Dual vs. Single: A Survey of Power Meters

Power meters can be segmented into two types, single-sided and dual-sided. This can also be considered single-leg or dual-leg. I would typically recommend dual-sided power meters over single-sided.

The landscape of power meters is bumpy, but can be put into one of two categories. Find out which is right for you.

Hunter Allen of Peaks Coaching Group recently updated one of his articles about power meters. This is a MUST READ for those that are considering purchasing a power meter – or, should I say dual-power meters. 

A power meter is generally defined as a tool that measures the power you are producing while riding a bike, via strain gauges coupled with other electronics. Essentially, as you pedal, you are applying a torque along the drive-train. This torque bends or deflects components such as crank-arms, crank spider, crank spindle, pedals and rear hub. Power meter companies place strain gauges on their chosen component and measure the force you are applying. This force is then calculated against how fast you are pedaling to compute the number of watts you are producing.

One is Fine, Two Can Be Divine

Power meters can be segmented into two types, single-sided and dual-sided. This can also be considered single-leg or dual-leg. I would typically recommend dual-sided power meters over single-sided. Most riders I fit initially show a 60%/40% imbalance between legs, typically in favor of their dominant leg. And, herein lies the problem with single sided power meters.

Single Leg Failings

Let’s say our hypothetical rider produces exactly 300 watts average power. Factoring the previous example of a 60%-40% discrepancy between the output of the legs, we can infer the dominant leg produces 180w and the non-dominant leg, a reduced outputs of 120w.

If our rider were to use a single-leg power meter, whichever leg is being measured would be multiplied by 2 and displayed as the power output. This can be problematic.

If the measurement were being taken at the dominant leg, our hypothetical rider would show a value of 360 watts (180w x 2). This value overstates the riders’ power, and when coupled with a training program calibrated against this inflated value, over-training would occur.

On the other side of things, if the measurement is taken of the non-dominant leg, it will understate the riders power. Training plans using the deflated value would lead to a lack of improvement due to under-training.

Because there is no way to know the differential between your dominant and non-dominant legs without measuring each individually, using a single-leg power meter would lead to training using wrong numbers and leaving you not getting the gains you are working so hard for.

A dual-sided power meter solves this issue by showing you the leg imbalance. In addition, the two-leg solution serves as a tool to train towards more equalized power output between legs, the ideal in terms of efficiency and fit.

Side profile of a PowerTap P2 pedal that integrates the technology needed to measure power in the pedal itself. Pedal-based power meters provide the ideal, dual-sided measuring allowing for more accurate measurements.

Edge Case

Though dual-sided pedal-based power meters are a great option for many riders, I do not recommend them for criterium races. The components in the sensing pedals typically increase the pedal stance or make the pedal ‘thicker’. Both scenarios increase the chance of clipping the pedal on the ground when pedaling through a corner. For the rest of us, pedal-type dual-sided power meters will work well for your training goals.

What Else Can I Use?

Leomo Type-R is a motion capture and analysis system which can indicate why you have an imbalance.

As a coach, I can send you off do perform a workout based on a training plan. When you use a power meter, I can tell what power you output. With the Leomo Type-R, I can tell how you output that power.

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