Can the ground reaction move for you? (competition with small prize)

Thought I’d do something different and run a little competition with the chance of winning a copy of  my book. It’s based on one of the learning exercises we give to our students on our Masters in Clinical Gait Analysis by distance learning  If you’ve got students, trainees or junior colleagues maybe you’d like to forward the URL of this post to them so that they can have a go. Our students enjoy the exercise and I assume they will too. They also learn a lot about how we walk and how to measure the ground reaction.

This exercise requires students to experiment with walking in different ways to modify the characteristics of the ground reaction. You can download  a full description here. First of all they are simply asked to walk at different speeds and record the ground reaction. They then compare the data with those in Mike Schwartz’s paper on how gait patterns in general vary with walking speed. Generally there is good agreement but occasionally we’ll find someone who doesn’t vary speed in the same way that the average person does (whoever that is!).

Then I give them a number of different graphs of theoretical ground reactions and ask them to try and walk in such a way that they match the shape of the graph. The two below, for example, are to walk with exaggerated peaks of the vertical component and then with a flat pattern.


The students generally find these reasonably easy. The more alert ones spot that the flat pattern is simply what you get if you walk slowly but it can be reproduced in a normal speed walk if you think about what you are doing..

Then  come two more – one with the first peak higher than the second and finally the second peak higher than the first.


Again the first is easy. It is what happens if you walk faster (but like the flat peaks there are also ways of recreating it at normal speed). The second is much harder and so far (over two years now) none of the students has come up with a convincing example of walking with a higher second peak than first.

This interests me because a few years ago Barry Meadows and some of his colleagues published a paper based on their observation that in patients with a wide range pathologies you almost always find that the second peak of the ground reaction is diminished – never the opposite. They called this Ben Lomonding, after a mountain in Scotland that has two peaks – one of which is higher than the other.

Ben Lomond

So I just wonder – is it possible to walk in this way? I’m prepared to offer a copy of my book (signed of course!) for the person who can provide the best version of the fourth graph above (2nd ground reaction considerably higher than the first) as real ground reaction data.

Part of the aim of the learning exercise is for students to think about the relationship between the ground reaction and the movement of the centre of mass and we ask them to explain how they have changed their walking pattern in order to alter the  ground reaction.

I suspect it will be a lot easier if you adopt a highly asymmetrical pattern or adjust your gait for the particular step when you hit the force plate. I’ll be more much more impressed if you can illustrate the phenomenon with a symmetrical, repeatable gait pattern.

I’ll use these last two criteria (convincing explanation, and repeatability and symmetry of gait) to judge the winner in the event that more than one person comes up with a solution.

Maybe we need a few rules. Two weeks feels like about the right time. Send entries to me (r.j.baker@salford.ac.uk) by midnight (UK time) on Monday 29th February. They should include:

  • a graph of the vertical component of the ground reaction (you might want to include the GRF from both legs if you want to impress me with your symmetry)
  • a video of you walking over the force plate (or you could send a link to one you’ve uploaded to YouTube of Vimeo or somewhere else publicly accessible – this is what I encourage our students to do). These are particularly useful if you can overlay the ground reaction vector but  I won’t insist on this as a lot of people still don’t have the technology (if all you’ve got is a smart phone then use that). Try and capture at least one step before and one step after the measurement if you want to impress me with the repeatability of your gait pattern).
  • a biomechanical explanation of how you have changed your walking pattern in order to change the ground reaction in this way.

To ensure that entries are genuine I will be try to replicate the best entries in my lab here on the basis of the explanations provided. If I can’t do this I may ask for proof that the data is real (e.g. data in a .c3d other file format that has obviously come directly from a force plate).

I’ll assume that in submitting these you’ll be happy for me to use the graphs and video  in a future post reporting the results. (Note that I won’t publish the explanations – I feel people should be free to write what they want without fear that it will get posted publicly).

Finally, if you enjoy the exercise and would like to engage more, why not think about enrolling on the Masters programme. You can do it as part time study in your current workplace and do not need to travel to Salford at all. You can find details at this link.



No comment

I’ve just been invited to write a “Commentary” for Developmental Medicine and Child Neurology. This is one of those journals that publishes brief articles (I’ve been offered a 650 word and 5 reference limit) commenting on a recently accepted paper. For this particular journal the practice would appear to be to ask one of the reviewers to write the commentary. My first reaction was to feel flattered and start writing immediately … but then I remembered that I often read similar articles written by other people with a sense of annoyance and even indignation.

It takes a lot of hard work to conduct research and write it up to the point of acceptance for a major journal. I remember reading somewhere (haven’t a clue where I’m afraid) that the average clinical paper costs more than a £100,000 to produce once you factor in full direct and indirect costs. Teams of authors spend a considerable time analysing the data and preparing and discussing successive drafts of their manuscripts. The final draft is then subject to cautious scrutiny through peer review to ensure that the resulting product is a fair and considered report of the study and its implications. Given the effort that goes into the article itself I’m not particularly comfortably with the idea that a single individual who’s probably only spent a couple of hours reviewing at the submitted version is given the platform of expounding their views alongside those of all the individuals who have done the real work. That individual is often granted considerably more freedom than the original authors to comment about what he or she likes whereas the original authors are constrained to comment only on the evidence provided within the paper. All in all it just doesn’t feel right.

I’ve held this opinion for some time but was particularly stung last year when we published a paper reporting a substantial clinical trial into the effects of progressive resistive strength training (PRST) on walking and mobility related function in children with cerebral palsy (Taylor et al., 2013). This was the culmination of 7 years work on a project that recruited 44 participants to one of the largest randomised clinical trials recorded of any physical intervention for cerebral palsy. Obtaining the quarter of a million dollar grant from the Australian National Medical Health and Research Council before we started was a substantial achievement in itself. The results were clear (if disappointing for clinicians) that whilst PRST results in stronger muscles it doesn’t appear to lead to any improvements in gait or other measures of mobility. Not only were the findings of that study unambiguous but they substantiated the findings of the three previous (smaller) randomised clinical trials that had been published investigating similar interventions.

The published commentary, however, chose to damn the article with faint praise of its strengths and a focus on minor limitations. It went on to conjecture that the problem was that, although we had put in place a rigorous PRST programme, we hadn’t specifically “trained gait”. Whilst I can’t argue with this, I feel incensed that conjecture about what might work has been used to trump evidence of what clearly doesn’t. The commentary’s conclusion that that, “therapists who look to evidence in the literature to design their interventions will not find this article useful”, is particularly galling. Even if the author of the commentary is correct, that a combination of gait training and strength training is required for functional improvement, it must still be useful to know that strength training alone will not achieve this.

The situation is often exacerbated when the evidence in a paper goes against what the clinical community wants to hear. In the example I’ve cited we would all love to believe that adolescents with cerebral palsy can make substantial functional gains by going to the gym. As optimistic human beings (rather than dispassionate scientists) that’s what our team hoped we were going to provide evidence of when we embarked on the research. For similarly enthusiastic clinicians reading the two articles side by side it will be all too easy to allow the optimism of the conjecture to displace the reality of the evidence.

A particular problem of having commentary published alongside research articles in this fashion is that it can be cited in exactly the same manner. The informed reader will be suspicious of papers that are just one or two pages in length, but not everyone is an informed reader and considerable caution is required to prevent “expert” conjecture entering the evidence base on the same terms as genuine research results. There is also the issue that the model of publishing is of peer review. Inviting one of those peers (equals) to write a commentary implicitly elevates them to quite a different status. The invitation I received referred to an “authoritative background piece by an expert“.

Of course I can be fairly criticised for writing similar opinion pieces in this blog. My only defence is that this is very clearly a blog – it doesn’t make any pretence to be anything else. The banner picture across the top shouts out that these are “personal reflections”. I don’t suppose anyone has ever tried to cite what I’ve written for a journal article but if they do it will be very clear from the citation that these are no more than the ramblings of a bigoted biomechanist.


Three day gait course in June

Hi, I’m struggling to find time to write proper blog articles at the moment but readers may be interested to know that one of the projects that is taking up my time is a new three day clinical gait analysis course that we will be hosting in Salford from 4-6 June this year.

I’m quite excited by it. It builds on very successful courses I was involved in developing while I was in Melbourne based around the impairment focussed approach to interpretation and reporting of clinical gait analysis data that I’ve been working on for the last ten years or so. I hope what will differentiate our course form other similar courses is this strong over-arching framework within which all material will be presented. Certainly the feedback we got from clinicians who attended its predecessors was very positive.

It’s really designed for health professionals (from any background) either working in clinical gait analysis services or referring patients to them. The approach has been developed for children with cerebral palsy and the case exercises will focus on these. We’ll spend some time towards the end of the course, however, discussing how the techinques can be adapted for other patient groups.

If you are interested in coming then look at the University of Salford web-site for further details.

Formatting spreadsheets to make your life easier


This is another short video blog describing how you can format Excel spreadsheets when analysing gait data which uses the spreadsheet template for calculating GPS, MAP and GDI that you can find on the Resources page of this blog-site as an example.

In summary:

  • Put the data in columns on one worksheet, one column for each gait cycle.
  • Put any analysis that operates on data for individual gait cycles on  another worksheet arranged in columns in the same order.
  • Put any analysis that works across gait cycles in a further worksheet.
  • Put tables and graphs of output in this or another worksheet.
  • Label the worksheets sensibly and put in a logical order.
  • If you want other people to use the spreadsheet put instructions on the left-most tab.
  • Save the document looking as you want it to look when the next person opens it up.

If the analysis gets too complex then learn a programming language, it’s generally much more efficient than using spreadsheets!

Who profits from academic publishing?

Apologies for following up the last post so quickly particularly as the theme is a little away from the biomechanics of walking but Jon’s comment to my last entry has prompted some web surfing that leaves me feeling really angry. I remain suspicious of producer pays publishing but realise that the open/closed debate is all a bit of a diversion when you look at the role of the commercial publishers in all this.

I now know that academic publishing is dominated by three companies Elsevier, Springer and John Wiley who between them handle 42% of all papers published. Elsevier publish Gait and Posture and the Journal of Biomechanics which are two of the most influential journals in gait biomechanics so I’ll focus the rest of this post on them but I suspect the others are not much better. Elsevier is part of Reed Elsevier. The academic publishing arm (which includes journals and text books is listed as “scientific, technical and medical” within the company accounts and reports) publishes a third of a million research articles each year in 2,00o journals with 700 million downloads last year.

All well and good but if you look at their financial statement you’ll see that over the last two years (2011 and 2012) they had an annual turnover of just over £2 billion (yes billion) and an operating profit of around £700 million. That’s a profit of about 35% of turnover (click here for similar figures for other publishers).

This is a business that publishes other peoples products. They don’t pay the authors anything for the content they publish (indeed the gold open access deal is that authors will pay them about £3,000 per article) and they don’t pay reviewers anything for peer review. I’m not sure what the Editor of Gait and Posture get’s paid but I’m an Associate Editor and receive about  £1,500 per year (half the open access fee for just one article – and will probably handle about 100 papers this year). The £700 million that Elsevier’s shareholder receive each year is thus essentially a product of the academic community’s good will. 

Like any responsible multinational Elsevier are engaged in political lobbying to protect their profits. They have been strong supporters of three bills (Stop on line piracy [SOPA], Protect intellectual property  [PIPA] and the Research Works Acts) presented to the US government. Whilst all have positive sounding names and objectives they are essentially bills that protect the vested interests of holders of copyright. In Elsevier’s case this is particularly outrageous as the copyright they hold stems from other people’s intellectual endeavour.

I’m not the only one to feel unsettled by this. George Monobiot is a campaigning journalist who put’s the case against the publishing cartel very strongly.  In January 2012 mathematician Sir Tim Gowers called for a boycott of Elsevier  which has given rise to the Cost of Knowledge movement that now  lists over 14,000 academics who have chosen to boycott Elsevier’s activities in one way or another. 

I find this really challenging. I probably regard Gait and Posture and Journal of Biomechanics as the two premier journals in my field but  I feel really angry about the size of the profits that someone is generating from my labour. Any suggestions?