Every fitness device promises to help you get in shape by measuring and understanding your activity data, but can trackers actually help you become a healthier person? I strapped on eight different devices and apps and set out to learn everything I could about my body while taking a jog. My mile-and-a-half run up New York City's west side was tracked by RunKeeper, S Health Walking Mate, Fitbit Flex, Fitbit Zip, Withings Pulse, Jawbone Up, Nike+ Fuelband, and the Scosche MyTrek (which has been replaced with the Scosche Rhythm).

Most of these fitness trackers are designed for all-day use, so they didn't have any special features that provide feedback during the run. The three exceptions were the RunKeeper app, which is only designed for workout tracking, the Scosche MyTrek heart rate monitor, and the Withings Pulse, which provides both run time and distance. RunKeeper shows plenty of useful information such as time, pace, distance, and splits, but jogging with a smartphone is annoying — that's why the dedicated devices exist in the first place. My iPhone arm strap was uncomfortable and made quick screen glances awkward, but was still superior to the phone bouncing around in my pocket. The Pulse was a little easier to manage, but didn't show me all the information I really wanted, like run time or current pace.

Both the Scosche MyTrek and the Withings Pulse measure heart rate, which is the key to differentiating between fat-burning and aerobic workouts. The MyTrek app, like RunKeeper, has an app that shows real-time information, but I wish there was a display on the actual device. I wanted to know whether I should slow down or speed up while exercising, and viewing a chart of my heart rate history after the run didn't help me make that decision. Likewise, the Pulse's post-workout heart rate measurement only gives a snapshot of information rather than helping make important decisions in the moment.

The bracelets I wore — the Jawbone Up, Fitbit Flex, and Nike+ FuelBand — were comfortable at first but became less so as I started to sweat. They're all completely useless during a run, with only the FuelBand displaying any information at all — limited information like time and daily Fuel point levels. The information is a little more useful after a jog, where I could view activity levels within certain time parameters, but there is still no real delineation between "running" and "taking a lot of steps."

The same is true for both the Fitbit Zip and the S Health Walking Mate app, which are the two most basic services I took on my run. Like the bracelets, the value comes post-run, and even then it's not very useful. An increased activity level in your step history is the only thing that represents the run.

The Withings Pulse was a little better, automatically detecting that I was running and displaying both the total run time and distance. But digging around in a pocket or messing with a belt clip is a pain while you're running, and holding the tiny tracker still enough to look at while running is a feat itself.

All the services clocked roughly the same amount of steps for the run. The S4 counted the least number of steps at 2,526, followed by the 2,535 steps counted by the Jawbone Up. The Pulse and the Fitbit Zip were nearly identical, with 2,539 and 2,540 counted steps, with the Fitbit Flex somehow measuring five more at 2,545. The run earned me 590 Nike+ Fuel points, which is about a fifth of the recommended activity for an active day.

What I really wanted was some meaning to all the data collection. Lifelogging devices fail when it comes to making meaning of individual workouts, and devices geared towards marathon runners fail to account for any activity beyond training. By design, RunKeeper was the best service to use, but it knows nothing about my previous night's sleep or the food I ate that morning. Is today's run easier because I got an extra hour of sleep last night, or am I just unknowingly running slower than usual? Maybe I walked double my usual amount of steps yesterday, which is why my legs feel more sore after the workout today. This is the type of information that will help me improve as a runner, and there's not yet any service that ties everything together.

There's a missing link between lifelogging and tracking individual workout sessions. Daily trackers are good at giving a view of a person's overall activity, but it's up to other services to give any real meaning to actual exercise. I need a device or app that learns my daily habits and can understand how exercise fits into the big picture. Understanding how my life impacts workouts and how my workouts impact life is the key to building the ideal tracker.

For now, I'm going to stick with a combination of two devices: the RunKeeper app for run tracking and coaching and the Fitbit Zip for an overall sense of my daily activity levels. Although the perfect service doesn't yet exist, today's trackers tell us more about our daily lives than ever before. We'll have plenty of data to process while we're waiting for the product that pulls everything together.