Place G1 just anteroinferior to the navicular tuberosity; stimulate behind the medial malleolus and proximally in the center of the popliteal fossa.
01 · Placement
Place G1 over the abductor hallucis motor point on the medial foot, about two finger widths distal and slightly anteroinferior to the navicular tuberosity.
Table 2 · p.373 ↗Place G2 distally using the belly–tendon method, just distal and medial to the first MTP joint and completely off the abductor hallucis muscle.
Table 2 · p.373 ↗Stimulate 8 cm proximal to G1 in the groove posterior to the medial malleolus, between the malleolus and Achilles tendon; orient the cathode distally.
Distance · 8 cm from G1
Table 2 · p.373 ↗Stimulate over the tibial nerve in the center of the popliteal fossa; press firmly because the nerve is deep and confirm plantar flexion rather than volume conduction.
Distance · Variable—measure the S1–S2 segment on the patient
Table 2 · p.373 ↗Place the ground on the posteromedial calf between the ankle and popliteal stimulation sites.
Table 2 · p.373 ↗02 · Reference values
| Measure | Reference limit | Basis |
|---|---|---|
| Distal CMAP amplitude | ≥4.4 mV | 3rd percentile lower limit |
| Conduction velocity | ≥39 m/s | 3rd percentile lower limit |
| Distal motor latency | ≤6.1 ms | 97th percentile upper limit |
| Amplitude drop ankle–knee | ≤10.3 mV or 71% | 97th percentile upper limit |
03 · Technique
Primary evidence
Adult tibial motor reference values recorded from abductor hallucis; see the source table for age- and height-stratified limits.