Electrical-tomographic imaging of physiological-induced conductive response in calf muscle compartments during voltage intensity change of electrical muscle stimulation (vic-EMS).

Objectives: The electrical-tomographic imaging has been achieved for exploring differential tendency of physiological-induced conductive response in calf muscle compartments during voltage intensity change of electrical muscle stimulation (vic-EMS). Approach: In the experiments, the differential tendency of conductivity distribution images σ during vic-EMS were clearly imaged as three responsive muscle compartments, which are called M1 compartment composed of gastrocnemius muscle, M2 compartment composed of tibialis anterior, extensor digitorum longus, and peroneus longus muscles, and M3 compartment composed of soleus muscle. Main results: The differential tendency of spatial-mean conductivity M1 is the same as the differential tendency of venous blood flow velocity vbl and blood lactate concentration Cbl during vic-EMS by the increased tendency of spatial-mean conductivity difference Δ M1, venous blood flow velocity difference Δvbl and blood lactate concentration difference ΔCbl. The M1 is increased with the increase of voltage intensity from M1 = 0.142 [-] to M1 = 0.442 [-] (pre: pre-training, l14: voltage level during vic-EMS l=14) by Δ M1 = 204.2 % (n = 16, p M1 suggests an increase in muscle extracellular volumes during vic-EMS due to the co-effect of venous blood flow velocity and blood lactate metabolism. Based on the conductivity second-order difference images ├ (∂^2 σ_M1^φ)/(∂φ^2 ) ┤|_φ and spatial-mean conductivity second-order difference ⟨├ (∂^2 σ_M1^φ)/(∂φ^2 )┤|_φ ⟩, optimum voltage intensity φOVI is discussed among sixteen volunteer subjects, which increased with a thicker subcutaneous fat layer.