Running barefoot vs shoes

Barefoot running - new evidence, same debate

It's been a rather frantic week, and I know there is a series on weight hanging in between Part 3 and Part 4.  I'm hoping to get to that next week, when hopefully I'll have a little more time!

But today, I have to comment on this latest study, which I know will become bigger in the coming days - it is a new study that will reignite the barefoot vs. shoe debate, one of the more controversial issues in running.

I am actually planning a whole series on this topic, because I was recently interviewed by a Dutch Running magazine, Run2Day, and I'm going to post that entire interview (with additions) on the site at some point in February.

The study 

For now though, the paper is called Foot strike patterns and collision forces in habitually barefoot versus shod runners, and it is published in Nature (Full reference: Lieberman et al., Nature, 463, 531 - 535).

The scientists took five group of runners and had them run both barefoot and in shoes. The groups were: Habitually shod adults in the USA, Recently shod adults in Kenya, Habitually barefoot adults in the USA, Barefoot adolescents in Kenya, and Shod adolescents in Kenya.

Each group ran in shoes and barefoot and they measured foot-strike pattern (whether the runner lands on the heel, midfoot or forefoot) and kinematic and kinetic variables like impact force, loading rate, and joint angles.

The findings - a shift in landing, a reduction in force


It turns out that people who run barefoot, even when shifting from shoes to the barefoot condition (the habitually shod groups),  shift the landing point to the forefoot.  There's nothing new there - it's been known for many years that running barefoot changes the footstrike.  Hundreds of studies exist to show this.  The next difference is the ankle angle - the barefoot runner has a more plantarflexed ankle when they land - what this means is that the toe is pointed away from the body more (compared to dorsiflexion, when you pull it back towards you at the ankle).  Again, hundreds of studies have shown this.


Next are the impact forces.  Here's where there is some disagreement.   Previous studies have occasionally disagreed on how barefoot running affects impact forces - some say it actually increases them, with high variability between individuals.  Most suggest a reduction, particularly early on during impact (first impact).   The Nature study has found that being barefoot AND landing on the forefoot reduces both the loading rate and the peak impact force.  In fact, it's three times lower in barefoot runners who forefoot strike (which is most of them) than in heel strikers wearing shoes.  In theory (though this too is disputed), higher impact forces and loading rates equals greater injury risk, and so the study is suggesting that perhaps people who are barefoot or minimally shod have a better chance of avoiding injury.

A stimulus plan for physical therapists and podiatrists?

And here is where it gets tricky.  I must point out that the title of the paper is Foot strike patterns and collision forces in habitually barefoot versus shod runners.  I highlight the word "habitually", because it's quite important to appreciate the impact that this word may have on how you apply this finding.

I guarantee that the media are going to be all over this and they are going to tell you that you should be running barefoot or in Vibrams.  You will hear how science has proven that being barefoot will prevent injuries, and that those of you who are injured should blame your shoes as you lob them into the garbage bin.

None of these suggestions is true, yet.  And Dan Lieberman who headed up this latest study would not even be suggesting this himself.  The final sentence in the paper in fact reads "controlled prospective studies are needed to test the hypothesis that individuals who do not predominantly RFS either barefoot or in minimal footwear, as the foot apparently evolved to do, have reduced injury rates" (good science always recognizes what it DOESN'T say, and Lieberman and co fit this category).

What the Nature study hasn't measured is the long term (or even the short term) effects of the change on loading rates on different joints.  If you wish to guarantee yourself an injury, then go out for a 2km run barefoot on a hard surface, and you will be asking your calf muscles and Achilles tendons to do work that for perhaps 30 years, they haven't had to do.

And I will illustrate this with our own insight into footstrike and injury.  When the Pose research was done in Cape Town, athletes basically had their footstrike patterns changed through 2 weeks of training in the new method.  The biomechanical analysis found lower impact forces (sound familiar? Same as the Nature paper), and even less work on the knee joint.  This was hailed as a breakthrough against running injuries, because lower impact plus lower work on the knee meant less chance of injury.  Jump ahead 2 weeks, and 19 out of 20 runners had broken down injured.  Why?  Because their calves and ankles were murdered by the sudden change.  And the science showed this - the work on the ANKLE was significantly INCREASED during the forefoot landing.  

The point is, changing how you run, whether by technique training or a change in shoes (like running barefoot) will load muscles that may be very weak, and joints and tendons well beyond their means.  If however, you are a habitually barefoot runner, then you can do this, because your body has been prepared for it.  For everyone else, I think we may be underestimating the time it will take to transition successfully to barefoot running (or forefoot striking, if you're going to force that change 'unnaturally').

And there is my point - taking this kind of interesting study, and dispensing advice, is a risky business.  As a friend pointed out yesterday - the media's interpretation of this study will be a "stimulus plan for physical therapists and podiatrists".  Going from years of shoes into minimal shoes or barefoot will injure you if you are not careful. 

Conclusion

The Nature study provides a good discussion point.  It's intriguing, and certainly does suggest advantages to barefoot running.   It is not the last word, but rather the latest word in this debate.  Nor is it revolutionary, because for many years, we've known that being barefoot changes ankle angle on impact, footstrike and loading rates (though quite how they change is not agreed upon).

I'm sure a lot more will be written - I'll even cover some of it when I do that interview series on this topic in the coming weeks.  For now, that's the last I'll say on this particular issue, but debate is always welcome!

Ross

P.S.  Daniel Lieberman has launched a website on this topic, and it's well worth a look.  It is obviously based on his research (this study forms the bulk of it), but it's a good, clear explanation of the concepts.  Again, the same word of caution applies - don't jump from one to the other.  If there is one section of that website that you should read over and over, it is the Training tips section.  Most will not, and they'll become the statistics (and the stimulus for physical therapy), but if you manage it right, then the site will be a great help to you!

Haile Gebrselassie 2:06:09 in Dubai

Fast for Geb in Dubai, but the record was never on

2:06:09 can never be deemed a disappointing performance - it's a time that ten years ago would have scared the world record, been comfortably in the top 10 of all time, and would signal a great effort.  It's testament to how the marathon has progressed, and to what Haile Gebrselassie has achieved in his running career, that when he achieves this time, it's met with some disappointment.

Gebrselassie spends most of his racing time hunting world records - I've said before what a pity this is and how great it would be to see him take on the likes of Lel, Wanjiru and Kebede, but he has been content, for the last five or so years, to race the clock in a couple of races a year.  His first attempt for the last few years has come in Dubai, where huge incentives, both upfront and for winning and breaking records, are a big draw.

And Dubai has been very fast for Gebrselassie - he has run 2:04:53 and 2:05:29 (2nd and 8th fastest ever at the time, respectively).  But 2010 has produced the slowest of his three Dubai Marathons, 2:06:09.

Dubai 2010 - close for a short time, then a gradual slide away

And the record was on for a short time only.  The graph below shows the kilometer splits, and then I've worked out the projected time at 5km intervals (based on the cumulative time, not the last 5km, note), shown in green where he sped up over the interval, red where the pace slowed.

Remember that the world record of 2:03:59 requires an average kilometer pace of 2:56.  Gebrselassie was close to it, but never below it, until 5km had been covered, and his 5km time of 14:54 was 3 seconds per kilometer off that required pace.  We've discussed before how incredibly precise the pacing has to be in order to succeed over 42.2 km - it is remarkable.  In previous Dubai races, Gebrselassie has gone out much too hard - in 2008, he was on course for about 2:02 after 15km, and then slowed considerably to run 2:04:53.

This time, if there was a pacing error, it was on the slower side of desired, because the early pace was just outside the target - Gebrselassie averaged 2:59 for the first 5km (14:54 split), 2:58 for the second 5km (10 km split of 29:42), but then began to slow progressively.  At halfway (1:02:51), his projected time was 2:05:42, which some would say meant the record was still on, but when you need to run the second half of a 2:04 marathon in 61:07, then the record is pretty much gone. That the pace was slowing after 10km is a sign that it was never going to happen today, and from that point onwards, only eternal optimism would have kept record hopes alive.

A race in the final kilometers?

The pace held steady at around 2:58/km from halfway to 35km, and then the pace really did slow down - a series of 3:05 or slower kilometer times and the projected time dropped outside 2:06.  It is very interesting to note that Gebrselassie's final kilometer was 2:36, an increase in pace which suggests that he took the foot off the gas in those earlier slow kilometers, because by then the record was clearly gone - it would have required something in the range of 2:50/km for the final 10km to challenge his mark.

Also of interest though, is that he "only" won by 24 seconds today, making this the closest marathon "race" he's run in a while.  He may have entered looking for a paced record, but he seems to have found himself in a tight battle at the end.

And, given a final kilometer of 2:36, the 24 second winning margin would have been largely, if not entirely, created in the final kilometer, which means that Gebrselassie was not alone at 40km, and definitely not at 30km.  It seems likely, then, that the presence of other runners in a group from 30km onwards, combined with Gebrselassie not feeling quite up to the world record (as shown by the relatively sluggish start, particularly from 10 to 20km), resulted in a tactical race which slowed the pace down in the latter kilometers.

I confess that I didn't see the race, it wasn't televised and SA internet is so poor that watching online doesn't happen at the best of times, so I don't know the circumstances in those middle kilometers.  The temperatures and wind certainly don't seem to have been too limiting - the temperature at the finish of the race was 18 degrees with no wind, though the humidity was up at 80%, which may have contributed to that progressive decline.

Nevertheless, it's a good, not great time, for an athlete who has inspired expectations of great every time he runs.  It really doesn't help that he only runs in time-trials (with the exception of Berlin last year, where Duncan Kibet might have, but didn't, provide some opposition), and that he talks up the chances every time he races.  Before this one, he spoke of perfect preparation, and the ability to run 2:03:30.  There's always the proviso that the conditions must be absolutely perfect, and so I suspect in the aftermath of this race, there'll be some problem with the conditions, perhaps that humidity.

We'll see, and update the post a little later, and maybe debate in the comments below!

Ross

IOC calls for treatment in sex ambiguity cases

The complexities of gender verification:  Legal, medical and performance dilemmas

I thought I'd interrupt the weight management series for a day to cover very briefly the news being reported out of Miami, where a panel of medical experts met to discuss the complexities around gender verification.  The meeting, convened by the IOC in response to the huge controversy over Caster Semenya's win in the IAAF World Championships last year, addressed how authorities manage the minefield of equality of competition vs the rights of individuals and the medical concerns over such conditions.

It turns out, however, that fairness of competition didn't feature.  That's according to one delegate, Joe Leigh Simpson.  His words:  “We did not address fairness.  The entire concept was that these individuals should be allowed to compete.”

And the means to compete, according to news reports, is to treat the condition medically and not from the point of view of performance.  That is, if they wish to compete as females, but have a condition which gives them masculine characteristics, they should seek a diagnosis and treatment.  “Those who agree to be treated will be permitted to participate,” said Dr. Maria New, a panel participant and an expert on sexual development disorders. “Those who do not agree to be treated on a case-by-case basis will not be permitted.”

If this is the agreed upon approach, then fairness is very definitely an issue.  One cannot be forced into medical treatment as a condition for participation, surely?  The only reason to make medical treatment compulsory is to ensure fairness of competition, and so while delegates may say fairness was not an issue, it has to have been.

Other delegates have challenged this on the basis of fairness.  The previously mentioned Dr Simpson admitted that the guidelines would be deemed unfair by some female athletes, but that “we have to balance fairness to female athletes to fairness to other competitors."

The question is, does the right to compete with a possible advantage as a result of masculinization trump the right to fair competition for those without it?   Whose rights are more important, because balancing fairness requires that somebody assign a value to each side's arguments.

And legally, if an athlete decides not to seek medical treatment, can they be excluded from competing, unless some very clear guidelines are developed for how potential performance advantages can be evaluated.  Can medical treatment be bartered against competing?  As I see it, the only way this would be feasible is if athletic competition with such a sex ambiguity poses a risk - then authorities could say that they do not wish to be party to the increased risk and deny the athlete the right to participate.  The risk of having such a condition alone would not entitle the IOC to ban an athlete, surely?

This discussion may in fact be happening as we speak, with Caster Semenya's lawyers and the IAAF locked in negotiations.  Part of that discussion may involve terms for return to competition, and whether medical treatment is a pre-requisite.

As we've learned over the last few months, this is an incredibly difficult issue, with no obvious solution.  Regardless of which way you swing, there are going to be winners and losers in the debate - someone is either excluded, or large numbers of athletes are possibly disadvantaged.

My personal opinion agrees with that of Doriane Coleman, a law professor at Duke University, and a former elite 800-meter runner. “If you start to do this you are making a joke of the fact that there are two classifications — male and female.  They might as well open it up and have women competing with men.”

But that's because my paradigm is performance, advantage and fairness.  Unfortunately, it's never quite that simple.

I'll get back to other "weighty" issues next week - feeling rather burned out at this stage, I must confess.  Luckily the year is nearly over...

Ross

Exercise and weight loss Part 3: Fat

Fueled by fat:  Fat burning 101

There are many reasons to want to burn fat during exercise.  For obvious reasons, in the context of the series I'm currently doing, people want to burn fat during exercise to lose weight.  In that regard, one must emphasize that as much as we talk about weight loss, fat burning (or rather, a change in body composition) is the priority for most people who commit to exercise and diet to lose weight.

I must emphasize (and this is a late addition to the post) that the principles we've been speaking about in our previous three posts in this series do not suddenly cease to exist - in other words, the fundamental issue is still total calorie balance, not necessarily fat burned.  And so this post looks at fat use during exercise, but I don't want to overplay the concept that you can burn fat to accelerate fat loss.  In fact, in the long term, it's the creation of the calorie deficit that is needed, as we discussed in Part 2 A and B of this series.  If in doubt, read the whole series as one "book" and it should be clearer...

For those who are more interested in performance, fat burning is equally important. Ever since the 1970s, when the muscle biopsy technique first allowed scientists to "look inside" our muscles during exercise, we have understood that fatigue and performance are associated with a depletion in the body's glycogen stores.  Delaying this depletion of your body's carbohydrate stores is seen as an important adaptation to training, and we know that highly trained endurance athletes have a much greater capacity to use fat.  This is also the reason why science has looked at all kinds of strategies, like caffeine use, fat-loading, high fat diets and fat during exercise to try to delay carbohydrate depletion.

So, having made the case for fat burning, let's look at how it plays out.

A car with multiple fuel tanks:  Fat vs carbs

You'll know that our body is capable of using numerous sources of energy during exercise - think of your body as a car with multiple fuel tanks.  The first tank is glycogen, the storage form of carbs in the muscle and liver.  The second is fat (strictly speaking, it is free fatty acids), which is stored in the muscle and in adipose tissue as triglyceride.  This is summarized in the diagram below.

The problem we face is that our body's glycogen stores are finite - muscle and liver glycogen supply energy for exercise for about two hours (depending, of course, on the intensity, level of training and habitual diet, among other factors), and once they are depleted, hypoglycemia (from liver glycogen depletion) and fatigue are the result. 

On the other hand, much to most people's dismay, fat stores are not limited.   "Infinite" is not the correct word, because they're not, but in terms of physiology, you have more than enough fat to power exercise for much longer than you can ever exercise, even if you're an elite athlete.  Most of us are not, and so our objective is to cut down these already abundant fat stores into something a little more "acceptable"!

For now, I won't go into the concept of "preferred fuels" and how the heart can use lactate, while the brain is able to use ketone bodies.  I've also oversimplified by leaving protein out, but that's because I want to focus on fat vs carbs today.



Burning fat - how fast, how long?


Perhaps the best approach to this topic is to ask when each of the fuel stores is used?  In otherwords, how does your body decide when to use fats versus carbs as a source of fuel, and to 'fuel' the discussion by starting with some of the theories around fat burning.

The first theory is that you burn more fat when you exercise at a low intensity.  That is, walking is better than running, and cycling slowly is better than cycling fast, and so on.  The idea is that your body uses carbs more and more as exercise intensity rises - this is the basis for target heart zones and the fat burning zone you see in books and on gym equipment.

Let's look at that in more detail.  Below is a diagram that shows an example of how the use of fat and carbs are related as exercise intensity rises. 

So, on the left, in the pink shaded box, you can see that at low intensities (walking, slow cycling), about 80% of your energy comes from fat, while only 20% comes from that carbohydrate (CHO) "tank".  As the exercise intensity rises, the relative contribution of fat falls while CHO rises.  The result is that at about 60%, shown by the green zone, the contribution is equal - 50% from fat, 50% from CHO.  This point, at which the contribution from CHO becomes greater than that from fat, was called the Cross-over point by George Brooks, a very famous exercise physiologist, who wrote a great textbook on the field (the book that was prescribed to us in my studies, in fact).

Then, as exercise intensity rises even more, the contribution from fat declines, so that by the time you're exercising vigorously, between 80 and 90% of the energy comes from CHO, and only about 15% from fat.

Just to comment on how you can measure intensity, my value is calculated as a percentage of VO2max, which is not accessible to many people.  It's impossible to say exactly what heart rate that corresponds to, because it is very much dependent on the person and the context of exercise.  For some, it's a one-to-one relationship, so that 50% VO2max is 50% HRmax, whereas for others, heart rate will be higher than VO2max - 50% of VO2max would correspond to say 60% of heart rate max.  I wouldn't get too hung up about this, for reasons explained below.  I know it sounds simple, but if you're wondering what 60% corresponds to, it's 6 out of 10 on a scale of exertion, where 10 is maximum effort.

Note also that the cross-over point, and in fact the whole pattern of the two lines is quite 'malleable' in that training, diet and genetic differences affect the relative percentage.  For example, a highly trained athlete burns fat more efficiently than an untrained person, and so they tend to use more fat at a given intensity.  People who habitually eat high fat diets are also shifted to the right, meaning that they burn more fat at a given intensity.  Sympathetic nervous system activity does the reverse, shifting the lines to the left, so that you burn more CHO and less fat at any intensity.  So the point is, the above graph is an example, not an absolute guide.

Low intensity is better, right?

So, what you're probably thinking is that theory that low intensity exercise is better if you want to burn fat is correct.  Well, think again.  It is true that at low intensity, when you walk, most of your energy comes from fat, and that as you increase the intensity, less and less comes from fat.

But what is missing in this picture is the TOTAL amount of energy.  Let me phrase it this way:  Would you rather have 20% of the money in Jonathan's bank account, or 80% of the money in my bank account?

Your answer of course, should be that you don't know.  And what you should be asking is "How much money is in your bank accounts?".  The reason is, you'd be pretty annoyed if you took 80% of my money, because my bank account might be empty.  Jonathan, on the other hand, might be loaded, and 20% of his money sees you retiring at 40! (Truth is, neither of us retiring early, which is why your donations are welcome! Kidding...)

So, look at the graph again.  You should not be too pre-occupied with the percentage, but rather the total amount of fat that you are burning, because that 50% that comes from fat in the green zone might be more than the 20% that comes from fat in the pink zone.  For answer to that, we look at a study done many years ago by Romijn.

Below is a graph that I've redrawn with some calculated figures, based on Romijn's study.

So, you're looking at the same kind of graph as before, showing how much of your energy comes from fat and CHO at different intensities (I've further divided it into muscle, liver and adipose sources, but that detail is not vital right now.  Note, however that "Plasma FFA" refers to the fatty acids that originate from the adipose tissue - the triglyceride is broken down into free fatty acids which are used).   This time though, there is also a measure of HOW MUCH total energy is being used, shown by the y-axis (in kCal/hour, for an 80kg man in this case)

So again, at low intensities (25% VO2max), you'll see again that most of the energy comes from fat (75% in this case), with only 25% from CHO.  Jump to 60% and the fat contribution falls to 48% and then at 85%, fat provides only 20% of the total energy.  This confirms what we saw in the first graph.

But, the key is that the TOTAL energy, shown here on the y-axis, rises as well, and so the 48% of energy from fat that you get at moderate intensity actually adds up to more TOTAL fat use than the 25% did at low intensity.  Think of the y-axis (total energy) as the size of the bank account, if you will.  The green boxes above each bar show the total amount of fat burned in an hour - 24g, 37g and 23g per hour at the three intensities.

The moral of the story, which is shown further in the graph below, is that if your objective is to maximize fat burning, low intensity is not necessarily the best option.  Rather, moderate intensity burns more fat per hour, before a decline in fat use as the intensity rises beyond about 60%. The reasons for these shifts, incidentally, include increased sympathetic response to exercise, activation of different muscles as intensity increases, local regulation of metabolism in the muscle, and also the exponential nature of physiological responses to an increase in intensity.  That's a post of its own!

Remember also that these are graphs based on calculations and measurements for a typical person - the actual values may vary for different people depending on training, diet and sympathetic activity, as mentioned.  One also has to make some assumptions, such as VO2max values, the RER during exercise and how it changes with intensity.  But I want to highlight the principle, not the values, so bear with those assumptions.

What does this all mean?  The role of time and putting it into perspective with diet

So, what this means is that if your goal is maximum fat use, then lower intensities may mean a greater relative contribution, but it is moderate intensity that gives you greater fat use per unit time.

Time is key though, as many of you are no doubt thinking.  If you do a low intensity session, walking (25% VO2max in the above graphs), then while your total fat use per hour is not as high as at say 60%, you might be able to do this exercise for three hours, compared to only one hour at a moderate intensity.  Three hours with 24 g per hour (see figure) beats one hour with 37g.  So duration plays an equally important role.  What I am emphasizing is that for a given time, you will be better off at a moderate intensity somewhere between 50% and 65%.

The next point, before we get too carried away, is that the actual differences are pretty small.  Not to discourage you too much, because exercise is vital for weight management and health, but one rule of thumb is that you can estimate total energy use during running by saying that you burn 1 kcal per kilometer per kilogram.

So, taking our 80kg man, who runs 8km (5 miles), he'll burn about 640 kcal.  It doesn't matter how fast he runs, thid amount is the same (the difference, of course, will be how much time he spends burning it).  Now, assume that half his energy comes from fat and half from carbohydrates.  That means 320 kCal from fat, corresponding to 35 g (this is about the same as in the graph, since I based that graph on this kind of calculation).

So, 35 g of fat in 8 km or 5 miles.  To burn 1 kg of fat, he therefore has to run 230 km (142 miles).  Not very encouraging.  There is an additional 'after exercise' effect, which one can't ignore, but I want to make the point that actually burning fat is not as simple as we often assume.  In the words of Bengt Kayser, who pointed out this principle, it puts into perspective the resolution that says "I want to burn off 10kg of fat by running".

You can work out a similar thing for cycling.  If you ride for an hour at 200W, your energy use is probably going to be about 800 kcal.  If 50% of this comes from fat, then you've got 400kCal, or about 44g of fat.  That is about the same rate of fat use as your 8km run gives you, and a lot of cycling to burn those 10kg of fat.

The value is in energy, not necessarily one fuel

And then perhaps most significantly, the key is still to create a calorie deficit, which means that you need not worry too much about whether your energy use is coming from fat or carbs - the key is to create that deficit, because in the long run, the energy will have to be provided and you will achieve similar results regardless.  Again, I'm oversimplifying a little, because we have discussed how efficiency changes, and there are some issues as to how the nutrients are oxidized as they are ingested, but the principle is not necessarily to burn the most fat, but to create an energy deficit.

And this is where diet comes into the picture.  If you want to create the energy deficit in order to lose weight, and notwithstanding that this is an oversimplification as we described in Part 2B of this series, then the combination of diet and exercise the way to do it, because to actually burn energy directly is a lot more difficult than people think.  This is why the combination, and the long-term approach is so important.  Things do not happen overnight in physiology, particularly when it comes to weight loss.

The progress can be slow, and invariably, when it is not, it's not sustainable.  Crash dieting, starvation might lead to rapid results, but they also lead to subsequent rebounds, and health problems that we won't go into now.

But for the purposes of this post, which I'll wrap up because it's been rather heavy on numbers, the key point is that burning fat during exercise happens right across the range, and the ideal intensity, if you are looking to make the most of your time, is a moderate intensity, and not the low intensities that you'll often hear recommended.

Next time, we'll look a little more at energy use during exercise and the role of diet.

Ross