Aerodynamic optimization – a thing for elite-athletes and rich people!? Not at all. Every athlete who is interested in performance on the bike should definitely take up this topic.
There are various possibilities for aerodynamic analysis in cycling, which cover a wide range of budgets. Why aerodynamic optimization in cycling should be approached by all persons interested in performance and how this is possible is discussed in the following lines.
Why aerodynamic optimization?
A major performance parameter in cycling is the displacement velocity of both cyclist and bicycle. Speed depends on power output of the rider and total resistance impending forward motion.
speed = power output/ sum of all resistive forces
At the same power output, the achieved speed is determined by the sum of all resistive forces. Conversely, more or less power output is needed to achieve a certain speed depending on the total resistance. In competitive cycling or triathlon cycling, the aim is to cover a distance in the shortest possible time and/or with the least amount of energy. According to the above, the total resistance impending forward motion play a central role in this endeavor, as the level of these forces should be as low as possible to achieve the aforementioned goals. In road cycling on level ground at constant racing speeds greater than 14 m/s, aerodynamic drag represents approx. 90 % of the total resistance forces.
Aerodynamic resistance is a function of velocity squared (v2), the air density (ad), the projected frontal area of the bicycle and rider and a coefficient called the drag coefficient that is influenced by the shape of the bicycle and rider.
aerodynamic resistance = ½ * CdA * ad * v2
CdA values have become established in sports science as well in practice as a measure for assessing the aerodynamic profile of an athlete. Different methods are used to evaluate aerodynamic drag under actual conditions or in the laboratory. In cycling none of them can be mentioned as reference technique.
Measuring aerodynamic drag and CdA
One test method that is often used both in top sports and in science is the wind tunnel. Also triathlon professional Laura Philipp recently tested in such a facility.
Although wind tunnel measurements are often called the gold standard, it is important to remember that tests in such a facility are equivalent to laboratory situations. While wind tunnel testing is expensive and not accessible to everyone, various field methods allow a wider range of people to determine aerodynamic drag or more precisely CdA in cycling. In addition to commercially available analysis tools, the linear regression method or the virtual elevation method are two options which also permit lower cost testing. These methods, based on mathematical modelling, proved to be valid, reliable and sensitive in several studies. The latter is also implemented in the open source cycling analysis program Golden Cheetah.
How to minimize aerodynamic drag – considered and with care
A trial-and-error approach has proven to be the most effective way to optimize the aerodynamic performance of cyclists. The support of experienced professionals can be worth its weight in gold, since it is well known that a “smaller” position is not necessarily faster and it is no longer a well-kept secret that certain equipment, if placed in the right place, can optimize airflow.
At this point at the latest, it is important to note that a multidisciplinary approach is also required in the endeavor of aerodynamic optimization. Because one thing is clear: the best aerodynamic position is useless if, for example, it can no longer be maintained after a short distance, or if it is almost impossible to apply more power to the pedals. Therefore, it is elementary to test every (presumed) aerodynamic optimization under realistic competition conditions to check whether the measures taken can actually have a time-saving effect. It is more the rule than the exception that it makes sense to look at it from different perspectives such as aerodynamics, physiology, biomechanics, thermodynamics, etc. Often compromises have to be made to let the athletes ultimately enter competitions with a promising overall package.
This is also the case with Laura Philipp. For several years now, she has been receiving advice from a competent team of experts from various fields. They continuously try to generate knowledge from different perspectives and find the best temporary solution. The last position of Laura Philipp on the bike was very “streamlined”, but over the 180 km of an Ironman it became increasingly difficult for the top athlete to hold this position. For her coach Philipp Seipp, already shortly after comparing the latest results of biomechanical tests with those from the wind tunnel, it became clear, that he would prefer a more “comfortable” position, in which his athlete could pedal with a higher power output, rather than an aerodynamically slightly more optimal one. Both assume that this choice will lead to faster cycling times. At the level of Laura Philipp details can make a difference – but perhaps the decisive difference. On the other hand, people who have hardly ever dealt with the aerodynamics on the bike can often save a considerable number of watts after aerodynamic optimization.
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