What Is A Power Meter?
One of the best things you can invest in for your bike is a power meter, however, there’s a lot more you’ll have to do than just buying it as it’s essentially useless without the knowledge on how to interpret it and what it’s telling you about your cycling.
A power meter on a bicycle measures the power delivered by the cyclist. Most bicycle power meters use strain gauges to measure applied torque and, when combined with angular speed, calculate power.
Power meters generally transmit wireless data and can be paired with standard bicycle computers. They provide instant feedback to the athlete and allow for a more accurate analysis of the rider’s sessions and races making them extremely popular among professional cyclists.
The use of a pedaling power meter has been used in professional cycling for years, both in training and in managing the rhythm of the race. Even in the amateur world, albeit more slowly, they’re becoming more popular however, they’re still pretty pricey which is probably the reason they haven’t quite entered the mainstream market for amateurs.
While power meters are much more affordable than they were 20-30 years ago they still don’t come cheap so you’re going to want to know every detail and how it relates to your cycling, from pedal stroke to sports physiology.
Why Use A Power Meter?
Most training systems only allow you to measure your body’s response to the work so the actual amount of work you perform can only be summed up with an estimate. When power is measured, total work can be measured and the rate of work.
This gives a more concrete baseline for comparisons both in the past and looking forward. While heart rate and your own perceived exertion is the best way to measure your body’s response, power measurement is the best way to measure intensity and work. Most notably, having a constant measure of power can help an athlete to:
- Establish their benchmark fitness level
- Precisely measure even the slightest fitness gain
- Accurately quantify their intensity, duration, and frequency
- Prevent overexertion
- Accurately measure energy use for nutrition planning.
- Pace themselves effectively for events.
So, the main reason you’ve purchased a power meter is to measure certain stats and properly innovate your routine and cycling method to improve your power output and other key factors. Now, let’s get into what these metrics you’ll see on your power meter actually mean.
Power is the rate at which energy is used and is measured in watts. In cycling, energy is expressed in terms of work. This can be the amount of work put in to climb a steep incline for example. It’s the building block from which all power-based training flows. There are different variations of the power statistic but the core meaning is your power input and output while riding.
Power to Weight Ratio
Winning at cycling has a lot to do with your power to weight ratio or “watts per kilogram”. Power equals the amount of work divided by time into simple terms, and on a bicycle that’s how hard you pedal multiplied by how fast you pedal.
You propel your body and your bike down the road battling counter forces like wind resistance. But, the biggest counter force is you, or your mass. So, to put it simply, if you decrease your mass and increase your wattage, you’ll go faster.
Average power probably won’t be on your home screen, but it will be a feature and it’s worth using when analyzing your cycling regiment. It’s as simple as it sounds. The average of your power output throughout the whole ride.
Functional Threshold Power
There’s a sustainable output that applies to each individual athlete, this is the Functional Threshold Power or FTP.
FTP is the amount of wattage a rider can sustainably produce for an hour. This is the easiest way to judge an individual’s cycling ability. It’s less important in short-range, sprint events, such as track or BMX where events are only 200-1200m. However, since this is something of a niche, the vast majority of you should know your FTP.
How to calculate your FTP: You can estimate FTP with your best recent 20-minute power value, then multiply that value by 95% to get your FTP.
So, as an example:
- Your average power for a 20-minute ride is 280w.
- 280w would be 100% of your power so to find 5% divide it by 100 to get 1%.
- This gives you 2.8. Then multiply this by 5 to get 14 which is 5%.
- So 14 is 5% of 280, now subtract this from your 280 which results in 266.
- 266 is 95% and your FTP.
Now it may seem odd to measure it in 20-minute intervals if FTP is your 60 min best wattage for a time trial but there is a logical reason for this. Unfortunately completing a 60 min time trial isn’t something we can all do without collapsing to the ground and gasping for air.
So, using the 20 min test and deducting 5% is much easier, and is relatively accurate bar a few percentage points. Of course, if you do have power numbers from a 60 min TT such as from a race, that’s even better and you’ll have a much more precise reading of your FTP.
You now have your FTP and can see what your longer-duration abilities are. But if you’re a rider that doesn’t compete in long trials, instead opting for short-distance you might be thinking is FTP important for me?
Well, yes of course.
Your FTP is the starting point around which you will base your future training. When going on shorter time trials you might find yourself whizzing away as fast as you can and putting in maximal efforts but only being able to maintain that force power for a minute or two. The more intense the effort, the shorter you can hold it. And alternatively, the less intense the effort, the longer you can maintain it.
This is again where your FTP comes into the picture. This effort is 100%. Efforts below FTP are sustainable for longer and longer periods of time as the intensity decreases away from FTP. 120% of FTP is hard but maintainable for shorter than an hour.
It’s true that power is a more precise measurement of training but that doesn’t mean you should give up on heart rate (HR). This is your body’s response to the work. And it’s a good way to tell how you feel.
Let’s say you go ride, and you feel awful on a climb; your heart rate spikes but your power isn’t representative of what you normally achieve. The human body is great at giving warnings as to when something is amiss and so it could show you’ve overtrained or sick.
An unusually high HR signals that something’s not right and so training that day won’t be very productive in which case it’s better to rest. Likewise, a low resting heart rate will indicate that you are fully recovered from the last workout, so you can get back to riding.
If you’re trying to lose weight, then kilojoules (KJ) are one measurement to focus on, but our bodies burn a different ratio of fat to carbs at different exercise intensities, so it’s not entirely straightforward. This is where the power meter comes in as it keeps you honest about how much work you actually did, and how much fuel you actually need to power that workout.
What You Should Know About Power Meters
Power meters have become very popular in recent years, especially for cyclists and this popularity is only increasing due to the drop in cycling power meter prices.
Using a power meter, a cyclist can get instant feedback and measurements by way of a handlebar-mounted computer, which can display the power output a cyclist is producing at any given moment as well as provide average power data over time. A key aspect of power measurement is that power produced is unaffected by hills, wind, terrain, or other environmental factors.
As with anything, power meters have their disadvantages and it’s important you know what you’re in store for before you take the plunge and get one.
- Although becoming cheaper, accurate power meters for cyclists are still expensive and most will set you back a few hundred dollars at the least.
- As fitness levels change, your sustainable power outputs will change considerably, which means that you’ll need to recheck your power output/blood lactate concentration regularly, especially if you’re a relative novice or are returning from a layoff, which is when large fitness changes can occur in a relatively short timescale.
One thing worth keeping in mind is not to use a power meter to limit yourself. Many riders fall under the age-old curse and become slaves to the number which makes the power meter their worst enemy, regularly telling them that they’re slow, tired, or just flat that day.
Be sure to learn your body and its limits by feeling out the efforts internally as well as learning to use your power meter. Use the data both objectively and subjectively and above all else, take it with a pinch of salt. It should be a guideline, not an answer book.
Frequently Asked Questions
Will a power meter improve my cycling?
A power meter is a great tool for every cyclist and triathlete. It teaches you how to ride stronger, more consistently and allows for tracking, planning, and training with a specific focus on your unique needs and goals. However, it requires a lot of effort to be put in and an understanding of how it works and how it can be applied to your cycling. Luckily, we’ve explained everything you need above.
How do you monitor power on a bike?
A crank-based power meter is a simple addition to your bike. All you do is put a new crank arm on one side of your bike, and it will measure the power.
Why is power important in cycling?
You need power to overcome air resistance and other forces such as gravity. Power will propel you forward on your bike. There is also a small amount of friction to overcome, both in the bike and between the bike and the road. Power will help you overcome this and go faster when battling more difficult terrain such as inclines and declines.
It’s worth saying that power meters aren’t going to make you faster. All the best athletes push beyond what they are supposed to be able to do. If you learn how to use your power meter to measure cadence, kilojoules, power output values, and other factors you can get on track to improving how much power you produce while doing long-distance and even sprint-cycling.
While they may be expensive, power meters are a fantastic accessory for your bike and will make a difference if you use them right. So, if you want to take cycling to the next level then get one. You won’t regret it. Just bear in mind that it requires effort to get the most out of your force power meter.
So, good luck with your training, whether it’s with a power meter or without, and most of all…