FluidAxis from Asics

Dana Wrote

Dana

I can see where your coming from when you are considering the shoe construction in terms of the statement in the 1st paragraph above. However, in terms of the second statement there is kind of a circular logic in that the conclusion is contained in the proposition, i.e. When using a flexible shoe the non pathological foot doesn't need a stiff shoe to restrict motion to stop pathology occurring. This doesn't imply that a stiff shoe will cause injury to the non pathological foot but indeed the stiff shoe may be heavier and so increase metabolic energy use.

Is there a correlation between shoe stiffness and metabolic energy use?
Is there a correlation between shoe stiffness and rates of foot pathology? If there were then I would imagine it would have to be relevant to and within certain initial and boundary conditions e.g.. narrow exclusion criteria for the subjects and only track running?

As a podiatrist I am concerned with the pathological foot or the foot that has the potential for pathology. My ability to discern the metabolic energy losses or gains from various shoe designs is limited and verging on being outside my scope of practice. Obviously I can determine that a 400 meter runner would use less energy during the run in a pair of light flexible running shoes than in a pair of steel reinforced work boots. However if they had a severely valgus forefoot and lateral STJ axis then they might be less liable to inversion sprains in the work boots and so if this runner always ran in these boot they may never experience pathology on the other hand may never win any races.


Dave Smith

 

Just for fun I wanna know what DrSha thinks!!! (hehe)

 

Dave, good post and good questions. I don't know if there is a relationship. I can speculate that the shoe companies must think there is a relationship. The shoe companies are the ones who decided to provide a rigid shoe with the introduction to the "board last" a very long time ago and still offer shoes with rigid soles today.

The introduction of the board last was to cure the problem they were having with runners developing issues from the ever increasing cushioned shoes they were developing. It was also a cheap way for department stores to make shoes that posed as running shoes. I remember the shoe magazines used to recommend new runners buy shoes based on price to steer them away from cheap shoes designed to look like running shoes.

I believe that if you are a healthy runner that does not have a history of motion pathology that you won't benefit from something intended to fix what you don't have. My opinion stems way back to the early 1980's, long before the internet, long before the barefoot thing and long before running shoe companies started marketing "minimal" shoes. In a prior post I gave two shoe examples. These two shoe models did more to help me formulate my opinion than any other shoe. The first model came out in 1981, the Nike Terra TC. For the time, it was a very light, soft shoe that was Nike's first shoe to use Phylon in the midsole. Very soft and super light compared to EVA of the time. The shoe had no added stiffening plates was built on a curve last and was fairly flexible from heel to toe. I found the shoes ideal for training and for racing. In 1984, the Onitsuka Tiger X Caliber GT was introduced. This was also a great shoe for it's time. It had a board last the full length of the sole and was the first to introduce dual density foam in the midsole. This shoe really led the industry in the area of stability/motion control. I bought a pair of these shoes out of curiosity from all of the hype. I found them to be comfortable but I sincerely felt that I ran much better in the Terra TC's because the TC's where far less cumbersome and lighter. I concluded that I definitely did not need shoes with stiffeners or motion control devices. Not only did these shoes not help me, I felt they slowed me down for multiple reasons. Did they help other runners? Since the shoe companies are still using dual density foam technology and have replaced the cardboard stiffener with molded plastics, I'm sure the shoe companies think so.

Fast forward over 20 yrs and rather than the discussion being about board last vs slip or curve last, we are now talking about traditional vs minimal shoes. Trust me, I have not needed the minimal shoe web sites to tell me about the benefits of minimal shoes. They aren't telling me anything I haven't learned from 30 yrs ago!

I have grown to despise labeling or categorizing of shoes because it doesn't work. I understand the need to simplify the sea of options for the new runner who is overwhelmed with options but for an experienced runner, shoe selection should always be based on a specific set of characteristics that are important to and work for that runner. The shoe companies and retail stores should be listing the characteristics of their shoes not trying to pigeon hole them into some predefined broader labeled category.

There is at least one study that I know of that tried to measure energy return and usage. This was discussed at length in 2007 on this forum. Simon Spooner pointed it out here: http://www.podiatry-arena.com/podiat...ead.php?t=3990

The study tried to compare using a carbon fiber insert of varying stiffness into a shoe to measure it's effect on energy storage and usage. The findings were confusing and found contradictory even to Simon.

When you ADD something to a shoe, you are always adding weight so there will always be a trade off between any energy benefits you get with the energy cost of carrying extra weight. Of course when you add something, you might be able to take something else away. I just haven't seen any break through technology that has made us faster, healthier runners other than the use of stronger, lighter, more durable materials.

I think the jury is still out on this one, although Mizuno is betting the farm on their "wave" technology. A wavy rigid thermoplastic plate in the midsole that is supposed to store and return energy. We'll have to see how many marathon records fall over this one.



If you look back at the first few posts in this thread, it was about the fluid axis technology. I have had my opinions about rigid soles for over 30 yrs now. Putting that aside, people can buy and wear whatever model running shoe they want and people in the health industry can recommend whatever they want. I was just really encouraged to see that Asics and Simon Bartold were communicating a different look or point of view of the rigid sole. This is not trivial, a shoe company has to be pretty serious about a shift in ideas before they start sinking big money into development and marketing.

If you divide runners into two categories, those that have pathology and those that don't. With respect to running shoes, those two categories of runners may very well have different shoe requirements or they may not. This point seems to be a big source of debate and discussion these days and I don't think anyone has convinced anyone of their point of view with compelling evidence in either direction. As a healthy runner, I know what works for me.

Dana