PezCycling News - What's Cool In Pro Cycling : Toolbox: Pedaling Dynamics

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ToolBox

Toolbox: Pedaling Dynamics
Cycling is, at its most basic, about pedaling, though its rhythmic nature belies the complexity required to do it well. If you think of pedaling as the mere act of following the crank through a full rotation then you are missing both the art and some key elements that can improve performance. Let’s look at some of the factors that contribute to pedaling well.

By Matt McNamara

In coaching we often talk about pedaling dynamics as a path to improved performance, but what does that mean, really? To be sure, it’s more than just pedaling faster. Pedaling dynamics is a way of thinking about the entirety of the pedal stroke through all 360 degrees, from knee to ankle to hip, and involving all of the different motor patterns and musculature with the goal of maximizing mechanical effectiveness and optimizing gross efficiency. Simply put, it is the process of looking at your pedal stroke in its entirety and understanding how to improve it most efficiently.

Muscle Dynamics
The graph below represents muscle activation profiles of the 8 primary movers in cycling in relation to the crank angle.




You can clearly see that where you are in the pedal stroke has a direct impact on the muscles activated and the degree of that activation. In this example 0-degrees represents Top Dead Center (TDC) of the pedal stroke, while 180 Degrees represents the bottom, or 6-o’clock position. Using one of the quadriceps muscles, the Vastus Lateralis (VL), as a starting point we can see that it is very active in the first 90-100 degrees of the pedal stroke and then largely inactive until the last phase of pedaling, much as you would expect.

On the other hand the degree and longevity of activation for the hamstring muscles would seem to be particularly noteworthy. The hamstring muscle group consists of the Semitendinosus, Semimembranosus, and Biceps Femoris. In the graph above the Semitendinosus (ST), and biceps femoris (BF-LH) are both active throughout the pedal stroke, and most active between 90 degrees (3 o’clock) and 180 degrees (6 o’clock). This runs counter to the common perception of the quadriceps doing all of the work during the ‘push’ phase of the stroke and reinforces the vital nature of hamstring recruitment and efficiency. Look also at the Gluteus Maximus (the rear-end) – it is very active in the first 90 degrees of the stroke, less so later. Can you recognize when your glutes are under load during hard efforts?

Finally, of interest to developing a fluid pedal stroke is the relationship of the Tibialis Anterior (front of the calf) to the pedal stroke. Notice how late it comes into play, mostly in the last 90 degrees of the stroke while striving to get the ankle and lower leg around the dead spot between 9 o’clock and 11 o’clock (try to ‘feel’ that TA working as you pull up through the top of the stroke). Focusing on the Tibialis Anterior will help increase mechanical effectiveness by sharpening the joint/lever angle between the ankle and the knee as you transition through the dead spot.

Efficiency vs Effectiveness
At this point it is important to note the difference between efficiency and effectiveness. Efficiency is commonly expressed as minimizing energy expenditure, thus retaining more energy for later use or, alternately, providing the most power for the least effort. Effectiveness is a measure of how well the forces applied translate into forward motion.

In a 2007 study, Korff et al, looked at the effectiveness/efficiency relationship of four different pedaling techniques: pedaling circles, “stomping,” the riders own self-selected style and the classic “pull up” through the bottom of the pedal stroke approach.

Their study established that mechanical effectiveness is greatly enhanced by using the “pull up” technique; it ranked higher on an effectiveness index than pedaling circles, self selected or ‘stomping’ the pedals. Gross efficiency, on the other hand, was significantly lower using this technique. It took more energy to use the ‘pull up’ technique than to simply pedal in circles or stomp. Unfortunately, Korff et al, didn’t delve into the efficacy of the trade off. Is it worth the decreased efficiency to get the greater effectiveness?

Self Selected Cadence
Let’s add another element – cadence. Since Lance Armstrong’s return from cancer, high cadence pedaling has become de rigeur. It is oft cited as the path to increased efficiency and better performance and there is certainly an argument to be made that diluting force across more revolutions is a worthwhile approach. Yet, not every athlete sees better performance with higher cadence. This suggests that an individual pre-disposition may come into play.

Indeed every athlete has a pedaling profile that is either fast or slow. Often this is expressed as a function of their muscle fiber profiles – their genetic orientation to be either fast twitch like a sprinter, or slow twitch like a time trialist, but that is not what I mean here. Instead I am speaking of their tendency to pedal fast or slow as a normal rhythm.

Jan Ullrich exhibited the classic slow profile – powerful and efficient at lower cadences he could diesel his way up climbs. Alberto Contador, by comparison, is much more a fast cadence climber, capable of rapid accelerations and nearly always turning a high cadence. Whatever their actual muscle fiber profiles (probably more on the slow twitch end), it is fair to say that for each the act of climbing requires a high fast twitch recruitment pattern, but they go about it differently.

In 2008 scientist from the Norwegian School of Sports Science looked into this idea of a freely chosen pedaling rate in an effort to understand if was influenced by either internal or external factors, or both. Hansen and Ohnstad had eight participants cycle at self-selected cadences while manipulating the conditions to elicit an internal or external response.

The internal response (cardiopulmonary loading) was altered by simulating riding at either sea level or 3000m, while external response was in the form of increased power and force demands. Each athlete’s self-selected cadence was tracked across trials over a twelve week period.

In the end they found that each athlete’s voluntary rhythm remained consistent across internal and external responses. In addition the athlete maintained these patterns longitudinally and each athlete displayed a unique preference. Hansen and Ohnstad argued that cadence is, therefore, an innate voluntary motor rhythm acting under the influence of central pattern generators and not subject to internal or external factors during sub-maximal efforts. I’d be curious to see what happened during maximal efforts!

The unanswered question, to my mind, is does this set point change with experience and exposure. Is one’s motor rhythm altered by years of practice and thousands of kilometers?

Summary
Every cyclist pedals a little differently than their peers. While the motor recruitment patterns of the primary movers can be isolated and used to teach the athlete the central tenants of the pedal stroke, it is important to realize that one approach to pedaling efficiency doesn’t work for everyone.

Indeed, Korff et all demonstrated that the while the overall effectiveness of the ‘pull up” technique is much greater than is shown by pedaling circles or stomping, the overall efficiency of that technique is lower. The question remains whether the increased effectiveness is worth the trade off in efficiency.

Similarly, Hansen and Ohnstad were able to establish that during sub-maximal efforts each individual has an innate voluntary motor rhythm that plays a significant role in cadence despite the introduction of internal and external variables intended to alter performance. While we all may have an internal rhythm I think the question remains whether or not this is amenable to training effects or not.

The practical application of this information is to become a student of your stroke. Take the information above and go apply it in your own real-world experiments and technique drills. There can be no doubt that having an arsenal of pedaling skills and knowledge will serve to ultimately help you arrive at your own best pedaling practices.


References
Hansen, EA, Ohnstad AE: Evidence For Freely Chosen Pedalling Rate During Submaximal Cycling To Be A Robust Innate Voluntary Motor Rhythm. Experimental Brain Research 2008 April: 186(3) 365-73

Korff T, Romer LM, Mayhew I, Martin JC. Effect Of Pedaling Technique on Mechanical Effectiveness and Efficiency in Cyclists. Medicine & Science in Sport and Exercise 2007 June: 39(6): 991-5




About Matt McNamara: Matt is a USA Cycling Level 1 coach with over 20 years of racing, coaching and team management experience. This spring he is continuing his Performance Webinar Series that explores a variety of ways to improve your racing and training. Archived versions of these webinars can be found at www.performanceweinbars.com. He is the founder and president of Sterling Sports Group, a performance coaching company located in Northern California. Learn more by visiting his website at www.sterlingwins.com.
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