Constant sitting in a mostly unhealthy posture – that's what I feel in my everyday office life. I often have back pain accordingly. What can I do against it? Before I change jobs, I test the Posture PC 100 Control posture trainer from 8sense by Beurer.

Behind the bulky name is a sensor that is clipped to the neck of a sweater, t-shirt or shirt in the neck area. From there, he is supposed to record micro-movements himself using body scanning and algorithms. If I sit in one position for too long, the wearable emits a vibration. This tells me that I should change my seating position. In the app I can look at more precise measurements.

8sense: back health in the neck

Before I can use the sensor, which I call 8sense for the sake of simplicity, I have to charge it. To do this, I plug the posture trainer into the supplied USB charging adapter or use the USB extension cable. When charging, the LED on the 8sense lights up orange. When the light goes out, the sensor is charged and ready for use.

The sensor measures 60 x 25 x 7.2 millimeters, which is about the size of a thumb and weighs 14 grams. That sounds like a little, but I also feel this light weight after I clipped the 8sense onto the collar. Or actually on the t-shirt under my sweater. It is winter and too cold for a shirt, I only put one on for the photos.

Since the sensor is attached to the T-shirt under my sweater, it hangs a little lower. I still get feedback. The only difficulty: If I lean on, the 8sense can switch off because it reacts to pressure. But that only happened two or three times during the test.

Speaking of switching on and off: According to the tutorial in the associated 8sense app, the sensor only needs to be pressed for a second to switch it on. However, that was not enough in the test. I had to press hard for longer until it turned on. I already thought that the battery gave up when I couldn't start the sensor right away.

And promptly recharged it. Unnecessary, as it turned out. Long press and firmly, and the 8sense comes to life. The same applies to switching off. I can read the battery level in the settings of the manufacturer app, as I unfortunately only noticed after a few days … And the battery easily lasts for five days.

App sensitizes to seating position

To use all functions of the posture sensor, the already mentioned 8sense app is necessary. The application provides an introduction to how harmful lack of exercise and too much sitting are. And I learn that sitting is not just sitting. Above all, it is the long stay in a sitting position that damages the back. Ideally, you change position and posture more frequently and move regularly in between. Let's see if 8sense can motivate me to do it. There is also a feed called "Better Knowledge" in the app. It provides helpful tutorials on the sensor and the structure of the spine, as well as so-called mobilizing exercises to imitate.

So that the sensor does its job, I still have to calibrate it. To do this, I clamp the 8sense in the middle of the back of my T-shirt. I start the calibration in the app. I am asked to sit straight on the chair, have to hold still for a few seconds – and it is already over. I have to repeat the calibration every day so that the sensor takes correct measurements.

Good vibrations? 8sense in everyday tests

As soon as I put the clip into operation, I feel the first vibration. From now on, 8sense always vibrates if I haven't moved for more than ten minutes. Since I do not really know whether it is enough to just sit down a little differently, I open the app. She gives me a recommendation: "Time for exercise! Get up and take a few steps." Since I have just sat down at the desk, I don't really want to get up straight away. But I obey the coach and briefly disappear into the kitchen. The sensor notices that, after the little trip I read in the app: "The movement was good for you". Good to know.

The application also analyzes my sitting behavior. 8sense breaks down my movements according to upright phases, reclined phases and steps taken. My first insight: there is a lot more movement when sitting in the game than I thought. The second insight: it is still not enough. In my office fitness score, I barely get over 50 percent. The app attests to me exhaustion, which would affect my productivity and back health. I would not have assessed the situation as dramatically. But it motivates me to take the app's suggestions to heart.

Back mobilization in the open-plan office

And then the sensor vibrates again. This time I should mobilize my back. The application also has the right exercise ready. I am supposed to stretch my back muscles by stretching my arms up and leaning left and right for 30 seconds each. The clip directly records how well this works. The only irritating thing is that he perceives left as right and vice versa. I clipped the clip to the outside as requested by the manufacturer. Anyway, I attach the 8sense with the clip inside. This makes me feel the sensor more on the skin.

What bothers me a bit: I had to carry out the aforementioned mobilization exercise in the open-plan office. The colleagues only looked up briefly and then went back to their screens, but the action was uncomfortable for me. The posture challenge offered in the app is much less noticeable. The challenge: sitting upright and straight for five, ten or fifteen minutes. According to the app, this is the healthiest posture for the back. Sounds simple, it is at the beginning. But holding out for five minutes at a time is exhausting. And all mistakes are recorded live in the app. Needless to say, I couldn't get past the five minutes.

Office fitness: exhausted to tight-fitting

Back to the office fitness score: it rates my sitting behavior on a scale of 0 to 100 percent. With and without 8sense. For example, in one day my normal fitness is almost 50 percent (still in the area of exhaustion), shown in blue on the scale. Using 8sense increases my fitness to 68 percent, the difference is highlighted in orange.

The app attests to my good, confident sitting behavior with room for improvement. Office fitness can go up or down throughout the day, depending on how much or how little I exercise. It is not entirely clear what the application determines, how 8sense affects it. Probably based on my direct physical reactions to vibrations and following the instructions.

Shock-like biofeedback

According to the operating instructions, the vibration is gentle – unfortunately an understatement. For one thing, the vibrations are so loud that my colleagues in meetings thought I had my cell phone with me. Subtly different. On the other hand, the posture trainer is not visually noticeable because it disappears on the T-shirt under the sweater. The vibrations on the back didn't usually bother me, but I would not classify them as gentle. Unfortunately, there is no option in the app to attenuate the vibrations.

And so the sensor regularly pulls me out of my work. Especially since the vibrations are followed by a look at the smartphone. If this bothers you in the long run, you can deactivate this biofeedback in the app. However, I doubt whether you will regularly look into the application on your own initiative and check your seating behavior.

History? Wrong!

I usually leave the sensor on during the lunch break. 8sense rewards me for the fact that I exercise a lot during the break: My office fitness status is then over 80 percent, so I'm full of energy. I can't keep the level for long. "Sit straight", "sit back", "get water", "visit the coffee machine" – the app has countless suggestions to inspire me to exercise. But what happens to me when I was testing Garmin's seat sensor happens: After a few days, I start to ignore the sensor, maybe look at the suggestions in the app from time to time, but follow them less and less.

What I miss most about motivation: I can not see the progress of my office fitness. Although it is shown to me in real time in the app, there is no history or trends about how it develops from day to day or week to week. It was different with Garmin's seat sensor that I tested two years ago. And the competitor has another advantage: the Garmin sensor is attached to the chair instead of on the body. You get messages directly on the screen. So you are not startled by vibrations and do not always have to look at your phone. Both of them got me out of rhythm one time or another when I was working.

Conclusion: Better on paper than in practice

The Posture PC 100 Control posture trainer from 8sense by Beurer actually succeeds in moving the rigid everyday sitting situation with instructions, exercises and posture challenges. The use of 8sense was exciting in the first few days and motivated me to exercise more. It's hard to say whether I had less back pain during the test. The posture sensor certainly didn't harm me.

However, I found it awkward to have to recalibrate the sensor every day. The vibrations and the following look into the app have repeatedly torn me out of my working rhythm. I think the idea behind 8sense is good and important, but due to the weaknesses mentioned, the posture trainer is not ideal for everyday work. For me, Garmin's seat sensor is the better alternative.

I enjoyed that	I didn't like it that much
+ easy to use	– excessive vibration
+ motivates you to exercise more	– Look in the app distracts
+ clearly structured app	– no trends shown
+ Battery lasts at least one working week