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system may give you more options for head units. Many wireless systems use what’s called “ANT+” technology. This is a type of wireless communication between the handlebar computer and the power-measuring device in the crank, bottom bracket, pedal, or rear hub. It’s becoming a common standard. Any ANT+ power head unit can be used with any power meter that is ANT+ compatible, which allows you to choose a handlebar display and user interface without changing system types. You’ll need to check the user’s manual for your power meter to see what type of communication method it uses.
    One of the main differences among head units is the amount of information they can show you at one time. Some have simple displays with only three data fields shown, while others show up to eight data fields all at the same time. Many head units allow you to customize the display. This is a great feature you should consider when purchasing a new head unit. Some head units are touch screens, while others rely on buttons for the interface.Minidisplay technology has even led to a wristwatch version from Garmin, which is ANT+ compatible and displays power meter data along with run data. It’s also waterproof for swimming, which makes it a good choice if you are a triathlete as all bike and run data are captured in one place.
    Regardless of all these options, here are the most common items displayed by power meter head units. Not all head units use the same display abbreviations I’ll use here, so you may need to consult the user guide that came with yours.
Power
    This is the most basic information you need from your head unit. If you can customize the display to put the fields on your head unit wherever you want, be sure to place the current or instantaneous power display (often called “WATTS” or “PWR”) in a prominent place, such as upper left, so that you can see it at a glance while riding. You’ll be referring to this field more than any other.
Heart Rate
    Just because you have a power meter doesn’t mean you are going to forget about your heart rate. It’s still quite valuable information. In Chapter 6 I’ll teach you how to compare power and heart rate to accurately gauge changes in aerobic fitness. Again, if you can customize your screen display on the head unit, I’d suggest putting the “HR” readout next to power so that they can be easily seen and compared.
Duration
    In addition to intensity (WATTS and HR), the other critical component of each workout is duration, or how long the ride was. This should also bedisplayed prominently on your head unit. You may be able to select either “TIME” or “MILES” (or perhaps “KM,” for kilometers) for this field. There may even be other options, such as kiloJoules (“KJ”), that I’ll explain later in this chapter. I prefer to use the TIME setting as I believe that is more valuable information when compared with power than is distance. For example, as you’ll see later, intervals are usually designed based on time, not distance. And the length of time you can hold a specified power output is closely related to a given time, not a given distance. But if you want to set this field for distance and like to think in such terms about your ride duration, I won’t argue with you.
Cadence
    When I coach athletes who frequently use a gear I consider too high for the situation, such as climbing a hill or sprinting, and I think they could perform better in a lower gear with a higher cadence, then I recommend they set up the head unit with cadence (“RPM” or “CAD”) prominently displayed. If this doesn’t seem to be an issue for you, then you might want to use the next available field for other data.
Altitude
    Climbing a hill is one of the major challenges of riding a bike for all athletes. Most ANT+ head units allow you to monitor climbing by setting a field to display altitude changes in feet or meters (“ALT FT” or “ALT MT”). You may even have the option to set up