By Rick Schultz
Hunter Allen of Peaks Coaching Group recently updated one of his articles located at https://shoppeaks.com/balance-an-introduction-to-left-right-power-data/.
This is a must read for those that are considering purchasing a power meter – or, should I say dual-power meters. Please read the article first, then read my reply to my clients that ask me which power meter should I buy?
What Is A Power Meter?
We’ve covered this in previous articles, but, in short, a power meter measures the power you are producing via strain gauges coupled with other electronics. Essentially, as you pedal, you are applying a torque along the drivetrain. This torque bends or deflects components such as crankarms, 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 multiply by how fast you are pedaling and the manufacturer can then determine the number of watts you are producing.
Which Power Meter Should I Buy?
Power meters are divided into 2 main categories
- Single-Sided vs Dual Sided (or single-leg vs dual-leg)
- Location of Power Meters – hub, pedal, crank (spider), crank spindle, crankarm, chainring
I always recommend dual-sided power meters over single-sided, which I will explain below. For location, it’s more of personal preference. For example, I do not recommend pedal-based power meters for criterium racers, because a power meter in the pedal will either increase the pedal stance or make the pedal “thicker.” This increases the chance of clipping the pedal on the ground when pedaling through a corner. For the rest of us, any of the dual-sided power meters will work fine.
Why Do I Need A Dual-Sided Power Meter?
As a USA Cycling coach with Peaks Coaching Group and Master Bike Fitter, I test cyclists performance, efficiency and effectiveness. Most cyclists I test are initially 60%-40%, which usually leans in favor of their dominant leg, but not always. And, herein lies the problem with single sided power meters.
Let’s say the cyclist has tested at 300w FTP (nice round number). For this example, 60%-40% = 180w-120w.
A single sided power meter that measures left side power takes this power, multiplies by 2 and sends the data to the head unit.
Again, 300w FTP. If your strong leg is
- Left leg, then 180w x 2 = 360w. You will be over training if you use 360w.
- Right leg, then 120w x 2 = 240w. You will be undertraining if you use 240w.
Since you don’t know what you don’t know, you won’t know of your 60%-40% differential. You will continue to train using wrong numbers and won’t know why you are not getting the gains you are working so hard for.
Dual-Sided Power Meters
A dual sided power meter will help you by (a) showing you this imbalance, and (b) reminding you of this imbalance so you can mentally and physically train to mitigate this imbalance.
What Else Can I Use to See if I have an Imbalance?
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.
I would say there are three types: Single sided, total power and dual sided. Hub, chain ring and spider power meters measure total power, but have to make assumptions to separate left and right power (pulling up power is included in the other leg, and hubs probably can’t even do that). Only dual pedal and dual sided crank arm power meters are true dual sided and measure each leg separately.
This article assumes that you didn’t do you FTP test on a single sided power meter (located on the same side as the one on your bike). The same thing happens to my clients when they test there FTP indoors on there smart trainer and used the power coming from the trainer as their FTP. They then go out and train on the road using the power meter on your bike which usually gives them different results. If you are going to train based on FTP then you need to do your test on the same equipment that you use for training. That may mean that you need to have an indoor FTP and outdoor FTP. If you have multiple bikes with separate power meters (i.e. TT and Road bike) than you may have another FTP baseline.
One of the great features of the CompuTrainer was the ability to have power output presented visually. Using this feature, you could see the “shape” of power output for 360° of your stroke. Using this indoors, you could train yourself to essentially balance your power output between your left and right leg. The idea was to make the power output resemble a circle. I could never achieve that goal, especially at high power levels (I’m in my 70’s and that translates to an FTP of 240), but I could make pretty good ovals. By practicing this way, when I used my Stages Single Sided power meter, I knew I was fairly accurate with switching between the two for indoor and outdoor riding. I could achieve a power output balance (according to CompuTrainer) that varied between 48% to 52% for each leg. I would like to see some of the current indoor trainers providing the same ability. It is the only feature that I do not find on my current indoor trainer (Kickr Snap) that I have on the CompuTrainer.
Wrong point of view, with what instrument the rider was tested for FTP?