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Determinants of gait discredited?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by danisull, Dec 14, 2011.

  1. danisull

    danisull Welcome New Poster

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    Hello everybody, I am a first yr student so please go easy and forgive my lack of knowledge. I am a bit confused about the deteminiates of gait because in Kirtley (2006) clinical gait analysis, pg: 164; it states that the determinates of gait have been discredited. Is this just to do with center of mass displacement? Are the 6 determinants still the main determinants of gait? And what are determinants of gait anyway?? Is the inverted pendulum more accurate for describing gait or does this just show CoM displacement? Are these two rival theories? Basically trying to understand determinates of gait. Many thanks x
  2. danisull

    danisull Welcome New Poster

    Re: determinates of gait discredited?

    Extremely helpful, thanking you kindly!
  3. Re: determinates of gait discredited?

    No worries. Give them a read and ask any questions which arise. Just provide your real name when posting, you are more likely to get a response that way.
  4. David Smith

    David Smith Well-Known Member

    Re: determinates of gait discredited?


    Ask yourself are the two models mutually exclusive? Is one right and one wrong?
    I would answer no to both those questions and here are my proposals why:

    The Saunders - Inman model - determinates of gait, which in itself is a modified inverted pendulum model, is a descriptive observational presentation of the kinematic displacements of 'normal' walking gait.

    The spring mass model is a quantitative explanation of the kinetics and energetics of ambulation.

    The former observes the characterisation of forces as described by GRF measured and recorded by force plates. The kinematic observations are reasonable and the force characterisations are real enough. The writers postulate the correlation between observed force action parameters and observed kinematic displacements.

    The spring mass model for walking gait describes and quantifies the mechanical action and correlation of energy transfer from one leg to another and how this is achieved within the constraints of the observed kinematic displacements of the modified pendulum model

    The running gait has for a long time been described as a spring mass model and clearly the CoM does not progress in a flat line parallel to the ground. (usually anyway)

    The inverted pendulum theory demands an oscillating CoM progression, Saunders & Inman postulate that the optimum walking gait reduces CoM oscillation to a minimum and so describe the 6 determinates theory. The spring mass theory describes an optimum CoM oscillation that is llowed or determined by the transfer of kinetic and potential energy between each leg and is analogous to a double and overlapping spring loaded mass model and the 6 determinates probably describe a control system to achieve this optimum.

    You could make the analogy of observing a bouncing ball. We could accurately describe the motion of the ball by visual observation and we could measure and record the forces at the ball ground interface and we could describe the nature of application of the forces over time.

    We might also want to describe or postulate what actually makes it bounce, is there a grasshopper inside the ball that conveniently jumps at the right time to propel the ball or is it something to do with, its shape, the way the ball deforms and the nature of the material it is made of? The two theories, how the ball bounces and what makes it bounce, are not mutually exclusive and in fact it benefits the researcher to understand both if he want to make balls that bounce better (or normally or abnormally like the evil Rugby ball, which of course is just right for the game of Rugby but would be quite useless for football))

    Also remember (especially with regard to the evil rugby ball) the any model is only a reference frame for a standard or normal gait style and it is not necessarily important or optimal to make a patient walk normally but rather to enable them to walk in the most efficient way for their abilities, restrictions or requirements.

    All my opinion so I'll probably get blasted but that's ok.;)

    Regards Dave Smith
    Last edited: Dec 14, 2011
  5. Re: determinates of gait discredited?

    Sounds reasonable to me Smithy, but I have only read it once ;). Merry Christmas. I guess it depends on the concept of flat-lining. If Saunders is interpreted as the six-determinants are trying to create as near to a flat-lined centre of mass as possible, and that a flat-lined CoM is a good ting, then it's a flawed concept.

    What I know is this- compass gait, isn't even close; inverted pendulum cannot reproduce ground reaction forces observed in-vivo; of the models we have, the bipedal spring-mass seems to hit most of the bases. But I would reiterate what Dave said- they are just models.
  6. m.mouck

    m.mouck Active Member

    Re: determinates of gait discredited?

    Hi guys,

    I'd like to comment on this issue, since it's a central part of gait analysis.

    If you met Inman in a bar back then, and asked him what he'd been up to lately, he might say something like, "we've been trying to understand how people walk, and are going on the assumption that when a person walks, the focus of control is to minimise the movement range of the COM. This seems logical because that would minimise stress on the limbs due to excessive or abrupt mass shifts, and should minimise the energy expenditure as well.
    We made a compass gait model using sticks, which represents the lower body, and when we looked at different movements and relationships between the limbs, we found 6 values that we believe are primarily responsible for changes in the COM trajectory (COMtraj), and we're calling them "the 6 determinants of gait". We hope that by looking at these, we can simplify the complexities of gait, and once we catalogue how these 6 numbers vary depending on the pathology, it will be much easier to pin-point the physical causes of gait problems, and how they affect the overall gait pattern."

    So, the 6 determinants of gait can't be discredited, since they aren't a theory. The only things that can be discredited are the proposals that minimisation of COM displacement is a central element in gait and/or that the 6 determinants are the best measures to judge this element.

    They use the term "determinant" because they're saying that these 6 values (ie. body relationships) are the main ones which "determine" the important properties of the gait pattern.

    There are 3 relevant levels here, the proposal, the model and the measures.

    So, Inman et al.:
    1) made a proposal (call it a theory, it you like) that minimising the range of COM movement is a central control factor in gait, and
    2) used a 3d stick model and compass gait to illustrate the physical system, and
    3) defined 6 measures, or relationships or however you want to describe them, which they believed would be most influential on the COM trajectory, and called these the 6 determinants of gait. (these measures are not the theory, though)

    So, if a person came in for gait analysis, if you measured these 6 elements, differences in relative values, etc. would show what the problem was. If it was accurate enough, we could strap on the 3d markers, do a run, and problems with muscle action could be determined by the computer, and provided as output of pathologies that have shown these characteristics. All a matter of numbers. Naturally this would only be one part of a full analysis. That's the ideal.

    But, if it's been found that the 6 determinants aren't as indicative as was proposed or don't show what the original researchers thought they did, it's not necessarily the relevance of the 6 determinants, it's a problem with the proposal that COMtraj minimisation is a central element which is useful diagnostically, and/or that these 6 values are the ones which can show what we need to see.

    The 6 determinants, as with all measures, have a unique relevance, independent of any other context. Even if the proposal that the minimisation of the COMtraj is a central element in gait is not true, or at least not true enough as presented to be useful diagnostically, that doesn't mean that any number, up to all, of the individual values aren't important, in some way. Or, any or all of them could be totally useless.

    Although I don't have the references handy, I'm sure I've seen several reports stating that at least one of the determinants doesn't affect the COMtraj in the way presumed by the original researchers.

    If this were true, then of course you can see the problem when you try to correlate that value to COMtraj. Naturally there's going to be confusion and inconsistency.

    If someone is disputing the usefulness of the 6 determinants "theory", they're saying at least one of 3 main things:
    1) they could be saying that one or more of the 6 measures themselves may not show what the original researchers claimed, (which some are saying)
    2) that the original proposal of the central nature of the minimisation of COMtraj deviations isn't correct or suitable as a global indicator for gait, or (which some are saying, such as the pendulum people)
    3) that the 6 measures aren't sufficient to effectively describe the original proposal, so they need to be changed, looked at in a different way, or more measures added until the required movements are sufficiently described. (which I haven't seen people saying, but it's a critical factor nonetheless)

    Note that even if there are problems with the types of measurements chosen, like one doesn't show what they thought or they don't have enough, that doesn't necessarily mean the proposal is flawed, it could just mean they made bad choices in what to use to illustrate their proposal. It's important to distinguish the proposal from the measures used to describe or illustrate the proposal.

    If any of these 3 things are true, then there are big problems. Note that if 2) is true, the others are moot, but not vice versa. My personal opinion is that 2) is true, so I dispute the original proposal. From there you can just look at each measure as an individual.

    Did that make sense?

    So, the 6 determinants idea is just one research groups attempt to define a global control concept for gait - minimisation of the range in the COMtraj; and then recognise and define the body relationships which they thought most controlled that - the 6 determinants. They happened to use a 3d stick model, and it's an excellent one to illustrate what they're saying.

    Given the available resources then, it shouldn't be surprising if they were off the mark a bit. It was a good first try, and another step up on the stairway to enlightenment. When you think of it, nobody's done any better, even up until now. (Actually someone has, but that's another story.)

    As for your question about whether the 6 determinants and the inverted pendulum models are rival theories, the 6 determinants aren't a theory. They're body measures. The theory is that people try to minimise the COMtraj when they walk.

    So, they are conflicting, and it's between Inman et al.'s proposal that minimisation of COMtraj is what people are trying to do to control gait, vs the proposal from the other camp that a person tries to come closer to an inverted pendulum during stance, and aren't trying to minimise COMtraj deviations (or at least not all the time).

    The inverted pendulum model, assuming you're talking about the single pendulum and not the modified biped version, is a simplification of the 3d, ie. Inman's model, which removes the transverse plane component, as well as simplifies the body to a line from the CoP to the CoM.

    So, these models are physically different, even to the point that one is 2d and one 3d, and are meant to show different things and be used in different ways. The models themselves don't conflict in any way, notwithstanding the conflict in the proposals which they're being used to illustrate, and the judgement of which is more useful would depend on what you want to look at and how you want to describe it, which would depend on your specific proposal / theory. These are tools used to illustrate concepts.

    The spring model is a modification of the inverted pendulum model which was incorporated to account for observed differences in the integrated vertical force pattern, as well as observed deviations in real CoM trajectories. It uses the concept of a spring constant, and the biped version is just an expansion of the single one. Under controlled conditions this modification provides pictures of force and CoM trajectory (sagittal) which more resemble real patterns.

    Unfortunately, the spring model is totally unsuitable for use in instantaneous analysis. I've discussed this on one of these threads before, I think it was the sagittal spring model discussion. It does have it's uses, but not how it's currently being used with respect to instantaneous analysis, from what I've seen. I don't want to go in to that again here.

    Note: I'm not a formal gait analyst. My relevant expertise here is in the development of valid and useful analytical methods. Every idea, model, graph, figure or number that describes something has properties and a place within the given framework, whatever that is. You have to be able to understand those properties, that place, and what's required, in order to ensure that each element is suitable for the application. It's not as hard as I might make it sound.

    For Inman et al.'s work, it's actually fairly simple, but you have to distinguish the proposal (theory) (which there's debate about); vs the model used to illustrate the theory (which there's nothing wrong with, since it just describes a specific perspective); vs the measures used to describe / measure / judge the proposal (which there's debate about). Once you do that, I think it makes more sense.

    I hope the above discussion helps. If something's not clear, let me know, and I'll explain it in a different way.

    I also agree with Dave's ball analogy, as far as the models themselves are concerned, it's just different ways of looking at the same thing. And, I'd also add that when you look at the same thing in different ways, they all have to be consistent.

    To re-iterate, the 2 proposals we're talking about do directly conflict. However, as seems always to be the case with gait, there's a ripple.

    The 2 theories directly conflict, but they're not mutually exclusive as far as application. There's no reason the reality can't be that when vaulting on the planted leg the inverted pendulum idea is more relevant, and when going in to double stance and the next single stance, that minimising stress, abrupt shifts, etc. isn't the priority, or any such combination, even periods of "overlap". This would have to be investigated.

    If you like, I could outline some issues about using models, what you can expect them to show, why are different ones used, what you have to be careful of, etc. That may be more than what you want from this, though. And, as you may suspect by now, I can get a bit wordy.

    Since you're a student and this appears to be part of your course work, I urge you to show these discussions to your instructor and ask their opinion, since theirs is the one that should matter the most to you, till the course ends.

    Mike M

    PS I don't mean to go on, but a bit more to think about regarding "theories". If you didn't think I was wordy before, I'm sure you will soon.

    Let's say I propose that when people walk, the central control element in gait is that the person has a preferred point out in front of them, with respect to the position/direction of their pelvis, where they want to put their foot, and they're always trying to put the front foot there, with varying degrees of success (maybe straight out 12 inches or something). How they move onto the planted leg during stance is determined by exactly where the foot was placed, which in turn determines exactly how the pelvis is oriented for the next step.

    This is a proposal about how (why) gait is controlled, as is Inman's and the pendulum. Off the top of our head, we don't know if the proposals conflict or not, since they use different perspectives. However, each will lead to a different prediction of where a person would place the front foot, as well as others. If all the models were totally accurate, they must give the same prediction, exactly, ie. they must be consistent. Since that's not likely to happen, we have to judge varying degrees of inconsistency, realising we can never know what the "true" thing is, we can only infer it.

    Think about how you would show my proposal, in order to make that prediction. What model and measures would you use, existing or create new ones, and how would you describe how they vary. Ie. how can you prove what I said.

    This may seem a simple thing, but we want to measure and judge real gait patterns, and since the person uses the pelvis direction as the reference for where to place the foot, you have to account for the horizontal plane rotation of the pelvis, as well as deviations in the path itself, ie. deviations of the path direction from the sagittal plane in the global frame.

    Also, although it's not usually explicitly stated, all theories, or whatever, also imply that if there are deviations from the normal, they can be spotted and ultimately traced down to whatever level we need, with respect to relevant physical details. If they didn't, they'd be useless. If you see a change in a number and you don't know what it means, whether it's good or bad, or can't see it altogether, how useful is that number (cf. k(leg) when used in instantaneous analysis).

    Note also that I didn't include any reference to control of the direction of the pelvis. Overall control of gait, given my proposal, would be a function of the foot placement with respect to the pelvis as well as the pelvis position and direction in the global frame, since the position of the pelvis determines the potential range of foot placement in the global frame. But, my computer is almost out of power so I've decided that's too complicated to look at right now, and I want to isolate what's necessary to look at my narrowed proposal, while properly accounting for the other.

    This is the general process everyone goes through when developing theories of that type. If we figured out some good measurements to illustrate and/or judge what we're saying, and a good way to describe it, we just created and supported a new theory for gait control. If we'd been first to publish, maybe everyone would be quoting our work.

    It's just as valid as any other, including Inman et al's and the pendulum, until shown to be incorrect or limited in some way, as each of those have been in one way or another. However, there might be 100 valid theories, but it could be that only a few, or none or some or all, are useful, whether on whole or even just parts. Usefulness is the priority in my book. We're not creating ornaments for the Christmas tree.
  7. admin

    admin Administrator Staff Member

    Re: Determinates of gait discredited?

    Here is the 1953 paper on the Determinants of gait:

    Previous thread:
    The Determinants of gait

    A refined view of the determinants of gait.
    Della Croce U, Riley PO, Lelas JL, Kerrigan DC.
    Gait Posture. 2001 Oct;14(2):79-84.
    The six determinants of gait and the inverted pendulum analogy: A dynamic walking perspective
    Arthur D. Kuo
    Human Movement Science Volume 26, Issue 4, August 2007, Pages 617-656
    A refined view of the determinants of gait: significance of heel rise.
    Kerrigan DC, Della Croce U, Marciello M, Riley PO.
    Arch Phys Med Rehabil. 2000 Aug;81(8):1077-80.
  8. NewsBot

    NewsBot The Admin that posts the news.

    Contribution of the six major gait determinants on the vertical center of mass trajectory and the vertical ground reaction force
    C. Hayot, S. Sakka, P. Lacouture
    Human Movement Science Volume 32, Issue 2, April 2013, Pages 279–289
  9. Brian A. Rothbart

    Brian A. Rothbart Well-Known Member

    Re: determinates of gait discredited?

    Kudos!! Your reply was eloquent and quite compelling.

    I have found Inman and Closes work very spot on especially when looking at the kinetic link between hip and foot motion. Specifically I use this link to define normal from abnormal pronation. (See Hip Drive vs Gravity Drive)

    Professor Rothbart
  10. NewsBot

    NewsBot The Admin that posts the news.

    Quantitative Evaluation Of The Major Determinants Of Human Gait
    Yi-Chung Lin, Margit Gfoehler, Marcus G. Pandy
    Journal of Biomechanics; Available online 14 February 2014
  11. davidh

    davidh Podiatry Arena Veteran

    I did a short talk on walking gait for an audience of lawyers a couple of weeks ago. I wanted to show what could loosely be considered normal (vs-abnormal after injury).

    I boiled the determinants down to three - balance, support and power.
    If any one is adversely affected it will interfere with normal gait
    I really think these three are a good place to start for anyone wanting to understand normal walking gait, and I'm indebted to Whittle - the basics still hold true.

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