I have previously had a dig at the nature of the titles of a number of scientific papers, for example, this paper I previously reviewed was titled: “Forefoot strikers exhibit lower running-induced knee loading than rearfoot strikers“; when it could have just as easy been titled “Forefoot strikers exhibit higher Achilles tendon loading than rearfoot strikers“ as that is also what they found. In that context, the title of this new paper had me wondering:
Barefoot Running and Hip Kinematics: Good News for the Knee?
McCarthy, Colm; Fleming, Neil; Donne, Bernard; More
Medicine & Science in Sports & Exercise. September 8, 2014
Purpose: Patellofemoral Pain and Iliotibial Band Syndromes are common running injuries. Excessive hip adduction (HADD), hip internal rotation (HIR) and contralateral pelvic drop (CLPD) during running have been suggested as causes of injury in female runners. This study compared these kinematic variables during barefoot and shod running.
Methods: 3-D gait analyses of 23 habitually shod, uninjured female recreational athletes running at 3.33m.s-1 while shod and barefoot were studied. Spatiotemporal and kinematic data at initial contact (IC), 10% of stance (corresponding to the vertical impact peak) and peak angles were collected from each participant for HADD, HIR and CLPD; and differences compared across footwear conditions.
Results: Step rates when running barefoot were 178+/-13 steps.min-1 vs. 172+/-11 steps.min-1 when shod (P <0.001). Foot-strike patterns changed from a group mean heel-toe latency indicating a rear-foot strike (20.8ms) when shod, to one indicating a forefoot strike (- 1.1ms) when barefoot (P <0.001). HADD was lower at IC and at 10% of stance when running barefoot (2.3+/-3.6 vs. 3.9+/-4.0[degrees], P Conclusions: Barefoot running resulted in lower HADD, HIR and CLPD when compared to being shod at both IC and 10% of stance; where the body’s kinetic energy is absorbed by the lower limb. As excessive HADD, HIR and CLPD have been associated with knee injuries in female runners; barefoot running could have potential for injury prevention or treatment in this cohort.
This study did show changes in parameters at the hip that are correlated with knee injuries, so there are some good findings in this study.
The methods and analysis seem fine, but there are a couple of issues
- it was on a treadmill, so may or may not equate with overground running.
- this was an acute intervention, so the results may or may not be the same if they were habituated to the barefoot condition
- the participants were asymptomatic, so the results may or may not be the same in those with patellofemoral pain or iliotibial band syndrome
- they did not investigate, let alone report where loads went up to allow those changes to happen
Probably the biggest issue I do have is that last point above (and hence the title of the post and the introductory comments above) is that they did not investigate the costs to achieve those changes. You can not decrease the load in one set of tissues without increasing it in another. To get the changes that the authors found, there has to be changes elsewhere to achieve it. Most likely there would have been an increase in ankle loads (hence the title of the post) as was reported in yesterdays post and many other previous studies (eg) that actually reported on the entire kinetic chain. This lack of looking at what else changed is a shortcoming of the study and does somewhat negate the conclusion: “barefoot running could have potential for injury prevention or treatment in this cohort“. Yes, it does have the potential to help those with knee issues, but as the load would have had to increase somewhere else, its going to potentially increase the risk for injury in those tissues, so the blanket recommendation that it will have the potential to prevent injury is not supported by the data. Like a lot of studies I reported on recently, this was a lab based study on healthy people and not a clinical trial on those with an injury.
Which leads on to another issue that the authors did raise in their discussion: was it really the barefoot running that lead to the changes or the was it the change in foot strike pattern that they found (which you can do without going barefoot) or the increase in cadence which that they found (which you can do without going barefoot)? Without controlling for those factors, we do not know which one it was that was responsible for the kinematic changes that they reported. Having said that, barefoot or minimalist drills are a helpful tool to help teach different foot strike patterns and cadence manipulation when clinically indicated.
Back to where I started, the title: Even though there was a question mark at the end of the title, it is misleading as it ignores what the study did not investigate; ie the cost in other tissues to achieve those changes.
As always, I go where the evidence takes me until convinced otherwise…and there is always a cost to achieve a change. That cost in a particular individual may or may not be worth it.
McCarthy C, Fleming N, Donne B, & Blanksby B (2014). Barefoot Running and Hip Kinematics: Good News for the Knee? Medicine and science in sports and exercise PMID: 25207927
Thanks for the review Craig.
Why is it bad news for the ankle?
Because it increases the loads in the ankle!!!
So how much load is too much to make it ‘bad news’.
Any increase in the load in any tissue is going to increase the risk for injury in that tissue (bad news). Similarity any decrease in the load in any tissue is going to decrease the risk for injury in that tissue (good news). Its a zero sum game, You can’t change the way people run and make loads go away, you just move them around (with the exception of loosing weight which will reduce the overall load in the system) – how much goes where will depend the change that is made and on things like lever arms and joint axes variations.
So how much load is detrimental. You say its bad news for the ankle. Define the threshold at which its bad news. How can tissue adapt if it isn’t subjected to increased loads. I’m off down the gym to tell everyone to stop lifting weights as its bad news.
I have no freakin idea! Of course you have to increase the load to get a training effect and adaptation, but that increase also increase the risk for injury! Why can’t yo understand that?
Perhaps you can tell me how much of a decrease in load is needed to be beneficial?
No need to get your panties bunched up.
You don’t know what load is bad news yet your title suggestion is bad news for the ankle. Just because you increase a load doesn’t mean its bad. Perhaps the load was too low to start with, perhaps it wasn’t. You don’t know and cant say.
Craig,
i would also like to thank you for the review. Neither I nor Dr. McCarthy would argue with your comment that barefoot running redistributes joint loading away from the knee. Unfortunately, examining the ankle was not the aim of our study. Nonetheless, I am glad we are all in agreement on that point.
As to whether this redistribution is “bad news”, we should consider two things:
1) The knee joint is the most likely site of injury in runners (van Mechelen, 1992). It would therefore appear that this joint is not dealing with running load very well, and reducing it might be a good idea. This is especially true in females who have significantly higher rates of knee injury than males.
2) The ankle joint has evolved to absorb load better than the knee by virtue of the longer moment arm at the achilles tendon. The joint is designed to convert kinetic energy into rotational energy, help dissipate forces up the lower limb and transfer as much of this energy into locomotion as possible (via the stretch shortening cycle). Therefore it would seem from an anatomical perspective that the ankle is more suited to tolerate increased loading.
So what is the problem with redistributing load away from the joint most likely to be injured? So what if we increase the loading elsewhere? Maybe “elsewhere” is better designed to cope with the load.
The bottom line: our data was collected from a group at very high risk of knee injury (ie- female runners). Reducing the load on the knee is seen my many (including ourselves) as a priority in this group. If you’re a guy who’s never had any knee problems, the risk of change might not be worth it. We don’t know…
Perhaps “Good news for the knee. No news for the ankle” might be more appropriate?
Regards,
Neil Fleming, PhD.
Asst. Prof. of Exercise Science,
Indiana State University
Neil:
I would tend to agree with Craig that the title for your article “Barefoot Running and Hip Kinematics: Good News for the Knee?” is not the most scientific title for such a paper.
The barefoot running fad has come and gone within the last five years probably because most runners who tried to run barefoot got injured when doing so. Did they get injured at the knee? Not usually. However they did get injured quite frequently in the forefoot (e.g. metatarsal stress fractures) and in the ankle (e.g. Achilles and peroneal tendinitis/tendinopathy). My own practice and the practices of many other podiatrists, orthopedic surgeons and physical therapists were full of patients who became injured over the last five years trying to run barefoot all due to reading some article on the internet or reading a book such as “Born to Run” that was full of half-truths, at best.
To design a study that looked at hip kinematics in both shod and in barefoot running is certainly reasonable and clinically applicable. However, in my opinion, a more objective and scientific title for your article would have been the “Effects of Barefoot and Shod Running and Hip Kinematics During Running”.
It is pure conjecture to assume that looking at hip kinematics in asymptomatic runners in both barefoot and shod conditions and seeing a trend in one direction in the barefoot runners is “good for the knee” when, in fact, you don’t know if this trend could also be bad for the knee, have no effect on the knee, or be good for the knee.
Did you study the injury rate of the knee? No. I think a title such as you chose for the article detracts from this otherwise nicely done study and leaves the impression to me that you are not being objective in your opinions regarding the possible negative health effects on individuals who regularly run barefoot.
Also, please provide references for your statement:
“2) The ankle joint has evolved to absorb load better than the knee by virtue of the longer moment arm at the achilles tendon. The joint is designed to convert kinetic energy into rotational energy, help dissipate forces up the lower limb and transfer as much of this energy into locomotion as possible (via the stretch shortening cycle). Therefore it would seem from an anatomical perspective that the ankle is more suited to tolerate increased loading.”
I know of no reference that supports your contention that “the ankle joint has evolved to absorb load better than the knee”. And, by the way, the knee joint also converts kinetic energy into rotational energy, helps dissipate forces and transfers this energy into locomotion (via the stretch shortening cycle).
Kevin A. Kirby, DPM
Neil, could you provide references regarding the length of the Achilles moment arm versus the length of the quadriceps moment arm? Thanks.
It just that Kaufer’s (1971) resting average for quadriceps moment arm of 5.8cm seems to be very similar to Sargeant’s resting 4.3-5.6cm for the Achilles moment arm. I only scanned the literature briefly so perhaps you could point me toward references that support your contention?
Wasn’t there a study which showed that the fastest sprinters had shorter Achilles moment arms?
Simon:
You are right. The Achilles tendon moment arm to the ankle joint axis is nearly identical to the patellar tendon moment arm to the knee joint axis. I don’t have a clue where Neil came up with the idea that the Achilles tendon has a longer moment arm than that of the knee or how he knows that the “ankle joint has evolved to absorb load better than the knee”.
Maybe he will come back to enlighten us all.
Why wasn’t the article titled “Effects of Barefoot and Shod Running on Hip Kinematics During Running”? My guess? Such an objective and scientific research study title is simply not sexy enough for many of today’s researchers who feel they need to have provocative research titles to get their research, and themselves, talked about in the popular press.
Average moment arm length of achilles tendon during plantar-dorsi flexion is 53mm (McCollough et al. 2011).
Average moment arm length of rectus femoris tendon during knee flexion is 30mm and knee extension is 28mm (Fiorentino et al., 2013).
Kevin, the reference you’re looking for regarding ankle function in the conversion of kinetic impact forces during human locomotion is from Lieberman’s work which was published in Nature in 2010. Function of the achilles tendon in the stretch shortening cycle of human locomotion is from Roger Enoka’s textbook, “Neuromechanics of Human Movement” (or anything by Paavo Komi).
With regards to your comment about trends being either good or bad for the knee; there have been several studies documenting the correlation between excessive hip internal rotation and/or hip adduction and knee injuries such as PFPS (Noehren et al. 2013; Meira & Brumitt, 2011; Wilson & Davis, 2008). Based off this evidence, reducing these two hip kinematic variables would likely reduce the risk of damaging the knee. Our study showed that BF running reduced these two hip kinematic variables. Is this not good news for the knee?
REFERENCES:
McCollough et al. (2011) Moment arms of the ankle throughout range of motion in three planes. Foot Ankle Int. 32 (3): 300 – 306
Fiorentino et al., (2013) Rectus Femoris knee muscle moment arms measured in-vivo during dynamic motion in real time magnetic resonance imaging. J Biomech Eng. 135 (4) doi: 10.1115/1.4023523.
Lieberman et al. (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 463: 531-535.
Noehren et al. (2013) Prospective evidence for a hip etiology in patellofemoral pain. Med Sci Sports Exerc. 45(6):1120-4.
Meira & Brumitt. (2011) Influence of the hip on patients with patellofemoral pain syndrome: a systematic review. Sports Health 3(5):455-65.
Willson & Davis (2008) Lower extremity mechanics of females with and without patellofemoral pain across activities with progressively greater task demands. Clin Biomech. 23(2):203-11.
Neal:
While I agree with your moment arm for the Achilles tendon to the ankle joint axis, I can’t agree with your moment arm for the patellar tendon to the knee joint axis (why are you using rectus femoris tendon moment arms?).
In a 2004 article published in Journal of Biomechanics, Krevolin et al published a study showing the patellar tendon moment arm to be between 4 – 6 cm (40 – 60 mm) to the knee joint axis (Krevolin JL, Pandy MG, Pearce JC: Moment arm of the patellar tendon in the human knee. J Biomech, 37:785-788, 2000). So in this study, the moment arm for the Achilles tendon and patellar tendon is nearly equal, but obviously this is study-dependent and is dependent how they define joint centers, and at what joint angles the tendons are measured at, in addition to if they are being tested in resting or at full isometric contraction.
Also, I agree with you that the ankle ” converts kinetic energy into rotational energy, helps dissipate forces and transfers this energy into locomotion”. However, the point I was making is that many lower extremity joints, including the knee “convert kinetic energy into rotational energy, helps dissipate forces and transfers this energy into locomotion”. Therefore, the ankle joint and knee joint are identical in this regards so I don’t see how this helps your argument that:
“2) The ankle joint has evolved to absorb load better than the knee by virtue of the longer moment arm at the achilles tendon. The joint is designed to convert kinetic energy into rotational energy, help dissipate forces up the lower limb and transfer as much of this energy into locomotion as possible (via the stretch shortening cycle). Therefore it would seem from an anatomical perspective that the ankle is more suited to tolerate increased loading.”
First of all, we don’t know that the “ankle joint has evolved to absorb load better than the knee”, That is pure speculation with no research evidence to back up that claim.
Second, I’m not so sure the Achilles tendon moment is indeed much longer than the patellar tendon moment arm, but I will agree with you that is probably somewhat longer.
Third, I could claim that the knee is “evolved to absorb load better than the ankle due to the knee’s much larger joint surfaces and stronger and more robust muscles that cross the knee joint axis” which makes just about as much sense as your original statement that the “The ankle joint has evolved to absorb load better than the knee by virtue of the longer moment arm at the achilles tendon.” My point is, this is a weak argument, is speculative, at best, and does not necessarily takie into account all the biomechanical factors that contribute to the knee joint’s and ankle joint’s abilities to “absorb load” during weightbearing activities.
Fourth, I would not be so eager to use any reference from Lieberman’s et al’s 2010 paper from Nature since most running biomechanics experts I have talked to about this paper (some of the best in the world) said there are numerous weaknesses with this paper too numerous to list here. In addition, Lieberman’s 2010 paper from Nature and Lieberman’s Harvard Barefoot Running website was funded by Vibram USA, makers of Vibram FiveFingers shoes, which, to me, makes the whole paper suspect that it was done with the intent not to answer a research question but done with the intent to show that barefoot running, or running in minimalist shoes, such as the Vibram FiveFingers, is somehow better than running in traditional running or maximalist running shoes.
Finally, since when is reducing the load on a joint always good for that joint? Weightless environments reduce load on weightbearing joints but can cause serious degradation in muscle mass and strength over a very short length of time (LeBlanc A, Rowe R, Schneider V, Evans H, Hedrick T: Regional muscle loss after short duration spaceflight.Aviation, Space, and Environmental Medicine,66(12):1151-1154, 1995).
My good friend, Dr. Simon Spooner, and I like to talk about the Zone of Optimal Stress (ZOOS) for any anatomical structure and that it may not be always good to reduce load on a joint, or muscle, or tendon, or ligament, or bone since this may weaken the tissue, but excessive load may injure it. In other words, stress can be both good and bad for the structural components of the body and reducing load, as you speculate happened in your study at the knee, has as much chance of causing harm to the knee, by weakening it, as it has to reduce injury rate at the knee. You really don’t know then that this change in hip kinematics is either good or bad for the knee since you didn’t measure knee injury rates in your subjects or measure knee strength in your subjects so why even put that question in the title of your paper?!
All in all, adding a phrase such as “Good News for the Knee?” is what I call a “Leap of Faith”, a risky leap that most scientists try very hard to avoid in the journal articles they publish.
Quote from kirby ” since when is reducing the load on a joint always good for that joint? ”
Any decrease in the load in any tissue is going to decrease the risk for injury in that tissue (good news)
This is simply not true. Too little stress may increase the risk of injury too. See Mueller for a nice explanation of these concepts. http://m.ptjournal.apta.org/content/82/4/383
Our leap of faith:
1) A correlation exists between faulty hip kinematics and risk of knee injury.
2) Knee injuries are bad news for the knee.
3) Barefoot running reduces these faulty hip kinematics.
4) Maybe this is good news for the knee?
In my opinion a greater leap of faith is taken when drawing comparison between modest reductions in knee loading associated with barefoot running, and the complete elimination of knee loading associated with zero-gravity space flight. I absolutely agree that too little stress may cause injury. But ask yourself; why is the knee the most common site of injury in running? Too little or too much stress on the joint?
Neil:
But ask yourself, did you measure knee injury rates, knee kinetics, knee kinematics or knee strength? No. Then why even mention the something about knee in your title?
Neil:
This will be my last reply on this subject.
There is a big difference between making guesses in a running blog on the internet and making guesses in the title of a peer-reviewed scientific publication. Maybe I’m too “old school” about the way a scientific paper should be written, but since your study did not study the knee, I believe the knee never should have been mentioned within the title of your paper.
Otherwise, I had no other big issues with your paper and I congratulate you and your coauthors for taking the time to study this issue for the rest of us who have an interest in this subject.
Cheers,
Kevin
Kevin,
this will also be my final post on the subject.
Regarding your comment: “But ask yourself, did you measure knee injury rates, knee kinetics, knee kinematics or knee strength? No. Then why even mention the something about knee in your title?”
We actually DID measure knee kinematics! We specifically did this in order to relate any potential changes in hip kinematics with corresponding changes at the knee. We observed the following which were all clearly reported in the results section of our paper:
Significantly greater knee flexion at initial contact during barefoot running
Significantly lower peak knee flexion during barefoot running
Significantly lower knee ROM during barefoot running.
Perhaps you missed this section?
I can understand your side of the argument regarding the title of our paper, and perhaps another title may have been more “objective” in some critics eyes. I also thank you for taking the time to read our paper and providing your critical opinion. But it is simply not true to say our study had nothing to do with the knee.
Regards,
Neil
I agree Simon. The claim of any reduction in loading being good was a quote from Craig Payne.
Who would have thought it eh?