Photos: Tackling head injuries

Sensors built into a football helmet measure how hard a player is hit in the head.

The small sensors touch a player's head and wirelessly feed the impact data to a display monitored by trainers and coaches.

Sports equipment-maker Riddell is marketing the impact-monitoring equipment to pro and big-time college football teams.

An impact of more than 100 g's (a measure of gravitational force) could mean a player has suffered a concussion.

Using the impact monitoring system, a typical digital beeper can warn coaches when there's trouble.

Linebackers, who are always in the middle of the action, often receive the heaviest and most-frequent blows to the head during a game.

Virginia Tech, where star quarterback Michael Vick played his college ball, is one of the big NCAA programs using the new equipment.