Cadence and Torque: what are they? Why do we care?
Cadence is a critical part of your performance on the bike, but you may not know it.
Belgian superstar Eddy Merckx, the greatest champion ever known in cycling, once gave a talk at a schoolhouse, presumably in small town many years ago. 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?” Eddy replied “Excellent question young man. You should push a big gear quickly.” Mr. Merckx was alluding to the relationship between cadence and torque, which is how we make power on a bike**. The interplay of these two variables determine a rider’s power at any given instant during 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.
Power is Force multiplied by Velocity. 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.
Thus, our formula is: Power = torque x cadence. The question becomes, how do we make more power? This is where Eddy’s story applies: we can either:
- Increase the torque [assuming cadence stays the same]
- Increase the cadence [assuming torque stays the same]
- Increase both at once [increase both torque and cadence simultaneously]
#1 is equivalent to “pushing harder”. #2 is equivalent to “pedaling quicker”. #3 is doing both of these things at once.
Note that in order to accomplish #1, either the grade of the road has to change such that an increase in torque is required. Example: the rider has to begin climbing, maintain the same cadence, but push on the pedals with more force. Second example: on a flat road, the rider can shift to a bigger gear and push with more force but keep the cadence the same.
Note that in order to accomplish #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 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 #3, the rider must both push with more force and pedal more quickly. This is how a rider makes more power 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.
It is fair to say that 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. This sensation is due to the proprioceptive input of the pedal: as a rider climbs, he or she works against the same forces found on flat terrain [such as the coefficient of rolling resistance as the tires roll on the road surface, the friction of bearings and the chain interacting with chainrings, cogs and pulleys, and wind resistance which is a combination of moving though the atmosphere as well as working with or against the phenomenon of weather], but the force at the pedal changes perceptually due to the additional load of working against the force of gravity to gain altitude. The steeper the grade, the more the rider works directly against this force, effectively moving their center of gravity away from the center of gravity of the earth. in spite of the fact that wind resistance will go down on climbs in most instances, the load on the rider will go up as the grade gets steeper. This is why it feels like the pedal are harder to push down on a climb; the additional work done to overcome the force of gravity adds to the rider’s workload.
On a flat road, inertia 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.
As the rider climbs a steep hill, and more force is required to maintain a constant ground speed [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 [around 12 o’clock] and bottom dead center [or BDC, which is about 5:30, or when the crank is parallel to the seat tube]. The inverse is also true: flat terrain camouflages dead spots in a rider’s pedal stroke due to the effect of momentum.
Also note that fixed gear bicycles do the same: they camouflage poor pedaling technique. While riding a fixed gear on the road will sometimes mean higher peak cadence numbers and may help a rider develop supple pedaling motion, the effect of the fixed gear also “pushes” the foot through the dead spots [a point in the pedal stroke where a rider fails to produce positive tangential force on the pedal].
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.
A rider who lives in a location with mostly or all flat terrain may become accustomed to riding with a pedal technique that has more exacerbated peaks and dead spots. Riding on the flats will allow them to rely on momentum to overcome this technique of power application. Momentum is the mass and velocity of an object having a tendency to maintain the velocity, so once a bike, rider, full water bottles, and all the kit gets going on a flat road, a rider with a pretty choppy pedal stroke can keep speed going pretty well. This is why someone can buy a ten thousand dollar time trial bike, show up to a flat TT and basically axe chop the pedals to death with very sub-optimal technique and still average 27mph. There are two key points to recognize: 1. Bikes are amazing at converting our metabolic energy into mechanical energy. 2. Cycling, more than most other sports, camouflages poor technique, at least to the untrained eye.
To this point, there have been may sport scientists who seem to see only the metabolic side of the sport of cycling and speak about a rider’s efficiency, and thus claim that technique in cycling doesn’t matter. This type of thinking is focused on the amount of oxygen used during a given intensity, or the number of grams of carbohydrates consumed per hour and the resultant average power. There is nothing wrong with looking at a rider from this lens and it can tell us important things about a rider’s performance in a race or training. But to say that technique is a trivial in the outcome of performance cycling is complete bullshit. Bicycles do camouflage poor technique and relative to running [poor technique = injury], cross country skate skiing [poor technique = skier crash] or swimming [poor technique = risk of drowning], technique may play a lesser role in the outcome of a hill climb but this statement largely ignores the role technique has in the mechanical efficiency of bicycles. Just because modern bikes are very stiff in the bottom bracket and drive trains are very efficient in most conditions does not give the athlete a pass to ignore a proper pedal stroke. Just like any competitive sport, final outcomes can be the result of fractions of a percent difference and pedaling smoothly under load can make this difference.
This type of thinking also limits the scope of “technique” to how much tangential force a rider is applying to the pedals, which ignores a huge list of other aspects of riding that fall under technique that unquestionably influence the outcome of a competitive cycling event. These include positioning in a peloton, effective drafting in real world cross wind conditions, cornering, descending, out of the saddle riding, sprinting, using aero bars, becoming more or less aerodynamic dependent on air speed of the rider, eating and drinking while riding, etc.
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.
Below 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.
This old video of Eddy Merckx demonstrates his ability to pedal quickly on rollers:
** the Eddy Merckx school child story is paraphrased from my memory. Exact accuracy not guaranteed but you get the point.
*** J Johnson contacted me about this article and helped me explain my physics with greater clarity. I am grateful for his contributions.
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.
Warm up for 20-30 min progressing to Endurance pace when ready.
duration: 5 min
cadence: 100-110rpm target
Flush for 5-10 minutes with easy riding.
duration: 45 seconds seated
cadence: 105-120rpm target
recovery: 3 min Recovery
Warm down for the remainder of the ride duration in Z1 at self selected cadence.
- 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.
Warm up for 20-35 min progressing to Endurance pace as ready.
duration: 8 min
cadence: 110 rpm avg target
recovery: 4 min Recovery between efforts
Cool down with riding in Recovery for the remainder of the duration.
- Steady riding is an important part of these efforts. Try to maintain constant output.