The Apple Watch will be released in only a few weeks now, and the hype surrounding it is only growing. For health purposes, the watch is aiming to be a revolutionary in the way its tracking technology operates, as it consolidates the amount of time you’ve spent standing, moving, and exercising with your fitness goals — of course, heart rate, blood sugar, and calories burned are included in this. All of this will be included in the Apple Watch’s HealthKit, but how did the company develop the technology? It used it’s own employees.

Apple recently granted an exclusive interview to ABC’s Good Morning America, in which it showed Rebecca Jarvis the back-alley lab where it tested all sorts of health measures. Essentially, the lab is just a high-tech gym, full of treadmills, rowing machines, and yoga space. For two years, Apple employees have been hitting the gym decked out in instruments meant to measure everything from how heavy they’re breathing to their heart rate, all with the intention of improving HealthKit. The creepiest part: None of them were told what they were working out for. Nevertheless, they all seemed to be in good spirits.

The Apple Watch was originally intended to have sensors capable of tracking stress levels, blood pressure, and heart activity, similar to the way a polygraph test and electrocardiogram work. However, the sensors had problems working on people with hairy arms or dry skin. Whether or not the watch will work better than current fitness trackers on the market without these functions remains to be seen.