Hanging in means to remain just behind the group. This is energy-conserving and enables you to move as quickly as the group.
The riders remain together and concentrate on pedaling. They turn as little as possible and keep their upper body loose to conserve energy and achieve better riding. The riders do not attempt to pass others but let the top cyclists take the head position into the wind. Remaining together occurs during long events or hard stages where energy conservation for later, such as during the sprint, climb, or breakaway, is critical. You can succeed at endurance events by sitting well back in the group or peloton and being patient.