That was the whole reason that Goku-Son and Gohan went into the chamber.So that they could go beyond the stage of SSJ.
If I remember correctly,Goku-Son and Gohan only practiced in that chamber in SSj form so that it would feel so weird.And also so that they wouldnt waist any energy powering up because they were already in SSJ form.
Do you remeber the part where Krillin,Goku-son,and Gohan were in the field and Goku-son was laying there sleep in SSJ.Krillin thought that Goku-son could feel ever power level from miles away.But when he threw that Rock at Goku-son,he thought that Goku would Zap it,but he didnt and it hit him right in the face:therock: