2016 publications: From the armchair to the site, via these journals

18 Oct 2016 Posted by
I was going through my publication record from 2016, and thought I’d share some links to (and summaries of) the interesting ones, since most of the topics they cover have eventually found their way onto this site, or into Twitter discussions in some form over the last few years.  Topics range from rugby to barefoot running via Kenyan physiology.

So here are the more “academic” versions of the articles I’ve tried to explain, describe and discuss in various articles in the past:


Rugby research

1. Managing player load in professional rugby union, Quarrie et al, BJSM

This is a paper that was really carried by Dr Ken Quarrie, who works in New Zealand and is a colleague of mine on World Rugby’s Scientific Committee.  The background is that a few years ago, World Rugby brought a host of experts together for a discussion on the specific issue of how player welfare can improved through load management.  We know that the incidence of injury in professional rugby is relatively high, and managing load (either too high, or as recently been shown, too low) are predictors of injury.

So this paper is the summary from that meeting, and it offers some data on the load currently faced by rugby players, and practical ways that the load might be monitored and managed.  I’d really recommend it for any S&C coach, coach or medical role-player who is interested in the topic.

2. Rugby Sevens: Olympic debutant and research catalyst, Tucker 2016, BJSM

This is a brief editorial that I was asked to contribute to an edition of the British Journal of Sports Medicine.  I’m a big fan of Sevens – I worked with the SA Team from 2008 to 2013, and it was really my start in rugby.  You’ll hopefully have seen the sport debut in Rio, I think it was a highlight of the Games, and because of its relative “immaturity”, it’s ripe for research.  The exciting thing about Sevens is the “newness”, and that applies not only to the performance attributes, where the game is evolving rapidly, but also research.  There are many as yet unexplored issues, or challenges that have been researched but not yet perfected.  Sevens is on the steep part of the “learning curve”, and this editorial was basically a call to action to keep climbing.

3. Injury risk and the tackle ban in youth rugby. Evaluating the evidence to find effective interventions, Tucker et al, 2016. BJSM

This paper was actually inspired by this website, rather than the other way around.  At the end of February this year, a group of doctors and academics in the UK published a call to have the tackle banned from youth rugby.  I wrote a response to it on this website, and then a friend and research colleague, Dr Matt Cross, suggested that I might turn that article into something for a scientific journal.  A week or so later, this was the result.

It basically addresses the issue of rugby safety.  My big objection to the “ban the tackle’ call made by those academics was that it was unnecessarily extremist, something I explained in the lay article, and in this scientific piece.  The injury risk can always be reduced – indeed, for rugby, and in children, it must be, but calling for a ban on tackles is too divisive.  Case in point – a big focus for that group was actually to propose a reconsideration on compulsory rugby in schools, but that suggestion (which should be discussed) got lost in the ‘noise’ of the extremist thinking.

There were a few other issues around this rugby safety controversy that needed to be discussed – the research on quantifying the risk IS thin, and it does need to be improved, but the “Tackle ban” proposal used this variable research as foundational, and that needs to be addressed too.  This paper was an attempt to bring evidence, rather than emotion, into the discussion.


2. Kenyan running physiology

Back in 2013, the editor of the British Journal of Sports Medicine asked me if I’d like to contribute a review on Kenyan runners, which is a fascinating topic in exercise science.  So I worked with physiologist Dr Jordan Santos-Concejero (whose name you’ll see more of) and geneticist Prof Malcolm Collins to write this review, called “The Genetic basis for elite running performance”.

That was the start of a series of research studies on Kenyan runners, because Jordan was in SA doing his post-doc work on the subject.  So began a few years’ worth of collection of data on this fascinating topic.

The first paper we published was a statistical analysis of the Kenyan running phenomenon, which was published in the International Journal of Sports Physiology and Performance.  It showed the extraordinary risk of Kenyan, but specifically Kalenjin and Nandi runners in the 1990s, co-inciding with the ‘disappearance’ of previously dominant nations/continents.  A fun paper to write.

Then began the actual testing – thanks to Jordan, we got to test 15 elite Kenyans.  Not quite the Kipsang/Kimetto/Kipchoge caliber of Kenya (that would be fascinating, not least of all because it would allow some predictive modeling of performance ceilings to be made based on my own data), but rather a level below – we had guys who went on to win mid-level races in North America and Europe, and it was a real privilege to test them.

Here are the papers out of that research:

1. Maintained cerebral oxygenation during maximal self-paced exercise, Santos-Concejero et al 2015. Journal of Applied Physiology

One of the targets of recent performance-physiology research has been cerebral oxygenation, because some studies had showed that fatigue coincides with a drop in cerebral oxygenation, and that changes in cerebral oxygenation (specifically, its progressive decline) was associated with changes in muscle activation levels.

So it’s a good candidate to measure, especially in Kenyans, because separately, there’s research showing that habitual exposure to altitude, particularly through many generations (high altitude ancestry) can contribute to increased vascularization, including in the brain.  This may confer cerebral oxygenation advantages on Kenyans.  Add in their high levels of physical activity during childhood, and the elements are there for Kenyans to display different cerebral oxygenation patterns during maximal exercise.

And sure enough, that’s what this paper found.  A previous study on elite athletes from Canada showed a decline over a 5km time-trial, whereas our Kenyan athletes were able to defend cerebral oxygenation

2. Neuromuscular changes associated with superior fatigue resistance, Harley et al, 2016. J Sports Med Phys Fitness

We deviated from script a little to get this one done – it left the Kenyans alone for a bit, and looked back into some data that Dr Yolande Harley had collected in South African black and white runners a while back.  Difficult to get published because of that lag, it was nevertheless interesting because it looked at specifically isolated muscle function – runners performed sub-maximal isometric quadricep contractions.

The black runners took longer to fatigue (at the same % of maximum), and their muscles were more responsive to external stimulation than the white runners.

3. Gait characteristics, ground reaction forces and running economy in Kenyans, Santos-Concejero et al, 2016. J Sports Science

This was a paper where we discussed the data we’d measured in Kenyans with data that Jordan had measured during his PhD studies, on elite Spanish and Moroccan runners.  We found that the Kenyan runners were able to run the same speeds (5 min/km and 3 min/km) with ground contact times that were 10% shorter than those European/North African runners, and that their running economy (oxygen cost of running) was about 8% better.

This was important because a few studies had come out recently suggesting that the muscle-tendon unit in the Kenyan runners was more “efficient” because of its greater stiffness, and that this would account for both the ground contact time reduction, and the lower oxygen cost of transport.

That series of studies, and this one, also highlighted one of the real challenges in this field – when you measure the physiology or neuromuscular characteristics of an elite Kenyan runner, who do you compare them to?  If you compare them to non-running Kenyans, then all you’re finding is the difference between elite and non-elite runners.  In other words, whatever differences you observe might be training status related, and not ethnicity.  That’s what some of that work had done (Sano et al for example).

This study was able to at least compare groups of athletes who were more similar for performance and we still found some differences.  Are those differences unique to Kenyans?  Who knows?  Similarly, when you find similarities, it doesn’t tell you too much about potential population differences that may make Kenya more able to produce world class runners per 100,000 people than say, Spain, or South Africa.

This is one of the reasons this area of research is so much fun – some have said that the failure to find a genetic predictor of performance, or a gene variant that Kenyans/East Africans possess, is proof that there is no genetic advantage.  I’d argue that they’ve lost sight of the wood for the trees, or simply don’t understand the pipeline that produces world class athletes as a function of genes.  This requires a different level of thinking (strategic and tactical), whereas genetics (and sadly, most scientists) are very operational in their thinking.

4. Muscle co-activation and implications for running performance on Kenyans, Tam et al, 2016. J Sports Sci

Part of the testing we did on the Kenyans was a comprehensive biomechanics analysis during normal paced and sprint running.  We still have a lot to learn about how to piece together all those pieces, but this study measured kinematic, kinetic factors and muscle activation patterns during running at slow (5min/km) and fast (3 min/km) speeds.

We then linked them to work out the degree to which muscle activation (especially pre-activation – the activity of the muscle as it “prepares” for ground contact in the final 100ms) influenced joint stiffness.  This has implications for injury risk and performance.

For instance, we found that higher Rec Fem:Biceps Fem (agonist:antagonist) ratios during preactivation and ground contact predicted higher knee stiffness.  Not surprising.  But we also found that increased co-activation (turning them on at the same time) was associated with increased stiffness and greater energy cost of running.  So there’s a possible payoff between getting the stiffness (and potentially stability) of the joint high enough, while increasing the energy cost of doing so.

The problem with this study is the lack of a suitable control, something I mentioned previously as an issue when you test this level of athlete.  Also, there is the limitation that this type of study is short-term, whereas the clinical and performance outcomes are longer term, and that makes it very difficult to link the two, as we see in the next section on barefoot running.


3. Barefoot running

Back in about 2010, I spent three weeks in the USA, much of it in Colorado, and some in Boston.  On that trip, I met a handful of people who were the “first movers” in the whole barefoot running revolution.  People who were selling and making barefoot shoes, people who were already running barefoot, and even Prof Daniel Lieberman, who became of the field’s main research protagonists.

That trip was very stimulating for those reasons, and when I got back to Cape Town, I started chatting with Nic Tam, then a post-grad student with an interesting running biomechanics and we decided that we’d embark on his PhD in this field.

Mainly, we wanted to bring a “real”, practical approach to the question.  The research tends to be quite abstract, and in the field of biomechanics, very theoretical and ultimately non-commital – you read most of the barefoot running or running biomechanics papers, and you’ll see what I mean.

Our objective was to do studies that would lead to principles, and those principles could be adopted by therapists and coaches to help guide behaviour in runners.  That’s idealistic, and we knew that, but it’s a better goal than making murky the already murky waters.

So Nic set about doing a series of studies that wanted to answer two main questions:

  1. Do runners adapt to barefoot running in the “theoretical”, predictable way, and what factors might predict this?
  2. Can barefoot running be acquired as a skill over the course of a supervised barefoot running programme?

It seemed to us that the answer to these questions would go a long way to establishing whether the “Born to Run” inspired barefoot craze was sustainable or not.  Nic got his PhD, and he’s now continuing his work on biomechanics.  The papers that came out of it were the following:

1. Barefoot running review, Tam et al, 2016. BJSM

First we published what I think was a really excellent review on where the literature was at the time.  It identified the gaps, and asked what we thought were the pertinent questions of the time.  It set up Nic’s PhD studies nicely.  I think the content of this review article is still relevant today.

2. Running economy after 8-weeks of barefoot training, Tam et al, 2016. Int J Sports Med

The center-piece of Nic’s research study was a supervised 8 week training programme that very gradually built up the barefoot running volume from zero to 45 min.  We measured a range of things, mainly biomechanical because we wanted to see whether runners would adapt the so-called “favourable” barefoot running gait immediately (key to its safe and effective prescription), or whether it would take weeks, possibly months to see those changes (which has practical implications for how barefoot running is introduced, as I’m sure you can appreciate).

This particular study looked primarily at the oxygen cost of running, or running economy, because there was a theory that barefoot running would be more efficient.  We found no difference in oxygen cost between barefoot and shod running, but we did find that in the barefoot condition, runners had a lower oxygen cost after 8 week than at the start.  In other words, they were able to show some metabolic adaptations to barefoot running that lowered their oxygen cost as a result of barefoot training.

Biomechanically, there are many differences between shod and barefoot running, and we found that they persisted over the 8-weeks.  This is expected, and probably good, because you wouldn’t want barefoot running to start to resemble shod running as you do more of it!  If anything, you want the opposite.

What we did find was that in the barefoot running condition, the ground contact time increased from week 0 to week 8, and the stride frequency went up.  Quite why this happened, together with a reduction in oxygen cost, was unknown – it probably requires measurement of the tendon stiffness at the molecular level.  Or perhaps it is neuromuscular.

3. Individual responses to barefoot running and insight into injury risk, Tam et al, 2016. Am J Sports Med

This is the paper of which I’m most proud of, because it directly addresses the key issues I mentioned in the introduction.  Basically, we identified positive and negative responders to an 8-week barefoot running programme.  This was from a biomechanical perspective, and it sets up future research to look at clinical outcomes, but our focus was to use the existing theoretical basis for the advocacy of barefoot running and to ask “Does this even happen?”.

The answer is that in about half of runners who take on barefoot running, those supposedly beneficial changes don’t happen, and even 8 weeks of barefoot training don’t do anything to change it!  Some do benefit, at least biomechanically, but it’s a 50-50 call.  Loading rate, and associated biomechanics and neuromuscular activation patterns, don’t change in half of runners, and that would be food for thought to anyone who wants to stand up and “sell” a solution of barefoot running.

We’re now following this up with a longer study, looking also at clinical outcomes (but in minimalist shoes, rather than pure barefoot)

4. Loading rate increases during barefoot running in habitually shod runners, Tam et al, 2016. Gait Posture

This is similar to the previous paper, in that it looked at whether the supposedly favorable biomechanics changes actually happened.  Remember, at the time, thanks to “Born to Run”, and Lieberman’s key paper, the theory was that if you ran barefoot, you’d land on the front of the foot, your loading rate would be greatly reduced, and this combination of forefoot strike, plantarflexion and reduced loading rate was protective against injury.  You’d be running the natural, Kenyan way, and you’d be injury free!

Turns out that this isn’t the case, certainly not on acute exposure, and as we showed in Study 3 above, not after 8 weeks of progressive barefoot running.  In a sense this study should have preceded three – it did, in the real world, but getting it published took longer for various academic logistical reasons.

Nevertheless, it showed a similar thing – some runners did show these ‘favorable’ adjustments when they took their shoes off.  Others did not.  In fact, they went the other way – higher loading rates, and theoretically, increased injury risk.  We also found some interesting interactions between shoes and kinetic/kinematic variables, most notably that the people who showed the largest “negative” changes (judged by the biomechanical changes) were the ones most likely to benefit from wearing shoes.

Again, the implications for practical advice should be obvious.

What’s needed in all this research, by the way, is the clinical outcomes.  That’s where, as I said, we’ve looked to next, but if I could give totally unsolicited advice to anyone reading this, the area needs to establish the link between these measurable theoretical changes and actual outcomes, whether injury or performance.

That’s true in every single field of research, of course, not just this one, and is the greatest challenge facing exercise science.

Anyway, that’s some of the research from the last 12 months (plus one or two for context).  Hope it’s been of value to you.