Wbang, bang, bang – the handball fans’ drums rumble through the Wetzlar hall. As Emil Mellegard catches the ball in the green shirt of HSG, he sees a gap in Fuchse Berlin’s defense out of the corner of his eye. Mellegard accelerates – left, right, left – bounces off the blue ground and leaps past the opponent into the nine-meter space. Frank Leibmann watches from a platform above the grandstand Handball Bundesliga (HBL) attack. A laptop sits on the table in front of him. Green and black dots whiz by on the handball court. Mellegard is one of them.

Behind the point is a complex set of data: how fast he runs, how high he jumps, how hard he throws, how long he stays in the air—Mellegard’s every move is recorded instantly. A white sensor was stuck between his shoulder blades in the vest under his shirt; about the size of a postage stamp, weighing 14 grams. It registers its wearer’s movements and position and sends them to a dozen receivers that look like wireless LAN routers, hidden in the hall’s ceiling structure or on billboards on the edge of the field. A sensor is also hidden inside the ball, which continuously collects data and transmits it wirelessly every millisecond.