What is a Gasser?
Starting on one sideline of a football field an athlete will sprint across the field to the opposite sideline, turn and sprint back to the sideline, plant and sprint to the sideline, plant and sprint back to the sideline. Sideline to sideline is 53 yards or 48 meters. 1 full gasser will constitute four trips sideline to sideline for a total of 212 yards or 193 meters.
The exercise and demo page isn't up yet, but there is an exercise FAQ (WFS):