Hi hera,
G-V is a very sensitive technique used by many manual tharapists/ chiropractors and osteopaths. HVLAT/G-V's has many roles in terms of its mechanical/neurophysiological/chemical and psycological effects. It is one of the most researched techique used by the professionals, However there is still contravorsy about its efficacy. The evedince also suggests that cervical HVLAT can cause a stroke (VBI). At the same time there is no law restricting general physios from doing a HVLAT, But one should always keep in mind the adverse effects of the technique if it is not done correctly. So it is always better to get trained to do it and should know exatactly why and when to do the technique.Hope this helped you...
tanx..
naveen