Looking for a new watch to gauge your fitness? Monitoring you pace, distance and cadence with respect to your heart rate is the path you want to take, but which measure is the best, a GPS or a foot pod?
The answer is . . . It depends! If you are like me, your running can’t be easily categorized into one box. During any given week, I’ll be doing a 20 mile mountain run with 6,000ft of vertical gain, 800 meter repeats on the track and everything else in between.
The different technologies available all have their strengths and weaknesses. The good news is they are all super accurate when used appropriately!
Let’s start with accelerometers or foot pods as they are known. These prune size devices attach to your shoelaces or in the case of the Suunto Ambit, are built into the watch itself. A foot pod is so tiny and light, you will forget it’s there once it’s on your shoe.
Out of the box, the unit needs to be calibrated to your stride. A moderate run over a known distance gives you a calibration number, which is set into the watch. Quick and easy, but don’t forget to do it or blow it off, it is super important!
How accurate is a foot pod? I calibrate mine by running a mile at about an 8 min/mile pace. Using that calibration number, I’ve found footpods to be amazingly accurate at paces from sub-6 to13 min/mi. trots. A typical backyard trail run for me is 10 miles with 4-5 hundred feet of vertical and varying paces. Over that distance, the footpod will be +/- .03 miles difference from a GPS measurement. The real time paces that the foot pod generates achieve GPS like accuracy as well, and they tend to not jump around wildly like you sometimes see with a satellite-based watch. Cadence, a metric that you cannot get with any other device, is also spot on. Foot pods are a great choice as well if you find yourself running in places where your watch can’t see satellites . . . densely treed forests, steep canyon trails or skyscraper laden boulevards.
With all this awesome accuracy, why even bother to use a GPS? First of all, foot pod numbers are great, but without a GPS, you don’t get to check out all the cool maps of your adventures generated after you get home. You also miss out on satellite-based altitude information, which can often tell you more about the difficulty of the run than any distance measure . . . vertical gain is tough!
Rugged trail running with lots of ups and downs is the arena where foot pods really lose their gloss. During a 10-mile trail run with 2500ft of ups and downs, your pace, cadence and stride length will vary wildly. Steep down hills can easy bring your cadence up to 120 while the ups can slow your pace to 30 minute miles in the blink of an eye. The pre-programmed calibration number you set on your watch just can’t handle these swings. You will still get your cadence measurements, but your distance and speed accuracy will drop off considerably.
Thankfully, this type of terrain is where GPS steps up. In addition to cool mapping features, a GPS watch can give you super accurate distance measurements in difficult terrain. Additionally, GPS watches find great distance accuracy in easy terrain close to home!
Pacing accuracy with a GPS, I’ve found, can vary. While average pace over time is usually very good, real time pace at running speed can vary +/- 15 seconds per mile. Not much in the big picture, but try telling that to someone who missed a 10K PR by 5 seconds with her eyes glued to her wrist! If you want perfect pace measurement, it’s time to head to the track with your stopwatch.
If GPS is so great, why not pull the trigger on a satellite based watch? Well, most people don’t need a 3D, Google Earth map of their daily run. It is just plain overkill, and a foot pod will do just fine. Additionally, GPS watches tend to be bulkier, more expensive and short on battery life . . . factors that steal from the soul of the simplicity of running.
So what’s the answer, GPS or footpod? The answer remains . . . It depends! YOU need to decide what type of runner you are, what your needs and desires are and go from there. For me the best solution is using both a GPS and an accelerometer. I like to utilize each device where it works best and using them together covers all of their individual weaknesses.
Remember, the most important lesson a new watch can teach is how to listen to your own body. The numbers do not really mean much until you correlate them with your gut feelings on the run.
John Yarington is on a quest to set free his inner 9 year-old. And he’s starting by playing outside with his friends ALL DAY LONG. Unlike your classic tri-athlete, a dream multi-sport day for John might include 20 miles of mountain running, a scuba dive with hammerhead sharks and a sunset walk with a cold glass of chocolate milk.
John loves to mix it up in the mountains. His recent adventures include ski mountaineering The Grand Teton, a one-day 27 mile, 8000+ ft ascent of Montana’s Granite Peak, summiting Illimani, the highest point in Bolivia’s Cordillera Real at 21,122 ft. and sharing a 10,000 ft. backcountry ski day with his wife and #1 adventure partner, D.
Have fun out there,