Posted by: hagengreen | January 17, 2010

Accuracy Drives Motivation

I started getting serious into road cycling in 2002. While I loved to just get out and ride, it’s nice to put numbers to what I was doing. Especially for a left-brainer. So I did what most cyclists do: buy a computer. The first computer I bought was a $20 no-name brand that gives you speed and a couple odometers. I must admit: I chose a computer that matched the dark blue color of my frame. But the device got me only so far, especially when I wanted to up the ante on my training intensity and volume. I made a relatively large investment in enabling measureable progress by going with the peloton leader at the time: Finland’s Polar and their 720i cyclocomputer watch. The accompanying Polar Performance software was a nicely done complement to the watch which allowed me to visually track and archive my progress. The watch had a reasonable capacity, holding roughly 20 hours of data (with a 15 second sampling rate). I used that watch for nearly 5 years. One of the biggest gripes with the watch is common radio interference that artificially inflated or deflated speed or heart rate numbers – and it’s substantial. I may be going 20 mph and it’ll report 4 or 58mph. I often wondered if the mix of slow and fast ultimately averaged out. The other gripe was the rigidity of the heart rate monitor (HRM). It’s constructed of a hard plastic that isn’t malleable, even when warmed up. I don’t think my chest is any more rounded than the next guy, yet I felt like I had to tighten the strap more than necessary to maintain good contact. After one battery change and 5 years, I put it on the shelf. It’s replacement: Garmin Forerunner 305.

I could go on for several pages debating the pros and cons of a cyclocomputer such as the Polar watch vs the Garmin GPS. The obvious differences are size, battery life, memory, and location tracking. You can imagine I didn’t hesitate to dump the Polar 720i after getting the Garmin. I thought it was the most amazing thing to have a GPS unit on your wrist. It’s something our ancestors would consider magic. Little did I know I’d come right back to the Polar about 4 years later…

The Garmin was absolutely instrumental in my running endeavors. It’s amazingly powerful to have (nearly) instantaneous pace and distance measurements. Moreover, I could program complex workouts such as this: warm-up for 15 minutes, wait until lap button pressed, run for 3 minutes at 85% max HR, run for 2 minutes with no target HR, run for 2 miles at 6:00 min/mile, wait 2 minutes… you get the picture. And the coolest part about all this is you can program these workouts using the watch alone! Thanks in part to this Garmin, I placed in the top 250 in the 2007 Boston.

The GPS thing is very cool, but a few things pushed me back over to the Polar specifically for cycling. The biggest one was accuracy – but it may not be what you’re thinking. When I turn on the watch, it takes anywhere from 20 seconds to 3 minutes to lock with satellites. Worse, if you just take off when the watch hasn’t locked, as I do nearly every morning, it could take 5 to 10 minutes longer. More often than not I’m at least 2 miles into my ride when it finally gets going. That means the watch doesn’t know I’ve travelled the last few miles. Since 90% of my yearly mileage is riding to and from work, I really didn’t need to know where I’m riding. I just care how far. This is where the Polar wins big. The Polar uses a wheel-mounted magnet and fork-mounted wireless sensor to calculate speed which then informs distance. As such, you lose nary a foot or two between starts and stops. Sure, the tire pressure affects the distance the bike travels per wheel rotation, but I check my pressure daily and adjust as necessary.

The other issue with the Garmin GPS watch is the battery life. I used to get nearly a week and a half with it. Well, the battery recently took a dive. That’s what happens over time, despite the solid Li-Ion battery. Now I’m lucky to get half of its original life. It gets worse: the watch doesn’t give an early heads up on low battery. In the beginning, the watch would tell me low battery and I’d have nearly 3 hours left. No joke. These days the thing tells me low battery and it’s gone within 5 minutes. Many of times it’s conked out mid-ride. Sad to say, but my Garmin has lost my trust. At least on the bike.

My goal this year is to account for all of my cycling mileage and feel good about a big number. I might guesstimate how many gallons of gas and CO2 I saved, but those are secondary in nature. I’m just happy knowing I rode more miles than I drove. Now I’ll use my trusty ‘ol Polar to track the mileage.

The lesson here is newer isn’t always better, or, put another way, older can be better. I never thought I’d see the Polar again. In fact, I put it on Craigslist several times with no hits. I was asking too much, I admit it. But I thought it deserved more than people were willing to pay. Sometimes the old way to do something is better… in the name of accuracy.

Polar S720i heart rate ...... – Garmin Forerunner 305

The Polar 720i, left, and the Garmin Forerunner 305.

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