The invention relates to a system for monitoring a physiological parameter of players engaged in a sports activity and a method for evaluating and treating players when the parameter exceeds a predetermined level. The system measures, calculates and records the parameter and then alerts trained personnel to apply the method to evaluate and treat players. When the system is configured for use with football, hockey or lacrosse, the system generally includes reporting units, a sideline controller, a database, and a signaling device, such as a wireless personal digital assistant. The physiological parameter data measured and collected by the reporting units are processed by the sideline controller for meaningful analysis or use. When the physiological parameter(s) exceeds a predetermined threshold level the sideline controller generates an alert that is received by the signaling device, which is typically worn by sideline personnel, such as coaching staff or trainers. After an alert occurs, the method for evaluating and treating a player is initiated.