really? All his runs? Too bad the miminalist aspect of barefoot runners also applies to honesty.  Hall has been running( sucessfully) for over a dozen years in shoes but yeah, let’s blame a current issue on it. Get real.

Pete:

Alternatively, if you are wanting to improve the metabolic efficiency of running, the best place to lose mass is at the ends of the  lower extremities, on the feet.  So, this is one of the best reasons, in my opinion, why running shoes should be a light as possible, in order to decrease the work of running, as long as the reduction of weight doesn’t cause some other problems, such as injury.

A very interesting related case to this discussion is the case of Oscar Pistorius, the “blade runner”, where it was found that he had extraordinarily fast forward recovery phases which was thought to be the main reason why he had an unfair advantage versus his competitors who had legs.  This very short forward recovery phase was likely due to his “blade prostheses” having much less mass than other able-bodied runners and the moment of inertia at the hip being much less, therefore increasing the flexion acceleration at the hip during forward recovery phase.  This directly ties in biomechanically and physiologically with our discussion on the effects of masses added to feet and the metabolic cost of barefoot vs shod running.

Ross Tucker and Jonathan Dugas have done an excellent job of detailing the very interesting biomechanical, physiological, ethical and legal case of Oscar Pistorius in their Science of Sport blog.

http://www.sportsscientists.co…

Cheers,

Kevin

Pete:

If you read my example, the velocity of the runner is not being controlled, running both barefoot and shod, but their metabolic cost or oxygen uptake is being controlled, running both barefoot and shod.  There is a big difference between these two factors at submaximal steady state running velocities. 

What I am saying is that the use of lightweight racing flats may allow the runner to use a slightly longer stride for the same metabolic cost as when they are barefoot, at the same stride frequency, therefore making them faster runners.

It would be a very difficult study to do, to control for constant metabolic cost, but this certainly makes sense to me.

Looking forward to reading your book.

Cheers,

Kevin

What is the primary issue? Health. The ability to run free of pain, free of NSAIDs. That’s what shoes rob us of. That’s why so many who should be running are instead bikers, swimmers, or couch potatoes.

Pete:

Every single study that I know of that has measured the effects of added masses to feet/shoes on oxygen consumption during running have added the masses either medially/laterally on the forefoot or dorsally on the forefoot.  Of course, ideally, to best simulate the mass that is added to the foot by a typical running shoe, the weights should actually be located on the plantar foot, but I don’t know how you would do this barefoot or even in a shoe without possibly affecting the cushioning properties in the shoe. Such are the technical difficulties of such experiments.

Cheers,

Kevin

Robert:

How do you figure that “When adding weights to the foot I would expect the increase in moment of inertia about the ankle to be far greater than the increase in moment of inertia about the hip”??

The distance from the ankle joint axis to the added weights in this experiment is likely about 10-15 cm, whereas the distance from the added weights to the hip joint axis is closer to 80-90 cm.  Since moment of inertia will increase as the square of the distance of the added mass to the axis of rotation, then I would estimate that the mass added to the foot would have at least 28 times more effect on the moment of inertia at the hip joint than at the ankle joint.

Please explain your rationale for your statement “When adding weights to the foot I would expect the increase in moment of inertia about the ankle to be far greater than the increase in moment of inertia about the hip.”

Cheers,

Kevin

Ryan

Thanks for sharing your thoughts Kevin. I would always opt for shoes in a race situation for a variety of reasons, and I think even most competitive runners who do a lot of barefoot miles would agree (Mark Cucuzzella is a good example). One thing to consider though is that many people in shoes tend to overstride, and Hamill published a paper in the late 80s showing that decreasing stride length in shod runners can improve economy a bit, or at least not incur a metabolic penalty. Also have to consider that Nigg showed that running on a treadmill tends to shorten stride relative to running overground, so that needs to be considered when applying these results to overground running.

Pete

Robert:

I would expect the the main consideration of shoe mass on metabolic efficiency of a runner is not the moment of inertia relative to the ankle, but rather the main consideration will be the moment of inertia relative to the knee and to the hip, since moment of inertia varies as the square of the distance from the axis of rotataion to the added mass. I = mr^2

In addition, this additional moment of inertia from a shoe or mass added to a bare foot would only be important during the forward recovery phase, when the foot is being accelerated forward, off the ground, and wouldnt be as important during support phase, when the foot is relatively stationary on the ground.

In other words, it is likely the hip flexors and extensors and knee flexors and extensors are the main muscles that are working harder and causing the extra metaboic cost during the forward recovery phase of running with mass added onto a foot, rather than the ankle joint muscles.

Cheers,

Kevin

Mark:

Pete mentioned this problem of socks vs true barefoot in the research study in his article.  I think the biggest problem with the study is not the “stuff on top of their feet”, since the weights would need to be placed dorsally on their feet by some method, but rather that the socks could have caused enough foot to ground slippage (i.e. decreased coefficient of friction) during propulsion that this may have negatively affected running economy of the barefoot runners.

I wonder why the authors didn’t use true barefoot running on a treadmill and then just tape the weights on top of their barefeet to determine the metabolic cost of adding mass to feet for running. I see the sock problem being the biggest issue with this study.

Maybe they couldn’t get IRB approval from the University of Colorado due to too much risk of plantar skin injury from running barefoot on a treadmill?  I would think that experienced barefoot runners should have no problems of running on a treadmill without risk of injury.  Can you run comfortably on a treadmill while barefoot?

Cheers,

Kevin

I have no problem that the study looked at economy – that is the topic that Rodger Kram’s lab has been studying for many years. Different research groups focus on different sub-specialties, and there are plenty of recreational runners looking to gain an edge in an effort to set a PR or qualify for Boston. I agree that health trumps all else, but we all have our own reasons for running, and some of us do have a competitive side even though we know full well that we may never win a race – I say this because I am one of those people :). That being said, I don’t think most people are considering running barefoot because of any competitive edge it might confer. But, if he showed that running barefoot was 10% more efficient, you can bet some people, probably even pros, would consider it!