Power meter for bike

Until the early 1980s, with the advent of "modern" cycling, no suitable method had been found to verify performance on a bicycle in training or racing; athletes still relied on laboratory tests. This forced athletes to be divided between their actual performance data on the bike and that of the laboratory ergometer. With these laboratory tests, it was not possible to determine how an athlete's performance could change in training or racing; these tests actually represented only a snapshot of the athlete's current state at the time of the laboratory test itself.

Who invented the bicycle power meter? 

In 1986, German biomedical engineer Ulrich Schoberer, after many attempts and experiments, succeeded in the feat of measuring an athlete's power for the first time outside a laboratory in training/racing conditions.

Since then, the use of the pedal power meter has begun in professional cycling, both in training and in race pace management. Even in the amateur world, there is a movement in this direction with the advent of products increasingly accessible to all.

And how to measure power on a bike? Power meters rely on the principle of the strain gauge, a measuring instrument that detects deformations. Mechanical power is measured through the deformation of a body subjected to stress. The constant deformation of these calibrated parts allows the system to measure the torque (in N.m).

The measurement of angular velocity depends on the component in which the power meter is integrated. Thus, in the crankset or in the pedals corresponds to the cadence of the pedal stroke while in the hub corresponds to the rotational speed of the rear wheel.

It is possible to find a power meter in almost all components of the bicycle: hub, crankset, crank arms, pedals, bottom bracket, or chainrings.
Each choice has advantages and disadvantages, let's see them together: 

1. Power meter in the crankset: 

It was the first strain gauge system to be introduced, it is one of the most widespread and approved on the market but also the most expensive. This model measures the force near the point of pressure. Advances in this field allow for improvements in shape, compatibility, component weight, energy optimization, and durability. With the new generation electronic groups on the market, there is also a hybrid product: the system directly integrated into the chainrings allows the use of one's own crankset by integrating the chainrings at a competitive price.

2. Crank arm with power meter:

Sold as the most accessible, it can be less accurate in some cases if the power meter is only located on the left crank arm; however, the power generated by each leg can be different. One may be stronger and the other more fatigued (e.g. 48/52% split) or vice versa, and this phenomenon can become more pronounced with fatigue. The ratio also varies depending on the type of effort (flat/climb) and cadence. Thus, a sensor that only measures the left leg obtains the final value by multiplying the obtained measurement by two without taking into account these possible variations.

3. Power meter in the hub

The power meter in the rear wheel hub is one of the first to have been scientifically approved. It is useful when using multiple bikes because it easily transfers from one to another. Some teams have used it to assess the potential of cyclists. The disadvantage is that with this system, the wheel is tied to a single profile without the possibility of changing it.

4. Pedals with power meter

This power meter has several advantages: the measurement is made as close as possible to the power generated by the cyclist, and the system allows for the measurement of each leg (left/right). The dissociated measurement allows for precise analysis of the pedaling stroke. The cyclist can thus work on their pedaling and improve their technique. The power meter on the pedal axle can be easily and quickly moved to all bikes and is suitable for those with multiple bicycles.

Training with a power meter has become an increasingly common practice among amateurs.
To start a journey with various power meters, it is essential to undergo a test to assess the cyclist's "engine" together with a coach, in order to have a starting point to work on and to create a training plan.

The test should be conducted using one's own power meter (or if using the same product as the coach) to avoid marking errors. Each power meter is "calibrated" by the manufacturer according to its own standard, so doing a test with two different products could yield very different results and compromise training. The power meter provides a vast amount of data, and to optimize one’s training, it is essential to know how to interpret this data and, above all, to know what personal references to base oneself on. 

1- The first thing to do is to calculate the FTP (Functional Threshold Power) and from there the reference training zones. Additionally, the average wattage expressed on a climb or during a training session makes little sense if not parameterized with the athlete's weight. Tackling a 20-minute climb at 300 watts has a different value for a 60 kg athlete and one who weighs 80 kg.


2 - To make the most of your power meter, it is advisable to have some precautions.

• First of all, it is necessary to regularly perform calibration. The best practice would be to calibrate the device at the beginning of each training session or at least once a week to ensure maximum accuracy. The calibration process varies from device to device, but it usually takes just a few seconds.
• Another very important aspect, as with all electronic “devices”, is to periodically check for updates that can improve the functionality of the bike power meter and resolve any “bugs”. Each power meter usually has its own management app from which you can check and install updates.

3 - Those approaching the power meter for the first time might start by using the average power over 10 seconds. Power is a data point that is practically impossible to manage because it is subject to sudden variations, even of tens of watts. The most correct value to display on your cycling computer for training without going crazy is the average power over 3 seconds. In practice, this is the average power value expressed over the last 3 seconds and is much more stable than instantaneous power. While it is true that power is a more precise and objective value, it is important, at least occasionally, to “cross-reference” power data with heart rate data.

Today, the market offers a wide variety of power meters, but at Ciclimattio you will find the right expertise to choose the meter that suits you best! 
Among the power meters integrated into the crankset, SRM Origin PM9 is the flagship product, the best system, the most expensive and the most scientific. These products are the direct descendants of the first prototypes from the 1980s, those chosen by many professionals to assess their performance.
Regarding measurement in the pedals, we cannot fail to mention the Favero Assioma Duo and the Garmin Rally.

Finally, major manufacturers such as Shimano and SRAM incorporate bike power meters into the groups they launch on the market.