EFFECTS OF PATTERNED ELECTRICAL NEUROMUSCULAR STIMULATION ON KNEE JOINT STABILIZATION

Abstract

INTRODUCTION: Electrical stimulation has traditionally been used in rehabilitation settings for neuromuscular reeducation and to reverse the adverse effects of muscle atrophy. However a more functional form of stimulation, known as patterned electrical neuromuscular stimulation (PENS), has recently been developed to replicate typical firing patterns of muscles. There has been evidence to suggest that receiving this treatment while performing exercises may have the potential to improve functional performance in healthy individuals. PURPOSE: The purpose of this study was to examine the effects of patterned electrical nerve stimulation (PENS) treatment applied during a step-up exercise on knee stabilization during resisted strength and balance tasks. METHODS: Four females and one male volunteered to participate in this study. Subjects were randomly assigned into two groups, one receiving the PENS treatment or “Microcurrent” treatment (control/sham). Each subject met 8 times for familiarization, pre-testing, treatments and post-testing. Subjects received five 15-minute treatments while performing 3x15 step-ups on their left leg. Testing required subjects to attach a cord to their right ankle while resisting 15% of their body weight. They performed five pulls extending their hip backward and five pulls flexing their hip forward. Joint angles at the left hip and left knee and cord force tension were assessed at maximum, middle, and minimum cord tension. Alpha value was set at .05 to test for significance. RESULTS: For the back and front pull at the three sampled time points, there were no significant joint angle differences (p> 0.05) for abduction and adduction, internal and external rotation for hip and knee, hip flexion and extension, or cord force. There were several group x time interactions for knee flexion. For back pull at max tension there were pre to post differences for both the control and PENS group (F(1, 3) = 42.121, p=.007). The control group increased knee flexion by 6.8º±1.6º whereas the PENS group decreased knee flexion 6.7º±1.3º. For the front pull at minimum tension there were pre to post differences for both the control group and the PENS group (F(1, 3) = 13.352, p=.035). The control group increased knee flexion by 8.73º±3.146º whereas the PENS group decreased knee flexion by 6.1º±2.5º. CONCLUSION: We believe that the PENS group decreased knee flexion at the maximum tension for the back pull and minimum tension for the front pull suggesting that the PENS treatment may have increased eccentric control of the quadriceps by improving motor unit recruitment.