PezCycling News - What's Cool In Pro Cycling : Power Output and Cadence – Learning from the Pros

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Power Output and Cadence – Learning from the Pros
One of the continuing themes in cycling science, and therefore a continuing theme here in Toolbox, is the optimization of pedaling dynamics and especially of the question of cadence. Is there an optimal cadence, and how do factors such as mountains and climbing ability affect cadence selection? As often in sport science, the best thing to do is to start out by observing professionals at work…


Talking ‘bout a Revolution
With the off-season in full swing for most in the northern hemisphere, it’s time to systematically review how we’ve performed over the past season, plan goals for 2010, and then to figure out how to achieve those goals. One of the milestones or objectives for many riders is improving their pedaling dynamics, and potentially to “improve” their cadence by increasing the typical cadence at which they ride on both flat and uphill terrain.

It’s no secret that the success of a certain Texan riding around France has “revolutionized” the thinking behind cadence. It’s been highly touted that much of Lance’s Tour-winning fitness comes from increasing his cycling efficiency by increasing his cadence. The theoretical argument behind this is that, with a higher cadence at any particular power output, there is less muscular demand with each pedal stroke, thus enhancing efficiency and delaying fatigue. This has led many professional and amateur cyclists to try to copy this high-cadence pedaling style.

That’s all well and good in theory, but each of the links in that chain of logic has come under a great deal of scrutiny and debate in the past ten years, likely thanks to Lance’s success. We have dealt with many of these individual links in the past here in Toolbox, and by and large none of these arguments have held up to controlled scientific investigation:

Foss and Hallen in 2004 and 2005 investigated altering cadence on performance in national team riders.

Mora-Rodriguez et al.’s 2006 study on optimal cadence.

Pedaling cadence and effect on subsequent maximal effort.

Watching the Wheels Go Round
Even if no direct evidence exists yet for improving efficiency by increasing cadence, it doesn’t stop the debate or the questioning behind optimal cadence. There’s a wealth of scientific knowledge to explore, especially in terms of understanding about what affects efficiency and performance, and how to possibly improve both aspects.

Apart from lab studies, one of the best ways to start investigating an idea in sport science is to simply understand what happens with professional athletes. Besides being elite physical specimen that gives us a peek into the limits of human performance, it can be generally assumed that, by and large, pro cyclists are near the limits of efficiency. That is, in order to survive and reach the pro ranks, they have voluntarily or involuntarily adopted strategies, such as choice of cadence, that are likely optimal given their individual characteristics.

Climb Every Mountain
With the above assumption in mind, there is no greater peak or test for cycling physiology than le Tour. Being the biggest bike race in the world, the stakes are highest, and most of the racers in le Tour have built their season around peaking for it. This is true both for the top contenders, and likely also for their domestiques. Therefore, there is great scientific merit in naturally observing what happens during le Tour. Fortunately, the availability of direct access to physiological data from the pros have been greatly enhanced both by the big money involved in the sport, and also by advances in power monitoring.

A study in 2007 from the University of Freiburg* in the journal International Journal of Sports Medicine explored the specific question of what power and cadence did riders select during the mountain stages of the 2005 Tour (3). The study was quite interesting, and had the following methodological notes:

• Ten pros (mean 30 years, 178 cm, 69 kg) participated in the study. None were among the GC contenders (final GC ranged 40-150th, placing generally 40-120th for most stages).

• SRM cranks were used to record data during each of the major mountain stages during the 2005 Tour. After tossing out incomplete data (e.g. bike changes, bad readings), 108 climbs of Cat 1 or HC cols were analyzed.

• The analyzed climbs occurred during stages 9, 10, 11, 14, 15, 16. This incorporated 10 1st and 5 HC climbs.

• The 108 data files were further divided based on performance. The 47 files that finished within 9% of the stage winner’s time were classed as “climber” files, and the remaining 61 that exceeded 9% were classed as “helper” files. This was the authors’ way of broadly categorizing those that still “tried” for a decent finish versus those that had turned the motor off a bit or were in the gruppetto.

• The SRM was not calibrated specifically each day, but was zeroed by one of the investigators prior to each stage. Data were logged at mostly 2 or 3 s intervals, with a few at 4 s.

What’s the Frequency Kenneth?
As often tends to be the case, simply observing the natural world (or peloton in this case) brings up a host of interesting data and talking points. Some of the main findings of this study include:

• It ain’t easy. The 1st and HC climbs involved 20-80 min at high submaximal intensities.

• Not surprisingly, the Cat 1 climbs were shorter and generally less steep, resulting in a higher power output (312 W or 4.5 W/kg) compared to HC climbs (294 W or 4.3 W/kg).

• The Cat 1 climbs, with their higher power requirements, were also accomplished at significantly higher cadences (73+/-6 rpm) compared to HC climbs (70+/-6 rpm). This can be seen to support the idea that a higher cadence results in a higher power output, but it’s somewhat of a chicken or egg debate. The missing piece of the puzzle is what gear the riders selected, which was not logged but which likely differed too between the different classes of climbs.

• The “climbers” had a higher power output and cadences in both Cat 1 (321 W, 75 rpm) and HC (311 W, 71 rpm) than the “helpers” (292 W, 71 rpm for Cat 1; 287 W, 69 rpm for HC).

• When comparing cadence as a function of power output, the data was pretty scattered at <250 W. However, as power output increased beyond that (250-750 W), there was a general pattern of a direct relationship of higher cadences with higher power outputs. This same pattern was observed when comparing “distance covered with one pedal stroke” versus power output. This “distance covered” was the way the authors tried to indirectly back-calculate gearing choice.

Summary
First and foremost, this study provides concrete data on the high performance capacities of pro cyclists. To be able to sustain approximately 300 W for 20-80 min and often 350-400 W for >30, even at the end of a 190 km stage and after multiple days of pressure-packed racing, is quite astounding.

Secondly, the tendency of higher power outputs generally being achieved with higher cadences support the general idea of higher cadences being “better.” However, as pointed out in discussing the results, this is a bit of a chicken and egg question, and this study unfortunately does not answer it definitively because of the lack of gearing information. The back calculation of gearing suggests that the increased power output is equally due to both higher gearing and higher cadences, so better performance and faster speed is not as simple as just sticking it in the same gear and spinning faster.

This ability in real life to alter both the cadence and resistance (via gearing) also makes for a fundamental problem in many laboratory studies. In many lab studies, the use of a cycling ergometer, where the power output is fixed and resistance automatically adjusts to the subject’s cadence, means that the subject can only voluntarily control cadence but not resistance. Therefore, it may not actually be possible to extrapolate such data on cadence and efficiency to what occurs out on the road (2).

At the end of the day, the cadence question remains unclear, as pointed out by recent reviews on this specific topic published in 2009 (1). Studies like this do provide some evidence suggesting that a higher cadence may indeed be beneficial. Keep tuned to this continuing debate.

References
1. Abbiss CR, Peiffer JJ and Laursen PB. Optimal cadence selection during cycling. Int SportMed J 10: 1: 1-15, 2009.
2. Leirdal S and Ettema G. Freely chosen pedal rate during free cycling on a roller and ergometer cycling. Eur.J.Appl.Physiol. 106: 6: 799-805, 2009.
3. Vogt S, Roecker K, Schumacher YO, Pottgiesser T, Dickhuth HH, Schmid A and Heinrich L. Cadence-power-relationship during decisive mountain ascents at the Tour de France. Int.J.Sports Med. 29: 3: 244-250, 2008. *
*The two last authors on this article, A. Schmid and L. Heinrich, are the two medical doctors implicated in the doping scandal with T-Mobile and the U. Freiburg. I’m of the opinion that this scandal, and their role in it, did not affect the scientific merit of this particular study.



About Stephen:
Stephen Cheung is a Canada Research Chair at Brock University, and has published nearly 50 scientific articles and book chapters dealing with the effects of thermal and hypoxic stress on human physiology and performance. He has just published the book Advanced Environmental Exercise Physiology dealing with environments ranging from heat and cold through to hydration, altitude training, air pollution, and chronobiology. Stephen’s currently writing “Cutting Edge Cycling,” a book on the science of cycling, and can be reached for comments at stephen@pezcyclingnews.com .

 

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