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What muscle controls push-off?
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What muscle controls push-off? - November 13, 2002 11:24:00 AM
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Andrew M. Ball PT PhD
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I asked this question of chiropractors on the Chiroweb website, and as expected, the only chiropractor bold enough to give it a go got the answer wrong. At least according to my evidence-based search:
In outpatient ortho clinic last week, the clinic manager, the DPT student, and myself engaged in discussion about what muscles are most essential for producting the push-off and thrust in normal walking stride. The DPT student and experienced clinician, both thought, as I once had, that it was the _______.
I cited a study to be named later, that said that:
"The results of this sutdy indicate that although with increases of speed and upward tilt the absolute values of the integrated EMG increased more for the _____ than for the _______ muslces, the RELATIVE increaes of EMG were consistently greater for the ______ muslces, which reached their peek intensity of activity at moments during the walking stride . . ."
In talking about the article, I'll admit that I mis-spoke, chanting the virtues of a muscle that, while involved in push off, doesn't control thrust nor push-off --- confusing EVERYONE in the room, and undoutably going to erode my credibility in any future evidence-based discussion. As my other half (a DPT student) often says to her classmates, "Don't listen to him. Half the time he means one thing and gets his mouth moving so quick that he can't communicate what he means . . . the other half he's in his own little world. Give him a week to process what he's trying to say and then listen to him, it's probably important. Until that time, do what I do . . . ignore him." Okay, that's not exactly what she says, but it's close, and makes for a healthy relationship (those of you who meet me at CSM, by the way, may want to have her translate . . . but I digress).
I'm interested in what ya'll have to say, and if your answers fit the research. For those interested in discussion, if you're bold enough to give it a try, I'll reward you with a fax of the article so that we can discuss it on this forum.
I'd hope from the participation of at least SJ, Mcap, Bobcat, and Doug (if you're still out there), but also some of the lurkers on the site too. First let's hear from a few PT's, then let's see what the DC's have to say. For what it's worth, I answered the question incorrectly as a doctoral student, and was humiliated by one of my nationally respected mentors in public forum in the process.
The worst that can happen is that you submit an incorrect answer. After we get about 10 or 12 submissions, I'll chime in with the reference and what it has to say.
The results WILL (or at least, should) change the way that you look at and treat some of your patients, and as such, will likley have an immediate application to your daily practice, be you in ortho, neuro, or peds.
So . . . . who's first?!?!?
Drew
[This message has been edited by Andrew M. Ball PT PhD (edited November 13, 2002).]
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Re: What muscle controls push-off? - November 13, 2002 4:51:00 PM
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ScottO
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From: Va
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I'll be the first and take a dig at it.There are several answersthat I would say including the hip abductors for controlling deceleration and weight shift, the hip flexors for LE acceleration at toe-off. Or I would have to say that my answer would be the hamstrings secondary to their being used as hip extensors at heel-strike. So let's say hip flexors are my answer. Or I would say answer C
Scott O
[This message has been edited by ScottO (edited November 13, 2002).]
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Re: What muscle controls push-off? - November 13, 2002 5:00:00 PM
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flexion
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This study sounded pretty decent on the topic:
Contributions of the individual ankle plantar flexors to support, forward progression and swing initiation during walking.
(R.R.Neptune, S.A.Kautz ,F.E.Zajac)
Rehabilitation R&D Center (153),VA Palo Alto Health Care System,3801 Miranda Avenue,Palo Alto, CA 94304,USA
Department of Functional restoration, Stanford University,Stanford, CA 94305,USA
Department of Mechanical Engineering ,Biomechanical Engineering Division, Stanford University, Stanford, CA 94305,USA
[[Accepted 22 July 2000]]
The three main theories advanced in the literature have been that the ankle plantar flexor group (1) provide a controlled roll-off.(e.g.Sutherland et al.,1980; Perry,1992), (2)actively provide forward progression or push-off. (e.g.Winter,1983; Kepple et al.,1997) and (3)accelerate the leg into swing (e.g.Hof et al., 1993; Meinders et al.,1998).
Hof et al.(1993) examined correlations between changes in body segment mechanical energy and work of the triceps surae group determined from electromyogram to force processing and concluded that the primary function of the ankle plantar flexors is to provide the energy necessary for swing leg initiation.
[This message has been edited by flexion (edited November 13, 2002).]
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Re: What muscle controls push-off? - November 13, 2002 5:32:00 PM
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Bournephysio
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I think that the plantar flexors are generally considered to provide the most thrust but I saw a recent study that found hip ext just after heel strike, hip rot at mid stance and hip flex at toe off to be more important.
Doug
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Re: What muscle controls push-off? - November 13, 2002 5:34:00 PM
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Andrew M. Ball PT PhD
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From: Charlotte, NC
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Good points. So far flexion is closest, but the best study he cited looked at abolute EMG changes, there is at least one study that I'm aware of that looks at relative EMG changes, which I personally think is more important, comparing the ankle plantarflexors to _______.
Anyone able to track down the study? Here's a clue, it was in the American Journal of Physical Medicine, and published more than 20 years ago.
Drew
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Re: What muscle controls push-off? - November 13, 2002 5:58:00 PM
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ScottO
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Are you referring to the tibialis posterior function of decelerating pronation?
ScottO
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Re: What muscle controls push-off? - November 13, 2002 6:23:00 PM
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Bournephysio
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I've seen the abstract. There are problems interpreting emg. relative change is meaningless if they did not normalize the emg. Even if they did you can't tell if it is contracting isometrically, eccentrically or concentrically. I believe that power analysis is more accurate.
We learned in school that the ankle dorsiflexors produce most of the propulsion. My classmate in my graduate biomechanics class did his project on power analysis of gait. His lit review found that the ankle planter flexors produce the most thrust. His project found the same thing. The hip power was from a 2001 study that used a different statistical method.
Mcap or bobcat, do you know any more about the use of power analysis in gait?
Doug
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Re: What muscle controls push-off? - November 13, 2002 6:28:00 PM
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function
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I believe that there is a problem with the question. I have a problem using EMG to determine the most ESSENTIAL muscle or the muscle that controls toe-off. I would need to know the conditions off the EMG testing. Were the participants barefoot or wearing some type of shoe? How were the participants screened for the study? Was the muscle "screaming or singing" (to borrow a phrase from Gary Gray)?
Flexor hallicus longus contraction, peroneus longus contraction, plantar intrinsic contraction, Gluteus medius contraction, adductor contraction...they are all important. However, so are the muscle contractions that happen on the opposite side I personally and clinically have a hard time thinking of an essential muscle during gait. It doesn't fit with the functional view of rehab. Example...My exercise for the infraspinatus would not be the same as the movement they would use to demonstrate the contraction on EMG.
I gather that there is a muscle that registers the most on toe-off...I just can't extrapolate that to then saying that muscle controls push off.
Here is a test for you Dr. Ball...what is the function of the adductor longus and the adductor magnus during gait?
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Re: What muscle controls push-off? - November 14, 2002 3:00:00 AM
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Andrew M. Ball PT PhD
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Nailed by SJ!!!
One of the best, and certainly the most unique, of studies is the following:
Brandell BR. Functional roles of the calf and vastus muscles in locomotion. Am J Phys Med. 1977. Apr; 56(2) 59-74.
I believe that if most of you take a look at the entire article, it will be hard to continue arguing the gastrocs, hip extensors, low-back stabilizers, etc. The study concludes that:
"Although with increases of speed and upward tilt the abolute values of integrated EMG increased more for the calf than for the vastus muscles, the relative increases of EMG were consistently greater for the basti, which reached peak intensity of activity at moments during the walking stride, when their knee extending action stretched the gastroc heads across the back of the knee joint, and thereby [by non-active biomechanical muscle tension] assisted the calf muscles lift the heel, and plantar flex the ankle joint --- the most essential actions for producting the push-off and thrust in normal walking stride."
Thoughts?
Drew
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Re: What muscle controls push-off? - November 14, 2002 7:16:00 AM
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Bournephysio
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Drew, I'm not sure what you are getting at. Maybe I'm misinterpreting the question. SJ seems to be saying that it is hip flexion at terminal stance. You said she nailed it but you seem to be saying that the vasti are responsible. Could you clarify?
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Re: What muscle controls push-off? - November 14, 2002 10:38:00 AM
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Andrew M. Ball MS MBA PT
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Knee extensors/Vasti
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Re: What muscle controls push-off? - November 14, 2002 3:37:00 PM
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Andrew M. Ball PT PhD
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Perhaps, but isn't it strange that most PT's haven't ever heard of it, and then, usually without reading it, charge it as being "too old" to worry about it clinically?
This study strongly suggests that it is the vasti, and not the gastrocs, that control push off. There have been others that have shown similar results as recently as 2002, but I thought I'd pick the Bramell study as it was conducted 25 years ago and many clinicians still haven't changed their tune.
The biomechanists/kinesiologists that e-mailed me privately confirmed that this vasti hypothesis is looking more and more accurate, that it's taught as such in doctoral level programs (Ph.D. programs, not entry-level clinical ones), and that at least one expressed frustration (in a tone that rivaled one of my wildest rants), that, "most clinicians don't get it, either training patients from a 'swing-propulsion theory' often taught on the Con.Ed. circit, that's likely incorrect, or if they do view gait as pushing-off as opposed to being propelled by the swing leg, incorrectly think it's the gastrocs that are the propulsive force. It's not. It's the vasti, although the vasti pull on the gastrocs is an important part of the process."
This highly respected individual went on to say that I could quote only on the condition of identity being kept secret for obvious reasons.
Drew
Sorry for the spelling errors --- my spellcheck is busted.
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Re: What muscle controls push-off? - November 14, 2002 7:09:00 PM
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pablo w
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Someone may be able to answer this:
If the information discussed above (that the vasti are the most critical muscles for push-off and thrust in gait) is being taught in Doctoral programs, why is it not taught in entry-level programs?
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Re: What muscle controls push-off? - November 14, 2002 9:14:00 PM
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Bournephysio
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I'm still not sure how SJ nailed it then.
You have yet to answer my concerns on the emg analysis.
People who have emailed you don't help us understand. Anyone who is lurking who knows more about this please email me. My email is in my profile. As long as we are not dropping names, the classmate I was talking about recently presented at the world congress of biomechanics. His supervisor is a very well known scientist in postural control and gait. The course we were taking was graduate level (read masters or PhD).
I would like to know how the triceps surae eccentrically lower the foot to the ground after heel strike (your post on chiroweb)
Please post your more recent references. I'm interested in reading your reference I'll email you my number. I don't have a problem with the age of the article if it was done well. I do question the appropriateness of using emg.
The following articles do not support you vastus theory. The one on sprinting showed negligible knee power despite a large extensor moment. Notice the conclusion on the Sadeghi article. It suggests that ankle plantar flexion was thought to provide significant propulsion before this article. I may very well be wrong, I have not studied this area closely. But I think that I have shown that it is not common knowledge in the biomechanics world that the vasti provide the propulsion. If someone can see the flaws in my thinking please post or email me privately.
Simultaneous bilateral 3-d able-bodied gait
Paul Allard, Regis Lachance, Rachid Aissaoui, Morris Duhaime
Human Movement Science 15(1996) 327-346
Found that ankle plantar flexors and hip flexors provided the most propulsion for gait.
Muscle power patterns in the mid-acceleration phase of sprinting.
Johnson MD, Buckley JG.
Department of Exercise and Sport Science, The Manchester Metropolitan University, Alsager, UK. m.d.johnson@mmu.ac.uk
To assess the role of the lower limb joints in generating velocity in the mid-acceleration phase of sprinting, muscle power patterns of the hip, knee and ankle were determined. Six male sprinters with a mean 100 m time of 10.75 s performed repeated maximal sprints along a 35 m indoor track. A complete stride across a force platform, positioned at approximately 14 m into the sprint, was video-recorded for analysis. Smoothed coordinate data were obtained from manual digitization of (50 Hz) video images and were then interpolated to match the sampling rate of the recorded ground reaction force (1000 Hz). The moment at each joint was then calculated using inverse dynamics and multiplied by the angular velocity to determine the muscle power. The results showed a proximal-to-distal timing in the generation of peak extensor power during stance at the hip, the knee and then the ankle, with the plantar flexors producing the greatest peak power. Apart from a moderate power generation peak towards toe-off, knee power was negligible despite a large extensor moment throughout stance. The role of the knee thus appears to be one of maintaining the centre of mass height and enabling the power generated at the hip to be transferred to the ankle.
Lower limb muscle power relationships in bilateral able-bodied gait.
Sadeghi H, Sadeghi S, Allard P, Labelle H, Duhaime M.
Research Center, Sainte-Justine Hospital, Human Movement Laboratory, Montreal, Quebec, Canada.
OBJECTIVE: The purpose of this study was to test the hypothesis that limb propulsion is mainly associated with the interaction of a number of muscle power bursts developed throughout the stance phase and that the control actions are mainly achieved by the contralateral limb through different power-burst interactions. We also hypothesized that the power activities of the propulsion limb would be related to those of the control limb. DESIGN: Sixty gait trials of 20 subjects with dominant right hands and right legs were chosen for analysis. Each trial represents a performance of an able-bodied gait. Data were assessed using an eight-camera, high-speed, video-based system synchronized to two force plates. The muscle powers and their related mechanical energies were calculated at each joint and in each plane of the lower limbs by use of an inverse dynamic technique. The Pearson correlation method was used to determine the relationships within each limb by use of the data identified by principal component analysis, whereas a canonical correlation analysis was performed to illustrate the interaction between the limbs. RESULTS: Gait propulsion was an activity initiated by the hip shortly after heel-strike and maintained throughout the stance phase. Control was the main task of the left limb as evidenced by the power absorption bursts at the hip and knee. The left limb power generations were generally secondary to control activities and were possibly involved in adjustments to correct the other limb's propulsion. Interlimb interaction further emphasized the functional relationship between forward progression and control tasks developed by each limb and highlighted the importance of the frontal and transverse plane actions during gait. CONCLUSION: These results do not support the hypothesis that the ankle was a major contributor to forward progression.
[This message has been edited by Bournephysio (edited November 15, 2002).]
[This message has been edited by Bournephysio (edited November 15, 2002).]
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Re: What muscle controls push-off? - November 15, 2002 1:55:00 AM
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Andrew M. Ball PT PhD
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Doug
After scanning your articles, at least we're agreed that the ankle isn't the propulsive force by concentric contraction. That's what's clear in most programs.
Though that’s generally agreed upon, there is not agreement as far as I can tell, as to what muscle is actually responsible for the push-off. In other words, although it seems to be agreed that the gastrocs don’t control push-off, it is not agreed that the vasti do. One biomechanist who e-mailed me, for example, stated that, “I have always thought the "push off" was the combined action of hip extensors and the isometric contraction of the Gastroc-and especially the Soleus (which has 67% type I fibers. The calf muscles do not plantar flex but hold the ankle at 90 degrees. See Jacquiline Perry, Gait Analysis. [which, for those of you complaining about the Brandell study being too old, is a more current reference]. Also the extension of the knee during Mid stance to heel off is accompanied by criss cross action of hamstrings and gastro-soleus. The quadriceps is silent during heel off though the knee is fully extended.”
I don’t see anything I’d disagree with in that statement, but there is no mention of what the quads are doing from mid-stance through terminal extension, and that’s where I believe we should focus. As for my personal position on this issue , I’m still not convinced one way or the other, but the Brandell vasti hypothesis makes more sense to me at the present time, given my more limited grasp of the evidence-base in this area than most of the human movement science focused Ph.D.’s that have e-mailed me over the past few days.
What is however clear is that that among biomecanists and kinesiologists, the gastroc push-off theory isn't the foregone conclusion that it is in the minds of many, many, clinicians.
As for what's taught in PT school, I wouldn't generalize that it's all taught using the gastroc push-off and/or Rancho Los Amigos research in ALL entry-level programs, but there are still some entry-level programs where it is a clinical professor, not a professor of human movement science, teaching the course --- the most common clinical model used is the Rancho model. The question is, is it completely correct?
My personal question as a Ph.D. in management, is not clinical, but rather, "How effective are we managing patient care if we're focused upon treating the gastrocs instead of the vasti? Does treatment and/or outcomes changes significantly, and how does that impact the time and cost effectiveness of treatment?" On the other hand, is there a flaw in the hypothesis that "most clinicians assume and treat the gastrocs as though it controls push-off."
Drew
Doug, I'll fax you the Bramell study for discussion, however --- let's keep this focused on one study for now okay? Also, the quote you point out on chiroweb was a misprint caused by my brain moving faster than than my fingers. It should have read, "The triceps surae (gastroc, soleus, plantaris) it would seem from EMG study, work to control tibial advancement in an eccentric manner after heelstrike."
Make more sense now?
[This message has been edited by Andrew M. Ball PT PhD (edited November 15, 2002).]
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Re: What muscle controls push-off? - November 15, 2002 3:45:00 AM
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Andrew M. Ball PT PhD
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From: Charlotte, NC
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SJ,
Excellent points.
With all the various high technology stuff out there, would EMG done in 1977 be a gold standard? Probably not, but there have been follow-up studies over the past 25 years that have used more sensitive, and/or a combination of methods. I’m just surprised, knowing the Brandell study is so old, that not many have taken a hard look at the vasti hypothosis --- besides, although a newly appointed adjunct professor, getting articles is cheaper, but still not free. I’ve got the Brandell study, but not the others, in full text.
As far as management of patients go, I’m not assuming that clinicians are “workin’ the dickins” out of the gastrocs/soleus complex to get normalized push off. I’m not sure what’s happening in the field across the country with respect to this issue. Are the vasti ignored? Are the gastrocs stretched so as to make the vasti pull upon them less effective with the clinician unaware of the vasti impact upon the gastroc at this point in the gait cycle???? I don’t know the answer to that --- but if the “kinesiologic truth” could be established, it would make for a VERY interesting ethnographic qualitative study . . . and that’s, if ya’ll haven’t figured this out by now, is where I’m headed with all of this.
The stored energy theory is an interesting one, and I’d suspect that it’s the vasti that help to keep the knee in extension and the gastrocs stretched at one joint, so as to “not fire as much to give anything to the push-off.” Although there is some firing of the gastrocs at that point, that’s the general take home message of the Brandell study. Your point about people with amputation is a GREAT one, and I was just about to transition into that point --- if the gastrocs produced the propulsive force, wouldn’t the gait of individuals with ampulation look dramatically different?
Drew
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Re: What muscle controls push-off? - November 16, 2002 1:43:00 PM
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Bournephysio
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Drew, I'll try to read the paper this weekend. By the way, congrats on the appointment.
Just to clarify, the propulsion by ankle plantar flexors will be concentric by definition. Work is force times distance or torque times rotation. To have a positive work output you would need a shortening of the plantarflexors. If the contraction is eccentric the work will be negative, that is the work is being done to it. There seems to be little doubt that the plantarflexors provide forward thrust. What is the most important muscle seems to be up for discussion.
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