Power meters are becoming more and more relevant in cycling. Even people without one are more familiar with power numbers today than ever before.
Some Stock bikes are equipped with a power meter nowadays, indeed.
There are a bunch of good reasons to use power as the prime metric to quantify training. Undoubtedly, access to power revolutionized the way cyclists train.
When looking at training stress two things stand out: Duration and intensity. Duration is easy, it’s about how long you ride. You just need something to measure time. The letter is a little tricky. With measuring intensity, or how hard you ride, the power meter comes into play.
Let’s look at the value a power meter provides. A good way to do this is to look at alternatives first. Then we can look at how to use power in training and racing. And finally, I give you my recommendations on which power meters to choose.
Here’s to the common alternatives: perceived exertion and heart rate.
The Inner Power Meter
Perceived exertion is simply how hard you feel like you’re going – and drum roll… our internal power meter, behind our eyes, can be fairly inaccurate.
A study done on cyclists’ starting strategy and performance came to a similar conclusion. Subjects had 3-time trials (TT) to ride: The first one with a self-selected pace. The second one with the first 4 minutes at 15% below self-selected pace and the third one with the first 4 minutes with 15% above self-selected pace.
The findings were clear. When cyclists started with a slower pace, they were able to produce more power afterward, resulting in a faster time overall compared to the self-selected pace and fast start. Because they started too hard, overshooting is inevitable.
You find a similar pattern in races. People start too hard and later blow up. If you don’t use a power meter, the same can be said for interval sessions or segments. Because we are really bad at assessing what is doable.
You may think let’s use heart rate instead. However, even heart rate isn’t solving the problem…
The Problem with Heart Rate
The issue is that, unlike power, heart rate doesn’t adjust quickly for how hard you’re going. For example, when doing threshold intervals it may take a couple of minutes to reach the threshold heart rate. This makes it alluring to start too hard.
Of course, you can assume which zone you’re in during a long ride but good luck doing so for short intervals, climbs, or a time trial.
Using heart rate even to tell which zone you’re in can be difficult. Because heart rate is highly variable and affected by a lot of different factors. Some coming out of training and some not coming out of training at all. A study found that even a change in position at a given exercise intensity may affect heart rate. But of more importance is the increase of heart rate over time, called “cardiac drift.” This is even more common at higher temperatures or altitudes.
Even exposure to the cold gives us a lower heart rate, think riding outside in winter. And also as we get older heart rate decreases. Cycling wattage may be a better indicator for measuring intensity.
Therefore, training with heart rate is questionable. For example, 140 beats per minute (bpm) on a hot day may differ from a cold day. Keep that in mind when comparing winter heart rate with that of summer.
Even when conditions are the same, heart rate may not be the preferred option. When a study observed pro cyclists during stage racing to compare power zones with heart rate zones, they found the data didn’t match. Heart rate measurements underestimated time spent in Zones 1 and 3 and overestimated time spent in Zone 2, in a 3 Zone model.
Even though heart rate is better than perceived exertion, it has a lot of issues in measuring exercise intensity.
With a power meter, however, that’s a thing of the past.
The Benefits of a Power Meter
The great advantage of power is that it’s immediate. The moment you push the pedals, you see how hard you’re going. This is invaluable for pacing intervals, climbs, tts, or other solo efforts.
You can assess if you’re going too hard the second you start, instead of waiting minutes for your heart rate to adjust. And as you get more familiar with the power you get better at pacing. If you know you can get up a 20-minute climb at 280 watts, maybe don’t start that climb with 330 watts. Honestly, you will thank yourself 10 minutes into the climb.
One team that mastered this strategy to win Grand Tours is Team Sky (today Ineos). What they knew was that the fastest way up the climb was a consistent effort. No attack could break their train. Some even blame the power meter for Team Sky’s success.
That is because power is not variable as heart rate is. Power doesn’t care if your sleep is bad. If you soaked up way too much coffee. If it’s hot or cold outside. If you’re fatigued. A power meter simply shows you the output for that day.
Even bad days are reflected by your power meter. If you want to go for intervals, but your power is not there, probably rest and wait till the next day.
With that, It’s time to combine power and heart rate. I know I bashed a lot about heart rate, but I hope you didn’t burn your heart rate sensor yet. The combination of both can be effective in monitoring fatigue and overtraining. Let’s talk about the study of changing position and heart rate again. This study found that during overtraining maximum heart rate and sub-max may be decreased, while the sleeping-heart rate may be increased.
Something to keep in mind, when training with power and heart rate: If your heart rate is lower for the same power, you may need rest. Sure, after a hard block of training a lower heart rate is okay, but having it day after day is usually a bad sign.
Tracking Training Progress with a Power Meter
Power is superior in tracking improvement. There’s no single metric that can keep up. With a power meter, training sessions can be planned and tracked precisely.
While many riders try to look at their favorite loop or segment to track growth, the problem is how environmental conditions can affect speed: Temperature, humidity, and wind can all affect how fast you go at that segment. For example, if you go for a 10k segment during winter compared to summer you would ride more than half a minute faster during summer. Assuming you improved, when power is the same for both attempts.
If you then went on to compare the average speeds of different segments, you compare apples to oranges. Because elevation is mixed up with riding surfaces.
But with power, you can track improvement for any duration. See, just because you improved your 20-minute power doesn’t mean you improved your 1-minute power or your 2 hours power. It’s the power that enables you to focus on specific durations.
So, these are all reasons to get a power meter. Hopefully, you own one or are thinking about getting one. Because here are my recommendations.
Which Power Meter to Choose?
Let’s be honest, aero wheels, carbon frames, or aero bars are all great gadgets. But your biggest reserve capacity is a power meter. A power meter should be the first upgrade to make to your bike if you’re serious about cycling performance. I mean if you know how to use it. If not, don’t worry, read here about how to analyze power data.
That being said, today we’re overflowing with all kinds of power meters, which can be a little overwhelming of which one to choose.
As a bike racer and cycling coach I used and saw different power meters that give me a good idea of what to look for. And the two things you are looking for are reliability and accuracy. You don’t want a power meter that gives you wrong numbers all the time or that stops working right in an interval session.
My recommendation for a crank-based power meter is the FSA Powerbox. The accuracy with +/- 2% matches with the best on the market at a very fair price. There are inner bearings available for almost every frame. I saw the FSA Powerbox crank in many athletes and I never heard of any issue. And with the standard battery being a CR2032, it’s available in almost every grocery store.
The only downside of a crank-based power meter is flexibility. Especially, when you want to switch between bikes. Pedal-based power meters, however, solve this issue. With many options available today, I suggest the Favero Assioma pedals. They’re extremely accurate (+/- 1%), lightweight and rechargeable. And you get all this for a fair price. I have used them for two seasons now and didn’t experience any issues so far. This is in line with the reviews Favero gets.
If you’re serious about training I recommend choosing the Duo option. Because many riders have a disbalance in the amount of power they can produce with each leg. This is nothing to worry about, but it will affect the accuracy of the power meter if riding with a single-sided option.
Here are the links for my recommendations (these are no sponsored links as I just hope to help you out):
Favero Assioma – https://cycling.favero.com/
You can reject power meters, blame them and talk yourself out, but there’s no denying that a power meter is the most important upgrade for your bike.
Impact of Starting Strategy on Cycling Performance: https://www.researchgate.net/publication/11834285_Impact_of_Starting_Strategy_on_Cycling_Performance
Heart rate monitoring during training and competition in cyclists: https://pubmed.ncbi.nlm.nih.gov/22587722/
The Effects of Cold-Water Immersion on Power Output and Heart Rate in Elite Cyclists: https://www.researchgate.net/publication/11043623_The_Effects_of_Cold-Water_Immersion_on_Power_Output_and_Heart_Rate_in_Elite_Cyclists
Age-Related Changes in Maximal Power and Maximal Heart Rate Recorded during a Ramped Test in 114 Cyclists Age 15–73 Years: https://www.researchgate.net/publication/8053955_Age-Related_Changes_in_Maximal_Power_and_Maximal_Heart_Rate_Recorded_during_a_Ramped_Test_in_114_Cyclists_Age_15-73_Years
Power Output during Stage Racing in Professional Road Cycling: https://www.researchgate.net/publication/7376641_Power_Output_during_Stage_Racing_in_Professional_Road_Cycling