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April 12, 2019

The purpose of this study was to test the torquegenerating capacity of a portable battery powered NMES device (InTENSity Select Combo II) to determine the percentage of maximal volitional isometric contraction that can be achieved through the delivery of maximal tolerable electrically induced muscle contractions in the quadriceps muscle.

BACKGROUND: Previous literature indicates that electrical stimulation devices capable of producing quadriceps femoris muscle torque production ≥ 50% of maximal volitional isometric contraction (MVIC) can play an important adjunctive role in optimizing quadriceps strength recovery in the post-surgical knee. There has been conflicting findings in the literature with regard to the torque generating capacity of battery operated portable neuromuscular electrical stimulation (NMES) devices. OBJECTIVES: The purpose of this study was to test the torquegenerating capacity of a portable battery powered NMES device (InTENSity Select Combo II) to determine the percentage of maximal volitional isometric contraction that can be achieved through the delivery of maximal tolerable electrically induced muscle contractions in the quadriceps muscle. SUBJECTS: Twenty-four healthy volunteer subjects with ages ranging from 18 to 35 (13 female, 11 male). Subjects had no history of knee injury or presence of contraindications to the use of electrical stimulation. MATERIALS AND METHODS: An InTENSity Select Combo II - Model DI2195 (Compass Health, Middleburg Heights, OH) battery operated portable NMES device was used to deliver neuromuscular electrical stimulation to the quadriceps femoris at maximum tolerable intensity. The device was set to a symmetrical biphasic waveform with a phase duration of 200 µsec, frequency of 50 pps, ramp of 2 sec, on time of 10 sec, and off time of 60 sec. A 2.75 x 5.0 inch Dura-Stick Plus self-adhesive electrode (DJO, Vista, CA) was placed over the upper portion of the vasutus lateralis and over the vastus medialis oblique. Maxim

volitional isometric contraction (MVIC), peak isometric quadriceps muscle torque achieved during NMES, and the average quadriceps femoris muscle torque produced over 5 NMES contractions were assessed by measuring the lever arm of the lower leg and the force (kg) produced into a handheld manual muscle testing dynamometer model 01165 (Lafayette Instrument, Lafayette, IN). The average quadriceps femoris muscle torque produced over 5 NMES contractions was evaluated and reported as the % MVIC RESULTS: The InTENSity Select Combo II was able to produce a torque of 54.1% +/- 19.5% of the average maximum volitional isometric contractions for the 24 subjects. This was higher than the peak torque production of 50% that was found to be effective in previous studies.

CONCLUSIONS: Based on the findings of this study, we believe the InTENSity Select Combo II has the capacity to produce the necessary level of torque production to effectively deliver high intensity NMES to the quadriceps femoris. Further study is needed to determine the effectiveness of using the InTENSity Select Combo II in subjects with impaired quadriceps femoris strength. [Khuzeykin I, Coppinger S, Varnell M, Gallo JA. Quadriceps Femoris Muscle Torque Production When Using a Portable Neuromuscular Electrical Stimulation Device. Prepublication data from study performed at Salem State University, Salem MA. May 2016].