Ask any ultrarunner for his or her biggest complaint about GPS units, and you’re likely to get the following answers:
1) The unit is too large or bulky
2) The battery life is too short
3) The satellite signal doesn’t track consistently
4) They’re too expensive
So if you heard there was a speed and distance monitor that 1) was the same size as a wristwatch, 2) Had the battery life of a normal watch, 3) was unaffected by satellite signals, tracking under the heaviest tree cover or in the deepest canyons, and 4) costs about 100 dollars … wouldn’t you be excited to try something like that out?
That’s exactly how I felt when I received a TrailLeader 2 watch to review.
The TrailLeader 2 is made by a company called Tech4O (pronounced tech-four-oh), and is one notch below the top of the line – there is a more expensive model that also incorporates heart rate data – in their series of performance watches. The speed and distance data is obtained not by GPS, but by an internal accelerometer.
Prior to owning this watch, I didn’t even know there was such a thing as an accelerometer – it sounded like some kind of make-believe gadget from an old cartoon, like Spacely Sprockets or Mr Peabody’s Wayback Machine. But it turns out that accelerometers actually exist, so I turned to my local science geek for a brief lesson. I asked him to explain to me, in the simplest terms possible, how an accelerometer works.
Here is part of his reply:
The accelerometer works by measuring acceleration in x, y, z axes. A good analogy is driving in your car: when you accelerate forward (the x direction) you are pushed into your seat. As long as you are accelerating, you stay pushed into the seat. When you reach constant velocity, you feel no more push. When someone smashes into the side of the car, you suddenly accelerate to the side (the y direction) and you feel pushed toward the side of the impact. In an airplane, you feel similar forces in the z direction as the plane lifts and drops.
A force transducer in your seat could measure your acceleration in these directions. The vector of these forces describes your net motion. If you know how long you accelerated in all three directions, you can calculate your position at any moment.
The watch is just like your car, and the internal workings are like a little man being thrown around as your arm swings. The little man's calculation would be something like: "I felt N newtons in my X sensor for S seconds, therefore I am now moving 6 minutes per mile forward (it doesn't know north or east, just its starting point with coordinates 0,0,0). Until I feel another force, I know that I am still moving forward at this pace. Now I feel another acceleration of N newtons in the X sensor for S seconds, so I know that I am now moving at 5:30mi/min. But now I feel a force of N newtons on the Y sensor, so I know that I have deflected to the left. Now I feel N newtons on the negative X sensor, so I know that I have slowed down..." etc....
If the accelerometer knows its mass accurately, it knows its acceleration simply from the force it feels. More simply, at constant velocity, the watch feels motionless. But any change in velocity can be tracked, therefore the watch can keep track of its position in x,y,z space. If you plot x, y, z often, you get a good estimate of distance traveled, the time it took, and therefore pace.
So, um … there you go. Be thankful I didn’t ask for the complicated version.
As for the watch itself - it’s packed full of features that seem tailor made for ultrarunners: speed, distance, pace, barometric altimeter (including change in elevation and net climb and/or descent), digital compass, barometer and temperature readings. This is in addition to all of the normal watch features you’d get in a Timex.
The TrailLeader doesn’t interface with computer software, so if you’re someone who likes making maps and graphs of every single workout, you’re out of luck. Personally, I’ve never been too interested in plugging my workouts into a computer program, so it’s no big loss. The simplicity is also a major factor in keeping the price point low: the list price on the Tech4O website is $150, but on the same page is a coupon code offering $50 off – so you can have all of these features for 100 bucks. To my knowledge, there isn’t a reputable GPS in the world that sells for anything close to that.
Since the accelerometer doesn’t rely on on satellites, it’s not dependent on overhead clearance for accuracy. It doesn’t even matter if you’re actually moving – in theory, you could run 5 miles on a treadmill in the basement of your health club, and the accelerometer would record the distance. (On the flip side, if you rode your bike 100 miles in your aerobars, the accelerometer would read zero, since your arm wasn’t swinging).
Another huge advantage over most GPS watches is the battery life. All of the functions operate with the standard wristwatch battery, which runs continuously and never needs to be recharged. Therefore, you can use it for 50-mile, 100K, or other events that would normally drain a 10-hour GPS battery. (There’s one quirky caveat to this, though: according to the user’s manual, the speed/distance measure automatically resets at midnight – so if you’re doing a 100-miler, you’d have to check the distance at 11:59 and remember to add it to whatever you start accumulating at 12:01. No, I haven’t tested this specific situation.)
The TrailLeader 2 is also a decent looking contraption, and not much larger than a standard sports watch. I’m stealing a photo from Rainmaker (who also reviewed the TrailLeader 2 a few months back) of a Timex watch, TrailLeader 2, Garmin 405, and Garmin 305 to show a size comparison:
On your wrist, it doesn’t feel that much different than a sleek Ironman wristwatch. So far, everything sounds great, right? Let’s get to the drawbacks:
The primary frustration I’ve had in using this watch is the reliability of the speed/distance function. In addition to the internal accelerometer, the watch utilizes a pedometer to calculate distance. You don’t attach anything to your shoe; instead, you program separate values for your walking step length and running step length. There is a link on the website with instructions on how to do this, and it only takes a few minutes. However, in the months that I’ve used it, I find that the accuracy seems to vary in different circumstances, depending on what type of running you’re doing.
At the track, after some tinkering with the stride length, the accelerometer was accurate to within a few hundredths of a mile. It was on the trails that I started having difficulty.
Like most ultrarunners, I vary my pace quite a bit during a typical trail run, as much of the terrain I encounter includes very steep climbing. One of my regular climbs features about 1800’ of elevation gain in less than 3 miles; the slope is so steep in places that I alternate walking and jogging throughout the climb. Invariably, by the time I reach the top of the hill, the accelerometer’s distance is off, and not just by a little bit – sometimes by as much as two-tenths per mile.
My hypothesis is that there are two primary sources of error: 1) my stride length when jogging up a steep hill isn’t the same as my stride length when calibrating the watch on a flat surface, and 2) although there are different values for walking step length and running step length, the watch doesn’t bounce back and forth between the two modes in perfect rhythm with my actual movements. There may be a delay in switching from one value to another, or a very slow jog might be measured as walking.
Since almost all of my running is on trails like this, I’ve adjusted the stride length values one notch lower or higher about 100 times, then seeing if the distance numbers came close to a GPS reading. Here’s how determined I was to make it work: on several runs, I wore both my accelerometer and a GPS, and recalibrated every one or two miles. (Yes, I looked like an idiot. Thank God I do most of my running in the dark.) To my enormous frustration, I could never get the numbers to jive when there was a combination of running and walking.
I managed to get the numbers accurate for runs on rolling terrain, or where I could keep a fairly constant pace – say, only varying one or two minutes per minutes per mile instead of five or ten. In those circumstances, I found the accelerometer to be reliable for runs of more than 10 miles.
There are a few other downsides, but they’re relatively minor in comparison to the distance issue – so I’ll wrap this review up with a quick summary:
* Compact size, comfortable to wear
* Multiple functions for outdoor data gathering
* No need to recharge battery; no battery drain for ultra-duration activity
* VERY affordable
* Accelerometer technology works in all conditions, not satellite dependent.
* Accurate when running or walking at relatively consistent pace
* Stride length may need to be recalibrated a few times during initial use
* Inaccurate when running/walking with great variability in speed
* Since the accelerometer is useless for measuring cycling distance, the watch can’t be used for bike/run transition workouts.
* No uploading of workouts to your computer.
The TrailLeader 2 certainly presents an intriguing option for runners or hikers who are looking for an affordable alternative to using GPS devices on the trail. I would recommend it to anyone who just wants a general idea of the mileage they’re covering along with time, temperature, and elevation data. I wish the technology were a bit more refined to address the distance discrepancies I found; perhaps a future generation of this line will do a better job.
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