With grade one and grade two we are stimulating the A-beta fibres which travel through the dorsal root ganglia into the dorsal horn of the spinal cord at the level of lamina 2 in the substantia gelatinosa, with the purpose of closing down the pain gate ahead of any nociceptive signals by the A-delta and C fibres that travel up the afferent pathways in the spinothalamic and spinoreticular pathways.
A-beta fibres
■ The largest peripheral nerve fibre
■ Large diameter
■ Myelinated
■ Respond to low stimuli (and are therefore ‘low threshold’) such as light touch, pressure and proprioception.
■ Impulses transmitted 30-100m/sec to the CNS
■ Normally relate non-noxious ‘mechanical’