Do you really need a power meter?
If you have a hectic lifestyle with limited time & want to take the guesswork out of your training, then the answer is an emphatic YES!
No longer the preserve of pros, and amateurs with far too much money to spare, power meters are now an essential training aid for any serious rider.
Investing in a decent power meter allows you to focus on improving specific areas of performance.
A major benefit of training with power is that it allows you to accurately track your progress throughout the season.
Regularly testing your functional threshold power – the highest average power you can sustain for an hour – allows you to adjust your training zones as you progress. Without tracking your progress in this way it’s easy to stagnate, meaning you’ll never reach your true potential.
Setting training zones for power will also allow you to focus on specific parts of your performance, making every second in each session count towards a measurable goal. If you’re a sprinter, for example, it’s easy to dial in your training to target peak power output.
There are an abundance of power meters on the market. This can make choosing the right one for you a bit of a headache. But, luckily, there are options out there for all needs and budgets.
Types of Power Meters
Through the use of an electronic device, called a strain gauge, power meters measure the force that your mighty pistons (or tired old legs) are putting through the drivetrain. Your actual power output, in watts, is then derived from these raw measurements. This is then displayed on your head unit (e.g. Garmin device).
There are several key areas on a bike where you can place a power meter, each with distinct advantages and disadvantages:
- Pedals (either one or both)
- Bottom bracket
- Crank arms (either one or both)
- Rear wheel hub
Arguably the most popular type of meter, the major advantage of a pedal-based system is the ease at which they can be swapped across bikes. There are a few major companies which produce this type of meter, including Garmin (Vector) and Powertap (P1).
The accuracy of pedal-based meters is somewhat disputed compared to some other types, but they’re definitely worth a look.
They’re available as either a single or dual pedal system, and some of the more advanced meters even analyze your pedal stroke.
A potential downside is that pedal based meters are very exposed, meaning that they can easily be damaged due a crash or during transport. There’s also the fact that you may need to switch your cleats.
These are generally regarded to be very accurate and easy to maintain. A big drawback, however, is that it makes moving the meter between bikes hugely impractical. These means it would either have to stay on your racing bike or your training bike. A bit of a pain of you want to both train and race with a power meter.
The use of this type of meter is also restricted by compatibility. Your bike will need to take the correct type of bottom bracket.
Similarly to pedal-based systems, crank mounted meters can be relatively easy to swap between bikes. Not quite as simple as swapping pedals, due to possible compatibility issues, but it’s good to have the option. Also, like pedals, they can be both single or dual sided.
The makers of crankarm-based meters claim that they’re more accurate than other systems, but the jury is still out on this. Measurements from the crank-based Stages power meter, for example, are fairly consistent with pedal and hub meters such as Powertap and Garmin Vector respectively.
Crank-based systems have come down in price a fair bit in recent years, making them a good option for those on a budget. The Stages power meter is definitely worth a look, and they’ve got a good range of options to suit your current set-up.
It’s particularly easy if you’re currently using a Shimano crankset. Stages simply send you a replacement crankarm, power meter attached, and you swap your existing one out. Simple. Pioneer is another good option and provides similar compatibility options.
The only company with a rear hub meter on the market is currently Powertap, meaning it must be a fairly tricky one to get right. The rear hub takes a huge amount of force during a ride, soaking up bumps and dirt from the road. Powertap’s G3 offering is very reliable, however, and is widely considered to give a very accurate power reader.
Hub-based meters are by far the easiest to switch between bikes. The only issue is that to have a power reading whilst racing, you’d have to use the same wheels as when you train.
As power meters increase in popularity, more and more companies are coming up with imaginative new designs. An example being the Velocomp PowerPod. This interesting entry into the market sits just beneath your handlebars and measures the forces working against you, particularly air resistance.
This doesn’t sound like it would work, but anecdotal evidence suggests that it gives pretty accurate readings when compared to other power meters.
The main issue is that it won’t work on an indoor trainer. It is, however, very easy to switch between bikes. Probably the cheapest meter on the market, it’s certainly an option for the budget-conscious.
Power Meter Metrics
If you’re used to training solely with heart rate, or even no data at all, it can be difficult to understand the wealth of new metrics that a power meter will provide.
Functional Threshold Power (FTP)
The single most important thing to do once you’re fully set up is conduct an FTP test. This will be the baseline from which you will plan all of your training sessions; it allows you to set training zones tailored to your current level of fitness. FTP is basically the highest wattage you can produce for an hour. It’s a simple 20 minute test and all you need is an indoor training or 20 minute section of flattish road.
Normalized vs. Average Power
Whilst average power is fairly self-explanatory, the term ‘normalized power output’ can be confusing to newbies.
Simply put, normalized power estimates the physiological effort you put into a ride. As an example, let’s think of 2 very different races: a 10-mile time trial and a crit race. While power output for a time trial is likely to be fairly consistent, making average power very useful, a crit race will involve huge efforts often followed by coasting.
You’re likely to feel just as exhausted after both races, but average power in a TT is likely to be far greater. This makes the use of average power pretty useless for something like a crit race.
Normalized power comes in useful here. It’s basically a formula which smooths out the power readings to give a reading similar to if the effort was consistent the entire time. In the example of a crit race, this means that the sprints pretty much cancel out time spent coasting; this allows a reading similar to your FTP.
Normalized power, therefore, would give similar readings for both a one hour TT and a one hour crit race; this provides a much better idea of the effort put into a race, and how long it’s going to take to recovery.
Intensity Factor (IF)
This is the ratio of normalized power to your functional threshold power. IF gives a valid and convenient way of comparing the relative intensity of a given session or race either within or between riders. It helps gauge performance over the course of a season without the need for more FTP testing as the season progresses.
Training Stress Score (TSS)
TSS uses your power data to give a stress score for each workout you do. Knowing how much stress you are putting on your body helps with planning sessions and, more importantly, helps avoid overtraining. Your analysis software, such as Training Peaks, can also give a cumulative weekly and monthly TSS score; this helps to work out just how hard you should work your body for maximum performance gains.
With the huge wealth of data offered by power meters and analysis software, it’s easy to get overwhelmed. There’s plenty out there to help you make sense of it all, however. If you’re really serious about improving, then getting help from a qualified coach might be a good option.
Cateye/4iii Precision Power Meter
On a budget but still want to join the power meter party? Take a serious look that the 4iii from Cateye.
On the lower end of the price spectrum, the 4iii has been gaining ground recently within the cycling community. It’s a left-side only, crankarm based power meter. There are 2 options for getting your very own 4iii.
You can purchase it with a new crankarm or, alternatively, send off your existing crankarm to the company; they’ll then attach the pod and send it all back to you. Strangely, there doesn’t actually appear to be any price difference between these two options. The 4iii is very easy to fit, depending slightly on the crankarm manufacturer. Shimano is apparently particularly simple and quick.
The whole power meter pod adds only an additional 9g to your cranks, which is practically negligible; there isn’t a power meter on the market lighter than this.
Of course, there’s little use in having a power meter if it doesn’t accurately measure your power output. The manufacturer claims an accuracy of +/- 1%, which is pretty damn accurate if true. It’s difficult to verify this, but tests against PowerTap P1 pedals and the Tacx Neo direct drive turbo trainer give pretty similar power readings to the 4iii.
However, it seems that at higher outputs the readings become less accurate and actually differ a fair bit. This shouldn’t be much of a concern, however, as anything below a sprinting power levels has pretty decent accuracy.
Since the 4iii measure left leg power only, it is possible that this is where the inaccuracies at higher power outputs lies. The system will basically just measure your left legs power and double it to provide a power output.
This means that anyone with a slight imbalance in their legs could have less accurate results. Of course, a 1% difference between legs means a larger inaccuracy in power readings at high intensity that at low intensity. This is an issue with any one-sided meter, however, and certainly shouldn’t put you off the 4iii.
Imbalanced? The 4ii’s correction system can help
As a solution to the imbalance issue mentions above, the 4iii provides a correction system to help improve the accuracy readings. Essentially, if you know the intensity of your imbalance, you can a scale factor to automatically correct its measurements.
Amongst left-side only meters, this is a unique selling point for the 4iii. Obviously, this relies on the user knowing which leg is more powerful and by how much. It’s also worth noting that the imbalance may be more or less prominent depending on intensity.
4iii do actually make a dual sided unit (Precision Pro), but it’s vastly more expensive.
The 4iii is a great piece of equipment for the price. It gives accurate readings when compared to more established power meters. Slightly inaccurate readings at high intensities may put some people off, but the correction system goes a long way to address this issue.
All-in-all, it’s definitely worth taking a look at the 4iii if you’re anxious to get into the power meter game, but budget conscious.