April 26, 2022

Colby Pearce on the Science behind Cadence

As long as bikes have existed, riders have examined their cadence, or RPM, and used it to inform their training. What exactly does it mean though, and how can it inform your own approach? Well - to truly understand this metric, we asked Team EF Coaching's very own Colby Pearce to take a deep dive.

Cadence is a critical part of your performance on the bike, but you may not know it.

There's a famous adage about Belgian superstar Eddy Merckx, the greatest champion ever known in cycling, giving a talk at a schoolhouse. An aspiring young rider asked him, “Mr. Merckx I want to win my local time trial and be just like you when I grow up. Should I spin a big gear slowly, or a little gear quickly?” Without missing a beat, Eddy replied “Excellent question young man. You should push a big gear quickly.”

Now, the joke is pretty clear, but it deals with the fundamental relationship between cadence and torque. These are the two critical things that combine to produce power on a bike. The interplay of these two variables determine a rider’s power at any given instant during riding - and as such it's impossible to underplay the importance of cadence in your riding.

In order to understand more about what power is, it is useful to break it down into principles, understand what these principles are, and how they relate to each other.

The amount of power made can be measured in any physical activity [rowing, lifting weights, running, etc]. Power is simply how hard we push multiplied by how quickly we push. Another way to think about it is that power is a product of the strength we use and how quickly we use it.

Because we are making power in a circle on a bike [pedaling] we change the terms slightly:

Force in a circle is called torque.

Velocity in a circle is cadence.

The real formula for power

For cycling, our formula is this: power = torque x cadence.

The question for athletes then immediately arrises - how do we make more power? Well, this is precisely where Eddy story hit the nail on the head - to make more power, we can either:

1. Increase the torque [assuming cadence stays the same]

2. Increase the cadence [assuming torque stays the same]

3. Increase both at once [increase both torque and cadence simultaneously]

Option #1 is equivalent to “pushing harder”. Option #2 is equivalent to “pedaling quicker”. Option #3 is doing both of these things at once.

Note that in order to accomplish Option #1, either the grade of the road has to change such that an increase in torque is required. For example, the rider has to begin climbing, maintain the same cadence, but push on the pedals with more force. As a secondary example, on a flat road, the rider can shift to a bigger gear and push with more force but keep the cadence the same.

To accomplish Option #2, the rider has to maintain the average torque over each complete pedal revolution, but increase cadence. This could mean that road grade does not change, the rider does not shift, but increases their cadence with the same force on each stroke. In order to accomplish this while climbing, the rider may have to shift to a smaller gear.

In order to achieve option #3, the rider must both push with more force and pedal more quickly. The main time you'll see this type of approach is on a track bike, which only has one gear: both must happen at the same moment. In contrast, a rider on a geared bicycle can shift gears to keep cadence in a particular range while increasing force. Thus, riding on a track bicycle can require a greater range of abilities to produce high torque / low cadence power as well as high cadence / low torque power.

Unpacking how pedaling dynamics change with terrains

Most riders associate making more power with pushing harder on the pedals. This is probably why more riders report that it is “easier” to make more power on climbs than on flat or downhill roads and that's because the physics of pedalling are fundamentally altered depending on the terrain you're on.

Riding uphill

The feeling that hills are easier to is due to the proprioceptive input of the pedal - the force of inertia is experienced differently on a climb, as it has a tendency to slow the rider down. Inertia wants to keep you at rest on the surface of the earth; you are using mechanical energy to climb away from it and gain altitude.

To do this, your pedal stroke requires more even force application over a larger number of degrees of the pedal stroke. It's important to note that this isn't the same as more torque - it's longer duration of that even force - and overall a very effective technique. This extended duration is what creates the sensation that the pedal is pushing “back” against the foot in the shoe. This is what the rider perceives as force.

Riding flats

On a flat road, inertia and momentum will tend to keep a rider in motion; this is what the rider will perceive as a sense of ease on flat rides [once the bike is up to speed]. The bike “rolls along” almost on it’s own on flat roads. The consequence of this is that on the flats their pedalling techniques is somewhat effective, but when climbing, they are unable to deal with the longer duration of force application across a higher proportion of the pedal stroke.

Riding steep hills

As the rider climbs a steep hill, and more force is required to maintain a constant ground speed [technically climbing at a constant speed is acceleration, as the rider is working against the acceleration of the force of gravity while gaining altitude] the dead spots in a pedal stroke become “magnified”, or more obvious. Dead spots are typically at the “top” of the pedal stroke and bottom dead center.

If we think about this for a moment, we understand this has implications for a rider, given their pedaling technique, local terrain and bike position. A rider who climbs a lot is likely to develop the ability to handle more peripheral [muscular] stress, and possibly to develop a stroke with less dead spots and more even application of power. If a rider is climbing a steep grade, and their pedal stroke has large dead spots or is very “spikey” in application during the power phase, the bike will surge forward on every stroke; this is very inefficient as it accelerates the bike and rider over and over, effectively “see-sawing” up the mountain.

Athletes are highly intuitive and while they may not consciously realize it, they may “solve the equation” by learning to apply power more evenly across the stroke over time and with different riding experiences. Competitive situations help bring about these realizations, as seeing your performance through the lens of a ranking will force evolution of the practice.

How cadence changes with terrain

A physiological impact of climbing is that it emphasizes more muscular, or peripheral stress, on the athlete, rather than cardiovascular, or central stress. This is to say that it places more demand on the muscles, and creates localized stress to the muscles of the legs, in the form of mechanical load and fatigue to the muscle fibers. The fibers become fatigued under the load of producing force, and glycogen is depleted from the muscles.

On flatter terrain, or under higher cadence scenarios, a rider will have more centralized stress on the aerobic and glycolytic energy systems, which will place more demand on oxygen delivery to the muscles, clearance and utilization of lactate as fuel, and systemic metabolic load.

The higher the torque demand is, the more peripheral the load will be on the athlete. The higher the cadence demands is, the more central the load will be on the athlete. Using gears is one way an athlete can manipulate the load to their favor, to a degree, but there are limits. On an extremely steep climb, when the rider is out of gears and cadence is in the low 60’s, demand will be primarily peripheral. On the other hand, in a super strong tail wind or down a long descent, even in the largest gear cadence can exceed 130rpm.

How cadence x terrain x power = performance.

A physiological impact of climbing is that it emphasizes more muscular, or peripheral stress, on the athlete, rather than cardiovascular, or central stress. This is to say that it places more demand on the muscles, and creates localized stress to the muscles of the legs, in the form of mechanical load and fatigue to the muscle fibers. The fibers become fatigued under the load of producing force, and glycogen is depleted from the muscles.

On flatter terrain, or under higher cadence scenarios, a rider will have more centralized stress on the aerobic and glycolytic energy systems, which will place more demand on oxygen delivery to the muscles, clearance and utilization of lactate as fuel, and systemic metabolic load.

The higher the torque demand is, the more peripheral the load will be on the athlete. The higher the cadence demands is, the more central the load will be on the athlete. Using gears is one way an athlete can manipulate the load to their favor, to a degree, but there are limits. On an extremely steep climb, when the rider is out of gears and cadence is in the low 60’s, demand will be primarily peripheral. On the other hand, in a super strong tail wind or down a long descent, even in the largest gear cadence can exceed 130rpm.

A rider who has trained to use cadence as a method to increase power output will have more tools in the quiver for use over varying terrain. For example, over the top of a climb, if the road flattens before a descent begins, lifting cadence will help a rider accelerate without the need to “push” against a gradient. The same technique applies to tailwinds, false flat down hills, or riding in a good-sized peloton in still wind. A rider who can make a good spectrum of outputs [powers] at higher cadences will effectively negotiate all of these real world scenarios. A rider who is limited to making high power only at lower RPM’s may struggle in these types of circumstances. This can mean getting dropped or being “pinned” in the group – unable to do anything other than hang on for dear life.

Having the ability to generate high cadence at high force also helps a rider respond to the natural changes in pace and accelerations that happen in a peloton.

Above we can see a screen shot of data from a very fast, long group ride of about 160KM. On the X [horizontal] axis, we have power in watts and on the Y [vertical] axis we have cadence in RPM. The graph is divided into quadrants, with the upper right being high power and high cadence. The cross hairs are aligned at the average P and RPM for the entire file [80rpm and 190w, including all the “zeros”]. Each dot represents an individual data point from the file; notice the distribution of dots in the upper R hand quadrant. We can see that a lot of high power data points were generated at 100 rpm and higher, thus illustrating that the demands of a fast group ride: a lot of high force output which is also at high cadence.

Cycling is a sport that is highly subject to the rules of physics: inertia, momentum, aerodynamics, rolling resistance and complex fluid dynamics all play a role in how an athlete performs in an event or how quickly they cover the course. A rider who can make high power over a variety of different cadence ranges has the depth to perform in a wide range of real world conditions. This is why training at both high and low cadences will help an athlete become more effectively trained to handle the broad range of demands cycling offers, almost regardless of the nature of the event or ride being prepared for.

Two workout examples for high cadence riding

1hr 30 min - 6-8 X 45 SECOND CEILING BURSTS

Practical Application: Training the ability to go at maximum pace for 45 seconds is very useful in decisive competitive moments, or for going fast on rolling or undulating terrain. These efforts target the "extra gear" that well trained athletes have to close gaps or accelerate away from a peloton or small group.

Purpose: Build anaerobic strength.

Focus: Make the highest quality efforts possible for these short intervals. Today is about intensity.

Workout:

  • Warm up for 20-30 min progressing to Endurance pace when ready.

  • 5 minutes at tempo with a 100-110 RPM target

  • Spin gently for 5-10 minutes

  • Complete 45 seconds seated at maximum intensity and between 105-120 RPM

  • Recover for 3 minutes

  • Repeat two steps above 6-8 times

  • Warm down for the remainder of the ride at a self selected cadence.

Notes:

• These efforts are about intensity. Make each one maximal, but within the boundaries of good form. The goal is a quiet upper body with little to no motion in head or shoulders.

• Perform the minimum number of reps within the prescribed range that can be effectively executed

1hr:30m 3 x 8 HIGH CADENCE TEMPO

Purpose: Steady aerobic power at high cadence will develop the ability to maintain constant power while training muscles to be supple and efficient.

Focus: Motionless upper body, constant power output during efforts.

Workout:

  • Warm up for 20-35 min progressing to Endurance pace as ready.

  • 8 minutes at tempo pacing and with a cadence target of 110 RPM average

  • Recover for 4 minutes.

  • Repeat previous steps twice more

  • Cool down with riding in Recovery for the remainder of the duration.

Notes:

• Steady riding is an important part of these efforts. Try to maintain constant output.