Last September, Apple introduced its Watch Series 6 with the slogan “The future of health is on your wrist.”
But although the Apple Watch is certainly attractive, it's not the GPS watch for most serious athletes, because it doesn't have the battery life. Apple claims the Watch Series 6 can deliver seven hours of battery life in GPS mode, but unless you're Jim Walmsley, that's not going to be enough to get you to the finish line of a 100km ultramarathon.
The big names in the GPS-for-endurance-sport game are Polar, Suunto, Garmin and Coros, all of which produce a high-quality watch. In fact, I have owned watches from all those companies, albeit over a 25-year period, starting with Polar, and moving to Suunto, then Garmin, and finally Coros.
The watches themselves provide pretty much the same functionality, depending on how much you're willing to pay. What's interesting and useful to athletes is the data the watches can collect and present to you either on your wrist, in an off-watch app, or exported to a third-party app such as Strava, RunKeeper, MapMyRun or one of the shoe company apps such as Nike+ Run Club or adidas Runtastic.
What data do these watches deliver? Well, as soon as you press "stop" to finish your workout you can know your time, pace, distance, heart rate, and elevation gain.
Once you've exported your data to an app, there is so much more data you can attain. You can review your pace in kilometer (or mile) increments, which can show you if you perhaps started too quickly and paid a price toward the end. You can see your stride cadence, which also can show you if you may have started too quickly, but in addition can show if you may need to improve your leg strength e.g. most runners slow down at the end of a marathon not because they're winded, but because their muscles are not working as efficiently as at the start. Other data features include power and intensity measurements on estimates and an assessment of how much rest you (may) need before your next workout.
Everyone's physiology is different, of course, and the real value of fitness data comes after you've recorded enough of it within your chosen fitness application to establish benchmarks that are relevant to you.
The fitness apps and watches know this, and they're happy to help you "gamify" your training. Strava famously lets users demarcate "segments" e.g. Rifle Range Road, MacRitchie Reservoir Loop, Bedok Reservoir, etc, which allows you to measure your progress against yourself and your friends and even enemies! This can also potentially turn every workout into a competition even if is only against yourself but be careful not to overdo it to avoid training overload or possible injury.
The final piece of the running data puzzle brings us back to Apple and its health and wellness focus. Many running watches and apps monitor your heart rate, and the Apple Watch has sensors that can detect atrial fibrillation, an irregular heartbeat that can be deadly if not properly managed. Many watches now incorporate pulse oximeters that can monitor your blood oxygen levels. As with power and intensity measurements, the accuracy of this wrist-collected data is pretty good.
If you're not currently a GPS watch user you may be wondering about the accuracy of GPS tracking. There is a lot of comparative data on the Internet, but the big four GPS watch makers – Polar, Suunto, Garmin and Coros, and let's throw Apple in there as well – do a fine job of showing you where you ran and how fast. Some manufacturers go farther – the Coros Apex includes a pretty cool "Track Mode" that significantly increases the accuracy of recorded track workouts by ‘snapping’ to the track and even a specific lane.
One area in which not all watches are equal is battery life. The Apple Watch Series 6 can deliver seven hours of battery life in GPS mode. If you're running 10Ks, that's fine. If you're running marathons, and remember to charge your watch before the start, that's fine.
But if you're a member of the fast-growing ultramarathon community, battery life is probably the single most important feature you want to consider in buying a GPS watch. There are a number of factors that affect battery life (most manufacturers have a long-life mode that records fewer GPS data points), and with most manufacturers, the more you pay, the more battery life you get.
Garmin's top-of-the-line Fenix 6 claims up to 25 hours in full GPS mode. Garmin's Forerunner 945, more of a pure running watch, claims up to 36 hours.
The mid-range 46mm Coros Apex claims up to 35 hours in GPS mode, and the top-of-the-line Coros Vertix claims an eye-popping 60 hours.
Both the Garmin and Coros watches offer much longer battery life if you go into long-life mode. The Coros Apex will last up to 100 hours, and needs to be recharged only around once a month.
Back in the day before GPS watches, heart rate monitors and power meters, there were stopwatches and surveyors’ wheels, used for measuring courses. After each workout runners could look at their times and ask themselves how we felt. Today it’s easy to immerse yourself in metrics (and obsess about them), but it’s important to keep the data in perspective, to ask yourself how you felt afterwards or during the training.
If you struggled through a workout that yielded indifferent performance data, it’s probably time to take a recovery day. Or two. And yes, your watch may suggest this to you as well, but remember, your watch doesn’t know how you actually feel. Not yet anyway.