The hour record, performance determinants and thoughts on Jack Bobridge’s attempt

Four days ago, the 31^st of January of 2015, Jack Bobridge attempted to break the hour world record in Melbourne, Australia, at the Darebin International Sports Centre (DISC) velodrome.

His attempt provides an excellent opportunity to start this blog by discussing the performance determinants of the hour record. Inspired by his amazing effort and having experienced the vibe at the velodrome, I am well predisposed to attempt to shed some light on the following questions

What does make someone a potentially successful candidate to break the hour record? What are the main physiological factors that determine the performance on the hour record? Could Jack have broken the hour record?

Event overview.

The hour record is a very prestigious time-trial event, in which an athlete tries to cover as much distance as possible riding a bike that meets the UCI regulations during 1 h in a velodrome. Performance, in this event, is determined by sustaining a high-power output relative to the aerodynamic profile during the whole hour.

Determinants of performance.

Performance determinants can be broken down into two main categories: Physiological and Non-physiological factors (Figure 1)

Figure 1. Main determinants of performance for the hour record. VO₂max, maximal oxygen consumption.

Non-physiological determinants of performance

It is not within the scope of this blog in general, and this post in particular, to discuss these factors in depth. However, provided they are both important in determining performance and can affect physiological variables, I will cover them briefly.

Air is the main factor opposing resistance to the moving cyclist. Aerodynamic resistance represents >90% of the resistance at speeds >30 km/h [1] and it increases as the cube of the cyclist’s velocity. Therefore, minimizing the friction with air is of foremost importance to maximize speed at any given power-output, especially at high speeds. Friction with air can be minimized in two ways: by changing the shape and surface of the object going through it and the density of air. The aerodynamic drag (CdA) is a variable that indicates how aerodynamic a cyclist is, and can be manipulated by adjusting the position on the bicycle and the equipment utilized (disc-wheels, skin-suit, shoe-covers, etc). Anthropometric characteristics of the cyclist can also have a significant effect on the final value and although some positions minimize CdA, they can be sub-optimal from a biomechanical standpoint and reduce the capacity of cyclist to put out power. Therefore, adjusting the position on the bicycle is a trade-off between what is biomechanically more effective and what minimizes CdA.

A good example of how positions can be determinant for performance are those developed by Graeme Obree:

Figure 2. Obree riding in ‘praying mantis’ position (Photo: Public)

Obree broke the hour record in 1993 and 1994 using his ‘praying mantis’ position (Figure 2) on a frame designed and built by himself (and subsequently re-built by a frame building company). Later, Obree developed the ‘superman’ position (Figure 3) in which Chris Boardman broke the world record in 1996, the fastest hour record in history (56.375 km).

Figure 3. Obree riding in ‘superman’ position. (Photo: www.obree.com)

Both of these positions lead to very low drag coefficients [2] and they were serially banned (or changed for others) by the UCI. This historical series of events can be used as an indicator of how performances can also be determined by politics of the sport and conventions. Indeed, the main reason why there has been several attempts scheduled to break the hour record since 2014 is likely to be the  modification of bike geometry/position regulations by the UCI in May 2014 that allow for a more aerodynamic position than that established by the UCI in the year 2000.

Regarding air density - the denser the air, the more resistance for the moving cyclist. Air density is 1.255 kg/m³ in standard atmospheric conditions (15ᵒC, sea level) and it can be reduced by increasing temperature, humidity and reducing atmospheric pressure. Temperature and humidity can be regulated to a certain extent on the day (depending on the infrastructure of the velodrome), but not so much atmospheric pressure. Atmospheric pressure can be reduced by increasing altitude. Therefore, selecting a velodrome with optimal infrastructure and geographical position can be very important for determining performance. For all these variables, however, there is also a trade-off. Increasing humidity and temperature can reduce air density but temperatures that are too high can impede optimal thermoregulation of the cyclist leading to overheating and reduced performance. The same applies for atmospheric pressure. The low atmospheric pressure observed at altitude also means less oxygen in the air. With altitude as little as ~300 mts, the oxygen consumption capacity of the cyclist can be compromised, which leads to reduced physiological performance (see physiological variables affecting performance) and further increase in altitude will directly affect this variable [3].

In conclusion, non-physiological factors are very important in determining the 1 hour record performance. Nevertheless, there is a balance between how much they can improve speed and negatively affect the physiology of the cyclist, which can ultimately lead to impaired performance (Table 1).

Table 1. Non-physiological factors that affect 1 hour record performance, variables that can be modified to increase speed and physiological factors that can be affected. VO₂, oxygen consumption.

Physiological determinants of performance

The hour record is conceived by many people as the ultimate test of a cyclist’s ability. While a bit extreme and reductionist (from my perspective), it is true that when all non-physiological factors are left aside, the hour record can be the ultimate test for the main physiological variables that predict cycling performance across a wide range of cycling events.   

This leads to the following questions: What makes someone a potentially successful candidate to break the hour record? What are the main physiological factors that determine performance on the hour record?

The main physiological factors that determine performance for this event are the maximum oxygen consumption (also called VO₂max) and the capacity to maintain a high percentage of that VO₂max for prolonged periods of time. These two factors, together with cycling efficiency and how evenly the effort is distributed, will determine how much power the cyclist can hold for 1 hour.

Maximal oxygen consumption (VO₂max).

The VO₂max of an individual determines the maximal amount of oxygen that can be delivered from the atmosphere to the exercising muscles during exercise. The higher the VO₂max, the more power-output can be sustained without altering the intramuscular biochemical balance (homeostasis) at any given absolute intensity. In other words, a high VO₂max translates into the capacity of sustaining a high absolute work-rate (power-output) without significantly altering the biochemical milieu of the muscle and, thus, delaying muscle fatigue.

The VO₂max seems to be determined mainly by hereditary factors, although training can increase it to a certain extent [4].

Percentage of VO₂max.

The VO₂max is the main factor determining power-output in the hour, but most cyclists can sustain the power-output of their VO₂max for about 3-5 min. This is because the work-rate that elicits VO₂max has a significant contribution of anaerobic sources of energy, which lead to a fast loss of the biochemical balance within the muscle and, consequently, quick fatigue. Therefore, if the VO₂max represents the ceiling of the aerobic capacity, then the second important factor is how close to that ceiling someone is able to maintain his or her power-output. The percentage of VO₂max that can be held for 1 h correlates closely to the oxygen consumption (VO₂) at lactate threshold [2], and the power that can be maintained for 1 h is defined as functional threshold power (FTP, a the term coined and popularized by Andrew Coggan and Hunter Allen outside the scientific literature) or CP60.  

The percentage of VO₂max that elicits lactate threshold can vary significantly between individuals [5], and seems to be determined by genetic factors and the amount and type of training [4].

Efficiency.

Efficiency refers to the percentage of metabolic energy that can be turned into power-output. This variable can be an important determinant of performance but does not seem to be trainable, and may be affected by cadence, diet and fiber-type distribution.

Pacing.

If the maximal power-output that can be elicited for an hour is a key factor and it is determined by the VO₂max, % of VO₂max and cycling efficiency, then how that power is distributed during the hour can be as important as the other factors to determine performance. Amongst all, this is the main factor that can be manipulated during the event.

In theory, the best way to distribute the effort to go as fast as possible during the hour where there are no climbs, wind, opponents and there is only one heat, is a steady power-output throughout the whole event  [6]. In practice this is not really possible because it would be necessary to know the result a priori. And because performance is multi-factorial, the result is not known until the athlete well… performs. Instead, a close estimation can be made by balancing out the physiological and non-physiological factors and determining the average speed that can, in theory, be held for the whole hour [2]. But this close estimation still gives room for the athlete to exert the effort as he is feeling on race day, and distribute the effort using the best pacing strategy possible, as he feels.

Pacing strategies are determined by the integration of internal cues (physiological, rate of perceived exertion) and external information (distance to be covered, time left) by the brain in order to determine the best way to gauge the effort [7]. For events >10 min, athletes usually start off slightly harder than what they should, ease off below optimal levels, and finish off going over the average power-output. This phenomenon supports the idea that pacing strategies fulfil a teleological role (directed towards an end) by integrating internal cues and external information to achieve an optimal output while avoiding injury [8]. In this way the athlete can gauge the effort to exert the maximal amount of work and avoid early termination by integrating the knowledge of his previous experience and real-time information.

The real-time information indicative of the physiological status of the athlete is what I named above as rate of perceived exertion (or RPE), which can be defined as ‘how hard the effort is feeling at any given time’. At the start of the event RPE is low and it is difficult to use it to gauge the effort, because it is not representative of how hard it is going to feel in the end (or even in average). Since RPE is also a subjective appreciation, it is likely that it is affected by anything that affects the subject’s psyche (encouragement, pressure, etc). Therefore for an optimal output the athlete should ideally base his pacing on the information based on the estimation of his performance, maintain his speed close to what is thought as possible and then make an informed decision based on how he feels.

Could have Jack broken the hour record?

Jack’s performance was 552 mts short of the world record, which is about 1.06% less distance than what he needed to cover. What could have been the limiting factor?

Jack is the current world record holder for the pursuit, a >4 min long event, in which VO₂max is also a key factor, but which has more of an anaerobic component to determine performance. So this gives the idea that he is not only tough as coffin nails, but also his VO₂max is probably not a limiting factor and he has got the ‘engine’ when compared to the previous hour record holders.

Without knowing his specific power-output numbers it is hard to know what his threshold power is like and whether if it has much room for improvement, but provided that he is surrounded by a team of expert coaches and physiologists, it could well be assumed that they have taken care of optimizing this as well as his position on the bike.

Therefore, the two main variables that I see that can certainly be changed are the atmospheric conditions (i.e. velodrome) and pacing.

Regarding the velodrome, DISC is at 50 m altitude, almost sea level. The two recent world records were beaten in Switzerland at altitudes of ~450 (Voigt in Grenchen) and ~415 mts (Brändle in Aigle), where air density is lower than at sea level and the physiological negative effect on performance is minimal. Additionally, the long-time held world records by Eddy Mercx (12 years) and Francesco Moser (9 years) happened at an altitude of ~2200 mts in Mexico City. Therefore, it seems that attempting the hour record at a higher altitude would have benefited his performance.

Finally, pacing is probably the main factor to be modified on race day and the factor that was not tightly controlled. You might have seen floating on the internet an excellent figure made by Xavier Disley (Figure 4)

Figure 4. Hour Record Pacing. Speed vs distance. Taken from @xavierdisley twitter account.

To make it even clearer I prefer to express it as percentage difference from the average lap time (Figure 5).

Figure 5. Hour record pacing. Lap vs % difference from average lap time.

If the best pacing strategy to minimize the metabolic stress and maximize work-capacity is an even effort, then all the black dots should be closer to the y-axis line in Figure 5. Clearly, Jack went off too hard from the start. I do not know what their racing plan was, but by about the 10 km mark his average speed was close to 53.5 km/h, which is about 4.3% higher than his final time. Certainly too big of a difference; well above the ~1% day-to-day variation in performance for an event like this one [9]. This might indicate that either things went out of control right from the start or the estimation of his capacity was not accurate, or both. In either case, I’d say that Jack went through a lot of pain from about the halfway mark onwards and fought incredibly hard until the end.

Even though I do not know to what extent exactly a better pacing might have had in his final performance, I think is worth looking at some historical facts. Moser in 1984 and Obree in 1993 both had better performances on their hour record during a second attempt, shortly after the first one (Figure 6).

Figure 6. Performance (km) in two successive 1 hour record attempts spaced by 1 and 4 days.

All of this information together strongly suggests that Jack was, indeed, capable of breaking the hour record and that bridging the 1.06% difference between his best and the current record is definitely within reach even if he has an attempt under the same atmospheric conditions.

Even though these are the main things that I can think of, the status of other variables important for performance like gearing, sleep/rest, tapering, nutrition (e.g. carbohydrate loading) and ergogenic aids (e.g. caffeine) should be also be considered for a deeper understanding of the results.

Regardless, Jack put out an incredible show of determination and we expect to see him hitting the track back soon with a more accomplished racing plan, and smash the current record. But he should better try it before Wiggins, who will certainly rip apart the hour.

References

1.            Kyle, C.R., Energy and aerodynamics in bicycling. Clinics in sports medicine, 1994. 13(1):39.

2.            Padilla, S., I. Mujika, F. Angulo, and J.J. Goiriena, Scientific approach to the 1-h cycling world record: a case study. Journal of Applied Physiology, 2000. 89(4):1522.

3.            Wehrlin, J.P. and J. Hallén, Linear decrease in VO2max and performance with increasing altitude in endurance athletes. European journal of applied physiology, 2006. 96(4):404.

4.            Astrand, P.-O. and K.r. Rodahl, Textbook of work physiology. 3rd ed. 1986: McGraw-Hill.

5.            Coyle, E.F., A.R. Coggan, M.K. Hopper, and T.J. Walters, Determinants of endurance in well-trained cyclists. Vol. 64. 1988. 2622.

6.            Atkinson, G., O. Peacock, A.S.C. Gibson, and R. Tucker, Distribution of power output during cycling. Sports Medicine, 2007. 37(8):647.

7.            Tucker, R. and T.D. Noakes, The physiological regulation of pacing strategy during exercise: a critical review. British Journal of Sports Medicine, 2009. 43(6):e1.

8.            Gibson, A.S.C. and T. Noakes, Evidence for complex system integration and dynamic neural regulation of skeletal muscle recruitment during exercise in humans. British journal of sports medicine, 2004. 38(6):797.

9.            Hopkins, W.G., J.A. Hawley, and L.M. Burke, Design and analysis of research on sport performance enhancement. Medicine & Science in Sports & Exercise, 1999(31):472.