movement or organisation of skeleton and muscles that has anything to do with running. Unless you wish to run by goose stepping. And I can believe that is not the most economical. The most favourable interpretation I can make is that this kind of stretch is something someone might do after running to balance up again and  relieve the after-effects of constantly shortening the hamstrings during running, which one can imagine might be a good idea for life at least (if it works) and to maintain the ability of the muscle to have some kind of length from which to shorten – but it still doesn’t explain why all kinds of flexibility are apparently judged by this one very specific test.

what kind of flexibility do you need for running?

However, surely it is not beyond imagining that there are certain kinds of flexibility that do enable a better organisation for running. Some of them are well known. What coach would be happy with a runner who cannot open their chest at the front because of chronic tightness in places in the muscles of the chest (and/or belly) that mean the person runs bent over? What about the person who cannot release their shoulders and runs with them held up all the time? What about the person whose has a tight iliopsoas or other contributors to hip flexion that make it hard to open up the front of the pelvis and take the leg back?  (very common in this age of desk jobs, computers and television) What about a diaphragm held so tight it impairs breathing – or, along with other muscles of the back,  can hold the lower back tight? What about inflelxibility between the 26 bones of the feet that need some flexbility to store and release energy for elastic return? How will that kind of inflexibility help? OK so if you wear conventional running shoes you lose most of that possibility I gather, but even so you still need some compliance in your ankles,  calves and feet  (and I don’t mean sogginess/ lack of tonicity)  to reduce impact forces and adjust to the ground and to enable what elastic return your footwear allows). You may need a stiff spring for sure, but to repeat myself:, it must be a spring. Not a plank. And then there is that adjustability of the spine that gets very little mention: not just to enable the front to lengthen (very important) but for the pelvis to rotate. Vertical rotation gets a bad press but it is crucial. You try running without it.  Not wild, huge and ‘wasteful’ but enough to be able to swing the leg forward and back. And it will be more economical (I would put money on it though I can’t point to a piece of research) if that turning is shared through the spine so it can be very small in each place rather than bigger in one place. In fact often the big, wild rotation or other kind of pelvic displacement is a result of NOT being able to rotate high enough through the spine so it all happens in one place too much or has to do something else because it can’t rotate. I see that in my office all the time. And then of course If there is no rotation you can’t take the leg back and you are condemned to a knees – up style of running which is very hard work, not to mention the waste of energy in tightening up to stop the natural rotation happening. Now that kind of small movement through the whole spine is not a kind of flexibility you often find. Most of us use mostly the lower thoracics to rotate and don’t have the flexibility in the chest or between the shoulder blades to allow it through. But who ever talks about that in relation to running? And yet that’s what I find myself working with over and over. Then there is a kind of flexibility of the chest and back that enables you to really be on one leg – rather than on one leg with most of your waist and back still over the other leg (look for it and you will see it in most people, not just the ones who tell you they have a scoliosis). And there is a kind of flexibility in the top of the spine that allows the head to float as everything moves under it (think tiger). Tell me where are these kinds of functional flexibility for running tested in the stretch and reach test? And where are they improved by the kinds of stretches included in the research as ways of improving flexibility? Bits perhaps, especially if you focus on what the back and chest have to do for the arms to reach but I doubt that was the focus somehow. However, I think it is clear that it is very far from an adequate programme or test for the enormous statement the researchers then make in a announcing that flexibility impairs economy in running. Maybe they should say  ‘conventional stretching and reaching impairs or at best doesn’t help running’ – as only a couple of them do and certainly the eminent running sports scientist I was originally reading didn’t make clear. And then perhaps it isn’t so earth shattering as a statement and one might wonder why so much research has gone into it when there are many other aspects it would be great to look into.

(and by the way if you are interested in exploring these aspects of the organisation of movement for running that I have described why not come to my course of 4 weekend afternoons in Feb 2013? see previous blog or bottom of schedule page on this site)

Research examples:

Craib et al 1996
Gliem et al 1990
AM Jones 2002
Beaudoin & Whatley Blum 2005
TC Trehearn and RJ Buresh 2009
Nelson et al 2010
JM Wilson 2010