Bracing the contact means that the two hands must work together instead of each contacting the client separately. Less area of the client’s body will be covered this way, but stronger and more efficient pressure will be created at the area that is being worked, which is more important when deep pressure is needed.
Even perfect body mechanics cannot eliminate all physical stress to your body when doing massage. Ideal body mechanics merely minimize the stress. For this reason, when doing massage, especially deep pressure massage, it is wise to alternate which treatment hand contact you use during a session.