I have written two earlier articles on the importance of crank length and the variables that one might consider when selecting a crankset that will help optimize performance. Until relatively recently, most cyclists would adopt a rough proportional scale when identifying appropriate crank lengths--tall riders used long cranks (normally between 175 - 180 millimeters in length), small riders used short cranks (normally between 165 - 170 millimeters), while those riders in-between used mid-length cranks (170 - 172.5 millimeters). Some riders further refined this rule of thumb, going to slightly longer cranks if they were going to be doing events that skewed toward big gear, high force efforts, such as time trials. More recently, researchers have begun examining crank length in the context of bike fit and physiological parameters. I wrote about the relationship between crank length and hip angles in an earlier post and discussed the benefits of short cranks in terms of body position and power production; in another, I discussed how crank length also can be related to type one and type two muscle fiber recruitment. This entry will take a look at the relationship between crank length and overall pedaling efficiency, and how crank length can positively impact power production in ways that initially might be seen as counterintuitive.
Okay--to start, we need to think about how power is produced. Power a measure of how much work we're doing on a ride--the higher the power (normally expressed in watts), the harder we're working. Power is based on the factor of two variables:
Power = force x angular velocity
Power = how hard we press down on the pedals multiplied by how fast we turn the pedals in a circle (aka "RPM")
There are lots of way of generating power: you can push down very hard on the pedals at a relatively slow cadence, which privileges muscle strength over cardio fitness; or you can push down relatively lightly on the pedals, but turn them at a high cadence, which privileges cardio fitness over muscle strength. You can read more about cadence and power production here.
The goal of performance cycling is to product as much power as possible with as little physiological cost as possible. Riding exclusively at lower cadences can cause premature muscle fatigue, negatively impacting performance; riding at too high of a cadence can result in excessively high heart and respiratory rates, with lead to premature physiological fatigue. The key is figuring out how to balance the variables of force and cadence in a way that's sustainable for the duration of the event.
One of the best ways to visualize the relationship between pedal speed and crank length is to image a weight attached to the end of a two foot cord. The cord is spun in a circle at a constant rpm, say sixty revolutions per minute; if the weight is attached to a two foot cord, we can calculate the speed that the weight must travel to match the sixty rpm value. Next, imagine that the same weight now is attached to a six foot cord and is then spun at the same rpm. Because the cord is three times longer, the circle that the weight will travel has a radius that's also three times longer--in simpler terms, the longer the cord, the bigger the circle the weight will travel when spun 360 degrees.
Remember, though, in this example that while the length of the cords attached to the weight varies, the rpm of the spinning weight remains constant. So, in order for the weight to move at the same rpm, the weight on the long cord has to travel much faster than the weight attached to the short cord. Both weights have the same rpm, but each travels at a different speed to achieve this common value.
In terms of pedaling, we tend to focus almost exclusively on rpm, forgetting that pedal speed is another important factor in our calculations. For a given rpm, the pedal must travel faster when using long cranks than short; to pedal at 90 rpm on my 175mm cranks, my foot has to travel much more quickly than it would if I were to use 165mm cranks. Think of the pedal and crank relationship as we did the weight and cord, described above:
To achieve the same rpm, pedal A has to travel faster than pedal B.
In practice, this means that many riders experience an increase in cadence when they shift to shorter cranks. The reason for this is that they have adapted to the higher foot speed associated with longer cranks to achieve a given rpm; until full adaptation occurs with shorter cranks, cadence will be higher. Higher cadences also mean that less force needs to be applied to the pedals to achieve a given power value. Less force means that muscle strength--which fails more quickly than cardio fitness--is retained for a longer period of time.
Putting all of this together really isn't that complicated. Shorter cranks means that one can ride in an aggressively aero position without losing power; shorter cranks also are better suited to the recruitment of slow twitch muscle fibers, characteristic of most endurance athletes; and shorter cranks enable higher cadences, which can translate into increase power at lower muscular cost.
In the ideal world, one might consider training on long cranks and racing on short cranks as a way to maintain high pedal speed in competition. Short cranks are a viable option for most riders, and research has demonstrated that very short cranks will not negatively impact power production. Today, it is not uncommon to see elite athletes with crank lengths 165mm or shorter. Short cranks are worth consideration by age group competitors as well.
The single most important factor in achieving optimal aerodynamics on the bike is to focus on the position of your body. The latest and greatest wheels, frames, and helmets contribute no more than 20% of a rider's total aerodynamic drag under the best of conditions; before investing your funds on equipment that may or may not work for you, consider your bike fit first.
In general, there are no secrets to establishing a solid aerodynamic position on the bike: You want your head and shoulders low enough to reduce your front profile into the wind without significantly compromising your power and you want your hands and arms fairly close together. That’s it--sounds simple, doesn't it? The challenge is in how to meet these two objectives.
There are two physiological factors that impact on our aerodynamic positioning: our body size and morphology; our flexibility. In order to get down into a low aerodynamic position and still be able to ride powerfully, one needs to have fairly good hip, lower back, and hamstring flexibility. A critical component of this equation is the angle described by the top of a rider's thighs and his/her torso (this is called 'hip angle"). In the stick image below, the red arc indicates hip angle:
Now, the tighter one's hip angle, the more one feels constricted when riding in an aero position, and in extreme cases, a rider's thighs actually may hit the abdomen or chest while pedaling. Additionally, tight hip angles can reduce the amount of power generated by a rider because it is more difficult to move the crank over the top of the top of the pedal stroke (tight hip angle=less leverage).
Achieving an aero position on a road bike is difficult in that most road frames are designed to be ridden with the seat set back behind the cranks. This design works very effectively when riding with traditional handlebars--it really hasn't changed in over one hundred years--but it doesn't work so well when aerobars are added to the equation. Adding aerobars to a road bike significantly tightens the rider's hip angle:
While one can establish a remarkably aero position with aerobars on a road bike, the tradeoff most likely will be loss of power, lower back and hip pain, and potentially compromised bike handling.
The reason why triathlon bikes have steep seat angles (i.e., the seat is positioned much more forward of the crank than on road bikes) is to enable a rider to get down into a low aerodynamic position without constricting the angle of the hip. Try visualizing it like this: one can keep the hip angle the same when lowering the aerobars by moving the seat forward, which will rotate the entire body clockwise. Because the body itself is being rotated forward, the hip angle remains the same, while the arms drop lower:
Figure 2: Aero position on triathlon bike:
Arc=hip angle; rectangle = seat; circle = crank
Figure 3: Aero position on a road bike:
Arc=hip angle; rectangle = seat; circle = crank
In figures two and three, note the relatively positions of the seat and crank: the more forward the seat, the lower the aero position can be, while preserving a relatively open hip angle. The take away is relatively straightforward: in most instances, if one wants to use traditional aerobars and achieve a good aerodynamic position, then a triathlon frame with a forward seat position is a must. Putting aerobars on a standard road bike will result in either a significantly impinged hip angle (not great for power or comfort) or aerobars placed so high as to negate any aerodynamic advantage that they might offer.
But suppose you already have a triathlon bike and want to get lower to be more aerodynamic, or suppose you already have a pretty good aero position but want to get a little more power. The next variable to look at after seat position is crankarm length.
There are many studies that indicated that crank length in itself does not measurably impact power output. Traditionally, long crank arms have been used for time trials because they provide, the argument goes, more leverage than short crank arms; the more leverage one has, the bigger the gear one can push at a given cadence, which means more speed. The problem with long crank arms is that they describe a much bigger circle that a rider's legs must travel for each revolution of the crank; making this circle bigger effectively tightens the hip angle, as the leg must travel higher in relationship to the torso to complete one pedal revolution.
If an open hip angle is advantageous to power production and comfort, and if one wants to maintain or achieve a lower aerobar position, then it would make sense to go with a shorter crank arm length, especially as short cranks have little to no impact on overall power production. In other words, by moving from a long crank to a short crank, one can either open up the hip angle for one's current position, or realize some play to drop the aerobars for a more aggressive position. But in order to go the same speed with shorter cranks, the rider will need to slightly increase his/her cadence to compensate for the loss of gain.
This is where a little math is needed, but it's not so bad and you're almost there. Traditionally, riders have measured gear size by expressing it as a ratio (which is not too intuitive) or distance traveled per revolution of the crank (called "development"). For example, suppose that you're riding a bike with a 50 tooth chainring and a 25 tooth cassette cog; this combination can be expressed in a variety of ways:
The problem with each of the expressions above is that they don't take into account the effect that crank arm length has on gearing. The concept of gain ratio factors in the circle described by the crank; while the math is fairly simple, the real take away is that long cranks have a greater impact on overall gearing than short cranks. Here's an example based on my own riding:
I've been using 175mm cranks for lots of years for TTs; I prefer a large gear and a slower cadence (~75-80), which has tested well for me in terms of power and HR. I'm also 5'7" tall, which makes 175mm cranks long for me by most traditional standards.
Okay--if I figure out the gain ratios for 175 and 170 cranks, I get the following approximate values for a top gear:
- 170-->radius ratio ~2; 2(56x11)=10.18 gain ratio
- 175-->radius ratio ~1.95; 1.95(56x11)=9.92 gain ratio
- Difference between the two gain ratios is ~2%
What this tells me is that while the numbers say that I'd need to spin slightly faster for the same gearing to be at the same speed if I went to shorter cranks, the difference would only be 2%--which isn't very much.
But--by going with a shorter crank, I would reduce my hip angle, which means that I either can get lower in front for a more aero position (which I don't need to do), or I should be able maintain my current position, but push the same watts more efficiently. In other words, it looks like a shift to a shorter crank length for one my height might have more value than the benefits traditionally associated with using longer cranks for TTs.
What does all of this mean?
Body position is the single most important variable in establishing an aero position on the bike.
Tight hip angles can mean lower power output and greater physical discomfort.
Low front positions on the bike generally mean better aerodynamics.
Moving the seat forward (or adopting a triathlon-specific bike) enables the aerobars to be lowered while maintain an open hip angle.
Short cranks (say 165mm or less) can be advantageous in further opening up the hip angle.
Switching to shorter cranks means that there needs to be a slight increase in cadence to achieve the same speed for a given gear ratio.
Again, there are many variables that factor into a good, aerodynamic bike position and it is worth the time and expense to visit a professional fitter to help you get started. One you have a solid baseline position, you'll be able to experiment with seat position and crankarm length to further optimize your performance.
I'm frequently asked questions about cadence and whether there is an preferred cadence for racing. Over the years, there has been a good amount of research into cadence, but interest in this topic really came to the fore during the Lance Armstrong years, when he dominated his rivals in the mountains with a much higher RPMs than we were accustomed to seeing. A number of riders have tried to emulate Armstrong's high cadence, not fully understanding the relationship between cadence and performance. And coupled with cycling's long traditions--always ride at 90 rpm or you'll hurt your knees--it might be time to review some the research associated with cadence and performance.
First, to provide some reassurance: your body is a remarkable machine, and the vast majority of riders automatically self-select their most natural preferred cadence, depending on the demands they they are placed on their bodies and the demands required by the course. In general, most riders will self-select higher cadences for shorter events, and lower cadences for long events; also in general, most riders seem to adopt cadences in the range of 80 - 95 rpm, though there certainly are riders who perform optimally beyond either end of this range. There is a good amount of research that suggests that artificially varying cadence independent of physiological or event considerations does not always yield performance improvements. Simply saying something like, "I need to ride at a cadence of 95," doesn't take into account the many factors that determine how we perform during the course of an event.
Cadence describes the movement of the foot and lower leg around the center axis of the crank. Power is the measure of how much work we're doing on a bike. The higher the power, the more work that we're doing and (in most cases) the faster we ride. Power is calculated by a simple formula: how hard we press down on the pedals (force), multiplied by how fast we spin the pedals around (cadence). High cadences require less application of force than low cadences; a cadence of 70 rpm requires a greater amount of force applied to the pedals than a cadence of 100 rpm. Low cadences depend much more on strength than high cadences; high cadences depend much more on overall cardiovascular fitness than low cadences. Short form is this: if your legs feel tired and heavy, shift to a smaller gear and increase your cadence; if your breathing and heart rate seems overly tasked, shift to a bigger gear and decrease your cadence. And above all else, trust your bodies--some people naturally perform more effectively at lower cadence, while others at higher rpms.
Now for some nuances. In events in which there are lots of accelerations (such as a road race, criterium, or segment of a triathlon/TT course with lots of turns), it often is advantageous to ride at a slightly higher cadence than your normal, as a smaller gear would require less force to increase speed than a big gear (think: you're in a car at a stop light; it's easier to accelerate in first gear than in fourth). A slightly higher cadence in a ride with lots of accelerations will carry a higher toll on your heart and respiratory rates, but a much lower cost in terms of strength, and your legs should feel stronger near the end of the race. If you know that your ride will end with a series of long, difficult climbs, consider starting the race at a slightly higher cadence, saving you leg strength for later. If it is hot on race day and you're feeling tired and having a difficult time raising your heart and respiratory rates, consider using a slightly bigger gear and lower cadence to accommodate the environmental and physiological stresses on your body. If you're going down a long hill, when it's difficult to generate watts, consider using a big gear and low cadence, this time with light pressure on your pedals, to enable you to recover both your legs and your heart rate. If you're approaching a long climb, shift to a smaller gear early on its slopes, as this may help you save some strength for later in the climb. At the top of a climb, accelerate to speed in a small gear, using the same strategy that you'd use in a course with lots of transitions.
Here's the short version. It's useful to occasionally train yourself to ride at very high and low cadences to expand the range of your effective cadence. (You'll have more opportunities to determine your efforts--rather than have the course dictate your efforts--on the course if you have an effective cadence range of 20 rpms than you would with a range of 10 rpms). Pay attention to the cues offered by your body and adjust cadence to meet the needs of your legs and your heart rate/breathing. Don't slavishly emulate the cadences of your favorite athletes, as their physiological and biomechanical requirements likely will be different than your own.
Back to Armstrong, If you carefully watch Armstrong's performances during his Tour de France runs, you'll note that Armstrong's cadence wasn't all that different than that of his rivals. It only was when he attacked on the major climbs did you see a significant increase in cadence. Armstrong did this--and was able to do this--to leverage his tremendous cardiovascular capacity, while saving his legs for later in the climbs. His rivals did not have the same reserves as Armstrong, so their emulation of his cadence on the climbs as met with mixed success.
©Vmps/Don Vescio 2013
Structuring training sessions used to be easy. A coach would specify either a distance (ride 25 miles) or time (ride for 120 minutes) for a cyclist’s workout, and the rider would report back whether the session was completed as planned. More advanced coaches might combine the metrics of time and distance as a way to specify intensity: “Ride 25 miles in one hour,” or “Ride 30 miles in two hours, small gear.” Specifying distance or time certainly was much better than less scientific forms of coaching, like, “ride hard for awhile, and then do some hills.” Specifying time and distance introduced some measurable parameters into the cyclist’s training program, though they were not perfect (one can ride a hard hilly 25 miles, or an easy, flat 25 miles, for instance). Combining time and distance metrics helped coaches and athletes determine the relative intensities associated with specific training sessions.
Today, coaches and athletes can adopt a much more sophisticated approach to how workouts are scheduled and how these sessions can be assessed consistently and accurately. With the affordability of a wide range of training tools, such as heart rate monitors, power meters, and GPS devices, it never has been easier to capture performance data. With all of this availability of data, the issue becomes one of determining which data is of greatest value when describing a training session’s intent, or in assessing the efficacy of a training session after the fact.
There are two schools of thought regarding data use for planning and assessing workouts. The first relies on a fixed metric, such as power or heart rate; more sophisticated versions of fixed metrics are normalized power, intensity factor, and (for running) Vdot values. Fixed metrics are based on an understanding that specific performance values must be met in order to achieve success in a workout or competition, and if these values are not reached, then the athlete will not reach his or her goals. For instance, to ride a 25 mile time trial in one hour, the athlete must be able to maintain a 25 mph average pace; in more detail, this rider may need to average 380 watts and maintain a heart rate between 155 - 162 to ride the 25 miles in one hour. In this model, training sessions would be based on meeting specific performance minimums, regardless of how the athlete might feel at a given training session. The thought behind this method of training is that by hitting specific values, an athlete will be better prepared to me the target goals of competition.
The only problem with this method is that frequently coaches and athletes don’t factor in the more qualitative variables that impact training and race performance, such as fatigue, motivation, injury, or physical exhaustion. For example, later this week I am scheduled to do four VO2 efforts (these are very hard three minute intervals); for each interval, my target wattage will be 410 watts. If I'm rested, I can complete this session and not struggle too much; if I'm tired, at the end of a cycle, etc., then I might not be able to complete the repetitions. While the performance measure--watts, pace, etc.--are pretty fixed, my physiological response to the efforts is not. This is where Recorded Perceived Exertion (RPE) comes in.
When I schedule a session for my clients, I'll specify three values: heart rate zone(s), watts (pace or Vdot can be used for running and swimming), and RPE. All of them cross-reference each other. A session might read something like:
3VO2 efforts, 400 watts, HR Z5, RPE 8-9.
Here's where the interesting part comes in. I need to make sure that my client understands that the progression of values, from most to least important, run like this:
RPE = our physiological and psychological response to the work being done
Watts (or Vdot, etc.) = amount work being done during the activity
Heart Rate = how our bodies are responding the work demands being placed on it
If RPE is too high for the specified effort, then we cut back on repetitions and/or duration. If RPE is too easy for the specified workout, then we'd consider adding additional intensity for subsequent workouts. HR is used as a general gauge for recovery (if HR is too low or too high for session, then recovery might be in order).
Now, there is a huge amount of research that indicates that for event pacing, RPE should take priority over specific metric like pace, watts, etc. If I am not recovered, motivated, etc., then telling me that I need to ride at 300 watts for my HIM won't help me--it only will cause me to blow up early in the event. Similarly, telling me to ride at 300 watts when I'm recovered and peaked might encourage me to ride easier than I could have.
It's important to have specific performance metrics that can be used to establish baseline performance, and I think that's what things like Vdot, normalized power, and intensity factor come in. That said, all of these values need to be contextualized in terms of the impact that the effort has on the athlete, as exclusive use of the quantifiable metrics can yield premature exhaustion and over-training.
As for athlete's who overestimate their suffering quotient, use the HR/power data to normalize their response:
"Elaine, what the hell are you talking about? A RPE of 9, and a zone two heart rate, and you were mostly riding down hill? Are you sure that the session was as hard as you thought?"
Think of all of this data as having the most value when considered over time. Always use multiple metrics when specifying workouts, and regularly cross reference and correlate quantifiable data with recorded perceived exertion. Over time, athletes will find that RPE will become their most powerful pacing and on-the-spot assessment tool in their preparation kits.
Rate of Perceived Exertion
©Vmps/Don Vescio 2013
Maximal: Almost impossible to continue; completely out of breath; unable to talk
Extremely Strong: Very difficult to maintain exercise intensity; can barely breath and speak a single word
Very Strong: On the verge of becoming uncomfortable; short of breath; can speak a sentence
Strong: Heavy breathing; conversation punctuated by gasps
Moderate: Moderately heavy breathing; can hold short conversation
Light: Can exercise for hours; relatively easy to breath, can hold a conversation
Very Light: Basic movement and activity
This is the time of the season when it’s important to
incorporate intervals into one’s training plan to build the cycling strength
and speed necessary for successful competition.
The basic concept behind intervals is simple—ride at an intensity much
higher than you’d race, and you’ll race faster at lower intensities.
The keys to successful interval sessions are duration and
pacing. Keep the interval durations
relatively short, and try to pace the intervals as evenly as possible. In a good interval session, the last few
intervals should feel much more difficult than the first few, due to
accumulated fatigue. Another way to look
at interval pacing is that opening intervals should seem a bit easier than the
intervals that conclude a session.
I’ll cover a lot more about interval length, duration, and
intensity in another article. For now,
let’s take a look at the data captured from an athlete’s interval session (click image for full size view):
There are three lines on this graph: yellow = cadence; red = heart rate; pink = watts. By looking at these lines, one can get a good
sense of the pacing of the athlete’s interval session. Looking at the watts (pink) line, the
athlete’s wattage was both higher and more variable for the final two efforts than
they were for the first three; also note how the heart rate line trends up more
steeply and reaches a higher point for the final two intervals as well. The average watts for the final two intervals
was 310; the average watts for the first three was ~290.
The take away from this graph is that the athlete could have
ridden his first three intervals at a slightly higher intensity, say ~300
watts, which would be sustainable across all five efforts. For this specific session, a little more
intensity at the start of the workout probably would have resulted in less
variation across the full set of efforts.
Tracking your data is important not only when you’re
riding—it’s even more useful after your ride, when it can be used to determine
how well you met your session’s goals.
Adjust Cadence and Gearing for Recovery
Power is the measure of the amount of work that you’re doing on a bicycle. Power is determined
by how hard you push down on your pedals (force) and how fast you turn them in a circle (RPM). Force draws heavily on leg strength; sustaining a fast cadence requires good cardiovascular fitness. In a race, if your legs feel tired, shift to a smaller gear and increase your cadence, which will require less leg strength for a given effort. If your heart and respiratory rates are high, shift to a bigger and decrease your cadence, which offloads some stress to your legs.
When riding, most of your energy is used to overcome wind resistance. Aerodynamics are important, whether you are a fast or slow rider. The three most effective aerodynamic purchases one can make, in descending order of importance, are: aerobars (and a good bike fit to go with them); aero helmet (generally, fewer vents means a faster design); aero front wheel (think in terms of 50 - 60mm rim depth). Additional aero purchases will yield additional incremental benefits. And for slower riders, the percentages gained by aerodynamic savings are greater than for fast riders, as slower riders are on the course for a longer period of time. Aero matters for all riders.
Train Indoors--Even in the Summer
A number of professional triathletes do the bulk of their training indoors, and you should consider doing so, too. Indoor cycling eliminates many of the variables that can disrupt your training when riding outside, such as traffic, terrain, weather, and other distractions. Indoors, it’s far easier to control your performance variables, such as cadence, power, perceived exertion, and heart rate; as a plus, riding indoors also eliminates soft pedaling and coasting during your session, thus maximizing the productivity of your training time. So consider doing some of your rides indoors, even in the summer--you’ll find that it will increase the effectiveness of almost any training program.
Use an Alarm
While I capture a wide range of performance data (power, cadence, altitude gain, etc.) every time that I ride my bike, mostly it’s used for post-session analysis. When I race, I keep things as simple as possible to minimize distractions, preferring to set my pace by perceived exertion (which is later correlated with the data from the ride). What I do, though, to ensure that I don’t ride too hard in a long event is to set my computer to send an alarm when my cadence drops below a certain level (which means I’m pushing too big of a gear), or if my heart rate exceeds a maximum level for the event (which means my level of exertion may be too high for the event). The alarm settings help ensure that I don’t work too hard in a long event, which may negatively impact my pacing.
Based on Cervelo's remarkable success with their P series bikes, most top-level time trial and triathlon frame design emphasize tight clearances so that wheels and other components can draft frame members, with the goal of presenting as continuous of an aspect possible into the airflow, so that its disruption is minimal. (You can click on the images below for more detailed views
Note the close proximity of the rear wheel to the seat tube in the photo above.
Not withstanding the success of this school of frame design on the road and triathlon circuits, there is a competing philosophy that attempts to factor in the impact that a forward rotating wheel has on overall aerodynamics.
As the thought goes, when a wheel rapidly spins forward, it also is creating forward rotation of air; when a wheel if fitted tightly to a frame, the frame's tight clearance creates a dam that blocks this secondary airflow, thereby creating unwanted drag. The company Look is a proponent of this philosophy. In the photo below, note the clearance between the rear wheel and the frame's seat tube:
In the 2012 Olympics, see how Great Britain's track bikes were designed with ample clearances around the crowns of their forks:
Recently, I've begun testing this design philosophy (greater wheel clearances mean less drag) on a Kestrel Talon, which has long proven to be a top aero performer in static wind tunnel tests. My goal is to establish how effective the Talon's rear wheel design is in comparison to the industry standard Cervelo P3C. So far, the preliminary results are interesting.
It generally is assumed that the most efficient way to pedal is by applying maximum force on the downstroke of the pedal cycle, while simultaneously pulling upward during the upstroke. The intent of this model is to establish a cycle in which variations are minimized, resulting in the smooth generation of power. For years, cyclists have referred to this model--that of pushing down hard, while pulling up on the opposite site--as "pedaling in circles." Riders would spend hours doing drills to maximize the upward pulling force in the pedal cycle (think of one-legged pedaling drills, for instance) to "smooth out their pedal stroke."
Interestingly, as early as as 1991, research documented that elite cyclists tend to focus primarily on the downward force component of the pedal stroke (and pulled up less) than non-elite riders during periods of submaximal and maximal efforts. In simpler vernacular, what this means is that elite cyclists tend to stomp down on the pedals very powerfully during hard efforts, and that they demonstrate little upward pulling force during the other phases of their pedal strokes. This finding runs contrary to the accepted wisdom that one needs to pedal smoothly and consistently if one wants to ride fast. When looking at the data, it became apparent that riders who attempted to pull upward on the pedals rode at a higher metabolic cost and were less efficient than those who simply stomped down on their pedals, suggesting that the muscles that flex the leg on the upstroke are less efficient than those that extend the leg during the downstoke.
To better understand this dynamic, the concepts of positive and negative forces need to be described:
- Positive Force: The force that we apply to the pedal as it moves from the top of the pedal stroke to the bottom (in terms of a clock metaphor, think: from 12.00 to 6.00). Positive force generates forward movement of the bicycle. Positive force also can be described as a productive force.
- Negative Force: The force on the pedal associated with our body weight as it moves from bottom of the pedal stroke to the top (think: from 6.00 to 12.00). Negative force also can be described as a retardant force.
Now, these two forces are closely linked. As we press hard on a pedal during the downstroke of a pedal cycle, our bikes move forward; but as we press down on one pedal, the other pedal ascends, and we have to overcome our body weight as the pedal rises. The more energy that we reallocate from pressing down on the pedal to overcome the weight of our body on the opposite side of the crank, the less positive force is generated that contributes to the forward motion of our bike. In other words, a portion of our energy is being used to lift out body upward, which lessens the efficient use of our power. The more weight that we apply to the ascending pedal during the upstroke, the more energy we shift away from the productive force associated with the downstroke. Efficiency, then can be seen in terms very different than "pedaling circles": efficiency could refer, instead, to maximizing the production of positive force during the pedal down stroke, while minimizing the impact of negative force associated with the pedal upstroke.
If we accept this characterization of pedaling efficiency, it then makes sense that we should do whatever we can to press down as hard (and as long) as we can on the pedals. It also would make sense that we try to actively pull up on the pedals during the upstroke, as this would eliminate the negative force associated with having to lift our body weight. The problem with this is two-fold: there is a higher metabolic cost associated with flexing the leg during the upstroke than there is in extending the leg during the down stroke; negative pedal force comprises a greater percentage of the overall pedal stroke than productive positive forces. The following diagram illustrates the application of positive and negative pedal force:
Remember, positive forces are associate with pushing down hard on a pedal; negative forces are associated with the amount of weight the rider has to lift during the pedal upstroke. Additionally, riders pay a greater metabolic cost if they pull up on their pedals, as opposed to pushing down on them. The most efficient pedal stroke, then, relies on the high application of positive force during the downstroke, which comprises approximately less than 50% of the entire pedal stroke. In practice, the most effective and efficient cyclists are those who stomp down hard on the pedals during the power phase of the pedal stroke, while unweighting their opposite feel during the upstroke, when little positive power is generated. Unweighting the foot simply means making the foot and leg as light as possible on the pedal during the upstroke--top riders essentially are balancing their feet on their pedals during the non-productive phases of the pedal stroke. This cycle of pressing hard on the pedal/unweighting the pedal is consistent, whether one rides with a rapid or slow cadence.
A simple way of understanding the pedal stroke is to view the phase between 12.00 and 6.00 (see diagram above) as centering on positive (productive) force; and the phase between 6.00 and 12.00 as centering on negative (retardant) force. This understanding, however, does not take into account the transition phases that occur at 6.00 and 12.00, when the rider is shifting from one force form to another. Traditionally, the 6.00 and 12.00 positions of the pedal stroke are referred to as "bottom dead center" and "top dead center." At these positions, the rider is able to generate very little positive force; on the other hand, negative force also is minimized in these positions, too. In order to move the pedal more effectively through bottom dead center and top dead center, a rider can take advantage of vector geometry and the mechanics of elastics. When approaching the 12.00, top dead center position, riders can drop their heels as they begin to push down, thereby enabling an earlier application of positive force to the pedal stroke. When passing through the 6.00, bottom dead center, position, riders can allow their heels to be snapped upward by the lower leg muscles, enabling them to take advantage of these muscles elastic properties by imparting a slight secondary acceleration of the pedal during the upstroke, which has the effect of unweighting the foot from the pedal.
What is interesting about the pedal stroke dynamic discussed above is that it also can help a rider understand why climbing while seated is more efficient than climbing while standing. Many studies have demonstrated that climbing cadences tend to remain the same, whether one climbs seated or standing. Climbing while standing is associated with greater peak positive forces (uo tp 130% greater than positive forces generated while seated), but it also is associated with much larger negative forces on the upstroke, which mitigates positive force gains. So, for climbing at a given wattage, riders who stand will experience greater variations of power than those who climb seated. Because riders shift their bodies forward in relationship to the center of the crank when the climb standing, the phase in which positive force is generated also is shifted forward by 15% to 30%. Shifting the positive force phase in this manner results in little to no torque being applied to the pedals top and bottom dead center, which can create a choppy pedaling motion. Because riders who climb standing necessarily are supporting a greater portion of their body weight than those who climb seated, and because the amount of torque generated top and bottom center center is less, standing climbers realize a higher metabolic and muscular cost than their seated competition. In addition, because of greater peak power variations, riders who climb standing also experience additional metabolic and muscular cost as they experience greater accelerations and decelerations during their pedal strokes.
While all of this might sound complicated, the take-aways are quite simple.
- Push down hard on the pedals during the down stroke;
- Make your foot as light as possible during the upstroke;
- And climb seated to minimize metabolic and muscular cost.
Activities such as one-legged pedaling drills are useful because they help riders habituate themselves to unweighting their pedals during the upstroke; such drills are not intended to build strength to enable riders to actively pull up on the pedals in normal cycling situations. Cycling efficiency has little to do with pedaling in circles in a narrowly prescribe cadence range. Rather, effective cyclists understand the dynamics of the pedal stroke in such a way to maximize the application of positive force to the pedals, while eliminating sources of loss.
Click here to read Vaughters' opinion piece
, which was published in the NY Times Sunday Review
I just read the Vaughers' opinion piece in the NY Times Sunday Review. While some might question the timing of his decision to speak in public on this topic--and there was a recent Twitter feed that seemed to suggest that something like this was forthcoming--I do appreciate that he wrote at length on the choices that he made. Very, very human--and much more identifiable than "I ate tainted cow," or "someone doped me."
On the other hand, you have characters like David Anthony, the Masters rider who tested positive after a grand fondo event in the US:
Paraphrase--"I got caught up in the sport--and I didn't have any fun in the end."
Did Vaughters go public to proactively manage potential fallout from possible future disclosures? Even if this is true, I'd rather see disclosure given in advance, rather than disclosing after all attempts at obfuscation fail. While I still believe that the culture of cycling is such that it makes it very difficult to live according to an ideal, it still is not acceptable to see how others are hurt by the peloton's omerta--see Filippo Simeoni and Christophe Bassons.
Can one atone for one's past? Maybe Vaughters is through his work with Slipstream. But what about the likes of Vinokourov? What is his atonement, other than sitting out for two years? Contador? Basso?
And then one wonders why so many Masters amateurs are getting popped for PEDs...
Edit: The Twitter feed can be found at
A good amount has been written on cycling and cadence, with many coaches and athletes assuming that higher pedal cadences (+90 RPM) are better than lower cadences. Lance Armstrong's Tour successes often have been seen as predicated on his higher than average cadence selection, and a review of the hour record on the track indicates that almost all record holders pedaled in cadences in excess of 100 RPM. Most professional cyclists will race at cadences between 90 and 105 RPM, and cadences in excess of 150 RPM are not uncommon in some events on the track. Based on all of this observational data, it's easy to assume that one should ride in cadences greater than 90 RPM if one wants to be competitively successful.
But before we look at cadence specifically, it might be useful to describe how we generate power on a bike, which is directly tied to the cadences and gearing that we select. Basic terminologies as applied to cycling:
1. Strength: the amount of downward force or energy that is applied to the pedals
2. Torque: the ability to rotate the pedal/crank (strength is the limiter of torque)
3. Power: the application of strength over time
4. Speed: the register of power over distance
Power is delivered to the bike as follows:
1. Pushing forward through the top-center of the pedal stroke
2. Pressing down on the pedal on the down stroke
3. Pulling back through the bottom-center of the pedal stroke
4. Unweighting the pedal on the upstroke
Most elite cyclists focus almost all of their strength on pressing hard on the pedal during the down stroke, while trying to minimize the weight of the foot and leg on the upstroke. In other words, elite cyclists don't apply force smoothly throughout their pedal stroke--they do not pedal circles, but rather they stomp down hard for a limited portion of their pedal stroke, while trying to reduce loss on the remaining portion of their cycle. To go fast, they "stomp" down on their pedals.
Above is a representation of how force is distributed in a pedal stroke. Note that the larger the arrow, the greater the force. According to Broker, cycling power is the product of instantaneous crank torque and instantaneous crank angular velocity; what this means is that for a given average power at a given average RPM, instantaneous power (the power of a given moment) will fluctuate significantly through each pedal revolution.
Okay--now that we have some basic concepts out of the way, let's take a look at a simple way of describing power as applied to cycling:
power = force x angular velocity
A more expanded form of this description might look like this:
power = ability to push really hard on the pedals x the ability to spin the pedals rapidly in a circle
Here's an easy way to think about all of this--in order to ride, say, 25 mph, a rider may need to generate an average power of 250 watts (power on a bike is measured in watts). To achieve this average power that will enable the realization of this target average speed, I have two basic options:
1. I can push down really hard on the pedals when I'm in a big gear (this emphasizes the force side of the power equation, which is tied to physical strength)
2. I can spin my pedals really fast when I'm in a bigger gear (this emphasizes fitness)
Cycling cadence has a specific metabolic cost. Athletes who are very fit and who have a high VO2 value have greater metabolic capacity than those who are less trained or who are less genetically gifted. In practical terms, higher cadences generally result in higher heart and respiratory rates, which carry a high metabolic cost. The fitter one is, and the higher one's VO2, the greater metabolic cost that can be carried. Lance Armstrong's success was in part tied to his high sustained cadences, which were possible due to his tremendous aerobic capacity (think: he had a large metabolic bank account).
A low cadence carries an increased cost of muscular fatigue. Pushing down really hard on the pedals while in a big gear requires a considerable amount of strength in one's quadriceps, hamstrings, and gluteus maximus; the cost, here, is muscular fatigue, which is the failure of muscular strength. All riders are predisposed to cadences that average above or below the ideal 90 RPM marker--and this is perfectly okay. In fact, the most recent thought is that a cyclist should simply self-select his or her cadence and not worry about cadence as an absolute value in itself--just let your body decide what is the most effective cadence for a given effort.
This is not to say that riders should ignore their cadence--far from it. Rather, one should be attentive to cadence in relationship to its impact on one's perceived exertion. Sounds complicated? It really isn't. We know that
1. That pushing down hard in a big gear results in a slow cadence that taxes the strength of our legs;
2. That spinning a small gear results in a fast cadence that taxes our heart and respiration rates.
So, if you're in a race and you find that your heart rate is drifting up and your breathing is becoming quick, you can slow down a bit to recover (which never is good for one's performance!), OR you can shift to a bigger gear and decrease your cadence, which will shift greater emphasis to the force/strength side of the power equation, enabling your heart and respiratory rates to decrease. Similarly, if you're in a race and your legs are getting tired and heavy, shift to a smaller gear and increase your cadence, which shifts emphasis to the part of the power equation that privileges fitness over muscular strength.
Successful cyclists will adjust their cadences and gearing not only to meet the challenge of changing terrain, but also as a way to balance out the various stresses placed on their muscular strength and overall fitness during the course of an event.
Next Discussion: the myth of pedaling in circles.