This site advertised a vertical jump number until August 2026. It is gone, and it is gone because we did the arithmetic and it does not work from an arm.
There are two ways to get jump height out of this pod. The air pressure sensor is one. A 40 cm jump changes the pressure at the sensor by about 4.7 pascals. Raising your arm over your head without jumping changes it by about 3.9. Swinging the arm through the air at 5 metres per second changes it by about 15. Two of the three things that look like a jump are the arm itself, and they happen at the same moment as the jump, so no filter separates them. Opening a gym door is worth about 50.
The motion sensor is the other. The best published result we could find used a sensor at the waist at 100 Hz, with motion capture as the reference and a machine learning model over 145 features, and it landed on a band of plus or minus 14 centimetres. A well known commercial jump device in that same comparison scored worse than guessing the average. Nobody has published jump height from an upper arm at all.
So the number was going to be wrong, and worse, we would not have been able to tell when it was wrong. We count jumps. We do not measure how high they were.