3 November 2021 - Weather Update!!
It's a beautiful day in Aquascalientes and that's NOT a good thing for Alex!
Why? Nice weather means high pressures and high pressures mean high air density.
Through much of last week air pressures in Aquascalientes were around 1013 mbar and today the pressure is 1026 mbar. For today's temperature, pressure and humidity, this equates to an increase in air density from 0.933 to 0.945 kg/m^3.
This is the equivalent of losing 100m of altitude and increases the power requirement for Alex to go 55.2 kph by 4.4 watts. From a record perspective, it will cost him 240m of distance or right about 1 lap!
It's bad luck, but in no way eliminates the potential for him to beat the record, and if he can hold his planned power, he will still surpass Campanaerts.
Tomorrow Alex Dowsett will again attempt the hour record, often referred to as the most painful event in all of sports. He previously held the record with a sponsor correct attempt that resulted in a distance of 52.937 km at the Manchester velodrome in England (elevation 80m)
The hour record is unique for many reasons, first and foremost, is that the event is limited in time and not distance as most every other sporting event is designed. It’s also unique in that there is great freedom in designing the event itself, with the rider able to choose the track type, location, time of day, etc to maximize the opportunity. This creates many interesting opportunities and tradeoffs that must be considered, so let’s look at some of the decisions the rider must make:
There are two starting points for athletes in their equipment selection for an hour record attempt: Sponsored or Self Funded
We make this distinction as riders taking the sponsored route may end up stuck with some sub-optimal components and as we know, every single detail is huge in this event. For the Dowsett record, he has chosen to go unsponsored, tapping into some of his trade team suppliers while also being very selective in some particularly meaningful areas.
Areas of note:
Of note, the Factor Hanzo TT bike has been custom made into a track bike using a 3D printed rear end from SILCA. These are the largest parts we’ve ever printed and will also be used to make production versions of the bike as UCI rules state that the bike must be commercially available.
The Hanzo is notable for its extremely narrow width which makes is exceptionally fast at the low yaw angle airflow on the track.
He has sourced a lenticular chainring from Aerocoach as well as a 3D printed Aerocoach cockpit. The 3D printed extensions give an airfoil profile to the front of the arms and very cleanly blend into the forearm for optimal aerodynamics. Combined I’d estimate these save 12-15 watts over his trade team options.
Alex is using Vittoria Pista Oro tires. These are exceptionally thin track specific tires with coefficient of rolling resistance less than 0.0020 which will save him 4-5 watts compared to anything his trade team sponsor could offer.
Alex will be riding a Vorteq skinsuit and shoe coverings that utilize separate fabrics in laminar flow zones compared to separated zones, as well as silicone features in transition zones that can help improve flow attachment. This suit is similar to ones ridden by Ashton Lambie to break the 4000m pursuit record and more recently used by Dan Bigham to set the UK hour record.
Altitude is a double edged sword when it comes to rider speed. On one hand, higher altitudes have lower air pressure and density which reduces aerodynamic drag. On the other hand, this reduction in air density reduces the rider VO2 max and ability to output power.
The opportunity here for the athlete is that the reduction in VO2 max is slightly non-linear, while the reduction in drag force has a linear relationship to air density, the reduction in power required to overcome that force is non-linear. Remember our velocity/drag/power relationship:
2x Velocity = 4x Drag Force = 8x Power Increase
The result of this non-linearity is that when we plot rider speed (distance since this is the hour record afterall!) against altitude accounting for this drag reduction AND the loss of power, we find that an acclimatized rider benefits more from aerodynamic drag reduction than they lose in power out to around 2700m of altitude.
Using Alex Dowsett’s 52.937km record at Manchester as a baseline, we have plotted his theoretical distance covered out to 4000m altitude. We’ve also shown here the theoretical performance for a non-acclimatized athlete, you can see that the benefit is smaller and peaks at around 1500m altitude, but we know Alex has been appropriately acclimatized so we’ll stick with the blue line!
This attempt is at the Aquascalientes Velodrome in Mexico at 1800m altitude, so from our plot we can see that an identical attempt should net him around 55.3km
As my good friend Robert Chung has said (paraphrasing Tolstoy), ‘All successful hour record attempts are similar, while all failed attempts fail in their own unique ways.’ Once the rider has chosen a velodrome and the equipment for the attempt, their biggest challenge becomes managing the pacing.
This is made extremely difficult by the rules stating that the rider cannot use a cyclecomputer or power meter for feedback, so the only feedback they have is the ability to have a coach calling out lap split times once per lap.
The feedback loop for the rider is gruesome, each lap realizing that they have to pick it up slightly, or slow it down slightly, not too much, wait, that was too much.. every single lap. For Alex in this attempt, that feedback loop will happen in ~16.5 second intervals.
The biggest risk to an attempt is going out too hard. If the rider pushes too hard for too long (even just a few minutes) they can completely flood the legs with lactic acid making the rest of the attempt impossible.
However, if they go out too slowly, then they will never be able to catch up as time runs out later in the attempt.
The perfect pacing would be to achieve record pace by lap 3 and hold it exactly until the last few minutes, then pushing the rider into the red zone for the last few minutes, cracking right as the finish line is crosses. Yet, this is so much harder than it sounds!
Xavier Disley of Aerocoach scatterplots each and every hour attempt and his graphs tell us what we need to know. Perhaps the finest pacing yet seen was the masterclass put on by Bradley Wiggins:
Showing only slight degradation after lap 175 (likely due to the heat as they had the velodrome at 30C (86F) to try and help offset the abnormally high air pressure of that particular day.
On the other hand, we can look at the failed attempt of Jack Bobridge, who went out WAY too fast, only to have things fall apart roughly 1/3 of the way into the attempt.
Another interesting strategy is what’s called the ‘Negative Split’ where the rider starts slow and tries to go slightly faster each lap. This strategy has unique mental and physiological benefits for the rider, yet has not yet proven successful for the overall record. Here is Dan Bigham’s negative split strategy plot from his UK record, which fell slightly short of the overall record. Looking at the data it is very plausible that he might have been successful had those handful of peak speed laps been slightly slower allowing him to maintain speed in those last few minutes.
We don’t know what strategy Alex will be on for this attempt, but it will become clear in the first 5 minutes of the event.
Line holding is extremely crucial for hour record events as the distance is measured by the measurement line of the track (black line) and not the actual distance covered by the rider. Every single lap counts as 250 meter no matter where on the track the rider actually rides.
Riding just 15cm (6 inches) outside the line on the 41 degree banking of the Aquascalientes track will cost the rider an extra 75cm per lap! Over the course of the 220+ laps necessary to break the record, that adds up to more than an additional 165m or 0.165km.
However, as the rider fatigues, the line holding gets worse and worse and even our 15cm example becomes improbably. The foam blocks on the track prevent the rider from gaining any of this distance back and the high forces in the corner make actually holding the black line nearly impossible.
The expectation for Alex’s attempt would be that he will likely ride an extra 400-500 meters relative to the final distance. This means that his actual speed will have to be as much as 0.5kph higher than he gets credit for.
Note the line Alex is riding to see how many extra meters he’s riding!!
Due to the banking of the track, the rider experiences ~1.4 times the force of gravity when in the banking at 55kph. This takes an unbelievable toll over 220+ laps both mentally and physically. It also plays a part in the line holding difficulty as the forces required to handle and steer the bike are also increased by around 40%.
Just think about the rider’s neck. The human head weighs around 5kg, add a 500gram aero helmet and we have 5.5kg of mass. The rider now has to hold their head stable not just for an hour, but when riding the turns the head and helmet now feel like 7.7kg, and there are 2 turns per lap. For a 220+ lap attempt, Alex will have to do the equivalent of 440+ neck lifts!
Further, the rider’s saddle area becomes a huge issue over the course of the hour. Again, this is not like a 1 hour time trial on the road as the rider’s body mass is being amplified by a factor of 1.4x in every turn, so the rider’s saddle area is experiencing an additional 40% load two times per lap.
The last piece to really look out for is rider cadence or pedal rotational velocity throughout the event. Because of the steepness of the track, a very interesting thing happens in velodrome cycling. The rider center of mass in the turns traces a smaller radius than the contact patch of the tire with the track. As a result, the velocity of the bicycle has to be slightly higher than that of the rider’s body.
The result of this is that the pedaling cadence increases through the turns. Each turn will see an acceleration of the bicycle early in the turn and a deceleration at the end of the turn. On a 250m velodrome, the rider will experiencing this acceleration/deceleration about every 8 seconds, and of course this is happening in conjunction with the G forces coming and going.
This acceleration/deceleration phenomenon adds greatly to the difficulty of holding a consistent pace lap to lap (and also adds to the line holding challenge!). From the rider perspective, each lap is really 4 distinct phases, and each of those are hard to repeat consistently within a single lap! Of course, as the body and mind fatigue, consistently managing these accelerations and decelerations becomes even more difficult which further explains the ever increasing variability in lap times toward the end of the attempt.
In conclusion, we can see that for Alex’s attempt to be successful, he has to put together a perfect pacing strategy and ride the shortest possible line, all while managing the screaming pain in his neck and saddle area (as well as his legs and lungs!!). He has to put together not just 220+ perfect laps, but really 880+ perfect lap segments. If you want to watch live, tune in to Alex's YouTube channel at 6pm EST, 10pm GMT.
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