Figure 7.

TENS induced blockade of afferent input from peripheral neurons. Impulses generated by TENS are conducted in both directions along the axon (white arrows). Those conducted toward the periphery (antidromic) extinguish nerve impulses arising from distal structures (dashed arrows) such as sensory receptors cells that are traveling in the normal direction (orthodromic). Nociceptive input conducted in higher threshold (A-delta and C-fibre) afferents is more likely to be blocked when higher amplitude currents of TENS are used to activate higher threshold axons (e.g., A-delta), but this is likely to produce uncomfortable TENS sensation that may not be tolerated by the patient.