what is the pack on the back of rugby shirts

The pack on the back of rugby shirts is a GPS tracking device used by coaches to track a variety of statistics about every player. The visible part of the device is a padded casing that surrounds a unit commonly referred to as a GPS tracker, although it contains other measuring devices. The device measures a host of physical data emitted by the player, including distance covered, speeds reached, and overall heart rate. The device is designed and cleverly positioned to sustain collisions and scrums. Players can wear the tracking unit in a specially made pocket on the back of the shirt or in a harness worn under the shirt. The primary use of tracking systems is to manage a players workload to make sure that they stay healthy and able to perform at their peak for the entire season.