Wide-pulse neuromuscular electrical stimulation compared to traditional NMES parameters for changes in muscle volume and fatigue.
1Forrest G, 2Rejc E, 2Harkema S
1Kessler Foundation, West Orange, NJ, USA; 2University of Lousiville, Lousiville, Kentucky, USA
Objective: To determine the effects of multi-muscle wide-pulse neuromuscular electrical stimulation (WP-NMES) compared to traditional NMES parameters when combined with dynamic stand training on restoring muscle volume and function after chronic, motor-complete, SCI. We anticipated that this unique combination using WP-NMES would be more effective to promote muscle hypertrophy in multiple muscle groups below the level of lesion after a SCI. The stand with NMES groups were compared to stimulation alone (participants in supine position) and to stand alone (without stimulation) groups.
Design/Methods: Individuals with chronic motor complete SCI were enrolled in one of these five interventions: (1) Stand alone (ST), (2) NMES supine, (3) ST+NMES, (4) WP-NMES supine, (5) ST+WP-NMES. The electrical stimulation groups were given symmetrical biphasic pulses of 300 µs (groups 2 and 3, NMES) and of 1ms (groups 4 and 5, WP-NMES) delivered at 35 Hz across a 1000 Ω load bilaterally on quadricep, hamstring, tibialis anterior, and gastrocnemius muscles. All participants completed 60 hours of intervention (1hr/training session). At pre and after intervention. T1 images of bilateral thigh from the origin of the iliopsoas to the insertion of achilles tendon (1cm thick and separated by .5cm) collected on GE 1.5-T magnetic resonance imager using a whole body coil (40 FOV, 2 NEX, 256 X 192 matrix) 201,202. Images analyzed by customized analysis program. Software automatically i) detects muscle, bone, and fat based on image contract parameters; ii) measures cross sectional areas of each region outlined by integrating the area of each pixel (0.41mm2) in the image. In a subset of individuals enrolled in groups 1, 4 and 5, torque output of knee extensors, knee flexors, plantar flexors and dorsi flexors was assessed during non-fatiguing and fatiguing electrically stimulated isometric contractions by Biodex dynamometer.
Results: Significant increases in thigh mean cross sectional area (CSA) were determined in the ST+WP-NMES group compared to all other groups. Significant increases were also determined in anterior and posterior compartments for thigh mean CSA in the ST+WP-NMES group compared to all other groups. Median (50% percentile) of thigh CSA for WP-NMES supine group were greater than median thigh CSA for all groups using traditional stimulation parameters. WP-NMES parameters increased peak torque on average by 25% across 8 muscles tested.
Conclusions: Delivering 60 sessions of multi-muscle stimulation using WP-NMES parameters during weight-bearing standing in chronic SCI individuals improves muscle CSA and volume significantly when compared to traditional parameters of NMES
This work was supported by: NJ Commission on Spinal Cord Research 07B-SCR-1; NIH grant R01 NS049209; Kessler Foundation; Craig H Neilson Foundation 09521
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