Broadening is spreading muscle fibers sideways with the palm or forearm to widen a bunched muscle.
The stroke goes across the belly rather than along it, asking a packed muscle to take up more width. In 📝Deep Tissue Massage it is used after the surface is warm, often on a quadriceps, a calf, or a back that has gathered into a rope. It is a way of asking for space, not a diagnosis of a contracture and not a claim to split fibers. Pressure stays breathable and slow.
Clients feel a spreading, sometimes intense stretch across the muscle. If the tissue braces, the stroke is too fast or too deep. Sharp or shooting pain is a stop.