### 1. Pitfalls

Errors are often made when comparing two bicycles in terms of their speed. Pitfalls in that respect include:

1. Competitions
Direct confrontations between recumbent and regular racing bicycle riders are very telling about the difference between the riders in terms of pedaling power and stamina, but little about the difference in speed between the bicycles. Competitions do not provide information relevant to a comparison of the bicycles.

 Figure 1 Competitions mainly compare the riders amateur rider (Photographie L’Alpe d’Huez) professional cyclist (photo Cor Vos)

The pedaling power of men of the same weight varies considerably: between 150 to 425 watt (2). And so the drive (pedaling power) is not the same if you compare bicycles with different riders. In the case of a race between an amateur rider on a recumbent bicycle and a professional cyclist on a regular racing bicycle (figure 1), no one can expect the recumbent rider to be faster. The professional would also win if cycling on the recumbent bicycle because he has a much greater pedaling power. When comparing the speed of two types of bicycles, the driving force must be the same. And so you will need a power meter on both bicycles. When comparing the same rider on different bicycles, many parameters are equal. Such a comparison yields so-called ‘paired observations’ (figure 2).

 Figure 2 Paired observations compare the bicycles recumbent racing bicycle (Photographie L’Alpe d’Huez) regular racing bicycle (Photographie L’Alpe d’Huez)

2. Heart rate monitor
In the present year 2017, 99% of all non-competitive cyclists are still missing a power meter on their bicycle. Instead, a heart rate monitor is often used as a measure for the level of effort achieved (figure 3). Then the same heart rate would mean equal effort (pedaling power). However, the above only applies to the same rider on the same bicycle. Because the heart frequency is higher on a regular compared to a recumbent racing bicycle at the same level of effort (see Heart rate). Conversely, at the same heart rate, the pedaling power of the same rider on the regular racing bicycle is lower. And so a heart rate monitor is not suitable to compare the effort made on both bicycles.

Figure 3 Heart rate monitor: chest band and display

3. Air resistance coefficient
Air resistance is measured in a wind tunnel. But that is expensive. And so the air resistance is usually estimated. That may result in major errors in the calculated speed. The significance of the air resistance coefficient (Cd) for the speed is evident, for example, from the world endurance record on a time trial bicycle (figure 4) and on a streamlined recumbent bicycle (figure 5), namely 56.4 km and 90.6 km, respectively. Even minor errors in the estimate of the Cd-value have substantial consequences for the calculation of the speed.

Figure 4 Time trial bicycle, Cd = 0.85, world hour record 56.4 km (5)
(Chris Boardman; Getty Images)

Figure 5 Streamlined recumbent bicycle, Cd = 0.1, hour record 90.6 km (4)
(Sam Whittingham; Varna Innovation & Research Corp.)

4. Climbing plus descending
The ‘hill climb time trial’ of Beek-Ubbergen is held annually in the hills surrounding Nijmegen. Virtually all of the participants ride regular racing bicycles. Yet the record time was set by a recumbent cyclist. This suggests that you can climb faster on a recumbent bicycle. However, that conclusion is incorrect. Because this so-called hill climb time trial not only involves climbing, but an equal extent of descending as well: the difference in height between start and finish is just a few meters. And so, if your climb on a recumbent bicycle is slower, but your descent is much faster, you can make good on falling behind during a climb. Moreover, the slopes in this time trial come one after another, and so the greater descending speed of the recumbent cyclist will give him an extra boost when climbing the next hill. Which is how he can be faster, even though he is the slower climber. So if you want to compare two bicycles in terms of climbing performance, then the test should not involve any descending.

5. Preconceptions
A comparative study should preferably be conducted ‘double-blind’. For example, when testing a new drug, its effect is tested in relation to a placebo (fake pill), while neither the test subject nor the researcher know which pill is the actual drug. That is what double-blind means. This excludes the effect of preconceptions on the part of the test subjects and researchers on the outcome of the test. However, it is not possible to conduct a ‘blind’ comparative study of a recumbent and a regular racing bicycle. And so you must be aware of the possibility of preconceptions on the part of cyclists and researchers.

Conclusions
1. You cannot compare a recumbent to a regular racing bicycle using two different riders.
2. The heart rate monitor is not suitable to compare the effort achieved on a recumbent bicycle to that achieved on a regular racing bicycle.
3. An inaccurate estimate of the air resistance coefficient (Cd) has substantial consequences for the calculated cycling speed.
4. A comparative study into climbing performance on different bicycles should not involve any descending.
5. Preconceptions may influence the outcome of a speed comparison between a recumbent bicycle and a racing bicycle.

Sources
1. Wiel van den Broek (2013): Technische artikelen over de fiets; Vermogen en krachten
2. Guido Vroemen (2008) Triatlon duatlon sport:
‘Watt it takes’ Vermogensmeters als hulpmiddel voor de fietstraining
3. Wikipedia.en (2017): Bicycle performance
4. Wikipedia.nl (2017): Ligfiets
5. Wikipedia.nl (2017): Werelduurrecord (wielrennen)

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