Wednesday 24 October 2018

Going long: Factors of success for Cody Beals in the Ironman distance




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STAC Performance ambassador Cody Beals has had a fairytale year, from winning three 70.3 races internationally (Taiwan, Eagleman and Victoria) to then winning his Ironman debut at IM Mont-Tremblant (and setting the course record), capping it all off a month later by winning IM Chattanooga. Meticulous and  detail-oriented, it’s no surprise that Cody loves our Vitrual Wind Tunnel and worked hard with our team and his coach, STAC Performance partner David Tilbury-Davis, to optimize the small details that matter on the big day, such as bike position. As he made that jump up to Ironman racing this year, Cody and David tackled a handful of details to turn the 70.3 Uber-biker into a well-rounded long distance athlete that could push those big watts across the 180-km distance but back it up with a fast marathon, too. While Cody has had some great interviews on his two wins, we chatted with David about the adaptations they made for the full distance and the tweaks in bike position that contributed to Cody’s success this season in a sport that sees times dropping across the field every year. 

STAC Performance: Notably a course record holder on the bike in many 70.3s, Cody seems to only be getting faster, even while the rest of the men’s field is getting faster too. What’s to explain for the faster and faster 70.3 bike splits every year, from both a general and Cody-specific perspective?

David Tilbury-Davis: Generally speaking, my view is that folks are getting more and more attuned to the cumulative benefits of attention to all the inherent details of performing optimally. As the sport has evolved as has the influence of science, add that technology has grown and we’ve seen a progression from a purely “engine” focussed approach (‘get fit on the bike, getter fitter on the bike’) to a much much more holistic approach. That in no particular order, is now incorporating….

a) Individuality of adaptation to certain training stimuli
b) Bike fit being driven by “athlete centred” assessment mechanisms rather than formulaic approaches
c) Capacity to express comfort on the bike in metabolic as well as mechanical terms
d) The relevance of nutritional demands and adaptation to said demands
e) Aerodynamics both athlete, equipment and interaction between the two
f) Advances in principles of training and adaptation
g) Breadth and depth of talent at races, “a rising tide lifts all boats” 
h) Technological advances in cycling equipment
i) Advances in tools and methods for quantification of work, race environments and injury risk

Many of these existed in the past but where, to all intents and purposes, vapourware to anyone not with exceptionally deep pockets or part of a well-funded entity (professional team, governing body).

At its purist essence a bicycle is a metabolically motorised vehicle that travels at its fastest at maximal efficiency. When you think about it like that and tear the system down to every component of the system that can be optimised there is still a lot of “low hanging fruit” gains that can and are now being made by the everyday professional (and age group) athlete due to ten-fold cost reductions and the internet providing immediate access to far more knowledge.

What Cody has done over the last few years is pragmaticallly apply a cost-benefit ratio analysis to the “low hanging fruit” and over time these additive changes have allowed Cody to move to the upper end of the development cycle curve. My view is that it is his analytical background that has allowed him to critically think about any and all changes or sponsorships to ensure he is making value add choices.
Photo credit: Korupt Vision


STAC: What are the key differences in 70.3 and full Ironman biking?

DTD: How stochastic the racing can be and the brinkmanship or gamesmanship so to speak. It differs between the two. Also resilience in all its forms…aerobically, psychologically, neurologically, cardiovascularly and gastric emptying wise, more being demanded in Ironman racing.

STAC: How has Cody adapted physiologically for the 180-km bike ride?

DTD: I think adaptation is not really the correct choice of words. It is more a case of layering the right attributes on top of existing ones. 70.3 racing demands a lot of fitness and capacity to surge and recover as you respond to the race dynamics. Whilst Ironman still has aspects of this the greater need is for the capacity to maintain posture and form and effort for a long time. Cycling wise we incorporated multiple 6hr rides.

STAC: Talk about how aerodynamics play into both 70.3 and full Ironman biking. How do these considerations affect Cody’s position on the bike for each distance (does his position change between both?)

DTD: Broadly speaking a 2% reduction in drag is worth 2mins over an Ironman (assumes 0.260 CdA & reduction of 0.005 & racing at 39kmph). Making that kind of gain is not particularly difficult from that starting point and it could be the difference between making a draft legal pack and not making it into a draft legal pack. Similarly in 70.3 racing the same applies, just half the saving.

With the technology we have today we can take this example and quickly find 6-8mins over an Ironman. But importantly if the bulk of these gains have come from positional adjustments the athlete must spend time adapting to holding that position comfortably physically and, importantly, mentally.

This is the biggest mistake I see some pro athletes making today. They invest time and energy into finding a really fast position then spend a limited amount of time acclimating to it such that come race day by 120km into the Ironman race posturally they simply can’t maintain form.

Some years ago the video footage of the fastest bikers on the Kona Ironman course was analysed and they were, on average, sat up out of aero position for an approximate total of 2mins!

What Cody has been diligent about is taking his honed 70.3 position and simply spending more time holding that position so that come the Ironman race days his body wasn’t in shock staying in aero for so long.

STAC: What does it take to build a world-class triathlon cyclist? Besides coaching and bike fit, what are the smaller or unexpected details that contribute to this success?

DTD: Making sure they are making smart equipment choices foremost. If you can get this right such that the athlete can be comfortable, digest food easily, be aero and be riding a bike that handles well you’ve built a really solid foundation to work from. This seems obvious but many a professional athlete have bike sponsor that sends them a frame size of the manufacturers choosing and I’ve seen many occasions where this has resulted in performance compromises either on the bike or on their ability to run well post ride.

Once you have this right it becomes about assessing the athletes physiological strengths and weaknesses, what are the course demands or weather demands of the races they are choosing etc… Then you do a realistic performance gap analysis and start to plan how you address that gap. Either with training and adaptations or equipment choices for quantitative gains or subjective feelings for the better in the athlete.

SP: We've heard Cody mention that one of his strengths is attention to detail in his race preparation.  Is there anything that he does that's unique or different from other athletes that you've worked with?  

DTD: Much of what he does are aspects that he & I have worked on over time and certainly from my side of that equation the principles and practises applied are applied by all the athletes I have and do work with. Of course, I can’t comment on whether past athletes continue to embrace some of these principles nor whether athletes I don’t work with consider some of these things relevant or irrelevant but if the trend in bike performances in 70.3 and Ironman is anything to go by more and more professional athletes are realising small thoughtful practises or choices can pay performance dividends.

STAC: In both of his races, he's mentioned that he's hit a low point coming off the bike, so is there anything that you would recommend athletes do to prepare for breaking through this mental barrier?



DTD: Firstly manage their fuelling and nutrition strategies appropriate to their effort and distance racing, the brain needs glycogen to function!

Secondly when they practise any “efforts” during longer rides make a point to do these towards the end of the ride, this will help the body adapt and provide mental training.

For a more in-depth look at some of these topics from Cody's perspective, we recommend reading his interview with Ventum 


Tuesday 22 May 2018

STAC Thinks About: Cornering

These guys are way better at cornering than the author
Credit: Wikimedia
Two years after finishing on the podium at the 2015 Tour de France, Alejandro Valverde's 2017 Tour ended on stage 1 after hitting the deck on a slippery corner and breaking a knee cap. Cornering can be tricky in the rain, but even in optimal conditions, riders miss out on free speed by not cornering as efficiently as possible.  The magnitude of the time gains available help explain why the pros like Valverde push their cornering speeds all the way to the limit and sometimes beyond.

Today we're going to dig into the physics of cornering on a bike and run some simulations to see just how much time can be gained, or lost, every time the race course changes directions.

 About the author:
Multisport Canada K-Town Long Course 2016: Where others see a well-marked, well-paved corner, I see my imminent grisly demise.

Ever since a crash on a mysteriously slippery roundabout in 2014 that resulted in a bruised ribcage, I’ve been very hesitant and cautious while cornering on my triathlon bike.  Often during a triathlon, I will be passed just before, during, or shortly after a corner because of my extremely cautious approach to each corner.  In my mind are always the thoughts: “What if there’s gravel on the exit of the corner?”  “What if I need to suddenly dodge a pothole?”, and most often: “what if this corner is as slippery as that roundabout?”.  Because of this, I’ve had competitors mention, unprompted, that my cornering ability is pretty lackluster.  So today, I want to do some research on just how much time my poor cornering is costing me.

Cornering
Cornering in a triathlon is an underappreciated but very important skill.  Every time you corner, there’s three phases: braking, cornering, and re-accelerating.  During the braking phase, you bleed off speed so that you can safely go around the corner.  During the cornering phase, you lean over and change direction, usually at a constant speed.  Once you’ve straightened out enough, you start applying power to the pedals and re-accelerate to your cruising speed.

The first two phases are affected by a rider’s bike handling skill.  The re-acceleration phase is primarily governed by the rider’s athletic/cardio capabilities and strategic considerations about power output.  This means that the first two phases represent an opportunity for true “free speed” - faster bike splits without needing greater cardio OR better equipment.

Let’s go through each phase in turn:

Phase 1: Braking
Despite the fact that braking is all about _reducing_ your speed, the braking phase in a corner is possibly the easiest place to get some speed.  If you brake a little later and a little harder, it means that no matter your ultimate speed during the cornering phase, you will have carried your speed from the previous straight for as long as possible.  Braking too early means you spend more time moving slower.  The optimal braking point is when it isn’t possible to slow down any faster before the spot where you start turning.  If you flip your bike over while braking, you braked too hard.

Phase 2: Cornering
During the corner, your speed is ultimately limited by the amount of grip your tires deliver against the road.  Imagine cornering on ice or wet pavement: since you have less grip, you need to reduce your speed in order to complete the corner upright.  Cornering is ultimately an extremely skill and confidence-based ability: you need to be able to smoothly lean your bike over and accurately complete the _widest_ corner possible so that you carry as much speed through the corner as possible.

Phase 3: Re-acceleration
Once you’ve straightened out, it’s time to mash on the pedals and get back up to speed.  This is primarily cardio-oriented, and the length of the re-acceleration phase is mainly determined by how much speed you carried through the corner and your level of fitness.  There is some strategy in determining how much effort to put into re-acceleration: if you do a sprint out of each corner you may burn too many matches and pay for it later with fatigue.  If you keep up a steady-state wattage, it may take you extremely long to return to your peak speed.

The Simulation
In order to compare apples to apples, I’ve written a simple simulation that goes through these phases.  In the simulation, the rider attempts to complete a 4km course with a single 90-degree corner in it.  This seems to me like a decent approximation of a triathlon course, which typically has long straight stretches interrupted by terrifying 90-degree corners.

Fixed Parameters:
  • The lane in the road is 3.7m wide.
  • The corner is a 90-degree corner, which results in an optimal corner radius of 12.63m
  • The rider outputs 250W
  • The air temperature is 25C, leading to an air density of 1.184kg/m^3
  • The rider weighs 80kg (=176lbs)
  • The rider’s CdA is 0.27, which is a pretty-good-but-not-elite aero position
  • The rider’s tire Crr is 0.0033, which is a fairly good race tire
  • All these parameters result in a cruising speed in a flat, windless straight line of about 40.1km/h.

Varied Parameters
  • We will independently vary the rider’s maximum braking grip and maximum cornering grip, expressed in Gs. The fastest cyclists or cars will corner at about 1g, or 9.8m/s^2.  This will let us simulate riders that are scared of braking and cornering (like me!) as well as riders that are aces on the bike.

Results
  • We will look at the time taken to complete the course and average speed.


Results

As you would expect, riders with more confidence on the brakes and cornering did better, with a big bias towards riders that carried more speed through a corner.  The interesting question to me was _how much_ better.  With a bit of research, I found that a skilled rider can brake at about 0.83g before their bike starts catapulting them over the handlebars.  For cornering, I’m going to assume that the best a bicycle rider can manage is about 0.9g, as the physical limitation of rubber-on-pavement is about 1.0g.  Read below for the results.

Hesitant rider (that’s me!)
Braking: 0.5g
Cornering: 0.25g
Time on course: 6m 7s
Average speed: 39.15km/h

This rider brakes lightly and then corners hesitantly.  They decelerate from 40.1km/h down to 20km/h, then re-accelerate back to cruising speed.  Most of the time loss compared to their competitors below happens as they’re bringing themselves back up to speed - their harder-cornering competitors are doing several km/h more than they are once the corner ends, so the slower rider has to watch them fade into the distance while both riders pick speed back up.  This rider can compensate by sprinting out of the corner, but each sprint means energy spent that their competitors didn’t have to.

Hard-braking rider:
Braking: 0.8g
Cornering: 0.25g
Time on course: 6m 7s
Average speed: 39.16km/h

This rider has learned how to brake hard.  They might surprise riders behind them with their pavement-ripping stopping power, but they still are very hesitant with their cornering speed, and that’s still where they lose time.  They take a couple tenths of a second out of the hesitant rider that we saw earlier simply from braking harder and later, but further improvements are possible.

More confident rider:
Braking 0.8g
Cornering: 0.5g
Time on course: 6m 3s
Average speed: 39.57km/h

After gaining confidence on the brakes, now our rider has improved their cornering skill.  Instead of slowing all the way down to 20km/h, this rider now holds a solid 28.3km/h through the corner.  Not only does this mean they complete the corner faster, but the real savings is that they don’t have to spend as much time and energy getting back to cruising speed.

Pro rider:
Braking: 0.8g
Cornering: 0.9g
Time on course: 5m 59s
Average speed: 40.02km/h

This rider has mastered both the braking and bike-handling aspects of cornering.  In fact, they only barely have to brake for this corner- their 0.9g cornering capabilities allow them to do the corner at 38.01km/h, just below their cruising speed of 40.12km/h.

Mitigation:
There’s one obvious way for a slow cornerer to compensate: sheer power.  If the slower cornerer simply puts out more watts, then they can negate the time that the more confident rider is gaining on each corner.  But how many watts do they need to put out?  By increasing the simulated rider’s watts in my simulation, I found what each rider would need to do in order to make up for the pro rider’s cornering abilities:

Rider
Watts needed to catch “Pro Rider”
Hesitant Rider (slow at corners, slow at braking)
268W
Hard-braking rider (slow at corners, good at braking)
267W
More-confident rider (medium at corners, good at braking)
259W
Pro Rider
250W

So we see that the “pro rider”, with their excellent cornering abilities, can maintain an average wattage 7% less than the hesitant rider and go the exact same speed, as long as the course has one corner every 4km.  In cycling, this could mean having more matches to burn during the final sprint.  In triathlon, this could mean a much stronger run.  It takes a lot of quiet time on your STAC Zero to build 7% more fitness!

Simulation Thoughts
In this short simulation, we saw a 0.9km/h (0.5mph) improvement in average speed simply from braking harder and cornering faster on a single corner in a 4km segment.  All these riders put out the same wattage, but the rider that did the lone corner aggressively saved 8 seconds over the rider that took the corner the most hesitantly.  Over the course of even a very straight 20km sprint triathlon (with maybe 5-6 corners), this might represent a 40 second savings in a 33-minute ride.  Over a 90km half-distance bike leg with a corner every 4km, the rider that took each corner quickly would save energy AND finish faster, to the tune of 3 minutes: that’s a 2-3% reduction in time.  

Training Opportunities
Much like flip turns or underwater work for a competitive swimmer, cornering on a bike represents a completely free source of speed that can be practiced with every corner you take during training.  With an opportunity to steal up to 8 seconds on your less-confident opposition on every single corner, leaning over and cornering hard is an angle (zing!) that can’t be ignored.  Finding a safe spot like a parking lot to practice can be an excellent way to work up the confidence to take every corner quickly.

Reality Check:
Simulations are all well and good, but how does this finding stack up in real life? Well, I have a perfect example. At the 2015 Wasaga Triathlon, I came out of the water just ahead of local FPRO Kristen Marchant, and we both had Strava running, so we both ended up on the awesome Strava Flyby feature. For the first half of the bike we were neck-and-neck: I would pull a gap on a straight stretch, then Kristen would blast past me on a corner. You can actually see this effect on the Strava time-gap chart: The blue line indicates the time distance between Kristen and I, and each little spike upwards correlates to Kristen gaining several seconds in a corner that I tip-toed through that she attacked. You can view this comparison on Strava at this link.

Tuesday 17 October 2017

Crosswinds of Kona - by Andrew Buckrell

Above: A rider on a windless day, and the same rider with a strong crosswind.

With the IRONMAN World Championships freshly finished, and the previous bike course record falling to not just one, but 3 separate athletes (!!), there is a lot of talk surrounding the notorious Kona conditions.  Whether it’s the heat, the humidity or the winds that get to you, Kona is a legendary challenge, and completing it is one of the pinnacles of the triathlon world.  But, what is it about the winds that precludes the use of disc wheels, and how much of an impact would this have on you, as a rider?

Figure 1: Why no discs at Kona?


First hand post-race interviews with podium finisher, Lionel Sanders, confirm that the crosswinds played a key role this year.  As a larger, more muscular athlete, Lionel was particularly hampered by the crosswinds, which forced him to put out an undesired bridging effort.  Since the Queen K lavafields are renowned for having savage crosswinds, up to 45mph (72km/h!!), we set out to answer the question: “How much would a crosswind actually affect you?”.  To set the stage for our analysis, we chose a relatively tame 40km/h crosswind, combined with a 45km/h forward speed.  It’s obvious that these kinds of speeds would only be achieved by the pros, but it does provide a good starting point for answering the question. 

Well, as a first step, the combined 45km/h forward speed with a 40km/h crosswind actually is like being in a wind tunnel with a 60.2km/h wind (who remembers the Pythagorean theorem from highschool math?) directed around 41° from the direction in which you’re currently facing.  See the figure below for reference.

Figure 2: How a 40km/h crosswind feels to you as a rider
When comparing a disc wheel vs. a 90mm deep section wheel (which is still more than some people choose to ride at Kona!), the effects are quite staggering!  We used our model library and STAC's Virtual Wind Tunnel to analyze the effects of these equipment choices both with and without a crosswind.

Drag and side force are tabulated below in grams.



In a crosswind, the drag you experience as a rider goes up by 23% upon encountering such a wind when riding with a disc, compared with 33% when using a 90mm section wheel.  This aligns with the commonly published data showing that discs are most effective when riding in crosswinds.  The real question is how much it would blow you to the side.  Disc wheels result in a force of more than 15kg(!!), while 90mm wheels result in a reduced, but still dangerous, 13kg of force.  If you were to experience a wind gust of this magnitude, it would move you roughly 1m sideways in the first second and an additional 3m sideways in the next second (if it went completely uncorrected).  I don’t know about you, but being blown off a road into a lavafield doesn’t strike me as a fun way to end a Kona race attempt!  Lionel’s, or any other larger riders’ additional surface area would exacerbate this effect, meaning that they would need to increase his wattage proportionally more than the smaller athletes to overcome the at least 20% increase in drag, leading to the gaps observed at the race.

What can we take from this information?  The first point is that you need to be careful in crosswinds! The analysis corroborates Lionel’s comments about being apprehensive during some of the descents – it would be a substantial side force that he was fighting at those speeds!  Because of Lionel’s larger size, it also explains why he was gapped slightly in the high crosswinds compared to the smaller athletes around him. The data show that discs do make you faster, even at Kona if they were allowed, but at the price of confidence, stability and safety. 


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