Cycling Article - The Art and Science of Understanding Power

Note - this article is about cycling, so you may or may not be interested. I hope that you are!

A power meter is the best tool ever developed for cyclists who want to reach new achievement thresholds.

Few things in life are so simple: push down on the pedals, and the bike moves forward; nothing’s changed about riding bicycles. But in a sense, a lot changed. Nowadays, cyclists measure everything: speed, cadence, calories, heart rate, and power. Not just power but average power, normalized power, 10-minute power, 1-minute power, peak power, threshold power, etc. Commentators are constantly remarking on how much power a rider puts out at certain times in a race. But what do each of these numbers mean?

Before power meters, we had to guess about a pro's effort climbing Mount Ventoux using time and speed. Nowadays, races are won and lost with power meters, we can know the secret sauce for winning a race. A good example is Mathieu Van der Poel winning last year's Strade Bianche. He covered the final 60 km in just 90 minutes, averaging 439 watts (w) and maintaining 5.8 watts per kilogram (w/kg). After 4 hours of racing, he launched his winning attack and produced 1,004w, according to his power data on Strava. Furthermore, Van der Poel's average power was 389w or 5.1w/kg for the 186 km race. Tadej Pogacar recently did the same thing, winning this year’s Strade Bianche with an 81-km solo breakaway. Another example is Ian Boswell's 2021 Unbound Gravel 200 power analysis. Boswell won the 331 km race in 10 hours and 51 minutes with an average power of 247w (3.6w/kg), a normalized power of 280w (4.1w/kg), and a max power of 1,032w (15w/kg). For most, these numbers are incomprehensible.

Your ability to pedal a bicycle varies due to terrain, wind, resistance, weight, coasting, surges, drafting, etc. Power isn't affected by outside factors like heart rate, altitude, temperature, wind, road surface, sleep, and hydration, which don't alter the readings. Power is currently the ultimate view of a rider's effort over time. Speed is just a result of that effort minus the outside factors.

What is Power?

Power is the transfer of energy. To ride a bike, energy is produced from our muscle cells, allowing our muscles to create the force to push down on the pedals. The force we produce, causing an object to rotate, is called torque. Power is a product of torque and cadence (multiply torque and cadence). Watts is the unit that represents power, and this is what a power meter measures and displays on our cycling computer. A simple way to view this is to imagine maintaining 300 watts on a climb. To obtain 300 watts, you can have a cadence of 60 rpm and a torque of 5. But you can also maintain 300 watts with less torque but a higher cadence, 95 rpm, and 3.15 torque.

What is a Power Meter?

Power meters come in many shapes and sizes, but they all are mechanical devices that measure force at the end of the day. The interior of a power meter contains a piece of wire called a strain gauge. When a force (torque) is placed upon a strain gauge, we can measure the amount of strain produced, and your computer calculates this into power. The torque is divided by the cadence, which is your power output in watts. Nowadays, the power data is transmitted via Bluetooth or ANT+ to a head unit computer or watch. Most head units record the data, allowing you to track your performance for later analysis. Nowadays, power meters are found in the hub, crank, chainring, pedals, and shoes.

A little history: how power meters were first incorporated into bicycles.

Dr. Allen Lim was one of the people who introduced me to cycling. Allen Lim and I were students at the University of California at Davis. When I joined the UC Davis cycling team, Allen took me under his wing and taught me how to ride a bike. I had no idea that he was once an aspiring junior racer. I knew he was an A rider, and I started as a D rider. Allen taught me the ropes of cycling, and we enjoyed many challenging rides together in the hills around Napa Valley. We were both physiology majors at UC Davis, one of the premier universities to obtain a physiology degree. After I left UC Davis for medical school, Allen continued the Ph.D. path and wrote his doctoral thesis on the power meter. His research developed the ideas surrounding the experimental use of the CycleOps PowerTap, making him a pioneer in using power meters.

In cycling, a watt is a snapshot of your power at any moment. One remarkable fact is that a watt is a watt on a bike or a horse. So, we can compare his effort using power to when Van Der Poel launched an attack. Another comparison: One horsepower is equal to 746 watts.

Standard Definitions of Power

Functional Threshold Power (FTP), maximal power, average power, and normalized power are all numbers you may see on a cycling computer screen. Have you ever wondered what all those numbers mean? Here, we break down power meter metrics; specifically, many terms always enter the conversation when discussing training with power.

Average Power and Normalized Power

Average power is exactly what it sounds like; it's simply the average power of your entire ride. The computer takes a snapshot of your power at certain times and divides it by the total number of snapshots taken.

In the Giro d'Italia, Peter Sagan reportedly produced more than 1400 watts in the final sprint, and his average power over the final sprint was 1200 watts. What about coasting? Most cycling computers have a non-zero averaging system that does take coasting into account.

Normalized power is produced from a more complicated algorithm than average power, but it’s important to understand. Normalized power is an estimate of the power you could’ve maintained for the entire ride while considering the same physiologic cost in terms of terrain, weather, glycogen utilization, lactate production, stress, and neuromuscular fatigue for a given effort if your power output had been perfectly constant rather than variable. It is a more realistic representation of your ride.

For example, if you ride a flat course for an hour at 250 watts, your average and normalized power will be the same. But if you ride a hilly course at 200 watts, normalized power will be greater than average power. A Tour de France rider will average 220 to 320 watts (or more) for a four-hour stage, but normalized power will be higher. Most amateur cyclists cannot sustain that power for even 30 minutes.

This is why Van Der Poel's Normalized Power was said to be 439 watts for the entire race. Normalized Power data will almost always be higher than average power because of the coasting aspect. Average power is still important, but Normalized Power provides a more accurate measure of the actual physiological demands of a ride, considering energy utilization and exercise intensity.

Functional Threshold Power (FTP)

This is a measurement of how much power you can sustainably produce over one hour and is a fundamental fitness metric. It's often expressed in watts produced per kilogram of body weight (see w/Kg). Testing FTP is easy. The protocol is a 20-minute all-out time trial, typically on a steady climb. Pros often perform a specific series of threshold tests to increase accuracy. Former professional cyclist Ben Day is an Aussie team Bike Exchange performance coach. He says the peak aerobic power test must precede the threshold or skew high.

After a warmup, perform maximal efforts in this order, with full recovery (5 to 10 minutes of easy pedaling) in between each effort:

5 seconds (peak neuromuscular power)

5 minutes (peak aerobic power)

20 minutes (FTP)

1 minute (peak anaerobic capacity)

Your functional threshold power is 95 percent of your 20-minute power number.

Power to Weight ratio: w/kg

Power divided by your weight is watts per kilogram (w/kg) and is an important number when trying to understand power. For example, when you and big Tommy (who weighs 100 pounds more than you) are riding together, the easiest way to compare efforts is to look at a specific segment/lap and understand that Tommy will need to produce more watts because of his size. You will suffer in the short term, but if you can put the screws to him in the long term, you will get away. Watts/weight (kilograms, not pounds), 350 watts/69kg (152 pounds) = 5 watts per kilogram (w/kg). 500 watts/100kg (220 pounds) = 5 w/kg.

To put this in a real-world perspective: Tommy weighs more than you and produces a max power of 1200 watts but has an average output of 150 watts. He will most likely get dropped. But if a rider has a max power of 450 watts and can have an average output of 350 watts, they will absolutely devastate a ride. This assumes the two riders are equal in weight (also known as power to weight).

On that same note, if Tommy could hold 350 watts and still have the "max power" of 1200 watts, he would still get dropped by you if you also held 350 watts because of how much more weight he must move over time. However, max sustained power will offset any weight discrepancy in a short effort (under 1 minute). So, being bigger (like Andre Greipel) can be good in a sprint, but you must make it to the sprint for it to matter!

A big rider like Andre Greipel must produce more watts on flat or rolling terrain than a climber like Romain Bardet to maintain the same speed because the sprinter weighs more. Thus, a better measurement, especially on climbs, is w/kg, which normalizes the weight difference. However, the highest w/kg will be the fastest for athletes who ride in the hills. Many coaches are critical of w/kg because most calculations do not include the bike's weight, just the rider's.

Better is Better

How much better are ProTour riders than the rest of us? Tour contenders like Roglic or Froome can produce above 6 w/kg on major race climbs. A domestic pro can manage 5 to 5.5 W/kg; a competitive amateur or masters' racer can probably produce around 4 W/kg, and an untrained cyclist would produce 2.5 W/kg. Anything above 3.5 watts per kilogram is pretty legit on efforts over 5 minutes.

How Do I Train Power to Weight?

First, calculate your power-to-weight ratio for a given power range. To do this, divide your body weight in kilograms (1 kg = 2.2 lbs) into average watts for a given range. Do this for several power ranges to know where you're strongest and weakest. W/Kg is not a static number but corresponds to different points on the power curve. For power profiling, most coaches use four standard durations of power, as described above. These durations best reflect neuromuscular power, anaerobic capacity, maximal oxygen uptake (VO2 max), and lactate threshold. Coaches can use specialized programs such as Training Peaks WKO4 to see where you're strongest and weakest.

W/Kg is relatively straightforward to improve.

Increase your power output while keeping your weight constant.

Keep your power output constant while decreasing your weight.

Increase your power output while also decreasing your weight.

Identify the best approach and develop a plan to properly integrate the training and lifestyle changes necessary to achieve your goal. By focusing on areas where you need improvement, you can begin to train those systems accordingly. If you want to be a great sprinter, 1-minute power will be necessary. If long climbs are your goal, work on 5-minute and threshold power efforts.

Weight Loss

Weight is power. Every rider will have an improved power-to-weight ratio by optimizing their weight. The gains are immediate, and you will observe an increase in your w/kg. For most riders, this is often the best approach to improving this metric. However, this should be approached cautiously, as dropping too much weight will negatively affect your health and performance. Finding a balance is essential.

Strength Training

When cyclists think about getting stronger, most think about riding longer and harder. However, one of the best ways to get stronger is to spend time in the gym. Strength training focuses on the fundamental cycling muscles (quadriceps, hamstrings, glutes, and calves). You will boost muscle efficiency and prevent muscle loss, especially during periods of high-volume training or during periods of weight loss.

Heart Rate

Although power is a more precise way to train on your bicycle, heart rate still matters. Your heart rate and response to certain powers and thresholds can tell how your body uses energy. Heart rate can indicate if you are dehydrated or overtrained and under-recovered.

Cadence

Cadence is the number of times you turn the pedals. Power is directly related to cadence: the higher your cadence, the higher your power. Allen Lim once told me there are two ways to increase your power: Increasing the actual force on the pedal or increasing the number of times the pedal turns per minute. If you ride with a power meter, you'll notice that it feels easier when you increase your cadence initially, but your power increases. This is because you do not produce the same force in each pedal stroke. Riders often increase cadence early in a race to save their energy for the end of the race.

I hope you understand more about what your power meter tells you and how it relates to cycling. Metaphorically, using a power meter removes some of the allure of riding a bicycle. Above all, riding bikes is a beautiful practice of human ingenuity, and using a power meter helps guide your journey.

An interesting fact: Power meters are popular in the U.S., but in European countries, power meters are used by pros and much less by amateurs.