Barefoot Running Debate

Anyone that calls themselves "America's podiatrist" needs more than just a chat to correct their behavior.:butcher:

 

Kevin, I thought about this while running this morning. I do believe my heal touches the ground first with midfoot a split second later. If I'm correctly interpreting what the nerves in the bottoms of my feet are telling me, they are saying that the bulk of the load from landing/impact is concentrated on my midfoot and disperses towards the heel and forefoot.

Connected to this, I thought about the shoes I was wearing this morning, Adidas Response Trail 14. They have a least a 12mm drop in height from the heal to the toe. Even if my foot was level as it approached the ground, the heal of the shoe would arrive first. It actually pretty difficult to NOT land on your heel without really pointing your toes toward the ground before impact.

It is probably safe to assume that my foot landing is like 80% of the other runners. It is also safe to assume that I wear shoes similar to what 80% of the other runners wear as well. I don't buy the Chi running, Pose running or the Lieberman comments about heal striking so I don't need to worry about their propaganda.

Getting back to Craig Payne's initial question: The gait pattern between barefoot and shod running is different, so is the less injuries that are particular runner gets when running barefoot really due to that change in gait pattern and nothing to do with the barefoot?

I thought Craig was on to something by looking at gait as the driver behind a change in injury rate, rather than whether the runner is barefoot or not.

Kevin and others, What are your thoughts about Craig's initial question.

I added that in addition to potentially reducing injuries, a change in gait pattern can lead to improved efficiency. Anyone have thoughts about that?

We got off on a tangent about heal striker vs forefoot striker. OK, I've come out of the closet, I'm a heal striker. I admit it, whether I wear shoes or not, my heal hits the ground first. But other than what part of the foot touches the ground first, what about the other components of gait with respect to injury and efficiency? What about the change in other components of gait with respect to wearing shoes or not?

Dana

 

I too am skeptical, unfortunately I only have 6 data points wearing VFF's. I could just be seeing statistical variation at this point. I will report back after I have 10X as many data points. With what I have, right now I can run on this hilly 6.7 mile trail at an average of 9 minute pace for the whole run and expect my HR to average 138 bpm give or take 2 bpm. I can expect that because that is exactly what it comes in at time and time again. What the 6 data points I have wearing VFF are telling me is that if I run that exact same route and keep my HR at an average of 138 bpm for the entire run, I can expect my pace to be 8:18 per mile. That is over an 8% improvement in pace at this point.

I am really curious to see how this plays out over the next year. Data collection will be slow because I will not wear VFF more than once/week because I don't want to risk getting injured! I'm sure the gap will close, who knows how much, if not completely. I sincerely believe I can run faster and further in traditional running shoes. If there is some efficiency to be gained by a change in gait from wearing VFF, I would hope to be able to transfer some of that learning to the gait I used when wearing traditional shoes. If so, I will be the one to benefit from it.

Dana

 

Bobba, I agree with what you are saying. What do you think of Craig Payne's initial question?

Dana

 

Dana:

Now that you have become a Podiatry Arena "regular", I will treat you like I treat all the other "regulars" on this forum:

Heel: the calcaneus or rearmost section of the human foot

Heal: to improve or cure a medical condition

Precise written language is necessary to optimize communication in scientific discussion.:drinks

 

forum terrorist group C.O.E.T strikes again.

















Before anyone goes what the ..... you should know better .........................

Children Of English Teachers

 

Kevin, sorry. Sometimes the spell checker fails me miserably. My grammar is what you should really be concerned with.

I would really like to have your thoughts to the questions in my post. Thanks. :drinks

Dana

 

So you heel strike in all shoes including VFF?

I'm getting a bit confused, you said:

Yet previously you have stated that you rotate your shoes to suit the variation in terrain you are running upon on a particular day. I can find the quotes if you want.

As Kevin stated previously heart rate in isolation is not a great indicator of metabolic cost. You could improve on this by calculating a physiological cost index.

So your leg stiffness is apparently unaltered by wearing VFF, your strike pattern is according to you also unaltered by wearing VFF, yet your heart rate is lower? What is the difference in weight between VFF and your lightest shoe you have data for ?

 

Thanks for the links DaVinci. That website really shows specific examples of how the research has been misinterpreted. I am surprised that some of those misinterpretations are coming from professionals in the medical community. I understand how a recreational runner with a blog can make that mistake, but a medical professional should know better.

Do you or anyone else here happen to have a copy of the Robbins and Hana study Running-related injury prevention through barefoot adaptations? I see many conclusions have been made from this study which seems to be unsupported. I’m particularly interested in the claim that injury rates are substantially higher in Haiti among the shod population.

What was his original question? I apologize for asking, but there have been so many posts it’s hard to keep track.

 

Simon, there you are. I do rotate my shoes to suit the variation in terrain that I'm running on for a particular day. In addition to rotating my shoes for the terrain, I believe I said I rotate my shoes every day as well. I do run the same route every WEEKDAY, the weekend routes are different. Although sometimes I have changed my weekday run. I guess I shouldn't have said exactly, but I was trying to be clear about what I was measuring and plotting my HR against which is EXACTLY the same route.

When wearing VFF, the nerve endings in my feet and my eyesight tells me that my whole foot comes in contact with the ground. Kevin has convinced me that I need a high speed video set up to confirm that. I might heel strike, maybe it's mid foot strike, I do know my heel touches the ground. I just don't know if it is at the same exact time as my midfoot or a split second sooner.

It would be great if I could get on a treadmill, set it at a specific pace and measure oxygen uptake while wearing VFF vs traditional shoes. Measuring AVG HR against AVG Pace is something I do everyday. I thought it was showing something interesting, that's all. Nothing I can debate.

Did you infer that my leg stiffness is unaltered wearing VFF based on the jumping test I did in my basement? If so, I would say there was too much room for error.

I sincerely doubt leg stiffness is the same wearing VFF. My heel MAY touch the ground first in VFF like in traditional shoes and it is possible that the load from impact may have shifted to a different location on my foot. I don't have a pressure plate to measure. You forgot to include that my stride rate is higher for a given pace, therefore stride length shorter. What about other possible changes in gait? Yes VFF weigh 5.7 OZ vs an average of 12 OZ the same size traditional shoe.

So, we have different leg stiffness, possibly different load/impact bearing location, possibly different strike pattern, different stride rate, different stride length, possibly a change in other gait characteristics, AND a change in shoe weight. Might this have an effect on efficiency? I would say there is a chance. Simon, what do you think?

Dana

 

That's not what you said above, you said you run the same route "every day". Please try to be accurate. What do i think? The jury is out on you, Dana. There is inconsistency in your responses to questions, I suspect there is a degree of BS, and that you are enjoying the attention.

 

Simon, for whatever your reason is, you are taking bits of my comments out of context. When I made the comment, I was trying to stress the fact that I'm measuring my HR and plotting it using EXACTLY the same route. You are right, I don't run the same route every day, it is very often but not necessarily every day, sometimes I even take a day off. I shouldn't have said every day but it is totally irrelevant to the point I was trying to make. I recognize you are trying to discredit me, oh well.

Trust me, I get enough attention at work and home, I don't need anymore here. What I do find predictable is that all I need to do is mention VFF and I get plenty of attention whether I want it or not.

What I find curious is that no one except me responded to Craig Payne's initial comment/question. Why is that?

I tried to answer your questions, now please try to answer mine: So, we have different leg stiffness, possibly different load/impact bearing location, possibly different strike pattern, different stride rate, different stride length, possibly a change in other gait characteristics, AND a change in shoe weight. Might this have an effect on efficiency? I would say there is a chance. Simon, what do you think?

If you could also look back at Craig Payne's comment about a different gait for barefoot vs shod and a different injury rate, I'd like to hear your thoughts about that as well.

Dana

 

Dana, I am taking your posts exactly within context.

Within the limitations of the test, which is what it is, but does appear to correlate with running, you didn't have any difference in your leg stiffness. Indeed, you are the only person I have ever known who had symmetrical leg stiffness on first testing.

You have told us that you strike rearfoot first regardless of shoes.

Your step rate was the same in the test.

Unmeasured, but since leg stiffness is dependent upon knee , hip and ankle kinematics, and your leg stiffness was the same....

Such as...?

What was that difference?

unless there is a difference in kinetic variables, there will be no difference in injury rate.

I think if you want to know more Dana, you need to go into a lab and have some proper testing performed.

P.S. why would I want to discredit you? What credit do you have?

 

Here in is the problem...That Haiti study does not exist and is made up. How often have you heard it mentioned?

 

It looks like it was an actual study and I can see the abstract at PubMed.gov.

http://www.ncbi.nlm.nih.gov/pubmed/2883551

Whether the study investigated injury rates, causes, etc. is what I would like to know. I see it referenced in the Warburton paper promoting barefoot running as a way to reduce injury.

http://www.sportsci.org/jour/0103/mw.htm

Based on the runningbarefootisbad website, I take it the Robbins and Hana study was not a study conducted on the injury rates of shod vs. unshod populations in Haiti. I have read the abstract and it doesn't appear to be a study done on injury rates in Haiti either. I just like to see the study for myself so I can draw so of my own conclusions about it. I looked for a full text version but was unable to find one.

 

Nope. It was not a study. In the Robbin and Gouw paper, in the abstract they make this claim: "A number of reports indicate an extremely low running-related injury frequency in barefoot populations in contrast to reports about shod populations.", but then in the full text they provide no references to support the claim. They provide any as no reports or studies have actually shown that.

They mention the Haiti study and provide no reference to it. No one has ever been able to find or locate that study. The conclusion has been the study does not actually exist.

Warbuton quoted Robbins and Gouw, but the study that Warbuton quoted from them was not done in Haiti, was not about injury rates and was a lab based study. Robbins, Gouw et al never did a study in Haiti and never did a study on injury rates.

Warbuton like many others are making fools of themselves by requoting the nonsense and not subjecting claims to scrutiny. I see the Warbuton article has been demolished here.

See what I mean about the misue, misrepresentation and misquoting of research.

 

Dana:

You must more patient waiting for your answers. You only asked this question this morning and then a few hours later, wanted to know why no one had answered your question. From the time you initially asked the question I had seen 16 patients, written and dictated 16 chart notes, ordered 2 pairs of orthoses, and spent 20 minutes emptying out my "in box" at my office. Therefore, some of us do also work and have responsibilities other than answering everyone's questions on Podiatry Arena......so give us at least 48 hours to answer your questions....when we have a little bit of free time between our busy work schedules.

In regard to Craig's statement, all he is saying is that a change in gait kinematics will also cause of change in gait kinetics. This is not a difficult concept to understand. If the runner is more comfortable being a heel striker while in Nike Pegasus, but then becomes a forefoot striker while barefoot running, then, of course, the internal loads on the structural components of the foot and lower extremity will be altered due to the change in gait kinematics caused by running without shoes. All factors must be considered when injury etiology are being considered, and running style is only one of many important factors. Here is a paper I wrote while a third year podiatry student that talks about some other important factors that should be considered when treating runners.

 

Craig, thank you for confirming what I suspected on the Robbin's paper.

It seems like in this case Warburton is not just misrepresenting the scientific literature, but making up research that doesn't even exist.

 

Here it is for you to see for yourself Bobba

 

while leaving out the context that surrounds it.

The test was grossly limited and flawed. It has no correlation to running what so ever. I could jump anywhere from 1 mm off the floor to 40 or 50 mm off the floor. Depending on the height, it produces totally different results. I even asked, how high do I jump off the floor? The number of hops I could count in 30 seconds was inversely related to the height I chose to hop. If my height varied over the course of 30 seconds, from leg to leg or shoe to shoe, it changed the results. In addition, if I kept my height as low to the floor as possible, I found it difficult to count fast enough to keep up. I sincerely doubt I have symmetrical leg stiffness. The results of the test must be wrong, no surprise there.

Yes, I think I do but I have also said it could be a mid foot striker and I need Video equipment to tell. I also discussed that my traditional shoes have a drop of 12 mm or more between heel height and toe height. That if my foot is parallel to the ground just before impact, the heel of the shoe will touch first.

The force at heel strike can vary greatly. If I am a heel striker, it is possible that I strike my heel with different levels of force depending on the shoe.

When I made my comments and asked my question, it had nothing to do with your test other than you inferring that my leg stiffness was the same based on the test. I was commenting, asking in reference to actually running with a HR monitor and measuring on exactly the same course. Yes my step rate was the same in the error ridden test. No my step rate is not the same when actually running in VFF vs traditional shoes.

Again, stride length is inferred in real running when stride rate changes for the same pace, stride length changes with it.

Referring to other gait characteristics. In addition to what I've mentioned, the entire movement of all all components of the body while

5.7oz or 6.0oz vs shoes that weigh 8.0 OZ up to 13.0 oz

Simon, I agree. Of course the lab won't help me when I say every day and should have been more specific.

Then why do you bother questioning me?

Dana

 

Simon, another thought regarding your test. You can think of the number of hops as stride rate and the height you jump off the floor as stride length. If you change stride length for the same effort you will probably change stride rate. Since your test is using rate as the variable to measure stiffness, it would make sense the length will impact the result.

Dana

 

Kevin, sorry. The reason I asked was because everyone had the time to respond to my efficiency and HR comments but left out their response to Craig's statement. I was just wondering why and I was interested in other's thoughts.

Thank you for your explanation, I'm sure I'll enjoy reading your paper. A question I have is if there is a change in gait kinematics and gait kinetics, will there possibly be a change in efficiency?

Dana

 

Thank you very much Ian, I appreciate it. I'm not doubting Craig but I also don't want to make the same mistake as some in "church of barefoot running" by blindly accepting someone's interpretation of a study without reading the actual study myself.

 

Kevin, I read your paper on Runner-Patient History, thank you. It was actually for the second time, it must be posted somewhere else. I really do understand that there are many factors that should be considered not only when treating runners but for runners to understand to help them avoid injury. I sincerely believe that in spite of not being a medical professional, I have been able to stumble my way through to a healthy running life.

What I'm enjoying on this forum is the fact that as I continuously express by point of view, I continuously get hammered. The reason is because you are all reshaping my head and I am learning from it. I am simply trying to apply what I've learned from 38 years of practical knowledge to what all of you know from research and applied studies and your own experience.

Some may not agree, but I have learned a lot and I'll continue to learn. I will not be discouraged from stating my ideas. I just need to learn that if they get shot down, I should look to understand the reason, learn and move on.

Coming from a time when there was only a handful of "running shoes" on the market to what they have now and combining that with the whole "minimalist" movement and it's potential impact to the shoe industry is really exciting. I have never bought into the barefoot hype, chi running, Pose running, etc. Rather, I came here to learn your perspective and point of view.

It has become very apparent to me that my views or opinions really don't carry any weight here, that is OK. When I give them, I am quickly corrected and I learn. I just have to wonder, what the heck have I been doing for all of those miles over all of those years to stay healthy? Makes me think of your comment about taking a sledge hammer to your shin. I had to have been smart enough to find a pair of shin guards before someone picked up the sledge hammer. :drinks

Dana

 

I think there are many possibilities of a change in efficiency when gait kinematic are changed. They may be an increase in efficiency, but there also might be a decrease in efficiency. There also might be no change at all.

It seems like it would most likely reduce efficiency when you change your gait away from it's natural form. This was investigated by Dallam et al. in Effect of a global alteration of running technique on kinematics and economy.

http://www.ncbi.nlm.nih.gov/sites/e..._uids=16195026&query_hl=1&itool=pubmed_docsum

Here's the Abstract:

Please note the bold part where running economy was reduced. This is the opposite of what an endurance athlete would want. By the end of the study the athletes were less efficient than before the study.

 

Craig, I had a chance to read the full text of the Robbin's study and I see what you mean about the misuse, misrepresentation and misquoting of research. This study is an excellent example of it. In the full text the authors give 5 examples of how injury rates are higher in shod populations vs. unshod. The fourth example happens to be the alleged Haiti report. However, I did not see a single reference in that entire section of the paper.

There are many references stated throughout the paper, but that section doesn't include a single one. I'm surprised to see a paper like this make it to publication. Don't these papers get peer-reviewed? There are some bold claims made in the paper without any reference to back it up. I would think a paper like this would be torn apart during the peer-review process.

I see what you mean and I completely agree.

 

There would have been a peer-review process in place and that sort of thing should not slip through, but it does happen all too often (see this for another really bad eg: Shockwave therapy for Morton's neuroma). The sad thing is that some of Robbins, Gouw's et al experiments were actually quite good, but it the spin and editorialising that they put on it that let them down. So many have fallen for the spin and not looked at the actual experiments they did (see: Robbins-Gouw Hypothesis - are Running Shoes Unsafe?)

Now go back and read McDougal's Born to Run in the context of the above and how he misues the research. This is why many have labelled it a semi-fiction and find it hard to belieie that so many were that gullible to actually fall for it.

 

Dana:

My guess is that your experience of a decreased heart rate with the use of the Vibram FiveFinger shoe versus your more standard running training shoes is that this is due to a decrease in shoe mass with the Vibram shoe. Reduced shoe mass will normally cause a reduction in oxygen consumption for a given steady state running pace due to the decreased metabolic cost of swinging a leg forward with reduced moment of inertia (i.e. lighter shoe) versus the increased metabolic cost of swinging a leg forward with increased moment of inertia. Moment of inertia is increased about an axis of rotation if a mass is added further away from the axis of rotation, such as mass added to a foot relative to the hip joint axis.

The question of whether a change in gait kinematics and kinetics during running causes a decrease in oxygen consumption (i.e. an increase in metabolic efficiency) is impossible to determine without actually measuring oxygen consumption. When I was an undergraduate student at UC Davis, I spend a lot of time in the Human Performance Lab either running on treadmills being involved in experiments.

As an aside, the most interesting experiment I was a subject in was one is where I ran in both a warm, humid room and in a hot dry room on a treadmill over a period of a month on a treadmill for 85 minutes at 6:30 mile pace with about 5 skin thermistors and a rectal thermometer inserted inside of me to monitor my core temperature (I was 21 years old at the time). I was weighed nude before and after the run to determine my sweat loss. I held the record for the group of male and female runners being studied with the most sweat loast in 85 minutes,: 3.7 liters of sweat lost in 85 minutes...that's 8 pounds!!) These experiences during my early 20s being a competetive distance runner, working in the human performance lab, being a subject in a number of experiments while running on a treadmill at the UCD Human Performance Lab and taking most of the graduate courses in exercise physiology as an undergraduate, taught me that running efficiency is quite variable and dependent on multiple factors. And shoes are only one factor, but not an insignificant one.

An interesting experiment for you to perform would be to calculate the difference in mass between your normal training shoe and the Vibram shoe, then add that mass to your Vibram shoe by attaching lead weights to the shoe upper so that the mass of the Vibram with weights attached is the same as the mass of your normal training shoes. Then go out and perform your standard run to see if your heart rate is affected. My guess is that running in the Vibram shoe with a mass attached that equals that of your normal training shoes will make your heart rate be fairly equal between both shoes.

And, Dana, don't worry about your questions....you are doing much better now here on Podiatry Arena since your first few weeks where you were a little shaky. I think you have now developed a much better understanding of how you can both learn and teach with some of the best podiatric biomechanics minds in the world here on Podiatry Arena.

 

NO.

You seem very certain.
http://www.ncbi.nlm.nih.gov/pubmed/11224825

 

Kevin, thank you, I really appreciate you spending the time. I certainly agree about shoe weight. Not being able to measure my own oxygen consumption, I have been really curious about other factors affecting oxygen consumption in addition to wearing a lighter shoe. What really grabbed my curiosity was the fact that my stride rate increased.

It has been demonstrated that changing stride rate will change oxygen consumption. The question I have is when I change to a shoe with no cushion that encourages me to increase my stride rate and decrease my stride length in addition to a change in leg stiffness, what affect that has on oxygen consumption. What I'm seeing with respect to HR might very well be due to a shoe weight difference but intuitively, since other variables are changing that more than shoe weight is contributing.

You make a good point, normalizing shoe weight would leave any change in oxygen consumption to other factors. In reality, I would never wear VFF for anything but playing out on the trails so it really doesn't matter. When I really want to be serious about training runs or competing, I would not be wearing VFF.

Dana

 

And that's where it gets even more confusing. When we increase the surface stiffness by decreasing shoe cushioning, according to several research studies we should see a decrease in leg stiffness. Now there are many ways that the body can achieve this, these include increasing stride length, not decreasing it (so your decrease in stride length might be seen to contradict research data). But I guess you can skin cats in many ways. So if with your shorter stride you also increase knee, hip and ankle flexion this could still result in a net decrease in leg stiffness = increase in metabolic cost... Also there is a link between knee and ankle stiffness: increase ankle stiffness = decrease knee stiffness and vice versa. Yet your heart rate analysis might lead one to conclude that metabolic cost is reduced when running on stiffer surfaces (which again is contradicting the research data); your hopping test seemed to demonstrate that your leg stiffness was unaffected by surface stiffness (which also contradicts research data)... Something doesn't fit. Like Kevin said, try adding the weights to your shoes.

 

Bobba, an aspect of "natural" form is stride rate. The study by Hunter and Smith, "Preferred and optimal stride frequency..." demonstrated that preferred stride frequency which you can consider "natural" was close if not the same as optimal stride frequency. Optimal stride frequency is defined as the frequency that minimizes metabolic cost. For aerobic running, optimal stride frequency is fairly constant across varying paces. With optimal stride frequency constant, stride length changes to change pace.

A fundamental component of Posse running dictates that when you change pace, you change stride rate. That would imply that efficiency will be lost as soon as the runner forces a change in stride rate. Given that, I am not surprised at all with the findings of the Dallam study.

My question is about whether you can make a change in gait that will change optimal stride rate and if you are able to change optimal stride rate, will there be a subsequent change in minimization of metabolic cost for a given pace?

Dana

 

Given that, when racing, should you wear 5 OZ racing flats with minimal cushion or 13 OZ cushioned shoes for increased leg stiffness? Does the economy you gain from lighter shoes out weigh the economy you lose from decreased leg stiffness?

Dana

 

That's the real trick. Modulating the leg stiffness with the minimum weight.

 

I think that means wear the 5 OZ shoes, right?

Dana

 

Not necessarily. That's why the Spira shoe was banned by the IAAF.

 

Dana:

It's no surprise to me that you demonstrate increased stride frequency with the Vibram FiveFinger (VFF) shoe since this shoe, like barefoot running, encourages forefoot striking patterns which will encourage shorter stride length and an increase in stride frequency, assuming identical running velocities.

If you could land heel-first with the VFF, then you would probably assume a longer stride length than you do currently, but since the VFF has minimal heel cushion, most runners elect to midfoot or forefoot strike with this shoe to prevent plantar heel contusions.

My bet is that most of your decrease in heart rate with the VFF isn't due to increased stride frequency and decreased stride length but rather due to a decrease in shoe mass with the VFF. I believe that it is pretty well-accepted within the biomechanics-exercise physiology scientific community that experienced runners are very good at self-selecting the most metabolically economical stride freqency and stride length for a given running velocity. You have simply chosen the correct stride frequency-stride length combination for each shoe already and because of the reduced metabolic cost of swinging your leg forward with reduced mass on your foot when wearing the VFF, your heart rate is decreased when wearing the VFF.

 

Kevin - I would concur with all of components of your premise, especially the issue of self-selected stride length/frequency being near optimal in efficiency among experienced runners (also have had some experience testing this in elite cyclicsts and the same can be said for their preferred cadence).

I'm having a hard time though attributing such a big reported change/decrease in oxygen consumption just/primarily to the difference in weight between shoes and the VFF (8% decrease in HR I think Dana reported?). Now, I have no idea what shoe she is comparing the VFF to and I have never weighed a VFF - never worn one either, just picked it up a few times at the shoe store. However, we've done some work comparing metabolic cost in various ankle bracing conditions and differences in O2 uptake aren't that great in spite of weight associated with various braces (plus the fact that bracing does tend to change gait and appear to decrease overall efficiency).

So, I have no idea on the weight numbers to start crunching differences in metabolic cost but do you think the weight difference is big enough to actually result in 8% HR decrease?

 

Simon, are you considering all of the factors? For a given pace, increasing stride length will shift the concentration of ground force towards the heel. Increase stride length enough and the heel will be the only thing that contacts the ground until the person's COM has a chance to catch up. Increase force to the heel while wearing shoes with no cushion is not a good idea. Shorting stride length will help the runner shift ground force from the heel.

Simon, are you considering all factors? My heart rate analysis is related to shoe weight and possibly stride rate. As you decrease shoe weight you decrease metabolic cost. As your stride rate approaches optimal, by definition you are at the lowest possible metabolic cost. This is not in contradiction. I don't know how much of a factor surface stiffness has on metabolic cost or heart rate, I was not trying to measure that.

The hopping test produced non-sense results. It could not demonstrate leg stiffness because hopping height could not be controlled and was not included in the calculation. There was nothing to contradict.

What doesn't fit is that you are not looking at or comparing relevant factors so of course it doesn't make sense.

Dana

 

An 8% decrease in heart rate does not correlate to a 8% reduction in oxygen uptake rate. In addition, an addition of 10 grams of mass to the ankle will cause less increase in metabolic energy during running than will the addition of the same 10 grams of mass added to the foot. The difference?.....moment of inertia of the limb is increased as the mass to axis of rotation distance is increased.