Running Footwear and the 2 Hour Marathon | Dr Wouter Hoogkamer

Summary

Dr. Wouter Hoogkamer and Stuart McErlain-Naylor delve into the biomechanics influencing marathon running performance, with a keen focus on running footwear technology's role in breaking the 2-hour marathon barrier. Dr. Hoogkamer shares insights from his research journey, touching on Nike's revolutionary shoe designs, the significance of biomechanics, and factors such as course design and drafting in marathon performance. The discussion explores how key elements like shoe weight, carbon fiber plates, and running economy work together in pushing the boundaries of human athletic performance.

Highlights

• Dr. Hoogkamer recounts his transition from a dreamer to a leading researcher, pushing past comfort zones for success. 🚀
• The development of Nike’s Vaporfly shoes was a game-changer in reducing runners' energy costs by approximately 4%! 👟
• The biomechanics of running involve complex interactions between shoe design, foot strike, and energy return. 🤓
• Strategic drafting can significantly enhance marathon times, showcasing teamwork in athletics! 👥
• The continuous evolution of running footwear technology blends biomechanics with cutting-edge materials! 🔬

Key Takeaways

• Biomechanics and running footwear are pivotal in shattering marathon records! 🏃‍♂️
• Dream big and step out of your comfort zone when opportunities come! 🌟
• Nike's breakthrough shoes like the VaporFly play a crucial role in running efficiency. 👟
• Drafting and strategic pacing can cut marathon times, further enhancing performance! ⏱️
• Scientific innovation in shoe designs continues to push the boundaries of athletic achievement! 🚀

Overview

Dr. Wouter Hoogkamer's lecture, hosted by Stuart McErlain-Naylor, is a deep dive into the intersection of biomechanics, marathon running, and groundbreaking shoe technology. Focusing on the influence of footwear like Nike’s Vaporfly in reducing marathon times, it sheds light on how scientific advancements in materials and design are reshaping competitive sports.

Exploring the details of shoe mechanics, from energy return to carbon fiber plates, Dr. Hoogkamer discusses how these features contribute to improved running economy and overall performance. Coupled with insights into course design and the concept of drafting, the talk provides a holistic view of the factors that are bringing the elusive 2-hour marathon within reach.

Personal anecdotes and interactive discussions make the session engaging, offering aspiring athletes and engineers insights into the meticulous research and innovation involved in sports science. The ongoing evolution in shoe technology, from reducing energy costs to tailoring stiffness, highlights the dynamic and interdisciplinary nature of athletic performance enhancement.

Chapters

• 00:00 - 00:30: Introduction and Overview Lecture 5 of the Sports Biomechanics Lecture Series, supported by the International Society of Biomechanics in Sports and sponsored by Vikon, introduces the presentation by Stuart McKerlie Nayla from the University of Suffolk. He is accompanied by special guest Foutre Ho Kamath from the University of Massachusetts Amherst, who will deliver a talk anticipated by many.
• 00:30 - 01:00: The Influence of Running Footwear on Marathon Performance The chapter focuses on examining how running footwear impacts marathon performance. It references research on various factors such as sub-two-hour marathons, running shoes, drafting strategies, and course design. The content implies that better understanding and technological advancements in these areas can significantly influence marathon outcomes.
• 01:00 - 01:30: Research Journey and Background The chapter titled 'Research Journey and Background' introduces the format for a talk or presentation where Wouter is likely the main speaker. The speaker explains how attendees can participate by asking questions through YouTube comments or by using a specific Twitter hashtag. The speaker, likely Wouter, thanks the previous speaker for the introduction. This section lays the groundwork for an interactive session, encouraging audience engagement.
• 01:30 - 02:00: Initial Research and Findings The chapter begins with an introduction from the speaker, who is an assistant professor at the University of Massachusetts. The speaker shares their contact information, including their Twitter and lab website. The main focus of the talk is on running footwear and attempting to achieve a two-hour marathon. The interest in this topic began approximately five years ago during the speaker's postdoctoral research in locomotion.
• 02:00 - 02:30: Lab Testing and Predicting Marathon Performance This chapter discusses a lab run by Dr. Crum at the University of Colorado, which collaborated with Nike on research focusing on the relationship between lab-measured improvements in running economy and actual performance in distance running. The aim was to explore if enhancements in running economy could predict better marathon results. The research was set to continue over the next five years, illustrating a significant progression from six years prior when such a project might have seemed improbable to the speaker.
• 02:30 - 03:00: Drafting and Course Design for Sub-2-Hour Marathon The chapter discusses the journey of a student studying human movement sciences in the Netherlands who has a passion for running and dreams of studying the biomechanics of running footwear. Despite being content in their comfort zone, they are presented with an opportunity to conduct research abroad for their master's thesis. Initially reluctant to leave the track and their routine, they are encouraged by those around them to seize the opportunity, highlighting the importance of stepping out of one's comfort zone to pursue greater academic and professional experiences.
• 03:00 - 03:30: Shoe Technology and Design Innovations The speaker reflects on a pivotal decision to move to the U.S. for a master's thesis, which significantly influenced their career path. They emphasize the importance of dreaming big and being prepared to seize opportunities. The narrative sets up a key takeaway message on the impact of innovative decisions in personal and professional growth.
• 03:30 - 04:00: Mechanical Properties of Running Shoes The chapter discusses the mechanical properties of running shoes, focusing on how laboratory tests can predict performance outcomes. It highlights a specific research study that concludes people run more efficiently, using less energy, which can be translated into increased running speed.
• 04:00 - 04:30: Biomechanics of the Nike Shoe The chapter discusses the exploration of biomechanics in Nike shoes for improving running economy and breaking the two-hour marathon record. Researchers analyzed various studies and factors such as aerodynamics, drafting, wind, and course design to apply them within the rules for record eligibility.
• 04:30 - 05:00: Energy Storage and Return in Shoes The chapter delves into the concept of energy storage and return in shoes, focusing on a study that explores the integration of technology within the existing rules of shoe design. A significant conclusion drawn from the study is that it is possible to implement energy storage and return technology in compliance with current regulations. The chapter includes scenarios that exemplify this integration.
• 05:00 - 05:30: Ankle Joint Mechanics and Shoe Design The chapter discusses a cooperative drafting strategy used in running, different from previous strategies used in races like those in Monza and Vienna. The new strategy involves a group of the world's best runners working together as a team. All members run the full distance while alternating who leads and who drafts, which potentially offers a strategic advantage.
• 05:30 - 06:00: Importance of Biomechanics in Shoe Design This chapter explores the significance of biomechanics in the design of shoes. It briefly touches upon the refinement of certain simulations related to footwear, and refers to additional publications for more comprehensive information. Additionally, it mentions the IWF's guideline that a marathon's downhill segment can constitute up to 0.1% of the course distance.
• 06:00 - 06:30: New Running Shoe Technologies The chapter discusses the development of marathon courses that incorporate specific downhill elements to enhance runners' performance. It initially focuses on designing a course with a 42-meter drop over a marathon distance of 42 kilometers, predicting a potential time gain of about 30 seconds for runners. This concept gained practical attention when the INEOS team sought input for their own course design, highlighting the ongoing relevance and application of this research in competitive running.
• 06:30 - 07:00: Impact of Drafting on Marathon Performance The chapter discusses the impact of drafting on marathon performance, specifically referencing the Vienna course with its various terrain challenges. It highlights recent studies and suggests improvements in footwear, notably a lighter shoe that could significantly enhance performance, potentially saving a runner around 30 seconds.
• 07:00 - 07:30: Conclusion and Future Research Directions This chapter wraps up with a discussion on the challenges faced while testing and reviewing new Nike prototypes, specifically the 4% shoe. The researchers had early access to these shoes and were aware of their significance, though they couldn't include the data in their review because it hadn't been published yet. It highlights the ethical considerations and the balance between sharing pioneering information and adhering to research protocols. The chapter ends by implying the promising yet untold story of the new prototypes, suggesting potential breakthroughs in athletic footwear technology, and setting the stage for future research avenues.
• 07:30 - 08:00: Q&A Session with Dr. Wouter Hoogkamer The chapter titled 'Q&A Session with Dr. Wouter Hoogkamer' revolves around discussing advancements in running footwear, specifically in the context of a two-hour marathon. Dr. Hoogkamer emphasizes the lack of freely available scientific data on the Nike alpha fly next percent shoes and the vapor fly elites manufactured for the Monza breaking attempt, thereby limiting the depth of information he can share on those specific models.
• 08:00 - 08:30: Final Remarks and Acknowledgments In the final chapter, the discussion highlights Eliud Kipchoge’s marathon achievements and the evolution of marathon shoe technology. It notes how Kipchoge wore early versions of the Vaporfly 4% shoes during his 2016 Rio Olympic marathon victory. The chapter reflects on advancements in footwear that have since evolved to set new records, although specific datas are not provided for the latest shoe versions.

Running Footwear and the 2 Hour Marathon | Dr Wouter Hoogkamer Transcription

• 00:00 - 00:30 hello and welcome to lecture 5 of the sports biomechanics lecture series supported by the International Society of biomechanics in sports and sponsored by vikon I'm Stuart McKerlie Nayla from the university of Suffolk and today I'm joined by a very special guest I have with me foutre ho Kamath from the University of Massachusetts Amherst and about is going to be delivering a talk that I know a lot of people have been
• 00:30 - 01:00 looking forward to since this series was first announced that we'll be talking on the influence of running Footwear on marathon performance with a specific kind of hint towards the sub to our marathon and better has a really interesting research portfolio on this topic and covering areas such as running shoes drafting an even course design so I think he's going to touch on a few of
• 01:00 - 01:30 those topics today but like me I'm sure you're looking forward to that so I'll hand over to fountains one last thing sorry if anybody has any questions if you can either use the comment or chat section on YouTube or use the hashtag at the bottom of the screen now on Twitter I'll keep an eye on though for those and then once the talk has finished I'll direct your questions to Wouter so over to you thank you all right thanks to her for the kind
• 01:30 - 02:00 introduction so yeah my there we go yep there we go yeah so I'm assistant professor at the University of Massachusetts sorry about that so I'm on Twitter and my lab has a website that you can find there and I will be talking about running footwear and a two hour marathon so this all kind of started for me about five years ago when I was a postdoctoral researcher at locomotion
• 02:00 - 02:30 lab run by dr. Crum at the University of Colorado and Nike reached out to us with a very specific question about whether we can use lab measured improvements in running economy to direct improvements in distance running performance and that I was going to do that research and to similar research over the next five years if you would have told me that six six years earlier I would have laughed at you because six years before I was back in the
• 02:30 - 03:00 Netherlands studying human movement sciences spending a lot of my time on the track running dreaming about studying the biomechanics of running footwear but not necessarily taking any steps that would get me there I was happily in my comfort zone and I was lucky enough that at some point his opportunity arose where I could spend some time abroad for my master's thesis research and I had to be pushed a lot by people in my clothes around me that's like this is great for you and I was like no I just want to run on the track
• 03:00 - 03:30 and stay where I am but people luckily kept pushing and I made the decision to go to the u.s. to do my master's thesis and that sort of started everything for me and I was probably the best decision I've ever made so eventually that got me here and that also got me in Colorado in 2015 specifically trying to answer this question so there we go we got our first take-home question for today or to stay home message dream big but be ready to
• 03:30 - 04:00 leave your comfort zone when an opportunity arises otherwise you don't get anywhere so going back to that question I don't have the time to go into the details of the research we did I can just tell you the conclusion that yeah at that time we learned that if we do a lab test where we see that people use less energy to run we can use that to predict how much faster they will run and at that time we even thought that
• 04:00 - 04:30 wasn't one-to-one relationship and sort of that finding allowed us then to go back to the literature and looked into all the different studies done in the lab where people try to improve running economy by ear different scenarios and then we could see if we could apply those to breaking the two hour marathon all with our goal within the rules for record eligibility so we looked at aerodynamics like drafting until wind we looked at a course design
• 04:30 - 05:00 and also about shoe technology obviously but like I said important for us for this study was that we kind of wanted to acknowledge the rules and try to do this within the existing rules and basically our conclusion was that it was possible so one of the the big conclusions we had from this paper was that was possible and one of the scenarios you see on the screen right now is we have for example
• 05:00 - 05:30 on the top corner we talked about forerunner drafting which is a cooperative drafting strategy so different from what happened at Monza in Vienna where kept Jogi was running behind a fresh team of Pacers every lap we sort of suggested that if we bring best together the best runners in the world and they sort of worked together as a team and all of them are going the full distance but they could still alternate who's leading and who's drafting they could still gain a lot of
• 05:30 - 06:00 time and after this review we actually followed up with more detailed simulations of these scenarios and two papers on that are actually below in the link but I won't have time to go into details about them right now another thing is well specifically to those rules so that IWF rules at the time said do the maximum allowable downhill you can have during a marathon should be about 0.1% of the overall course distance so in this case we're talking
• 06:00 - 06:30 about a marathon of 42 kilometers so you can drop about 42 meters so we then said okay let's try to find a course or design a course that exactly drops 42 meters and then we quantified how much time we could gain with that which was about 30 seconds and then that later became relevant again when the INEOS team actually reached out to us to get some advice about the course design so we then ended up writing up our analysis
• 06:30 - 07:00 over the Vienna course including the uphills and downhills and it turns and that's also a preprint that is freely available in the link downstairs and then finally we suggested that other than keep Denis key Meadows Adidas shoes which weigh about 250 grams it should probably be possible to make a shoe that is as good but only weighs 150 grams and I would save him about 30 seconds during
• 07:00 - 07:30 the first 30 SEC's during the second half of a marathon and even though in the lab we were already testing this new Nike prototypes you that eventually became the 4% shoe we couldn't really talk about it in the review because we hadn't published this data yet so sort of like two stories that we had to tell the one that we could tell and the one that we already know was going to be probably way more important than all of the other ones combined but that's just
• 07:30 - 08:00 how the timeline was at that time so I'm gonna be talking about running Footwear in a two hour marathon so there might be a lot of you that hope I will be talking a lot about the Nike alpha fly next percent shoes while there's not a lot of scientific data out there that is freely available so I can't really talk about that then I can't also not talk about the specific vapor fly elites that were made for the Monza braking to attempt
• 08:00 - 08:30 again because there's no data I also won't necessarily be talking about the next percent shoe that Kip Jogi was wearing when he said the official world record in a marathon in Berlin but we're gonna go all the way back to 2016 to when he won the Rio Olympic marathon and at that time people didn't really know but he was actually wearing one of the first iterations of what became the vapor fly 4% shoe so that's actually also the shoe that we were testing in
• 08:30 - 09:00 the lab so they look very similar and this eventually became sort of the vapor fly line starting with the 4% the leads the next to the alpha fly so we in Colorado studied issues like I said and we set out to compare the Nike prototypes you against sort of like the state of the our top-of-the-line running shoes at that time so we went with Nike streaks
• 09:00 - 09:30 you and the adidas boost agios boost to shoe that basically if you looked at the world all-time list in marathon times at the time we started the study the top 10 of times said we're all running either the Nike shoe or the Adidas shoe so we were really starting at top-of-the-line and used that as a baseline to compare the prototype shoe against and obviously
• 09:30 - 10:00 since we're in a sports buy mechanic lecture series we want to talk about the biomechanics but before I can start talking about the biomechanics of the Nike shoe I want to talk a little bit more just about the mechanics of the shoe so we were able to determine the mechanical properties of the footwear so the way we did that is in two ways one of them was just looking into sort of like the foam cushioning and energy return properties and we do that by
• 10:00 - 10:30 vertically loading the shoe in compression the midsole using this instrument and we in this case made sure that we not just loaded it we also made sure that we applied about a similar peak load as what a runner would experience during mid stance while running at a very fast marathon pace we also made sure that the loading cycle was short kind of also similar to simulate the time that the shoe
• 10:30 - 11:00 typically spends on the ground during a step and when we loaded this you with that loading rate that you see in the top graph we can then measure the deformation so we get this force deformation curve which shows how much a shoe deforms when loaded on their specific form and here you see what would happen if you would load a shoe in this case and it's a foam so it's not necessarily a linear coil spring so you
• 11:00 - 11:30 can see it's not a perfectly straight line but for this foam it's pretty close and then what we can do from that the slope of this line is X what we call the stiffness which is force over the displacement and we can rewrite that to show that the displacement is equal to force over the stiffness now the interesting part about this force deformation curve is that the area under this curve that is actually the energy mechanical energy that is stored in the shoe when you load it and
• 11:30 - 12:00 you can see that because we know that if this would be a perfectly straight line this would be a triangle and the area of this triangle would be equal to half times force times displacement and you can rewrite that in different ways one of the ways would be that the energy stored is equal to 1/2 times the spring stiffness times the displacement squared something that you all know of another way to rewrite it which I personally
• 12:00 - 12:30 prefer is sort of substituting the displacement by the force over the stiffness because what we see there is actually that energy storage goes up with the inverse of stiffness so if you want to store more energy in a midsole which you know the force of you want to take a less stiff midsole not as stiffer so same for a spring if you want to store more energy you want to have a
• 12:30 - 13:00 more compliance spring the stiffness is actually in the denominator of the equation now this is when we load a shoe if you then like you saw in a diagram we first increase the force then we decrease the force then we can also measure how quickly the shoe sort of bounces back so here you can see that when you unload it it's not following the same line it's actually coming down slightly lower which means that this is what we call hysteresis and it's the
• 13:00 - 13:30 energy the area between those lines is the energy that is lost during a loading cycle this also means that the area under the bottom line is actually the energy that is returned every loading cycle by tissue so we quantified all these properties so both the stiffness or the total amount of deformation and the relative amount of energy returned so looking at the three shoes we tested here we have this graph which basically
• 13:30 - 14:00 just showed you for the streaks you which deform to about six millimeters and returns about 65% of the energy during the loading cycle and then we can quantify that in joules it comes out to about 3.3 joules then we did the same thing for the leader shoe it's about the same compliance or stiffness it deforms about six millimeters when we load it with these two kilo Newtons and but what you can see in this graph clearly is that
• 14:00 - 14:30 the area between the lines is smaller which means that there is less energy dissipated in the adidas shoe than in the streets you if we quantify that less energy dissipated more returned in this case it's almost 76 percent that is returned again we can calculate that in joules and we get about 3.6 Joule energy return now what about the prototype the prototype sort of use that concept that I just showed you if you want to store more energy under the same force you
• 14:30 - 15:00 want to make less stiff or more compliance it's so and when loaded with two kilonewtons this shoe deforms about 12 millimeters so it's less stiff means that the area under the top curve is a lot bigger music more energy gets stored same time this new midsole material is also more resilient so it's it's wasting less energy or losing dissipating less
• 15:00 - 15:30 energy and there's less hysteresis so the area between the lines is also relatively smaller this case this more resilient bounce your midsole foam returns about 87 percent of the energy that is stored so combining those numbers we'll see that the total energy in return every step is about twice as high in the prototype shoe than any other two shoes obviously that's not the only feature about the shoe we also looked into so the bending stiffness of
• 15:30 - 16:00 the shoe because obviously we all know that it's enforced by a carbon fiber plate and which has a purpose to provide stiffness in bending so to determine that you can generally use a similar setup where rather than compressing the fool shoe now you put the shoe on two supports and then compress it right in between those supports and see how much it bends from that test we can calculate
• 16:00 - 16:30 how much torque we apply and how much it's resisting flexion and that gives us the bending stiffness typically expect expressed in either Newton meters per Radian or sometimes based on this three-point bending stiffness test in the amount of displacement in millimeters divided by the force applied so we applied a similar test to these shoes and found that adding the carbon fiber played to issue made sick about
• 16:30 - 17:00 twice based on the properties of this specific blade makes about twice as stiff as the other two shoes so we got a shoe that when loaded vertically returns about twice as much energy and when flex is about twice as stiff so how does that affect running performance or running economy so before we go into detail about the biomechanics based on the mechanics I just explained you first
• 17:00 - 17:30 gonna look into what is the overall response of the human runner with the shoe so we measure that by looking at their metabolic rate or we call it running economy so running economy is defined as a specific metabolic rate that we measure at a specified submaximal running velocity we do that in the lab we measure oxygen uptake and we make sure that the runners are sub maximally because we wanna we're only measuring aerobic contribution to them
• 17:30 - 18:00 metabolism so we want to make sure that when they're submaximal they're not relying on any anaerobic sources and that also helps us to test multiple shoes in a series without having the runners building up fatigue from the start to the end of the protocol and we measure that for the three different shoes and this would be the place where I would go into a lot of details about how much scare we took to all the details of this study but I don't really have a lot of time to
• 18:00 - 18:30 do that here today I just wanna give you that take home that in sports science you need to be paying attention to the details of everything you may measure because that's how you get your results and that's how you get reliable results so another take-home if you want to build a career in this field pay attention to the details and be careful with all your measurements and be careful with all your analyses so what did we find after what I think was a very careful study we saw that when we
• 18:30 - 19:00 looked at energy cost or metabolic rate or running economy that between Adidas shoe and the Nike streaks you the energy consumption was basically the same metabolic rate was on Everett's the same you can look at the gray lines each gray line represents one individual some people end up some people went down but then when we started adding in the third number for the prototypes you you can see that all of the gray lines are going
• 19:00 - 19:30 down which means that each of our 18 individuals in the study is using less metabolic comes less metabolic energy while running in a prototype shoe on average the group average was four percent less and then we didn't just test it at this velocity of 14 km/h we also tested it at 16 and 18 km/h and we saw that those savings were consistent at all speeds all runners use less energy in a prototype shoe and at all
• 19:30 - 20:00 the speeds the difference for the group was about 4% and that is then what eventually inspired Nike to name the shoe that day the next version of the shoe that Nike Vapor fly 4% well that's so great but we are by omegan is so we are mainly interested in how does that work we know the mechanical properties we know that it works people use four percent less energy but how does that come about and so that's why we need
• 20:00 - 20:30 biomechanics here you see a picture the lab set up when we did a second follow-up study where we specifically focused on the running back mechanics so our subject is running on forests measuring treadmill which is a lot of us to measure the forces ground reaction forces the forces exerted by the runner on the ground or the treadmill and also in the corner of the pictures hopefully not hidden behind my face is a bike on camera so we had markers on the
• 20:30 - 21:00 different joints of the legs and of the segments of the leg and we were able to measure kinematics so we have ground reaction forces from the treadmill and the kinematics from the cameras and that allows us to do a lot of joint mechanics and one of the joints there was a lot of interest to us was the metatarsal phalangeal joint so this is where I'm actually quickly gonna try to step out of my shared screen and go live where I
• 21:00 - 21:30 gonna show you the metatarsal phalangeal joint so this is a foot model and these bones here are the flange the metatarsal so this is the mid foot and then here there's a series of joints with the toes the toes are the phalangeal bones so this is the metatarsal phalangeal joint or in short to the MTP joint and it's important in walking and running because
• 21:30 - 22:00 it allows us to do a nice roll off with the foot and since this model is actually pretty stiff I'm gonna just show it with the shoe to make my point so when we have a runner coming in landing on the ground during the rollover there's a specific point in time where the mid foot moving against the toe segment and it's applying a force in the other direction and this part is actually where at this joint a
• 22:00 - 22:30 negative work is performed or energy is dissipated dissipated or stored we actually don't know that it could be dissipated it could be stored in the elastic structures of the food like the plantar fascia things like that either way you can't imagine that that is negative work and it might be dissipated and it might be active muscle contractions going on to restrict that movement so what if we add a carbon
• 22:30 - 23:00 fiber plate to issue to prevent that so this is my analog for a carbon fiber plate and we put it under this foot you can see that in this case there's no way that the toes aren't gonna flex because they're supported by this very stiff plate and so this is kind of what happens when you have a shoe like this like the normal shoe you have to flex the stiff shoe you don't have the flex
• 23:00 - 23:30 or you have a lot of less flex so that is the theory for the specific MTP joint so let's see if that actually holds up in the data all right and back on the data screen so what did we see when we measured at the MTP joint now first we measure the joint angle and you can see here in green we got in this case the
• 23:30 - 24:00 Nike streak which flexes a lot up to 30 degrees near the end phase of the stance phase just before takeoff and then you see that the prototype shoe in orange is flexing almost half as much so a lot less so yes the Tier II works if you apply a stiff structure to the food you get a lot less dorsiflexion at the MTP joint then we can also because we measure the ground reaction forces and know where the MTP joint is relative to the ground reaction force factor calculate the moment and we
• 24:00 - 24:30 see here that the difference in moments is is small well the next step what we can do is then use the joint angular velocity the derivative of joint angle multiplied by the moment during every instant during the stance phase and we can get a measure of joint power and what is interesting about joint power is that the area under the joint power curve is actually energy that is either
• 24:30 - 25:00 this updated or stored and when it's negative or when it's the area is positive that is energy that is either returned or generated so in this case you can see that there's less energy dissipation at the MTP joint because the area the negative area under the orange curve is a lot smaller than a negative area under the green curve so yes it works but since we knew the actual mechanical properties of the hues we can also calculate how much the shoe by itself is
• 25:00 - 25:30 contributing to this so this is measured at the MTP joint from a runner with his food in a shoe this is the overall combination of the food and the shoe but we know how much the shoe is resisting flexion and we know how much it's is flexion so we can measure that so using the angular changes at the MTP joint combining that with our stiffness measures we can calculate how much the
• 25:30 - 26:00 shoe is resisting flex and generating a moment when we do that you get these curves where you can see that it is fairly similar which is interesting it's sort of the result that we know that orange prototype shoe is twice as stiff but is only flexing half as much so it's about the same when you talk about the resistance as the other shoe then obviously next step is we can then again combine it angular velocity with the
• 26:00 - 26:30 moment to get the power that is specifically happening at the midsole of the shoe so we can quantify the energy that is stored and returned so again the area between zero and the line the negative area is the energy that is stored in bending and then the positive area is the energy that's returned from bending in this case there's no muscles in the shoe so this is all passive alla
• 26:30 - 27:00 statistic elastic storage and return so looking at this diagram we can confirm the carbon-fiber plate does function as a spring it stores energy and it returns energy we also know that the other shoe seems to do a lot a little bit of it as well and you can see that too and I flex it so the question then is is this substantial is this whole four percent of metabolic energy savings that we see from running as these shoes because there is some
• 27:00 - 27:30 energy stored in flexion and returned by the carbon fiber plate well we can quantify it and we quantified it and it comes down to about 0.16 joules per step and then we still don't really know is that a lot but let me go back to what I showed you earlier when we had the numbers when we vertically loaded two shoes from this test we saw that every
• 27:30 - 28:00 loading cycle the shoe returns about 7.5 joules just from vertical compression basically from the midsole foam interesting was because we loaded the shoe in a way that represents the forces that it actually experiences when somebody's running every step we know that this 7.5 joules that is returned is returned every loading cycle or if you want every step so here you can see that
• 28:00 - 28:30 the carbon fiber plate does return storing returned energy but it's it's almost about 50 times smaller than the total amount of energy that is returned in the shoe in vertical compression so we know carbon fiber plate sort of a good thing around the MTP joint but it's not a big contribution as compared to the vertical compression but what about
• 28:30 - 29:00 the ankle joint so let me step out this again briefly to show you another concept so I just showed you that we can stiffen up the MTP joint and so that there's less flexion there I also showed you like we have an MTP joint and we can flex there and that's usually a good thing and during normal
• 29:00 - 29:30 that helps us a lot so when we're running and we're flexing what happens we keep the moment arm between the ground reaction force and the Achilles tendon short so let me show you that again so in this case when we have our foot and we're flexing we means that we can apply to ground reaction force under the fool toe sub-segment so the pivot point right now is kind of like MTP joint is you can imagine that my Achilles tendons that having to lift the
• 29:30 - 30:00 whole body over this pivot point have a lot easier job doing this then when they have to lift it all the way over this longer moment arm right and if you don't believe that what you can do at home is start stepping on a step standing on a step and when you're standing like this at the edge of the step it's probably really easy on your calves but then you just go backwards and when you're standing like this you start feeling something in your calf muscles you can imagine that if you're all the way
• 30:00 - 30:30 forward your calf muscles are gonna work a lot harder and even at the point of your toes that moment is even bigger and your calf muscles need to work even harder so that is kinda what happens with the plate and the moment arms around the ankle so let's see if that is something that hold up held up during our tests as well there we go so what did we see well we saw small changes we
• 30:30 - 31:00 saw that the joint angle was slightly smaller it was a little bit less dorsiflexion at the ankle in the prototype shoes but we saw that even though I just explained you when this is stiffer we would expect a larger ankle moment it wasn't really there and that might be because what I just showed you was everything with a very straight
• 31:00 - 31:30 plate and we have this pivot point on the ball of the foot the way nike went around that is by giving the shoe a substantial Oh spring which is basically how much it comes up to the front so you can imagine if this was a plate that was fully flat and we have to go around this pivot point that's a lot harder which I just showed you but because of this toe spring the roll-off doesn't get as much
• 31:30 - 32:00 boost forward even though it's different the MTP joint it doesn't necessarily make it harder for the ankle so that was a sort of a surprising funding finding but we can explain it by the curvature of the shoe we also sort of quantified how much energy is negative energy is negative work happens at the ankle joint so this is energy that is either dissipated or stored and then the positive side is the energy that is returned or generated and we can
• 32:00 - 32:30 quantify that again remember for the plate we had about 0.2 joules for the full shoe and compression we have seven and a half if we just compare that to the full ankle push up that's that's 55 joules so that's a lot so this the spring function of the plate is so much smaller than what the angle is doing well the thing is let me go back to that one we have a
• 32:30 - 33:00 bigger push up but is that necessarily or we have a smaller push up actually in in the MTP joint in the prototype shoe than in the other shoe and is that necessarily a good thing or a bad thing we don't necessarily know that because we do know at the ankle a lot of the energy fluctuations are not necessarily energy dissipations and generations that are actively generated by muscle forces but a lot of that is energy that is stored in achilles tendon
• 33:00 - 33:30 and then later on returns so there is this stretch and release of a tendon so even though we can quantify these joint mechanics it doesn't necessarily tell us everything about how much muscle fibers are active to sort of generate these forces because we don't want if I are able to quantify the story the elastic tissues and we also are not capable to quantify or when you look at
• 33:30 - 34:00 if the individual joins you don't take into account any energy that is negative that might be then transferred negative from the one joint to be positive at the other joint so that's another thing to keep in mind when looking at join mechanics and there's a third phenomenon that I want to explain to you too about the plate which we didn't quantify but it's interesting because it might be an important contributor to the function of the shoe and that's related to the
• 34:00 - 34:30 muscle shortening velocity so I just said when we're looking at joint mechanics we don't know how much is happening at the level of the tendon and how much is level happening at the level of the muscle fibers so there's different approaches to that and first I want to show you the concept how we can look at shortening velocity so here we have a foot and it's traveling at to our marathon pace or 21 kilometers per hour and we can transpose the treadmill
• 34:30 - 35:00 velocity into the ankle angular velocity by using the external moment arm in this case between ankle joint and perpendicular to the velocity it's moving then when we know the angular velocity at the ankle joint we know the internal moment arm between the ankle joint and Achilles tendon and we can calculate how much total muscle tendon unit is shortening and this was the scenario without a plate if we add
• 35:00 - 35:30 in a carbon-fiber plate the concept still holds but things are slightly different so if we come start comparing the two sides the travel velocities are the same so we're still running into our marathon pace but in this case with this plate people get higher up on their feet and the external moment arm is slightly higher which means that the ankle angular velocity is actually slightly slower so for the same running velocity
• 35:30 - 36:00 the plate sort of allows the ankle to move at a slower velocity which then because the internal moment arm is similar between the two sides results in a shorter and slower shortening velocity of the muscle tendon complex so we talked about the calf muscles which involved Achilles tendon then that is at the level of the muscle tendon the next
• 36:00 - 36:30 thing we can then look at is how much the actual muscle fascicles in the calf muscles are shortening and people have done that not necessarily for the Nike shoe and not in the cell e4 running so go to Takahashi did a nice study in 2016 where he looked at this for walking and what we see on the horizontal axis is increases in bending stiffness or few conditions and you can see that at peak force the muscle fascicle shortening
• 36:30 - 37:00 velocity actually decreases with increasing shoe bending stiffness and that obviously can be expected to reduce the energy that is associated with generating those forces then recently and currently not published but it's out there in a preprint Owen bag did a study using similar Footwear where he actually measured shortening velocity of the muscle fascicles and by the way you do that by applying ultrasound probes on
• 37:00 - 37:30 top of the muscles and looking at the actual vesicles shortening length from the ultrasound imaging and he saw that overall maybe you could see that for the stiffest condition the shortening velocity was slightly slower but this wasn't significant and it's also important to note that the paper fly shoes are expected to sit somewhere around that 45 kilo Newton per meter
• 37:30 - 38:00 bending stiffness that they says so there it might even be higher Oh even though none of these things were actually significant so what's going on there we really don't know yet and there's a lot of things happening and this is a study done for study with shoes and flat carbon-fiber insoles we know that in this shoe there's a different geometry there's a curved plate all those things might different effects on all of these things so before I wrap up quickly we want to
• 38:00 - 38:30 touch on what's next so we just saw that things are complex and we can measure things but they don't necessarily explain us how they directly affect energy cost and now the next challenge is how to look into findings from the one study that used a one shoe versus the other study that used the other shoe with an insole or another way of stiffening it versus other companies
• 38:30 - 39:00 putting out different shoes in this case you see five shoes that are either just came out or are about to come out where different companies like New Balance and Saucony Hoka and Asics Brooks all have their own sort of next version of the vapor fly where they have a carbon fiber plate with some sort of geometry or curvature or not and specific location in the midsole combined with a high real resilient foam but all of these have
• 39:00 - 39:30 slightly different properties so what we're going to see in the next few years is maybe more studies into this but it's always important to keep in mind that the slight differences in geometry might have different effects on the ankle and the NGP joint and it's hard to predict the overall outcomes you also what we're gonna see is a lot more marketing on the one side and a lot more fake news on the other side so this is an example where right after hip shogi ran his sub two
• 39:30 - 40:00 hour marathon people were speculating about the shoes he was wearing somebody dug up and patent from Nike and pulled up one figure and then started claiming that hip Jogi was running in a shoe that had three carbon fiber plates and two layers of air pots then somebody went ahead and used Photoshop to actually add those second layer of airports which were not even in a picture of the shoes and guess what eventually came out that
• 40:00 - 40:30 there's actually about 60 different figures in the patent application and some of them have multiple layers and most plates some of them haven't got any plates and then when it was released we know that the alpha fly right now you know it has only one plate and only one layer of airport so again fake news other fake news people speculating about the costs they're gonna be $400 when the Alpha fly shoes came out and then somebody saw
• 40:30 - 41:00 that video or image and just made their own version and made them $450 so there's a lot of things going out there that you have to be critical and careful about other things is like this is gonna be next we already have a to us up to our marathon now but if we allow carbon-fibre Springs next thing we'll have it is people Bo going around and running a one-hour marathon well if you think about it this guy is not running a
• 41:00 - 41:30 one-hour marathon and if he could he probably would be doing it these things are really heavy so they're not gonna save him any energy but make it even harder so just as an another advice and a take-home message to think critically about what you see out there on the web and think if it makes sense and see if you can find the original sources and while I'm at it I also give you another X I advise that think critically about your own opinions it's always an opportunity when there's new data or new insights to update your own opinions
• 41:30 - 42:00 about things all right I think I'm gonna wrap it up quickly wanna acknowledge the people in the lab in Colorado we did the study with and the people at Nike you see here also wanna acknowledge that being a white male gives me privileges which gave me a step up to get where I am now and finally want to acknowledge my current lab at UMass people in the lab we have our website up there and our funding source is Puma VF and Nike thank
• 42:00 - 42:30 you I heard brilliant thanks laughter that was genuinely really really interesting and even from before we went on air just chatting about er I could talk for hours now this there are so many kind of interrelated components and it's really difficult trying to tease them all apart and so just as kind of one well maybe quick question I wanted to throw in just
• 42:30 - 43:00 one more component and how does foot strike pattern kind of interrelate with all of this that's a great question and that that that might be something coming back to my last point too about the think critically and the fake news so for some reason there's a lot of journalists that reached out to me talk about the shoe and they always bring up that the shoe is made for forefoot strikers and that they only work when you're a four foot striker and to be honest we don't really know that we in
• 43:00 - 43:30 our first study we looked at this we had these 18 runners and about half of them by random chance where were heel strikers and the other half were mid foot strikers and when we looked at the data there was a small indication that it was actually the heel strikers that saved about four-and-a-half percent and a forefoot strike of mid foot strikers only three and a half percent but that was just in our sample then other people have studied the same shoes and did similar analysis and they didn't really
• 43:30 - 44:00 see that to be holding but so it seems that across-the-board independent of foot strike they seem to work I mean I must acknowledge we tested very fit runners at very fast paces we don't necessarily know that what happens when we're talking about a 5-iron marathoner or four-hour marathoner and then like I said in the biomechanical so all the results I showed you were from the biomechanical study where we tested only heel strikers because those are the most
• 44:00 - 44:30 common type of runners but like I said throughout all these different studies performed with these shoes there is not a clear trend that it works better for either forefoot strikers or rear foot strikers and I think it it definitely there is this feel that when you put your shoes on you're sort of push more forward and things like that again something to think about things critically taking to account physics
• 44:30 - 45:00 when people start making claims about shoes that are breaking less and propelling more because overall when you're running at a consistent velocity and there's hardly any air resistance you're gonna be breaking as much as you're gonna be pushing off because otherwise you just keep accelerating and that's not what you do at constant speeds so things like that we could be critical when people start making claims and think about it and sometimes you just need to acknowledge that we don't have the data to answer the question okay yeah brilliant thank you and yeah
• 45:00 - 45:30 it's one hopefully last question I think if it holds across kind of different running speeds different foot stride patterns everyone's around the power 4% saving in running economy why are we not seeing kind of a four percent improvement in elite marathan times yeah that that's a great question and that it's some of the Articles that are also in the links below that we discussed that I didn't have a really time to go
• 45:30 - 46:00 into detail there today but to be true what they claim to be holding if we want to have a 4% saving translating to a 4% faster time that needs that can only happen when the relationship between energy cost and speed is perfectly linear and goes through the origin it's a directly proportional relationship because we're talking about relative changes on a one side and they're only translating to relative changes of
• 46:00 - 46:30 similar magnitude on the other side if we have a directly proportional relationship which we don't some for a long time we always thought that we can estimate the relationship between running speed and running economy to be linear but now we got more data and we look at this carefully we see that even on the treadmill this relationship is not linear we see that at higher speeds to go a slightly bit faster you need a lot more energy than you need at lower
• 46:30 - 47:00 speeds and then that is on the traveling when you translated to an overground racing situation we also have air resistance which generally is not as important in running but if we talking about Elliot Kip yoga to our marathon pace it becomes a thing so the combined effect of those two mechanisms the one increasing air resistance which becomes more and more important at higher speeds and the fact that at higher speeds you need more energy to make a small improvement in
• 47:00 - 47:30 speed results in the fact that the improvement that people can get in times with a 4% savings if we would assume that it was there for everybody for every runner with any food strike then still the people that run slower would see a bigger improvement in time than the people that run really fast I think we did the math in the paper that is first author is Shelia Kip and there we
• 47:30 - 48:00 we sort of show that for two hour marathon a four percent savings would only make you about two and a half percent faster if you're slower than a four-hour marathon that same four percent metabolic savings could even allow you to run more than four percent faster just because of that relationship being not directly proportional okay so while you're answering that we now have a couple more questions on YouTube so do you have time for a couple more I have
• 48:00 - 48:30 time for sure yeah okay brilliant so Mason Coffee has asked says you touched briefly on weight of the shoes in the first night prototype study did you normalize for weight yeah that's a great question and and and that is something that we did so we know that qu mass is really important for metabolic rate so we know that every hundred grams saves you that you add to issue makes you well one percent slower or increases your
• 48:30 - 49:00 metabolic rate by about one percent so making sure 100 gram less heavy would improve running gonna be about one percent just when we started this study we weren't sure about the differences that we were going to see between the shoes we didn't want to find a one and a half percent and then have a mass difference between the shoes that would have explained half of that so to be sure we made sure that all the shoes weighed
• 49:00 - 49:30 about the 250 grams that these shoes are so we added about 50 grams to or 60 grams to the street shoes and about 50 grams I think to the Nike prototypes so in that case the comparisons the 4% was purely based on the geometry of the midsole the foam and the plate and the mass was out of the equation in hindsight we could have also not normalized the mass because the difference was so big that people
• 49:30 - 50:00 wouldn't claim that it was just because of mass and that would be more fair comparison or ecological where you can actually compare the two shoes as they are out there in the field so that's sort of these decisions that you can sort of weigh on which one do you take do you really have an applied question do you want to go with the most ecological validity and take shoes that are out there as is or do you also have an interest in sort of like the fundamental underlying principles and
• 50:00 - 50:30 then do you need to start controlling some of these parameters as much as you can and obviously everything I showed you about the carbon fiber plate and comparing it to those shoes ideally what we would have done is have this exact same shoe with this exact same geometry and have a shoe that is the same foam but doesn't have the plate and have another version of the shoe that is exactly the same and does have the plate but doesn't have the fancy foam and that would give us more detailed fundamental
• 50:30 - 51:00 insights but it also is less of an applied because in reality we don't shoes don't exist so yeah it's always the trade-off between those kind of decisions do we go really applied or do we go fundamental brilliant and I think ties in with your second stay home message as well as meticulousness and tick all the boxes there and yeah last question at the moment at least
• 51:00 - 51:30 from Fabio Lanford eeny who says thanks Valtor can you comment a little about the effects of drafting for the two-hour break in the marathon yes so so like I said in this talk we explored this concept where we would have a team of runners drafting together so what happened during Monza in Vienna was Nike two different approach which obviously didn't meet the regulations for record eligibility but they made it a separate
• 51:30 - 52:00 event and then both events actually had a different approach where we saw in Monza this sort of arrow formation where there was the paces were in error formation and Eliot kept shogi what's behind them and then in Monza it was sort of this inversed arrow and all of those sort of scenarios were done by by guys who know a lot more about
• 52:00 - 52:30 computational fluid dynamics so in our simulations or in calculations we typically need to go back to some data by Griffith Pugh that was he collected in the late 60s published in the 70s which is an exercise physiologist from the UK and he had a wind tunnel and he had a runner in a wind tunnel and actually measured run economy of the runner running at a set speed in the wind tunnel on the treadmill and then
• 52:30 - 53:00 had the same runner run in a wind tunnel behind another runner and in that study they saw that running economy was about 6% better when drafting behind somebody else so that is kind of the number that we generally use to simulate the effect because right now we have the technology to use a lot of computational fluid dynamic simulations and we can theoretically simulate any scenario of air resistance but the outcome of those
• 53:00 - 53:30 simulations is always a drag force so if we have a specific configuration of runners and drafters and and Pacers if we simulate that we the outcome is the drag force experienced by the runner then we can see changes in drag force but how does that translate to differences in running economy and how does that translate to differences in running performance those are two additional steps that we always need to
• 53:30 - 54:00 make so we typically shortcut that and just go with drag force towards metabolic rate but actually in Colorado we have been doing a study that we're currently riding up where we did measure the relationship between drag force and running economy we saw that that it varies varies a lot interestingly enough the one guy that was tested back in the 70s that was a study on on one runner back then and that guy's right in the
• 54:00 - 54:30 middle of the 12 people that we tested in Colorado so that sort of works out so it so this this five five six percent savings is still what we can expect in Colorado we didn't have a wind tunnel we were using elastic band and and hanging weights over pulleys to pull people backwards with very tiny forces great study to do but we hope to follow up on that and and and try to recreate that scenario in a wind tunnel and then validate our findings and validate our
• 54:30 - 55:00 simulations okay brilliant I think well I could keep talking for hours but I will leave it there for now and then if anyone does think of any other questions will kind of they can take to Twitter or kind of ask and we'll see if we can try and get a response sounds good okay thank you and yeah it's just hopefully everyone enjoyed that as much as I did and got as much out of that and kind of if you did then please share with
• 55:00 - 55:30 friends students colleagues anyone that you think will find that talk useful and don't forget that's now five so we're halfway through the ten talks that we initially announced we've since got more lined up that will hopefully be announcing over the coming weeks but if you haven't already go back and look at those first four and keep an eye out for the five coming up which are all scheduled on YouTube I think last thing for me is just a huge
• 55:30 - 56:00 thank you to Wouter which I know everyone else on YouTube and Twitter is agreeing with me that was excellent and yeah hopefully I'll see you all again soon thanks fatty all right thank you