Features | Accessories

Heart rate monitors

By far the most common GPS watch accessory – and something worth considering even if you think you might not use it right away – are heart rate monitors. They’re a fantastic way to measure the intensity of your workout. You can use this information to push yourself harder or slower depending on the type of run you are doing. Additionally, once you determine your max heart rate, you can calibrate heart rate zones, which can be programmed on most watches, ensuring you exercise at the right intensity.

Using a heart rate monitor also ensures that variables like weather and terrain are factored into your workout. When it’s hot and humid, your heart rate will naturally be higher as your body can’t efficiently cool itself. A heart rate monitor helps prevent overexertion by displaying the true intensity (i.e. your heart rate) of your workout.

HRM-Run (Garmin Heart Rate Monitor)

Garmin’s specialized heart rate monitor has been designed specifically for use with Garmin’s new running watch, the Forerunner 620.

The HRM-Run includes an accelerometer which allows the Forerunner 620 to track new data such as vertical oscillation, ground contact, and cadence.

Wrist-based Heart Rate Monitors

Three watches – the Garmin Forerunner 225 and Forerunner 235, and the TomTom Runner Cardio – have come out recently with the ability to track heart rate without the use of a chest strap.

Traditional heart rate monitors rely on electric signals received directly from the heart and picked up by the device attached to the chest strap. Wrist-based heart rate monitors use an optical light-sensor to see blood pumping through your skin.

While the appeal of no longer wearing a chest strap might cause runners to rejoice, there are a few issues to note.

First, a wrist-based heart rate monitor won’t be as accurate as a chest strap HRM. Think of the wrist-based heart rate as a ballpark figure while the chest strap as highly accurate. There have also been reported issues of tattoos or dark skin interfering with the optics on the wrist-based HRM. But this seems to vary on a case by case basis.

Foot Pod (running accessory)

This small, pill-shaped accessory does two things: it acts as a substitute for GPS when running on a treadmill or out of satellite range (like in a tunnel) and it counts foot turnover to determine cadence. When calibrated, it’s actually fairly accurate. And given that short-stride, fast turnover is now widely considered proper running form, tracking cadence ensures you’re maintaining a quick stride.

Speed & Cadence Sensor (bike accessory)

Found on nearly half of the watches made today, this accessory is mounted on your bike and works in a manner similar to traditional bike computers: it counts wheel rotations to determine speed and distance. The cadence half of the sensor counts the number of pedal rotations.

While most watches support one sensor that tracks both speed and cadence, Suunto’s Ambit as well as some of the older Polar watches, require two sensors: one for speed and a second for cadence.

Power Meter (bike accessory)

While the bike cadence sensor tracks how fast you spin the pedals, it can’t tell you how much energy you are expending to do so. A power meter displays energy usage in real-time while you crank the pedals. This is a fairly advanced and very costly (think thousands, not hundreds, of dollars) accessory, so it’s not surprising that only the most advanced GPS watches support this.

Quick-release Mount

Coming out of triathletes’ desire to use one watch for both running and cycling, the quick-release mount allows you to quickly remove the watch from your wrist band and mount it on your bicycle (or vice versa). Mounting the watch on your bike makes it much more readable (rather than twisting your arm if it’s on your wrist). A workaround is to attach the entire watch, band and all, onto your handlebars with this nifty accessory. But that can get cumbersome, especially if you are in the middle of a triathlon and want an easy, fast transition.

Battery Extender Pack (Magellan accessory)

Available on both the Switch and Switch Up, the GPS watch battery is removable, allowing you to purchase an extender pack and swap batteries mid-activity. A nice feature if you’re doing something that will outlast a single charge.

Strap Extender

Offered with the Garmin Forerunner 610 and 910xt, the strap extender expands the watch band length, good if you want to wear the watch over a jacket during colder months.

Temperature Sensor (Garmin accessory)

Offered with the Garmin fenix, the temperature sensor is worn externally, giving an accurate reading of the outside temperature. While a few other watches have a built-in temperature sensor, the external sensor is more accurate as it isn’t skewed by body temperature.