C-35 Free Communication/Poster - Motor Units and EMG: MAY 28, 2009 7:30 AM - 12:30 PM ROOM: Hall 4F
INTRODUCTION: Neuromuscular electrical stimulation (NMES) has been shown to be effective in aiding the recovery of quadriceps femoris muscle strength after total knee arthroplasty (TKA). Yet, the training intensity (dosage) has not been well described. The purpose of this investigation was to establish a dose-response relationship for NMES in patients after TKA and examine immediate changes in quadriceps muscle fatigue and activation.
SUBJECTS: Fifteen patients with end-stage osteoarthritis were studied (67.7+19.4 years; 9 women, 6 men). Patients were simultaneously enrolled in a clinical trial for NMES for which exclusion criteria included the following: uncontrolled hypertension, uncontrolled diabetes, BMI >35, other significant lower extremity orthopaedic problems, or neurological impairments.
METHODS: Quadriceps isometric strength and activation were assessed preoperatively and again at 3wks and 6wks after TKA using an isokinetic dynamometer. Muscle activation was quantified using a doublet interpolation technique. NMES training intensities at 3 and 6wks were monitored by logging the electrically elicited knee extension torque and expressing this torque as a percentage of the involved quadriceps muscles' maximal voluntary contraction torque. All patients participated in a standardized rehabilitation program for 9wks after TKA plus NMES treatment using an Empi 300PV 2x/day for 15 minutes/session for 6wks beginning 2 days after TKA.
RESULTS: Higher NMES doses more effectively attenuated the quadriceps strength loss at 3wks (R2=0.45; p<0.05) compared to lower doses, but this relationship was weaker at 6wks. Furthermore, quadriceps strength loss at 3wks was significantly attenuated in the NMES group (24.2+23.2% loss) compared to previously reported 60% losses using similar methods in the absence of NMES. After a single session of NMES (at 3wks), average quadriceps muscle fatigue was 8.2+12.7% and activation dropped less than 1% (p>0.05).
CONCLUSION: Higher NMES doses were associated with less quadriceps strength loss than lower doses. Early NMES after TKA may help attenuate quadriceps strength loss to enhance functional performance after TKA when used at sufficiently high intensities.
Funding: Foundation for Physical Therapy, American College of Rheumatology, NIH 1 UL1 RR025780