The dummy tips backward in its chair: its head hits the floor. Inside the head, in three Petri dishes, live human nerve cells. They feel the impact just as a real brain would during a fall.

The experiment is simple: the dummy was dropped from a sitting position at angles of 30, 60, and 90 degrees. Six accelerometers (three on the surface of the head, three inside near the cells) recorded how hard the shake was. When dropped at a right angle, the head experienced an overload of up to 258g, as if a weight 258 times its own had momentarily pressed down on it. The head deformed by nearly a centimeter.

The cells responded to the impact with stress. Their level of oxidative stress rose: that's when aggressive molecules accumulate inside the cell, damaging its machinery. At a 90-degree impact, stress was twice as high as in cells that weren't touched. Some cells died, and their distribution across the dish was uneven: damage concentrated in distinct hotspots, as if the blow had struck specific points.

The same experiment was repeated in a computer model. It turned out that the stiffness of the surface the head hits has the biggest influence on head acceleration. A soft floor, less impact; a hard floor, more. This means protective coverings and shock absorbers could reduce cell damage from falls.

This approach, a living cellular sensor inside a dummy, for the first time links the mechanics of impact to biological response. In the future, it could help more accurately assess concussion risk and develop protection for athletes, construction workers, and the elderly.