The Effect of Electrode Placement and Interphase Interval on Force Production During Stimulation of the Dorsiflexor Muscles

Abstract

The aims of this study were to investigate whether introducing an interphase interval (IPI) to biphasic pulses during stimulation of the dorsiflexor muscles would affect force production and to determine whether the IPI effect is dependent on electrode position. Twelve healthy volunteers participated in the study. Each subject participated in one session during which electrically induced contraction (EIC) forces of the ankle dorsiflexors were measured with five different IPI settings ranging from 0 to 400 μs. Forces of EICs were assessed with the electrodes placed either with the proximal electrode positioned over the common peroneal nerve and the second electrode over the dorsiflexor muscles or with both electrodes located over the dorsiflexor muscles. The order of electrode placements and of the different IPI settings was randomized across subjects. The results indicated that the introduction of a 100-μs-long IPI may enhance force production when one electrode is located over the common peroneal nerve. However, increasing the duration of the IPI beyond 100 μs did not result in further increase in force production. In contrast, the introduction of an IPI did not increase force production when both electrodes were located over the dorsiflexor muscles. These findings may help to optimize stimulation settings during functional electrical stimulation to prevent foot-drop.

The Effect of an Interphase Interval on Electrically Induced Dorsiflexion Force and Fatigue in Subjects With an Upper Motor Neuron Lesion

“…This study demonstrated that introducing an IPI during ES of the ankle dorsiflexors in subjects with UMNL enhances muscle force production. The findings are in agreement with previous studies that show that the introduction of an IPI increases force of EICs in able-bodied subjects (15,16). Furthermore, this study found that the introduction of a 250 ms long IPI decreased muscle fatigue induced by ES.…”

“…Laufer who tested IPIs of up to 250 µs demonstrated no further increases beyond IPI = 50 µs. Springer et al who tested IPI of up to 400 µs reported that increasing the duration of the IPI beyond 100 μs did not result in further increase in force production. In another study by Springer that tested IPI of up to 400 µs, introduction of a 200 µs IPI increased force production (compared to IPI = 0 µs) while longer IPI duration did not.…”

“…Using only seven subjects and multiple test conditions, the study lacked sufficient power to demonstrate statistical significance. Two, more recent reports that involved stimulation of the quadriceps muscle (15) and the ankle dorsiflexors (16), have substantiated these findings. They reported significant increases in force production in response to increases in IPI duration ranging from 0 to 400 ms, without increased discomfort.…”

Optimization of Interphase Intervals to Enhance the Evoked Muscular Responses of Transcutaneous Neuromuscular Electrical Stimulation

“…Based on the activating function (Eq. In the case of the common peroneal nerve, it has a depth of around 10 mm (17) when stimulated as described by Springer et al (6), who used electrodes of 22.4 mm of radius. If the conduction velocity of an action potential in an a-motorneuron is considered as 80 m/s (18), the action potentials require around 156 ms, which is consistent with the results that the summation of this action potentials (CMAP) reaches a plateau at IPI5 250 ms.…”

“…Such difference is due to a "vulnerable period" after the stimulation (cathodic) phase, in which the anodic phase has properties to mitigate the evoked action potential (2). More recently, publications on transcutaneous neuromuscular electrical stimulation (NMES) have shown the differences induced by IPI on the contraction forces (5)(6)(7)(8) and the neuromuscular responses (M-waves) (9). More recently, publications on transcutaneous neuromuscular electrical stimulation (NMES) have shown the differences induced by IPI on the contraction forces (5)(6)(7)(8) and the neuromuscular responses (M-waves) (9).…”