Influence of Patterned Electrical Neuromuscular Stimulation on Quadriceps Activation in Individuals with Knee Joint Injury.

Authors:  Glaviano NR, Langston WT, Hart JM, Saliba S

Neuromuscular Electrical Stimulation is a common intervention to address muscle weakness, however presents with many limitations such as fatigue, muscle damage, and patient discomfort that may influence its effectiveness.  One novel form of electrical stimulation purported to improve neuromuscular re-education is Patterned Electrical Neuromuscular Stimulation (PENS), which is proposed to mimic muscle-firing patterns of healthy individuals.  PENS provides patterned stimulation to the agonist muscle, antagonist muscle and then agonist muscle again in an effort to replicate firing patterns.  The purpose of this study was to determine the effect of a single PENS treatment on knee extension torque and quadriceps activation in individuals with quadriceps inhibition.  Maximal voluntary isometric contraction of the quadriceps and central activation ratio were measured before and after treatment. The treatment intervention was a 15-minute patterned electrical stimulation applied to the quadriceps and hamstring muscles with a strong motor contraction or a sham group, who received an identical set up as the PENS group, but received a 1mA subsensory stimulation.  The authors found that there were no differences in change scores between pre- and post-intervention for maximal voluntary isometric contraction: (PENS: 0.09±0.32Nm/kg and Sham 0.15±0.18Nm/kg, p=0.713), or central activation ratio:(PENS: -1.22±6.06 and Sham: 1.48±3.7, p=0.270).  Therefore, a single Patterned Electrical Neuromuscular Stimulation treatment did not alter quadriceps central activation ratio or maximal voluntary isometric contraction. Unlike other types of muscle stimulation, PENS did not result in a reduction of quadriceps torque after the stimulation session.

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