Next to the computer was an antenna that received the signals from the sensors inside the players’ helmets. Mihalik crouched down and began paging through the data. In one column, the HITS software listed the top hits of the practice up to that point, and every few moments the screen would refresh, reflecting the plays that had just been run on the field. Forty-five minutes into practice, the top eight head blows on the field measured 82 gs, 79 gs, 75 gs, 79 gs, 67 gs, 60 gs, 57 gs, and 53 gs. One player, a running back, had received both the 79 gs and the 60 gs, as well as another hit, measuring 27.9 gs. This wasn’t a full-contact practice. It was “shells.” The players wore only helmets and shoulder pads, and still there were mini car crashes happening all over the field.