Do world-class sprinters really move their legs no faster than ordinary runners?

Posted by Dave on July 28, 2011 | 25 Comments

ResearchBlogging.orgThe speeds attained by world-class sprinters like Usain Bolt are simply unfathomable to me. During today’s workout, I ran at nearly top speed for a set of 400-meter repetitions: About a 6-minute-mile pace, or 10 miles per hour. Sure, I could probably hit 15 mph over 50 meters or so, but that would be about it. Bolt, on the other hand, attained a pace of .82 seconds per 10 meters during his world-record sprint: 27.3 miles per hour, or nearly twice as fast as I can run.

But this article, which has been making the rounds lately, suggests that despite Bolt’s prodigious speed, his legs are moving no faster than my own:

When Bolt established the current 100-meter world record in the 2009 world championships, running it in 9.58 seconds, he did so by moving his legs at virtually the same pace as his competitors. In fact, if you or I were to compete against Bolt, our legs would turn over at essentially the same rate as his.

How could that be? Don’t Bolt’s feet need to contact the ground during his run? And isn’t the ground moving past his feet at nearly twice the rate it does when I’m running at top speed?

The Yahoo Sports article I quote here mentions a 2000 study led by Peter Weyand, so I decided to look up the original study and see if Yahoo is getting it right. Indeed, the study’s title suggests that the Yahoo article is correct: “Faster top running speeds are achieved with greater ground forces not more rapid leg movements.” But it still didn’t make sense to me that the fastest sprinters move their legs no faster than ordinary runners, so I gave the article a close read. What did I find?


As you might expect, it’s a little more complicated than the article’s title suggests. To be fair, the Yahoo Sports article touches on the key issue: The length of time a world-class sprinter’s legs are on the ground: .08 seconds for a sprinter versus .12 seconds for an average runner. That 33 percent difference explains pretty much the entire difference between an Olympic athlete’s pace and an average runner’s pace. But it’s still not clear how Bolt’s legs could be moving the same speed as an ordinary runner. To understand what the researchers are talking about takes a bit more explanation.

Take a look at this figure from the original study:

The graph at the bottom shows the amount of force the runner’s foot applies to the ground with each step. It looks like the runner is spending about half the time in the air, but in fact each foot spends most of the time in the air, because the feet alternate. So when you look at the full range of the stride for each foot, in this case the foot is on the ground for about 180 milliseconds, but off the ground for about 450 milliseconds. Most of the time, your foot isn’t propelling you forward at all, it’s just getting ready for the next stride.

What Weyand’s team did in this study is recruit 33 runners of varying ability, from average to very fast. They set up each runner on a treadmill with a harness suspended from the ceiling to keep them from being launched off the back of the machine if they fell down. Runners held themselves over the belt using the handrails while it was brought up to speed, then lowered themselves down and ran, trying to match the speed of the belt. After they had successfully run at least eight steps, they stepped off the belt and the speed was increased. This was repeated until the belt was going so fast that the runners just couldn’t keep up. I’d love to see the video outtakes from this study, because I imagine there were a lot of stumbles and falls (though the researchers report that the harness setup was effective in preventing serious incidents).

For a typical runner, the results looked like this:

This graph shows the length and frequency of strides. As you might expect, the faster the runner went, the longer and more frequent the strides. Bolt takes about 41 strides to run 100 meters, while his competitors take more like 44. Fewer strides over the same distance means each stride is longer.

But the key to this research is found here:

These graphs compare all the runners, when running at top speed. In Graph B, we’re looking at the amount of time the runners’ feet are in contact with the ground with each step, and as you can see, the faster runners spent significantly less time contacting the ground. In Graph C, we’re looking at the time the runners spend airborne, with neither foot touching the ground. In this case, there’s no significant difference between the faster and slower runners. But if you add these two measures together, you do find a difference between faster and slower runners. The total time it takes to take a step is less for the fastest runners. What’s surprising is that this difference is fairly small—only about 16 percent, even though the fastest runners go about 80 percent faster than the slowest runners.

So while Usain Bolt doesn’t bring his foot forward any faster than I do, when his foot is on the ground, there’s no question that his leg is moving faster than my leg does. That means his stride rate is a little faster than mine, and when combined with the fact that his strides are much longer than mine, he can run a lot faster than I do.

So since Olympic sprinters spend most of each stride with the foot not in contact with the ground, it is true that most of the time their legs are not moving faster than ordinary runners. However, when it counts, they do indeed move much faster!

Weyand PG, Sternlight DB, Bellizzi MJ, & Wright S (2000). Faster top running speeds are achieved with greater ground forces not more rapid leg movements. Journal of applied physiology (Bethesda, Md. : 1985), 89 (5), 1991-9 PMID: 11053354

Comments

25 Responses to “Do world-class sprinters really move their legs no faster than ordinary runners?”

  1. Roberto
    July 28th, 2011 @ 10:44 pm

    Superb post. Very clearly explained.

  2. Roberto
    July 28th, 2011 @ 10:58 pm

    Okay, thinking more on this, I think there’s a hole in this story. Two holes. What about fast/slow twitch muscle composition? And what about muscle strength?

    Do you REALLY think your (or my) legs are moving through the forward in-the-air phase of the stride as fast as Bolt’s? I don’t. And while you’ve comprehensively and convincing addressed the application of force to the plant and push, that that does not translate to a faster leg return seems impossible to imagine.

    Simply, Bolt’s legs leaving (i.e. pushing off) the ground with probably exponentially more force than yours should translate to a faster leg return.

    No?

  3. Peter Larson
    July 29th, 2011 @ 2:30 am

    Great post. The 0.12 second contact time for the “average runner” is a bit deceiving. This is the contact time when the average runner is being pushed to their absolute max I assume? Can they keep this up for a 100m race?

    If you look at the top men and women from this year’s Boston Marathon, the fastest ground contact time I measured from a slow motion video clip was 0.14 seconds, with most ranging from 0.16 to 0.19 (some of these at sub 5:00/mile pace). The average runner running a comfortable pace is more on the order of 0.25-0.3+ sec contact time.

    If I’m racing Bolt on a track and you measure my contact time, I’d bet he blows me out of the water if you average all steps.

  4. Dave
    July 29th, 2011 @ 11:58 am

    Roberto: There is no question that Bolt is much, much stronger than nearly every runner out there. But that doesn’t affect his leg return so much as the amount of force he applies to the ground with each stride. The leg returns are no faster than anyone else’s, but the force applied and the speed of the leg while in contact with the ground are greater. It’s possible that the reason his return is not any faster than the average person is because it takes more effort to slow his leg and bring it forward for the next stride.

    Peter: Good question. They only had to maintain the pace in this study for 8 steps, so it’s unlikely they could keep it up for 100 meters. One point about contact time — because in this study it’s measured via a force plate, there can be some moments when visually it appears that the foot is on the ground, but there is no force detected on the treadmill. This makes for roughly a 15% difference between the results of the Weyland et al study and what you can observe on video. So video-observed contact times will always be longer.

  5. Peter Larson
    July 29th, 2011 @ 12:37 pm

    Dave,

    Good point. Did they have Bolt on a treadmill? I think they got his times from video? If so, the comparison might be even artificially closer than in reality because of the different techniques (unless they accounted for the 15% difference).

    One point is that a cutoff is typically applied to force plate data to avoid capturing noise, so I’m wondering which method is better. I’d have to assume that the moment the foot touches the ground some amount of force is being applied, but it may not be higher than the noise cutoff applied for the forceplate.

    Anyway, great post. I was very skeptical of the Yahoo article when I saw it.

  6. Dave
    July 29th, 2011 @ 1:25 pm

    Peter, no the study didn’t actually measure Bolt’s stride — I’m pretty sure that was just Yahoo’s way to build interest in the story. Good points about the force plate; that makes sense. The researchers did compare their data to video of Olympic sprinters and that’s where the 15% figure comes from — my hunch is that either way of measuring is reliable, but you probably shouldn’t compare one measure to the other.

  7. KC
    July 31st, 2011 @ 2:38 am

    Great post once again, Dave!

    I have a hard time believing people can lower themselves successfully onto a belt moving at their top speed. How does one find their footing when coming from a handrail, especially when arm motion is so critical? It seems like these folk would achieve the necessary balance and stride so suddenly only at speeds below what they would normally achieve when working up to it on their own terms (not the treadmill’s).

    On a related note, I would be interested to see changes in force and in the time feet spend on the ground over the course of a sprint, from beginning to end. In the video posted above, Bolt seems to take almost half the race (ca. 4 seconds) to reach his maximum speed. His form changes radically then, and I assume that once he reaches his maximum (i.e. is no longer accelerating), he exerts considerably less force upon the ground.

    I would also guess that most of those settling onto a fast-moving treadmill would be in desperate acceleration mode, neither running at their true maximum speed nor using the form that typically accompanies it.

    Bolt’s in the lead when he hits his stride, but he continues to pull away from many (though notably not Gay) after his from changes, too.

  8. JohnE
    August 1st, 2011 @ 4:39 pm

    This was a very interesting article. My thought is that how fast your legs are moving back and forth when running isn’t important, its how quickly your body is moving. If two runners are in the air (the point in the stride where neither foot is on the ground) for the same amount of time, then they have the same amount of time to return their foot ( and leg) to the front of the stride. However, a faster runner’s body is moving faster, so they cover more distance in the time they are in the air. So I guess the question is, do two runners running at different speeds spend the same amount of time in the air?
    For the tenth of a second that the foot is in contact with the ground, the faster runner’s leg would have to be moving faster, since relative to their body the ground is moving past them faster. However, it’s probably very difficult to measure the speed of the leg for that period of time, especially since the foot is actually *stationary* at that moment (relative to the ground).

  9. Roberto
    August 2nd, 2011 @ 3:33 am

    Dave, you may know that the IAAF and IOC for many years have permitted physiologists to record very detailed measurements of athletes in the World Championships and Olympics. I’m not sure where this data (and the resultant findings) can be found, but if you can’t Google that, the IAAF will be able to help.

  10. manuel87
    September 4th, 2011 @ 5:15 pm

    What makes runners/sprinters move faster
    (my theory) sry for my bad english
    1.)
    More ground reaction force means a longer jump/stride. That shows the study and we’ll accept it’s true. This ground reaction force is the part off the supporting leg.
    But therer is a 2nd force created from the lift off the swing leg. It’s a inertia force.
    For example stand straight and on one leg and lift the other legs knee as fast and as high as possible. You’ll jump forward if you have powerfull hip flexors! This neglected 2nd force is it that makes often the difference!

    2.) How frequently this forces will be produced. –> stride frequenzy.

    Ground reaction force is still the biggest factor.
    Why is Usain Bolt’s ground reaction force much higher than others.
    Look at what is FORCE? F=m*dv/dt
    It’s about how fast the eccentric (braking) phase off your supporting legs muscles are.
    For example throw a hard object like a golf ball onto the ground. It will spring back up much higher than a soft object like a beach ball. The extending muscles and tendons of the ankle and knee joint (more ankle), should be very very stiff and hard with extreme good eccentric properties. I repeat: The faster you can turn around the direction of your body mass, the higher the force will be.
    Is’s the eccentric strength who’s the limiting factor. That make sense because mostly TypeIIb fibres are used for eccentric strength.

    Tell me what you think about it.

  11. sprinter87
    January 4th, 2012 @ 8:19 am

    We want to accelerate the body in the right direction.
    F=m*a or F=m*dv/dt
    a…should be as high as possible,
    m…as low as possible, so F becomes high.

    v1=v0+a*t t…contact time
    only if the body (leg) is in contact with the ground, we can accelerate the body and produce velocity.
    That’s the reason why it’s BETTER to have LONGER contact times, especially on the first steps.
    KEY ASSPECT:
    Fast sprinting DON’T requires shorter contact times. Shorter contact times are an effect off fast sprinting. The faster you run the less time you have to produce enough or more Force/acceleration to hold or boost your velocity. That’s the limiting factor for locomotion. Forces we have to overcome are mainly gravity (vertical), and air resistance (horizontal).
    Lower contact times wouldn’t allow us to produce enough force. Usain Bolt’s long legs allow him to stay longer in contact with the ground, compared to shorter sprinters with the same running velocity.

    my contact:
    leonh.manuel@googlemail.com

  12. Outer Limits Sports - Speed Training Facility
    January 18th, 2012 @ 4:48 am

    Stride Length x Stride Frequency.

    Stride frequency is under extreme genetic control. You, I, or any John Doe can lay on our back and cycle our legs as fast as Bolt can. But, not while moving down the track because our bodyweight is involved!

    Stride Length is KING. How much force can one apply to the ground in the short 0.1s they have in contact to propel their center of gravity forward? With strength being the base, it all comes down to rate-of-force development (explosiveness), reactive force (tendon stiffness and recoil). All creating a very short amortization phase. Upon ground strike, the downward forces need to be absorbed by the tendons, stabilized, and returned into the ground efficiently. Bolt’s acceleration over the first part of the race has longer ground contact times, therefore is base more on rate-of-force development. But, notice once he gets moving his reactive force is phenomenal, and like rubber bands, the tendons take over and he just blows past everyone.

    Speed = Strength Base + Rate-of-force development (explosiveness) + reactive (plyo) force.

    There are many ways to improve all 3.

    My Contact:
    http://www.OuterLim.com
    train@outerlim.com

  13. Sprinters leg | Selenenet
    April 15th, 2012 @ 10:39 am

    […] Do world-class sprinters really move their legs no faster than …Jul 28, 2011 … To be fair, the Yahoo Sports article touches on the key issue: The length of time a world-class sprinter’s legs are on the ground: .08 seconds for … […]

  14. Matty C
    July 17th, 2012 @ 10:14 pm

    I agree with what the person from ‘Outer Limit Sports’ was stating.
    I’d also like to address the issue with using a treadmill rather than generating your own speed on the track. You can’t use Usain Bolt’s track data and compare it to artificial data taken on a treadmill where the subject is just ‘keeping’ up with the speed rather than creating it. Guaranteed, if you put any of those people on the track, they wouldn’t EVER be able to generate that speed at any point of a 100m run. My point being is that if Bolt has a stronger rate of force development (more powerful stride) then it’s obvious his leg will drive forward faster than someone with less leg drive. That’s like saying that if I’m 6’6″ and I can manage to build my strength to maintain a stride length as long as Bolts, then I can beat him right??? Nope!!!

  15. Beno Prabowo Aji
    July 21st, 2012 @ 10:49 pm

    Usain Bolt has shown the most effective way of sprinting. He takes 41 strides to finish 100 m and clocks 9.58 secs. When clocking 9.86′ Carl Lewis took 43 strides. Tyson Gay took 45.5 strides to clock 9.71′ Suryo Agung Wibowo takes 47 strides to clock less than 10.40 secs.I myself used to take about 50 strides to clock around 11 seconds.

  16. USA! USA! | PsySociety
    July 27th, 2012 @ 4:09 pm

    […] Do World-Class Sprinters Really Move Their Legs No Faster Than Ordinary Runners? by Dave at Science-Based Running (note: OK, this is not psychology, but I’m including it because I find this post incredibly cool.) […]

  17. rene vandenboom
    August 5th, 2012 @ 6:46 pm

    The answer: its all about fiber type gentlemen. All other things being equal, the greater the % type IIx muscle fibers, the fastest and thus most powerful human type, the faster you can (fatigue not really an issue here). Why? Because, for a given leg turnover frequency, the greater the % type IIx fiber population the greater the % of your maximal force you can exert against the ground. Sheer srength is not the point, power is (force x velocity). This means they produce a greater force impulse (at that high speed) against the ground and thus achieve a greater velocity.

    Sprinters lift weights to hypertrophy these muscle fibers (you cant really change type). Thus, because sprinters are those genetically predisposed to a fast twitch fiber population to begin with, the increase in cross-sectional area of these fibers makes these more forceful and the athlete even faster. Unencumbered by large % of slow twitch fibers, perhaps, world champion sprinters like Bolt are just more powerful in terms of the force-velocity of their leg “motors”. Of course I am discounting biomechanics here, but all things being the same the athlete with the most powerful population of type IIx fibers should win every time.

  18. Greg
    October 4th, 2012 @ 11:21 am

    Hi. Not sure if anyone will read this reply given it is so long after the original posts. Just to make it clear, so that the over-thinking going on here does not cloud the main point, sprinting is in fact completely all about leg speed. It is absolutely true that the faster runners (of the same height) move their legs faster. This cannot be denied. It is a true fact that all sprinters take the same number of strides, relative to their height (leg length more precisely, and of course subject to age/flexibility and really crap technique). The reason Bolt takes 41 strides and “the rest of the field” take 44 is because all (most) of Bolt’s compatriots at this time are short guys (you notice how the article says something like ‘all the others take 44 strides’ – they’re all about the same height – under 6′. When I used to run in high school I, being the same height as Carl Lewis, took the same number of strides as Carl Lewis (I thought it was 42 but the guy above said 43, so whatever, it was a long time ago). But CL covered the distance in more than a second quicker than me. Just do the maths. Same distance, same number of strides, he’s ahead by 10m – There can’t be any other answer but that CL is moving his legs quicker, ie CL takes 42/43 strides in 10 seconds and me in 11 seconds. He must be moving his legs quicker. It doesn’t take scientific research and treadmills with harnesses to work this out. All the research showed is that to be a sprinter you have got to have the ability to keep your legs moving through the instance that your foot hits the ground. That is not surprising in itself. Non-sprinters (of which I think most people are) have feet that seem to stick when they hit the ground. I think people need to be careful that they are not being duped into thinking there is some other magical thing going on. It’s just about moving your legs faster.

    As another interesting aside, all the junk in the media about Bolt having an advantage because he has a longer stride completely ignores that fact that it is harder to move longer legs. Hold a drumstick (not the chicken kind) in each hand and see how fast you can move them and then try the same thing with broomsticks. So the so-called advantage of having longer legs (longer stride length) is more than offset by the difficulty of having a longer lever to move from the hip. If having a long stride length is such an advantage, why are all Bolt’s competitors short guys with short stride lengths? I think one of the things that makes Bolt really amazing is that he has the ability to move his legs fast enough to run 9.58 despite his disadvantage of having longer legs.

    If you want to run faster, learn to move your legs faster.

  19. Billy
    January 7th, 2013 @ 7:39 pm

    Thrust drawn from each time the ground hits the foot. Say you bounce a golf ball off the floor, then do the same with the bouncy ball. The bouncy ball is faster. It thrusts off the ground faster, and therefore moves faster. Less time touching the ground multiplied by force put into ground = running speed. Stride and cadence are also factors – mid length stride so as the cadence does not slow, nor the cadence too quick to effectively leave the thrust non existent. Stride comfortably at a moderate cadence with a large force of thrust working with minimum floor time. Posture, breathing and arm thrust are the other three. Posture needs to have shoulders rolled forward with abdominal strength to keep you up, so you technically fall into place. In a simplistic manner. Feel comfortable with how far forward it is. Breathe deep before sprinting to rid the carbon dioxide in your lungs, and then use the same breathing technique as a deep diver. After that, short and quick breaths with a bias to outward so that CO2 is released. It’s not a lack of oxygen, but a build up of CO2. We have enough oxygen to last us more than a 10 second sprint. Thrust your arms in coincidence with your legs, and throw them as you do your legs. This will maximize forward momentum allowing your legs to focus on the running part. Oh, and believe you are a rocket ship. Hope I helped.

  20. Usain Bolt
    January 26th, 2013 @ 3:50 pm

    I am Usain. I am god. You are slow. I am fast. That is all.

  21. Billy Bob
    February 4th, 2013 @ 11:44 am

    What’s missing here is the amount of travel between strides.

    Yes the total time between strides is the same because gravity is the same for everyone, if we jump the same height we spend the same amount of time in the air. The difference is how far forward you travel in that time. Fast runners apply the force on the ground at a lower angle, which means more force in order to get the same vertical force. That all means higher forward force and more speed.

  22. Dimitry
    March 14th, 2013 @ 9:07 pm

    There might be an even easier way to anecdotally explain this study (which is entirely correct.)

    Film any comparably body-proportioned runner (different heights but relatively the same proportions) over 41 strides, including Bolt. They will appear pretty much the same (that is, they will pretty much have similar rate of leg movement, they strike the ground at the same time, they cycle through and strike the ground again at the same time, etc. — and you could even overlap the two runner’s videos and they appear the same.) However, the 12 second 100 meter runner will cover about 78 meters in 9.5 seconds, Bolt will cover 100 meters. Why? Like the article says – when he strikes the ground, much much more force is generated. So why aren’t world class weightlifters fast? Well – for one thing, most are actually really fast. Secondly, most are very big, meaning that they can’t cycle their legs though in the same rate. Okay, so why not get really strong and stay relatively small? Well, that actually will help with your speed a lot. But just getting strong, like weightlifters, will mean that you generate force over longer periods of time, where Bolt has to do it very quickly (different neuro-kinetics — weightlifting requires massive force applied over a long range of motion over a few seconds at low velocity, sprinting requires massive force applied though a shorter range of motion over a tenth of a second, at higher velocities) and lastly, they/we/you don’t have the “golf ball” elasticity others have mentioned here in other posts. (Try not to compare golf balls to red bouncy balls – they are both highly elastic, as are sprinter’s bodies. Compare golf balls to potatoes. Most of us are like potatoes striking the ground – not very elastic. Add lower strength, and there yo have it.)

  23. didi
    July 14th, 2013 @ 8:34 am

    the study is worthless because it uses the treadmill..

  24. Paul B
    January 6th, 2014 @ 3:26 pm

    So I guess my strike rate of 240 strides per minute when sprinting is above average. The good news is that increasing my stride by just one inch would lead to a 3/4 second improvement in my 100 meter time.

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